From 8397e648f3054505748b1f3c2770724f5f504f14 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Wed, 9 Aug 2023 14:45:06 +0200
Subject: [PATCH 01/19] Cleanup IOptionSelector API

---
 .../CoreDelegates/UiDelegate.cs               |  4 +-
 src/NexusMods.CLI/CliOptionSelector.cs        | 82 +++++++++++--------
 src/NexusMods.Common/UserInput/ChoiceGroup.cs |  2 +-
 .../UserInput/IOptionSelector.cs              |  4 +-
 4 files changed, 52 insertions(+), 40 deletions(-)

diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index e7a8d1a9cc..51565aa964 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -99,7 +99,7 @@ private static IEnumerable<ChoiceGroup<int, int>> ToChoices(GroupList groups)
             Id = group.id,
             Type = ConvertChoiceType(group.type),
             Query = group.name,
-            Options = ToOptions(group.options),
+            Options = ToOptions(group.options).ToArray(),
         });
     }
 
@@ -112,7 +112,7 @@ private static IEnumerable<Option<int>> ToOptions(IEnumerable<Option> options)
             Description = option.description,
             ImageUrl = option.image != null ? AssetUrl.From(option.image) : null,
             Type = MakeOptionState(option),
-        }).ToArray();
+        });
     }
 
     private static OptionState MakeOptionState(Option option)
diff --git a/src/NexusMods.CLI/CliOptionSelector.cs b/src/NexusMods.CLI/CliOptionSelector.cs
index 0bff01f65d..1943808370 100644
--- a/src/NexusMods.CLI/CliOptionSelector.cs
+++ b/src/NexusMods.CLI/CliOptionSelector.cs
@@ -1,3 +1,5 @@
+using System.Diagnostics;
+using JetBrains.Annotations;
 using NexusMods.Abstractions.CLI;
 using NexusMods.Abstractions.CLI.DataOutputs;
 using NexusMods.Common.UserInput;
@@ -7,6 +9,7 @@ namespace NexusMods.CLI;
 /// <summary>
 /// Implementation of an option selector for the CLI.
 /// </summary>
+[UsedImplicitly]
 public class CliOptionSelector : IOptionSelector
 {
     private const string ReturnInput = "x";
@@ -18,13 +21,12 @@ public class CliOptionSelector : IOptionSelector
     /// <summary>
     /// The renderer to use for rendering the options.
     /// </summary>
-    public IRenderer Renderer { get; set; } = null!;
+    private IRenderer Renderer { get; set; } = null!;
 
     /// <summary>
     /// If true, all option selection will throw an error, useful for automated installers and tests
     /// </summary>
-    public bool AutoFail { get; set; } = false;
-
+    public bool AutoFail { get; set; }
 
     /// <summary>
     /// Request a choice from the user.
@@ -34,10 +36,10 @@ public class CliOptionSelector : IOptionSelector
     /// <param name="options"></param>
     /// <typeparam name="TOptionId"></typeparam>
     /// <returns></returns>
-    public Task<IEnumerable<TOptionId>> RequestChoice<TOptionId>(string query, ChoiceType type, IEnumerable<Option<TOptionId>> options)
+    public Task<TOptionId[]> RequestChoice<TOptionId>(string query, ChoiceType type, Option<TOptionId>[] options)
     {
         var done = false;
-        var current = options.ToList();
+        var current = options;
         while (!done)
         {
             var input = GetUserInput();
@@ -54,47 +56,52 @@ public Task<IEnumerable<TOptionId>> RequestChoice<TOptionId>(string query, Choic
                 Renderer.Render(TableOfOptions(current, query));
             }
         }
-        return Task.FromResult(current.Where(_ => _.Type is OptionState.Selected or OptionState.Required).Select(_ => _.Id));
+
+        var res = current
+            .Where(x => x.Type is OptionState.Selected or OptionState.Required)
+            .Select(x => x.Id)
+            .ToArray();
+
+        return Task.FromResult(res);
     }
 
     /// <inheritdoc />
-    public Task<Tuple<TGroupId, IEnumerable<TOptionId>>?> RequestMultipleChoices<TGroupId, TOptionId>(IEnumerable<ChoiceGroup<TGroupId, TOptionId>> groups)
+    public Task<Tuple<TGroupId, TOptionId[]>?> RequestMultipleChoices<TGroupId, TOptionId>(ChoiceGroup<TGroupId, TOptionId>[] groups)
     {
-        if (AutoFail)
-            throw new Exception("AutoFail is enabled for this option selector.");
+        if (AutoFail) throw new Exception("AutoFail is enabled for this option selector.");
 
         var selectedGroupIdx = -1;
-        Tuple<TGroupId, IEnumerable<TOptionId>>? result = null;
+        Tuple<TGroupId, TOptionId[]>? result = null;
         IList<Option<TOptionId>>? selectedGroup = null;
-        string selectedGroupName = "";
-        var groupsArr = groups.ToArray();
+        var selectedGroupName = "";
 
         while (true)
         {
-            RenderOptions(groupsArr, selectedGroup, selectedGroupName);
+            RenderOptions(groups, selectedGroup, selectedGroupName);
             var input = GetUserInput();
 
             if (selectedGroupIdx < 0)
             {
-                selectedGroupIdx = ParseNumericalUserInput(input, groupsArr.Length) ?? selectedGroupIdx;
+                selectedGroupIdx = ParseNumericalUserInput(input, groups.Length) ?? selectedGroupIdx;
                 if (selectedGroupIdx >= 0)
                 {
-                    var group = groupsArr.ElementAt(selectedGroupIdx);
-                    selectedGroup = group.Options.ToList();
+                    var group = groups.ElementAt(selectedGroupIdx);
+                    selectedGroup = group.Options;
                     selectedGroupName = group.Query;
                 }
             }
             else
             {
                 if (input == ReturnInput)
-                    result = CreateResult(groupsArr, selectedGroupIdx, selectedGroup!);
+                    result = CreateResult(groups, selectedGroupIdx, selectedGroup!);
                 else
-                    UpdatedSelectedGroup(ref selectedGroup, groupsArr, selectedGroupIdx, input);
+                    UpdatedSelectedGroup(ref selectedGroup, groups, selectedGroupIdx, input);
             }
 
             if (input == ReturnInput)
                 break;
         }
+
         return Task.FromResult(result);
     }
 
@@ -121,15 +128,16 @@ private static string GetUserInput()
         return (Console.ReadLine() ?? "").Trim();
     }
 
-    private static Tuple<TGroupId, IEnumerable<TOptionId>> CreateResult<TGroupId, TOptionId>(IEnumerable<ChoiceGroup<TGroupId, TOptionId>> groups,
-                                                                                             int selectedGroupIdx,
-                                                                                             IEnumerable<Option<TOptionId>> selectedGroup)
+    private static Tuple<TGroupId, TOptionId[]> CreateResult<TGroupId, TOptionId>(
+        IEnumerable<ChoiceGroup<TGroupId, TOptionId>> groups,
+        int selectedGroupIdx,
+        IEnumerable<Option<TOptionId>> selectedGroup)
     {
         var updatedOptions = selectedGroup
-                                .Where(_ => _.Type is OptionState.Selected or OptionState.Required)
-                                .Select(_ => _.Id);
+            .Where(x => x.Type is OptionState.Selected or OptionState.Required)
+            .Select(x => x.Id);
 
-        return new Tuple<TGroupId, IEnumerable<TOptionId>>(groups.ElementAt(selectedGroupIdx).Id, updatedOptions);
+        return new Tuple<TGroupId, TOptionId[]>(groups.ElementAt(selectedGroupIdx).Id, updatedOptions.ToArray());
     }
 
     private static void FixSelection<TOptionId>(ref IList<Option<TOptionId>> list, ChoiceType groupType, int lastChangeIdx)
@@ -137,12 +145,12 @@ private static void FixSelection<TOptionId>(ref IList<Option<TOptionId>> list, C
         switch (groupType)
         {
             case ChoiceType.ExactlyOne or ChoiceType.AtMostOne
-            when (list[lastChangeIdx].Type == OptionState.Selected):
+            when list[lastChangeIdx].Type == OptionState.Selected:
                 DeselectAllBut(ref list, lastChangeIdx);
                 return;
 
             case ChoiceType.ExactlyOne or ChoiceType.AtLeastOne
-            when list.All(_ => _.Type != OptionState.Selected):
+            when list.All(x => x.Type != OptionState.Selected):
                 list[lastChangeIdx].Type = OptionState.Selected;
                 break;
         }
@@ -152,7 +160,7 @@ private static void DeselectAllBut<TOptionId>(ref IList<Option<TOptionId>> list,
     {
         for (var i = 0; i < list.Count; ++i)
         {
-            if ((i != lastChangeIdx) && (list[lastChangeIdx].Type == OptionState.Selected))
+            if (i != lastChangeIdx && list[lastChangeIdx].Type == OptionState.Selected)
             {
                 list[i].Type = OptionState.Available;
             }
@@ -164,7 +172,7 @@ private static void DeselectAllBut<TOptionId>(ref IList<Option<TOptionId>> list,
         try
         {
             var idx = int.Parse(input) - 1;
-            if ((idx >= 0) && (idx < upperLimit))
+            if (idx >= 0 && idx < upperLimit)
                 return idx;
         }
         catch (FormatException) { /* ignored */ }
@@ -185,10 +193,10 @@ private void RenderOptions<TGroupId, TOptionId>(
     private Table TableOfOptions<TOptionId>(
         IEnumerable<Option<TOptionId>> current, string selectedGroupName)
     {
-        var row = new List<object[]>();
         var key = 1;
-        foreach (var item in current)
-            row.Add(new object[] { key++, RenderOptionState(item.Type), item.Name, item.Description ?? "" });
+        var row = current
+            .Select(item => new object[] { key++, RenderOptionState(item.Type), item.Name, item.Description ?? "" })
+            .ToList();
 
         row.Add(TableOfOptionsFooter);
         return new Table(TableOfOptionsHeaders, row, selectedGroupName);
@@ -196,10 +204,10 @@ private Table TableOfOptions<TOptionId>(
 
     private static Table TableOfGroups<TGroupId, TOptionId>(IEnumerable<ChoiceGroup<TGroupId, TOptionId>> groups)
     {
-        var row = new List<object[]>();
         var key = 1;
-        foreach (var item in groups)
-            row.Add(new object[] { key++, item.Query });
+        var row = groups
+            .Select(item => new object[] { key++, item.Query })
+            .ToList();
 
         row.Add(TableOfGroupsFooter);
         return new Table(TableOfGroupsHeaders, row, "Select a Group");
@@ -207,6 +215,8 @@ private static Table TableOfGroups<TGroupId, TOptionId>(IEnumerable<ChoiceGroup<
 
     private static OptionState ToggleState(OptionState old)
     {
+        Debug.Assert(Enum.IsDefined(typeof(OptionState), old));
+
         return old switch
         {
             OptionState.Available => OptionState.Selected,
@@ -217,13 +227,15 @@ private static OptionState ToggleState(OptionState old)
 
     private static string RenderOptionState(OptionState state)
     {
+        Debug.Assert(Enum.IsDefined(typeof(OptionState), state));
+
         return state switch
         {
             OptionState.Disabled => "Disabled",
             OptionState.Available => "Off",
             OptionState.Required => "Required",
             OptionState.Selected => "On",
-            _ => throw new NotImplementedException()
+            _ => throw new UnreachableException()
         };
     }
 }
diff --git a/src/NexusMods.Common/UserInput/ChoiceGroup.cs b/src/NexusMods.Common/UserInput/ChoiceGroup.cs
index 9e07f7465c..7a6784c258 100644
--- a/src/NexusMods.Common/UserInput/ChoiceGroup.cs
+++ b/src/NexusMods.Common/UserInput/ChoiceGroup.cs
@@ -26,5 +26,5 @@ public record ChoiceGroup<TId, TOptionId>
     /// <summary>
     /// Contains all the items the user can select from.
     /// </summary>
-    public required IEnumerable<Option<TOptionId>> Options { get; init; }
+    public required Option<TOptionId>[] Options { get; init; }
 }
diff --git a/src/NexusMods.Common/UserInput/IOptionSelector.cs b/src/NexusMods.Common/UserInput/IOptionSelector.cs
index c793f4bde0..fefa5b52b4 100644
--- a/src/NexusMods.Common/UserInput/IOptionSelector.cs
+++ b/src/NexusMods.Common/UserInput/IOptionSelector.cs
@@ -17,7 +17,7 @@ public interface IOptionSelector
     /// <param name="options">The items the user can select from.</param>
     /// <typeparam name="TOptionId">Unique ID for each option.</typeparam>
     /// <returns>Number of picked options by the user.</returns>
-    public Task<IEnumerable<TOptionId>> RequestChoice<TOptionId>(string query, ChoiceType type, IEnumerable<Option<TOptionId>> options);
+    public Task<TOptionId[]> RequestChoice<TOptionId>(string query, ChoiceType type, Option<TOptionId>[] options);
 
     /// <summary>
     /// Requests the user to make a series of choices from multiple groups of choices.
@@ -26,5 +26,5 @@ public interface IOptionSelector
     /// <typeparam name="TGroupId">Unique ID for each group.</typeparam>
     /// <typeparam name="TOptionId">Unique ID for each option.</typeparam>
     /// <returns></returns>
-    public Task<Tuple<TGroupId, IEnumerable<TOptionId>>?> RequestMultipleChoices<TGroupId, TOptionId>(IEnumerable<ChoiceGroup<TGroupId, TOptionId>> choices);
+    public Task<Tuple<TGroupId, TOptionId[]>?> RequestMultipleChoices<TGroupId, TOptionId>(ChoiceGroup<TGroupId, TOptionId>[] choices);
 }

From 98a9ca7e3979f73d8358c213b38a5bec66257ff0 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Wed, 9 Aug 2023 14:45:31 +0200
Subject: [PATCH 02/19] Add FOMOD.UI project

WIP
---
 NexusMods.App.sln                             |  7 ++
 .../GuidedInstallerStepViewModel.cs           | 37 ++++++++
 .../GuidedInstallerWindowViewModel.cs         | 14 +++
 .../IGuidedInstallerStepViewModel.cs          | 15 +++
 .../IGuidedInstallerWindowViewModel.cs        | 10 ++
 .../NexusMods.Games.FOMOD.UI.csproj           | 13 +++
 .../NexusMods.Games.FOMOD.UI/Services.cs      | 16 ++++
 .../UiOptionSelector.cs                       | 93 +++++++++++++++++++
 .../CoreDelegates/UiDelegate.cs               |  7 +-
 src/NexusMods.App/NexusMods.App.csproj        |  1 +
 src/NexusMods.App/Services.cs                 |  4 +-
 src/NexusMods.CLI/CliOptionSelector.cs        |  6 ++
 .../UserInput/IOptionSelector.cs              | 11 +++
 13 files changed, 230 insertions(+), 4 deletions(-)
 create mode 100644 src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs
 create mode 100644 src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerWindowViewModel.cs
 create mode 100644 src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs
 create mode 100644 src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerWindowViewModel.cs
 create mode 100644 src/Games/NexusMods.Games.FOMOD.UI/NexusMods.Games.FOMOD.UI.csproj
 create mode 100644 src/Games/NexusMods.Games.FOMOD.UI/Services.cs
 create mode 100644 src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs

diff --git a/NexusMods.App.sln b/NexusMods.App.sln
index d65b0b8de4..22f0513fc4 100644
--- a/NexusMods.App.sln
+++ b/NexusMods.App.sln
@@ -125,6 +125,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NexusMods.Abstractions", "s
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NexusMods.Games.Generic.Tests", "tests\Games\NexusMods.Games.Generic.Tests\NexusMods.Games.Generic.Tests.csproj", "{AA95B93F-23AC-46D5-83B3-2E7AE4BD309C}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NexusMods.Games.FOMOD.UI", "src\Games\NexusMods.Games.FOMOD.UI\NexusMods.Games.FOMOD.UI.csproj", "{500CE772-93C3-4DA9-9AB3-E9E9EC0A9429}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -307,6 +309,10 @@ Global
 		{AA95B93F-23AC-46D5-83B3-2E7AE4BD309C}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{AA95B93F-23AC-46D5-83B3-2E7AE4BD309C}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{AA95B93F-23AC-46D5-83B3-2E7AE4BD309C}.Release|Any CPU.Build.0 = Release|Any CPU
+		{500CE772-93C3-4DA9-9AB3-E9E9EC0A9429}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{500CE772-93C3-4DA9-9AB3-E9E9EC0A9429}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{500CE772-93C3-4DA9-9AB3-E9E9EC0A9429}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{500CE772-93C3-4DA9-9AB3-E9E9EC0A9429}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -361,6 +367,7 @@ Global
 		{09B037AB-07BB-4154-95FD-6EA2E55C4568} = {897C4198-884F-448A-B0B0-C2A6D971EAE0}
 		{1E20E979-5F04-44FD-BE07-54B6686ECB13} = {E7BAE287-D505-4D6D-A090-665A64309B2D}
 		{AA95B93F-23AC-46D5-83B3-2E7AE4BD309C} = {05B06AC1-7F2B-492F-983E-5BC63CDBF20D}
+		{500CE772-93C3-4DA9-9AB3-E9E9EC0A9429} = {70D38D24-79AE-4600-8E83-17F3C11BA81F}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {9F9F8352-34DD-42C0-8564-EE9AF34A3501}
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs b/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs
new file mode 100644
index 0000000000..96957c9f02
--- /dev/null
+++ b/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs
@@ -0,0 +1,37 @@
+using System.Reactive;
+using System.Reactive.Linq;
+using System.Reactive.Disposables;
+using JetBrains.Annotations;
+using NexusMods.App.UI;
+using NexusMods.Common.UserInput;
+using ReactiveUI;
+using ReactiveUI.Fody.Helpers;
+
+namespace NexusMods.Games.FOMOD.UI;
+
+[UsedImplicitly]
+public class GuidedInstallerStepViewModel : AViewModel<IGuidedInstallerStepViewModel>, IGuidedInstallerStepViewModel
+{
+    [Reactive]
+    public ChoiceGroup<int, int>[] Choices { get; set; } = Array.Empty<ChoiceGroup<int, int>>();
+
+    [Reactive]
+    public TaskCompletionSource<Tuple<int, int[]>?>? TaskCompletionSource { get; set; }
+
+    public ReactiveCommand<Unit, Unit> NextStepCommand { get; }
+
+    public GuidedInstallerStepViewModel()
+    {
+        // TODO: other validation
+        var hasTaskCompletionSource = this
+            .WhenAnyValue(vm => vm.TaskCompletionSource)
+            .OnUI()
+            .Select(tsc => tsc is not null);
+
+        NextStepCommand = ReactiveCommand.Create(() =>
+        {
+            // TODO: set result
+            TaskCompletionSource?.TrySetResult(new Tuple<int, int[]>(0, Array.Empty<int>()));
+        }, hasTaskCompletionSource);
+    }
+}
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerWindowViewModel.cs b/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerWindowViewModel.cs
new file mode 100644
index 0000000000..148ade1fd2
--- /dev/null
+++ b/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerWindowViewModel.cs
@@ -0,0 +1,14 @@
+using JetBrains.Annotations;
+using NexusMods.App.UI;
+using ReactiveUI.Fody.Helpers;
+
+namespace NexusMods.Games.FOMOD.UI;
+
+[UsedImplicitly]
+public class GuidedInstallerWindowViewModel : AViewModel<IGuidedInstallerWindowViewModel>, IGuidedInstallerWindowViewModel
+{
+    [Reactive] public string WindowName { get; set; } = string.Empty;
+
+    [Reactive]
+    public IGuidedInstallerStepViewModel? ActiveStepViewModel { get; set; }
+}
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs b/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs
new file mode 100644
index 0000000000..8ecf3faa93
--- /dev/null
+++ b/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs
@@ -0,0 +1,15 @@
+using System.Reactive;
+using NexusMods.App.UI;
+using NexusMods.Common.UserInput;
+using ReactiveUI;
+
+namespace NexusMods.Games.FOMOD.UI;
+
+public interface IGuidedInstallerStepViewModel : IViewModelInterface
+{
+    public ChoiceGroup<int, int>[] Choices { get; set; }
+
+    public TaskCompletionSource<Tuple<int, int[]>?>? TaskCompletionSource { get; set; }
+
+    public ReactiveCommand<Unit, Unit> NextStepCommand { get; }
+}
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerWindowViewModel.cs b/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerWindowViewModel.cs
new file mode 100644
index 0000000000..92ea81b2d3
--- /dev/null
+++ b/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerWindowViewModel.cs
@@ -0,0 +1,10 @@
+using NexusMods.App.UI;
+
+namespace NexusMods.Games.FOMOD.UI;
+
+public interface IGuidedInstallerWindowViewModel : IViewModelInterface
+{
+    public string WindowName { get; set; }
+
+    public IGuidedInstallerStepViewModel? ActiveStepViewModel { get; set; }
+}
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/NexusMods.Games.FOMOD.UI.csproj b/src/Games/NexusMods.Games.FOMOD.UI/NexusMods.Games.FOMOD.UI.csproj
new file mode 100644
index 0000000000..5f6c8af9a3
--- /dev/null
+++ b/src/Games/NexusMods.Games.FOMOD.UI/NexusMods.Games.FOMOD.UI.csproj
@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <ItemGroup>
+        <ProjectReference Include="..\..\NexusMods.App.UI\NexusMods.App.UI.csproj" />
+    </ItemGroup>
+    <ItemGroup>
+      <Compile Update="GuidedInstallerWindowViewModel.cs">
+        <DependentUpon>IGuidedInstallerWindowViewModel.cs</DependentUpon>
+      </Compile>
+      <Compile Update="GuidedInstallerStepViewModel.cs">
+        <DependentUpon>IGuidedInstallerStepViewModel.cs</DependentUpon>
+      </Compile>
+    </ItemGroup>
+</Project>
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/Services.cs b/src/Games/NexusMods.Games.FOMOD.UI/Services.cs
new file mode 100644
index 0000000000..4a86f03c62
--- /dev/null
+++ b/src/Games/NexusMods.Games.FOMOD.UI/Services.cs
@@ -0,0 +1,16 @@
+using Microsoft.Extensions.DependencyInjection;
+using NexusMods.App.UI;
+using NexusMods.Common.UserInput;
+
+namespace NexusMods.Games.FOMOD.UI;
+
+public static class Services
+{
+    public static IServiceCollection AddFomodInstallerUi(this IServiceCollection serviceCollection)
+    {
+        return serviceCollection
+            .AddTransient<IOptionSelector, UiOptionSelector>()
+            .AddViewModel<GuidedInstallerStepViewModel, IGuidedInstallerStepViewModel>()
+            .AddViewModel<GuidedInstallerWindowViewModel, IGuidedInstallerWindowViewModel>();
+    }
+}
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs b/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
new file mode 100644
index 0000000000..c6464acac1
--- /dev/null
+++ b/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
@@ -0,0 +1,93 @@
+using System.Diagnostics;
+using JetBrains.Annotations;
+using Microsoft.Extensions.DependencyInjection;
+using NexusMods.Common.UserInput;
+
+namespace NexusMods.Games.FOMOD.UI;
+
+[UsedImplicitly]
+public sealed class UiOptionSelector : IOptionSelector, IDisposable
+{
+    private readonly IServiceProvider _serviceProvider;
+
+    private IServiceScope? _currentScope;
+    private IGuidedInstallerWindowViewModel? _windowViewModel;
+
+    public UiOptionSelector(IServiceProvider serviceProvider)
+    {
+        _serviceProvider = serviceProvider;
+    }
+
+    public void SetupSelector(string windowName)
+    {
+        Debug.Assert(_currentScope is null);
+        _currentScope = _serviceProvider.CreateScope();
+
+        // TODO: create/show window?
+        _windowViewModel = _currentScope.ServiceProvider.GetRequiredService<IGuidedInstallerWindowViewModel>();
+        _windowViewModel.WindowName = windowName;
+    }
+
+    public void CleanupSelector()
+    {
+        if (_windowViewModel is not null)
+        {
+            // TODO: dispose & close window?
+            _windowViewModel.ActiveStepViewModel = null;
+            _windowViewModel = null;
+        }
+
+        _currentScope?.Dispose();
+        _currentScope = null;
+    }
+
+    public Task<TOptionId[]> RequestChoice<TOptionId>(
+        string query,
+        ChoiceType type,
+        Option<TOptionId>[] options)
+    {
+        throw new NotImplementedException();
+    }
+
+    public async Task<Tuple<TGroupId, TOptionId[]>?> RequestMultipleChoices<TGroupId, TOptionId>(
+        ChoiceGroup<TGroupId, TOptionId>[] choices)
+    {
+        Debug.Assert(_currentScope is not null);
+        Debug.Assert(_windowViewModel is not null);
+
+        _windowViewModel.ActiveStepViewModel ??= _currentScope.ServiceProvider.GetRequiredService<IGuidedInstallerStepViewModel>();
+
+        var activeStepViewModel = _windowViewModel.ActiveStepViewModel;
+        activeStepViewModel.Choices = CastChoices(choices);
+
+        var tcs = new TaskCompletionSource<Tuple<int, int[]>?>();
+        activeStepViewModel.TaskCompletionSource = tcs;
+
+        await tcs.Task;
+        return CastResult<TGroupId, TOptionId>(tcs.Task.Result);
+    }
+
+    private static ChoiceGroup<int, int>[] CastChoices<TGroupId, TOptionId>(IEnumerable<ChoiceGroup<TGroupId, TOptionId>> choices)
+    {
+        // NOTE(erri120): FOMOD uses integer for IDs. This is the only thing currently supported.
+        Debug.Assert(typeof(TGroupId) == typeof(int));
+        Debug.Assert(typeof(TOptionId) == typeof(int));
+
+        // TODO: verify this actually works
+        return (ChoiceGroup<int, int>[])Convert.ChangeType(choices, typeof(ChoiceGroup<int, int>));
+    }
+
+    private static Tuple<TGroupId, TOptionId[]>? CastResult<TGroupId, TOptionId>(Tuple<int, int[]>? result)
+    {
+        // NOTE(erri120): FOMOD uses integer for IDs. This is the only thing currently supported.
+        Debug.Assert(typeof(TGroupId) == typeof(int));
+        Debug.Assert(typeof(TOptionId) == typeof(int));
+
+        if (result is null) return null;
+
+        // TODO: verify this actually works
+        return (Tuple<TGroupId, TOptionId[]>?)Convert.ChangeType(result, typeof(Tuple<TGroupId, TOptionId[]>));
+    }
+
+    public void Dispose() => CleanupSelector();
+}
diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index 51565aa964..a063331bcf 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -32,7 +32,6 @@ private static void DummyContinueToNextStep(bool forward, int currentStepId) { }
     private readonly ILogger<UiDelegates> _logger;
     private readonly IOptionSelector _optionSelector;
 
-    private string _moduleName = string.Empty;
     private SelectOptions _selectOptions = DummySelectOptions;
     private ContinueToNextStep _continueToNextStep = DummyContinueToNextStep;
 
@@ -49,16 +48,18 @@ public void StartDialog(
         Action<bool, int> cont,
         Action cancel)
     {
-        _moduleName = moduleName ?? string.Empty;
         _selectOptions = new SelectOptions(select);
         _continueToNextStep = new ContinueToNextStep(cont);
+
+        _optionSelector.SetupSelector(moduleName ?? string.Empty);
     }
 
     public void EndDialog()
     {
-        _moduleName = string.Empty;
         _selectOptions = DummySelectOptions;
         _continueToNextStep = DummyContinueToNextStep;
+
+        _optionSelector.CleanupSelector();
     }
 
     public void ReportError(
diff --git a/src/NexusMods.App/NexusMods.App.csproj b/src/NexusMods.App/NexusMods.App.csproj
index 25116014bf..3a5a543737 100644
--- a/src/NexusMods.App/NexusMods.App.csproj
+++ b/src/NexusMods.App/NexusMods.App.csproj
@@ -8,6 +8,7 @@
     <ItemGroup>
         <ProjectReference Include="..\Games\NexusMods.Games.BethesdaGameStudios\NexusMods.Games.BethesdaGameStudios.csproj" />
         <ProjectReference Include="..\Games\NexusMods.Games.DarkestDungeon\NexusMods.Games.DarkestDungeon.csproj" />
+        <ProjectReference Include="..\Games\NexusMods.Games.FOMOD.UI\NexusMods.Games.FOMOD.UI.csproj" />
         <ProjectReference Include="..\Games\NexusMods.Games.StardewValley\NexusMods.Games.StardewValley.csproj" />
         <ProjectReference Include="..\Games\NexusMods.Games.FOMOD\NexusMods.Games.FOMOD.csproj" />
         <ProjectReference Include="..\Games\NexusMods.Games.Generic\NexusMods.Games.Generic.csproj" />
diff --git a/src/NexusMods.App/Services.cs b/src/NexusMods.App/Services.cs
index 4b53bd23b3..4edb7e9ef7 100644
--- a/src/NexusMods.App/Services.cs
+++ b/src/NexusMods.App/Services.cs
@@ -10,6 +10,7 @@
 using NexusMods.Games.BethesdaGameStudios;
 using NexusMods.Games.DarkestDungeon;
 using NexusMods.Games.FOMOD;
+using NexusMods.Games.FOMOD.UI;
 using NexusMods.Games.Generic;
 using NexusMods.Games.RedEngine;
 using NexusMods.Games.Reshade;
@@ -33,7 +34,7 @@ public static IServiceCollection AddRenderers(this IServiceCollection services)
         services.AddScoped<IRenderer, Json>();
         return services;
     }
-    
+
     public static IServiceCollection AddListeners(this IServiceCollection services)
     {
         services.AddSingleton<NxmRpcListener>();
@@ -48,6 +49,7 @@ public static IServiceCollection AddApp(this IServiceCollection services,
         services.AddCLI()
             .AddFileSystem()
             .AddUI()
+            .AddFomodInstallerUi()
             .AddFileExtractors(config.FileExtractorSettings)
             .AddDataModel(config.DataModelSettings)
             .AddBethesdaGameStudios()
diff --git a/src/NexusMods.CLI/CliOptionSelector.cs b/src/NexusMods.CLI/CliOptionSelector.cs
index 1943808370..64045e1a77 100644
--- a/src/NexusMods.CLI/CliOptionSelector.cs
+++ b/src/NexusMods.CLI/CliOptionSelector.cs
@@ -28,6 +28,12 @@ public class CliOptionSelector : IOptionSelector
     /// </summary>
     public bool AutoFail { get; set; }
 
+    /// <inheritdoc/>
+    public void SetupSelector(string name) { }
+
+    /// <inheritdoc/>
+    public void CleanupSelector() { }
+
     /// <summary>
     /// Request a choice from the user.
     /// </summary>
diff --git a/src/NexusMods.Common/UserInput/IOptionSelector.cs b/src/NexusMods.Common/UserInput/IOptionSelector.cs
index fefa5b52b4..1a8e980210 100644
--- a/src/NexusMods.Common/UserInput/IOptionSelector.cs
+++ b/src/NexusMods.Common/UserInput/IOptionSelector.cs
@@ -9,6 +9,17 @@ namespace NexusMods.Common.UserInput;
 /// </remarks>
 public interface IOptionSelector
 {
+    /// <summary>
+    /// Sets up the selector.
+    /// </summary>
+    /// <param name="name">Name of the new selection.</param>
+    public void SetupSelector(string name);
+
+    /// <summary>
+    /// Cleans up the selector.
+    /// </summary>
+    public void CleanupSelector();
+
     /// <summary>
     /// Requests the user to make a choice from an individual group of choices.
     /// </summary>

From b70dbffcdd5fdad3ca98d663bc7a9b0d37a59c3d Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Thu, 10 Aug 2023 11:54:06 +0200
Subject: [PATCH 03/19] Update IOptionSelector

---
 .../GuidedInstallerStepViewModel.cs           |  9 ++--
 .../IGuidedInstallerStepViewModel.cs          |  4 +-
 .../UiOptionSelector.cs                       | 10 ++---
 .../CoreDelegates/UiDelegate.cs               | 41 +++++++++++++++----
 src/NexusMods.CLI/CliOptionSelector.cs        | 11 ++---
 .../UserInput/IOptionSelector.cs              |  2 +-
 6 files changed, 52 insertions(+), 25 deletions(-)

diff --git a/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs b/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs
index 96957c9f02..930f17c262 100644
--- a/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs
+++ b/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs
@@ -1,6 +1,5 @@
 using System.Reactive;
 using System.Reactive.Linq;
-using System.Reactive.Disposables;
 using JetBrains.Annotations;
 using NexusMods.App.UI;
 using NexusMods.Common.UserInput;
@@ -13,10 +12,10 @@ namespace NexusMods.Games.FOMOD.UI;
 public class GuidedInstallerStepViewModel : AViewModel<IGuidedInstallerStepViewModel>, IGuidedInstallerStepViewModel
 {
     [Reactive]
-    public ChoiceGroup<int, int>[] Choices { get; set; } = Array.Empty<ChoiceGroup<int, int>>();
+    public ChoiceGroup<int, int>[] AvailableChoices { get; set; } = Array.Empty<ChoiceGroup<int, int>>();
 
     [Reactive]
-    public TaskCompletionSource<Tuple<int, int[]>?>? TaskCompletionSource { get; set; }
+    public TaskCompletionSource<KeyValuePair<int, int[]>[]?>? TaskCompletionSource { get; set; }
 
     public ReactiveCommand<Unit, Unit> NextStepCommand { get; }
 
@@ -26,12 +25,12 @@ public GuidedInstallerStepViewModel()
         var hasTaskCompletionSource = this
             .WhenAnyValue(vm => vm.TaskCompletionSource)
             .OnUI()
-            .Select(tsc => tsc is not null);
+            .Select(tcs => tcs is not null);
 
         NextStepCommand = ReactiveCommand.Create(() =>
         {
             // TODO: set result
-            TaskCompletionSource?.TrySetResult(new Tuple<int, int[]>(0, Array.Empty<int>()));
+            TaskCompletionSource?.TrySetResult(Array.Empty<KeyValuePair<int, int[]>>());
         }, hasTaskCompletionSource);
     }
 }
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs b/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs
index 8ecf3faa93..3ae95fbd76 100644
--- a/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs
+++ b/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs
@@ -7,9 +7,9 @@ namespace NexusMods.Games.FOMOD.UI;
 
 public interface IGuidedInstallerStepViewModel : IViewModelInterface
 {
-    public ChoiceGroup<int, int>[] Choices { get; set; }
+    public ChoiceGroup<int, int>[] AvailableChoices { get; set; }
 
-    public TaskCompletionSource<Tuple<int, int[]>?>? TaskCompletionSource { get; set; }
+    public TaskCompletionSource<KeyValuePair<int, int[]>[]?>? TaskCompletionSource { get; set; }
 
     public ReactiveCommand<Unit, Unit> NextStepCommand { get; }
 }
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs b/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
index c6464acac1..8a5459256a 100644
--- a/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
+++ b/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
@@ -49,7 +49,7 @@ public Task<TOptionId[]> RequestChoice<TOptionId>(
         throw new NotImplementedException();
     }
 
-    public async Task<Tuple<TGroupId, TOptionId[]>?> RequestMultipleChoices<TGroupId, TOptionId>(
+    public async Task<KeyValuePair<TGroupId, TOptionId[]>[]?> RequestMultipleChoices<TGroupId, TOptionId>(
         ChoiceGroup<TGroupId, TOptionId>[] choices)
     {
         Debug.Assert(_currentScope is not null);
@@ -58,9 +58,9 @@ public Task<TOptionId[]> RequestChoice<TOptionId>(
         _windowViewModel.ActiveStepViewModel ??= _currentScope.ServiceProvider.GetRequiredService<IGuidedInstallerStepViewModel>();
 
         var activeStepViewModel = _windowViewModel.ActiveStepViewModel;
-        activeStepViewModel.Choices = CastChoices(choices);
+        activeStepViewModel.AvailableChoices = CastChoices(choices);
 
-        var tcs = new TaskCompletionSource<Tuple<int, int[]>?>();
+        var tcs = new TaskCompletionSource<KeyValuePair<int, int[]>[]?>();
         activeStepViewModel.TaskCompletionSource = tcs;
 
         await tcs.Task;
@@ -77,7 +77,7 @@ private static ChoiceGroup<int, int>[] CastChoices<TGroupId, TOptionId>(IEnumera
         return (ChoiceGroup<int, int>[])Convert.ChangeType(choices, typeof(ChoiceGroup<int, int>));
     }
 
-    private static Tuple<TGroupId, TOptionId[]>? CastResult<TGroupId, TOptionId>(Tuple<int, int[]>? result)
+    private static KeyValuePair<TGroupId, TOptionId[]>[]? CastResult<TGroupId, TOptionId>(KeyValuePair<int, int[]>[]? result)
     {
         // NOTE(erri120): FOMOD uses integer for IDs. This is the only thing currently supported.
         Debug.Assert(typeof(TGroupId) == typeof(int));
@@ -86,7 +86,7 @@ private static ChoiceGroup<int, int>[] CastChoices<TGroupId, TOptionId>(IEnumera
         if (result is null) return null;
 
         // TODO: verify this actually works
-        return (Tuple<TGroupId, TOptionId[]>?)Convert.ChangeType(result, typeof(Tuple<TGroupId, TOptionId[]>));
+        return (KeyValuePair<TGroupId, TOptionId[]>[]?)Convert.ChangeType(result, typeof(KeyValuePair<TGroupId, TOptionId[]>[]));
     }
 
     public void Dispose() => CleanupSelector();
diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index a063331bcf..e5f890fc64 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -29,11 +29,19 @@ private static void DummySelectOptions(int stepId, int selectedGroupId, int[] se
     private delegate void ContinueToNextStep(bool forward, int currentStepId);
     private static void DummyContinueToNextStep(bool forward, int currentStepId) { }
 
+    /// <summary>
+    /// Created by the executor, this delegate notifies the executor that the installer
+    /// should exist.
+    /// </summary>
+    private delegate void CancelInstaller();
+    private static void DummyCancelInstaller() { }
+
     private readonly ILogger<UiDelegates> _logger;
     private readonly IOptionSelector _optionSelector;
 
     private SelectOptions _selectOptions = DummySelectOptions;
     private ContinueToNextStep _continueToNextStep = DummyContinueToNextStep;
+    private CancelInstaller _cancelInstaller = DummyCancelInstaller;
 
     public UiDelegates(ILogger<UiDelegates> logger, IOptionSelector optionSelector)
     {
@@ -50,6 +58,7 @@ public void StartDialog(
     {
         _selectOptions = new SelectOptions(select);
         _continueToNextStep = new ContinueToNextStep(cont);
+        _cancelInstaller = new CancelInstaller(cancel);
 
         _optionSelector.SetupSelector(moduleName ?? string.Empty);
     }
@@ -79,17 +88,35 @@ public void UpdateState(InstallerStep[] installSteps, int currentStepId)
             .RequestMultipleChoices(choices)
             .ContinueWith(task =>
             {
-                var tuple = task.Result;
-                if (tuple is null)
+                var result = task.Result;
+                _logger.LogDebug("Status: {TaskStatus}", task.Status);
+
+                // TODO: figure out how to go backwards. Our internal API doesn't support this concept.
+                if (result is null)
                 {
-                    _logger.LogDebug("Status: {TaskStatus}", task.Status);
-                    _continueToNextStep(forward: true, currentStepId);
+                    // Result is null, the user wants to cancel installation.
+                    _cancelInstaller();
+                    return;
                 }
-                else
+
+                // NOTE(erri120): This _selectOptions delegate we got from the executor is
+                // fucking weird. It only accepts the selected options from a single group.
+                // Vortex: https://github.com/Nexus-Mods/Vortex/blob/82e8ad3e051ab4ad41df43d11803ee43d399a85f/src/extensions/installer_fomod/views/InstallerDialog.tsx#L450-L461
+                // This is "supposed" to be called whenever the user clicks on a button in the UI.
+                // However, this explicit relationship doesn't work in our case and is generally
+                // pretty stupid. As such, we get the "final" result from the implementation
+                // and push those all at once to the executor.
+
+                foreach (var kv in result)
                 {
-                    var (selectedGroupId, selectedOptionIds) = tuple;
-                    _selectOptions(currentStepId, selectedGroupId, selectedOptionIds.ToArray());
+                    var (selectedGroupId, selectedOptionIds) = kv;
+                    _selectOptions(currentStepId, selectedGroupId, selectedOptionIds);
                 }
+
+                // We need to explicitly call this, since our implementations
+                // return from RequestMultipleChoices when the user wants to go
+                // to the next step. Once again, the API is ass.
+                _continueToNextStep(forward: true, currentStepId);
             });
     }
 
diff --git a/src/NexusMods.CLI/CliOptionSelector.cs b/src/NexusMods.CLI/CliOptionSelector.cs
index 64045e1a77..46d1e4082b 100644
--- a/src/NexusMods.CLI/CliOptionSelector.cs
+++ b/src/NexusMods.CLI/CliOptionSelector.cs
@@ -72,15 +72,16 @@ public Task<TOptionId[]> RequestChoice<TOptionId>(string query, ChoiceType type,
     }
 
     /// <inheritdoc />
-    public Task<Tuple<TGroupId, TOptionId[]>?> RequestMultipleChoices<TGroupId, TOptionId>(ChoiceGroup<TGroupId, TOptionId>[] groups)
+    public Task<KeyValuePair<TGroupId, TOptionId[]>[]?> RequestMultipleChoices<TGroupId, TOptionId>(ChoiceGroup<TGroupId, TOptionId>[] groups)
     {
         if (AutoFail) throw new Exception("AutoFail is enabled for this option selector.");
 
         var selectedGroupIdx = -1;
-        Tuple<TGroupId, TOptionId[]>? result = null;
+        KeyValuePair<TGroupId, TOptionId[]>[]? result = null;
         IList<Option<TOptionId>>? selectedGroup = null;
         var selectedGroupName = "";
 
+        // TODO: update this to support selecting options from multiple groups
         while (true)
         {
             RenderOptions(groups, selectedGroup, selectedGroupName);
@@ -99,7 +100,7 @@ public Task<TOptionId[]> RequestChoice<TOptionId>(string query, ChoiceType type,
             else
             {
                 if (input == ReturnInput)
-                    result = CreateResult(groups, selectedGroupIdx, selectedGroup!);
+                    result = new[] { CreateResult(groups, selectedGroupIdx, selectedGroup!) };
                 else
                     UpdatedSelectedGroup(ref selectedGroup, groups, selectedGroupIdx, input);
             }
@@ -134,7 +135,7 @@ private static string GetUserInput()
         return (Console.ReadLine() ?? "").Trim();
     }
 
-    private static Tuple<TGroupId, TOptionId[]> CreateResult<TGroupId, TOptionId>(
+    private static KeyValuePair<TGroupId, TOptionId[]> CreateResult<TGroupId, TOptionId>(
         IEnumerable<ChoiceGroup<TGroupId, TOptionId>> groups,
         int selectedGroupIdx,
         IEnumerable<Option<TOptionId>> selectedGroup)
@@ -143,7 +144,7 @@ private static Tuple<TGroupId, TOptionId[]> CreateResult<TGroupId, TOptionId>(
             .Where(x => x.Type is OptionState.Selected or OptionState.Required)
             .Select(x => x.Id);
 
-        return new Tuple<TGroupId, TOptionId[]>(groups.ElementAt(selectedGroupIdx).Id, updatedOptions.ToArray());
+        return new KeyValuePair<TGroupId, TOptionId[]>(groups.ElementAt(selectedGroupIdx).Id, updatedOptions.ToArray());
     }
 
     private static void FixSelection<TOptionId>(ref IList<Option<TOptionId>> list, ChoiceType groupType, int lastChangeIdx)
diff --git a/src/NexusMods.Common/UserInput/IOptionSelector.cs b/src/NexusMods.Common/UserInput/IOptionSelector.cs
index 1a8e980210..c1c7eaa79d 100644
--- a/src/NexusMods.Common/UserInput/IOptionSelector.cs
+++ b/src/NexusMods.Common/UserInput/IOptionSelector.cs
@@ -37,5 +37,5 @@ public interface IOptionSelector
     /// <typeparam name="TGroupId">Unique ID for each group.</typeparam>
     /// <typeparam name="TOptionId">Unique ID for each option.</typeparam>
     /// <returns></returns>
-    public Task<Tuple<TGroupId, TOptionId[]>?> RequestMultipleChoices<TGroupId, TOptionId>(ChoiceGroup<TGroupId, TOptionId>[] choices);
+    public Task<KeyValuePair<TGroupId, TOptionId[]>[]?> RequestMultipleChoices<TGroupId, TOptionId>(ChoiceGroup<TGroupId, TOptionId>[] choices);
 }

From d423ac2ba35ff8511bd7cb92580d6af06da5ce46 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Thu, 10 Aug 2023 14:21:16 +0200
Subject: [PATCH 04/19] UserInput -> GuidedInstaller

Update CLI

Update

Update
---
 Directory.Packages.props                      |   3 +-
 .../GuidedInstallerStepViewModel.cs           |  23 +-
 .../IGuidedInstallerStepViewModel.cs          |  12 +-
 .../NexusMods.Games.FOMOD.UI/Services.cs      |   4 +-
 .../UiOptionSelector.cs                       |  53 +---
 .../CoreDelegates/InstallerDelegates.cs       |   6 +-
 .../CoreDelegates/UiDelegate.cs               | 158 ++++++-----
 .../Verbs/StressTest.cs                       |   6 +-
 src/NexusMods.CLI/CliGuidedInstaller.cs       | 212 +++++++++++++++
 src/NexusMods.CLI/CliOptionSelector.cs        | 249 ------------------
 src/NexusMods.CLI/CommandLineConfigurator.cs  |   2 +-
 src/NexusMods.CLI/Services.cs                 |   4 +-
 .../GuidedInstaller/GuidedInstallationStep.cs |  12 +
 .../GuidedInstaller/IGuidedInstaller.cs       |  28 ++
 .../GuidedInstaller/Option.cs                 |  20 ++
 .../GuidedInstaller/OptionGroup.cs            |  15 ++
 .../OptionGroupType.cs}                       |   4 +-
 .../GuidedInstaller/OptionType.cs             |  27 ++
 .../GuidedInstaller/SelectedOption.cs         |  18 ++
 .../GuidedInstaller/UserChoice.cs             |  50 ++++
 .../ValueObjects}/AssetUrl.cs                 |   4 +-
 .../GuidedInstaller/ValueObjects/GroupId.cs   |   8 +
 .../GuidedInstaller/ValueObjects/OptionId.cs  |   8 +
 .../GuidedInstaller/ValueObjects/StepId.cs    |   8 +
 src/NexusMods.Common/NexusMods.Common.csproj  |   1 +
 src/NexusMods.Common/UserInput/ChoiceGroup.cs |  30 ---
 .../UserInput/IOptionSelector.cs              |  41 ---
 src/NexusMods.Common/UserInput/Option.cs      |  41 ---
 src/NexusMods.Common/UserInput/OptionState.cs |  27 --
 29 files changed, 562 insertions(+), 512 deletions(-)
 create mode 100644 src/NexusMods.CLI/CliGuidedInstaller.cs
 delete mode 100644 src/NexusMods.CLI/CliOptionSelector.cs
 create mode 100644 src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs
 create mode 100644 src/NexusMods.Common/GuidedInstaller/IGuidedInstaller.cs
 create mode 100644 src/NexusMods.Common/GuidedInstaller/Option.cs
 create mode 100644 src/NexusMods.Common/GuidedInstaller/OptionGroup.cs
 rename src/NexusMods.Common/{UserInput/ChoiceType.cs => GuidedInstaller/OptionGroupType.cs} (86%)
 create mode 100644 src/NexusMods.Common/GuidedInstaller/OptionType.cs
 create mode 100644 src/NexusMods.Common/GuidedInstaller/SelectedOption.cs
 create mode 100644 src/NexusMods.Common/GuidedInstaller/UserChoice.cs
 rename src/NexusMods.Common/{UserInput => GuidedInstaller/ValueObjects}/AssetUrl.cs (69%)
 create mode 100644 src/NexusMods.Common/GuidedInstaller/ValueObjects/GroupId.cs
 create mode 100644 src/NexusMods.Common/GuidedInstaller/ValueObjects/OptionId.cs
 create mode 100644 src/NexusMods.Common/GuidedInstaller/ValueObjects/StepId.cs
 delete mode 100644 src/NexusMods.Common/UserInput/ChoiceGroup.cs
 delete mode 100644 src/NexusMods.Common/UserInput/IOptionSelector.cs
 delete mode 100644 src/NexusMods.Common/UserInput/Option.cs
 delete mode 100644 src/NexusMods.Common/UserInput/OptionState.cs

diff --git a/Directory.Packages.props b/Directory.Packages.props
index 3d4c3c8843..3e6581a032 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -89,10 +89,11 @@
         <PackageVersion Include="ini-parser-netstandard" Version="2.5.2" />
         <PackageVersion Include="Mutagen.Bethesda.Skyrim" Version="0.41.0-pr002" />
         <PackageVersion Include="NLog.Extensions.Logging" Version="5.3.2" />
+        <PackageVersion Include="OneOf" Version="3.0.255" />
         <PackageVersion Include="ReactiveUI.Fody" Version="19.4.1" />
         <PackageVersion Include="Sewer56.BitStream" Version="1.3.0" />
         <PackageVersion Include="Spectre.Console" Version="0.47.0" />
         <PackageVersion Include="Splat.Microsoft.Extensions.Logging" Version="14.6.37" />
         <PackageVersion Include="Vogen" Version="3.0.20" />
     </ItemGroup>
-</Project>
+</Project>
\ No newline at end of file
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs b/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs
index 930f17c262..a056654606 100644
--- a/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs
+++ b/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerStepViewModel.cs
@@ -2,7 +2,7 @@
 using System.Reactive.Linq;
 using JetBrains.Annotations;
 using NexusMods.App.UI;
-using NexusMods.Common.UserInput;
+using NexusMods.Common.GuidedInstaller;
 using ReactiveUI;
 using ReactiveUI.Fody.Helpers;
 
@@ -12,12 +12,14 @@ namespace NexusMods.Games.FOMOD.UI;
 public class GuidedInstallerStepViewModel : AViewModel<IGuidedInstallerStepViewModel>, IGuidedInstallerStepViewModel
 {
     [Reactive]
-    public ChoiceGroup<int, int>[] AvailableChoices { get; set; } = Array.Empty<ChoiceGroup<int, int>>();
+    public GuidedInstallationStep? InstallationStep { get; set; }
 
     [Reactive]
-    public TaskCompletionSource<KeyValuePair<int, int[]>[]?>? TaskCompletionSource { get; set; }
+    public TaskCompletionSource<UserChoice>? TaskCompletionSource { get; set; }
 
-    public ReactiveCommand<Unit, Unit> NextStepCommand { get; }
+    public ReactiveCommand<Unit, Unit> NextStepCommand { get; set; }
+    public ReactiveCommand<Unit, Unit> PreviousStepCommand { get; set; }
+    public ReactiveCommand<Unit, Unit> CancelInstallerCommand { get; set; }
 
     public GuidedInstallerStepViewModel()
     {
@@ -30,7 +32,18 @@ public GuidedInstallerStepViewModel()
         NextStepCommand = ReactiveCommand.Create(() =>
         {
             // TODO: set result
-            TaskCompletionSource?.TrySetResult(Array.Empty<KeyValuePair<int, int[]>>());
+            var selectedOptions = Array.Empty<SelectedOption>();
+            TaskCompletionSource?.TrySetResult(new UserChoice(new UserChoice.GoToNextStep(selectedOptions)));
+        }, hasTaskCompletionSource);
+
+        PreviousStepCommand = ReactiveCommand.Create(() =>
+        {
+            TaskCompletionSource?.TrySetResult(new UserChoice(new UserChoice.GoToPreviousStep()));
+        }, hasTaskCompletionSource);
+
+        CancelInstallerCommand = ReactiveCommand.Create(() =>
+        {
+            TaskCompletionSource?.TrySetResult(new UserChoice(new UserChoice.CancelInstallation()));
         }, hasTaskCompletionSource);
     }
 }
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs b/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs
index 3ae95fbd76..049bb44273 100644
--- a/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs
+++ b/src/Games/NexusMods.Games.FOMOD.UI/IGuidedInstallerStepViewModel.cs
@@ -1,15 +1,19 @@
 using System.Reactive;
 using NexusMods.App.UI;
-using NexusMods.Common.UserInput;
+using NexusMods.Common.GuidedInstaller;
 using ReactiveUI;
 
 namespace NexusMods.Games.FOMOD.UI;
 
 public interface IGuidedInstallerStepViewModel : IViewModelInterface
 {
-    public ChoiceGroup<int, int>[] AvailableChoices { get; set; }
+    public GuidedInstallationStep? InstallationStep { get; set; }
 
-    public TaskCompletionSource<KeyValuePair<int, int[]>[]?>? TaskCompletionSource { get; set; }
+    public TaskCompletionSource<UserChoice>? TaskCompletionSource { get; set; }
 
-    public ReactiveCommand<Unit, Unit> NextStepCommand { get; }
+    public ReactiveCommand<Unit, Unit> NextStepCommand { get; set; }
+
+    public ReactiveCommand<Unit, Unit> PreviousStepCommand { get; set; }
+
+    public ReactiveCommand<Unit, Unit> CancelInstallerCommand { get; set; }
 }
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/Services.cs b/src/Games/NexusMods.Games.FOMOD.UI/Services.cs
index 4a86f03c62..7e7c3c34b3 100644
--- a/src/Games/NexusMods.Games.FOMOD.UI/Services.cs
+++ b/src/Games/NexusMods.Games.FOMOD.UI/Services.cs
@@ -1,6 +1,6 @@
 using Microsoft.Extensions.DependencyInjection;
 using NexusMods.App.UI;
-using NexusMods.Common.UserInput;
+using NexusMods.Common.GuidedInstaller;
 
 namespace NexusMods.Games.FOMOD.UI;
 
@@ -9,7 +9,7 @@ public static class Services
     public static IServiceCollection AddFomodInstallerUi(this IServiceCollection serviceCollection)
     {
         return serviceCollection
-            .AddTransient<IOptionSelector, UiOptionSelector>()
+            .AddTransient<IGuidedInstaller, UiOptionSelector>()
             .AddViewModel<GuidedInstallerStepViewModel, IGuidedInstallerStepViewModel>()
             .AddViewModel<GuidedInstallerWindowViewModel, IGuidedInstallerWindowViewModel>();
     }
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs b/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
index 8a5459256a..23dd5d82ba 100644
--- a/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
+++ b/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
@@ -1,12 +1,12 @@
 using System.Diagnostics;
 using JetBrains.Annotations;
 using Microsoft.Extensions.DependencyInjection;
-using NexusMods.Common.UserInput;
+using NexusMods.Common.GuidedInstaller;
 
 namespace NexusMods.Games.FOMOD.UI;
 
 [UsedImplicitly]
-public sealed class UiOptionSelector : IOptionSelector, IDisposable
+public sealed class UiOptionSelector : IGuidedInstaller, IDisposable
 {
     private readonly IServiceProvider _serviceProvider;
 
@@ -18,17 +18,17 @@ public UiOptionSelector(IServiceProvider serviceProvider)
         _serviceProvider = serviceProvider;
     }
 
-    public void SetupSelector(string windowName)
+    public void SetupInstaller()
     {
         Debug.Assert(_currentScope is null);
         _currentScope = _serviceProvider.CreateScope();
 
         // TODO: create/show window?
         _windowViewModel = _currentScope.ServiceProvider.GetRequiredService<IGuidedInstallerWindowViewModel>();
-        _windowViewModel.WindowName = windowName;
+        // _windowViewModel.WindowName = windowName;
     }
 
-    public void CleanupSelector()
+    public void CleanupInstaller()
     {
         if (_windowViewModel is not null)
         {
@@ -41,16 +41,9 @@ public void CleanupSelector()
         _currentScope = null;
     }
 
-    public Task<TOptionId[]> RequestChoice<TOptionId>(
-        string query,
-        ChoiceType type,
-        Option<TOptionId>[] options)
-    {
-        throw new NotImplementedException();
-    }
-
-    public async Task<KeyValuePair<TGroupId, TOptionId[]>[]?> RequestMultipleChoices<TGroupId, TOptionId>(
-        ChoiceGroup<TGroupId, TOptionId>[] choices)
+    public async Task<UserChoice> RequestUserChoice(
+        GuidedInstallationStep installationStep,
+        CancellationToken cancellationToken)
     {
         Debug.Assert(_currentScope is not null);
         Debug.Assert(_windowViewModel is not null);
@@ -58,36 +51,14 @@ public Task<TOptionId[]> RequestChoice<TOptionId>(
         _windowViewModel.ActiveStepViewModel ??= _currentScope.ServiceProvider.GetRequiredService<IGuidedInstallerStepViewModel>();
 
         var activeStepViewModel = _windowViewModel.ActiveStepViewModel;
-        activeStepViewModel.AvailableChoices = CastChoices(choices);
+        activeStepViewModel.InstallationStep = installationStep;
 
-        var tcs = new TaskCompletionSource<KeyValuePair<int, int[]>[]?>();
+        var tcs = new TaskCompletionSource<UserChoice>();
         activeStepViewModel.TaskCompletionSource = tcs;
 
         await tcs.Task;
-        return CastResult<TGroupId, TOptionId>(tcs.Task.Result);
-    }
-
-    private static ChoiceGroup<int, int>[] CastChoices<TGroupId, TOptionId>(IEnumerable<ChoiceGroup<TGroupId, TOptionId>> choices)
-    {
-        // NOTE(erri120): FOMOD uses integer for IDs. This is the only thing currently supported.
-        Debug.Assert(typeof(TGroupId) == typeof(int));
-        Debug.Assert(typeof(TOptionId) == typeof(int));
-
-        // TODO: verify this actually works
-        return (ChoiceGroup<int, int>[])Convert.ChangeType(choices, typeof(ChoiceGroup<int, int>));
-    }
-
-    private static KeyValuePair<TGroupId, TOptionId[]>[]? CastResult<TGroupId, TOptionId>(KeyValuePair<int, int[]>[]? result)
-    {
-        // NOTE(erri120): FOMOD uses integer for IDs. This is the only thing currently supported.
-        Debug.Assert(typeof(TGroupId) == typeof(int));
-        Debug.Assert(typeof(TOptionId) == typeof(int));
-
-        if (result is null) return null;
-
-        // TODO: verify this actually works
-        return (KeyValuePair<TGroupId, TOptionId[]>[]?)Convert.ChangeType(result, typeof(KeyValuePair<TGroupId, TOptionId[]>[]));
+        return tcs.Task.Result;
     }
 
-    public void Dispose() => CleanupSelector();
+    public void Dispose() => CleanupInstaller();
 }
diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/InstallerDelegates.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/InstallerDelegates.cs
index 4fac992efa..fa9ee17330 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/InstallerDelegates.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/InstallerDelegates.cs
@@ -2,7 +2,7 @@
 using FomodInstaller.Interface.ui;
 using JetBrains.Annotations;
 using Microsoft.Extensions.Logging;
-using NexusMods.Common.UserInput;
+using NexusMods.Common.GuidedInstaller;
 
 namespace NexusMods.Games.FOMOD.CoreDelegates;
 
@@ -14,10 +14,10 @@ public sealed class InstallerDelegates : ICoreDelegates
     public IPluginDelegates plugin { get; }
     public IUIDelegates ui { get; }
 
-    public InstallerDelegates(ILoggerFactory loggerFactory, IOptionSelector optionSelector)
+    public InstallerDelegates(ILoggerFactory loggerFactory, IGuidedInstaller guidedInstaller)
     {
         context = new ContextDelegates(loggerFactory.CreateLogger<ContextDelegates>());
         plugin = new PluginDelegates(loggerFactory.CreateLogger<PluginDelegates>());
-        ui = new UiDelegates(loggerFactory.CreateLogger<UiDelegates>(), optionSelector);
+        ui = new UiDelegates(loggerFactory.CreateLogger<UiDelegates>(), guidedInstaller);
     }
 }
diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index e5f890fc64..055b923730 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -1,11 +1,11 @@
 using FomodInstaller.Interface;
-using FomodInstaller.Interface.ui;
 using Microsoft.Extensions.Logging;
-using NexusMods.Common.UserInput;
+using NexusMods.Common.GuidedInstaller;
+using NexusMods.Common.GuidedInstaller.ValueObjects;
 
 namespace NexusMods.Games.FOMOD.CoreDelegates;
 
-public class UiDelegates : IUIDelegates
+public class UiDelegates : FomodInstaller.Interface.ui.IUIDelegates
 {
     /// <summary>
     /// Created by the executor, this delegate notifies the executor about which options the
@@ -37,16 +37,16 @@ private static void DummyContinueToNextStep(bool forward, int currentStepId) { }
     private static void DummyCancelInstaller() { }
 
     private readonly ILogger<UiDelegates> _logger;
-    private readonly IOptionSelector _optionSelector;
+    private readonly IGuidedInstaller _guidedInstaller;
 
     private SelectOptions _selectOptions = DummySelectOptions;
     private ContinueToNextStep _continueToNextStep = DummyContinueToNextStep;
     private CancelInstaller _cancelInstaller = DummyCancelInstaller;
 
-    public UiDelegates(ILogger<UiDelegates> logger, IOptionSelector optionSelector)
+    public UiDelegates(ILogger<UiDelegates> logger, IGuidedInstaller guidedInstaller)
     {
         _logger = logger;
-        _optionSelector = optionSelector;
+        _guidedInstaller = guidedInstaller;
     }
 
     public void StartDialog(
@@ -60,7 +60,8 @@ public void StartDialog(
         _continueToNextStep = new ContinueToNextStep(cont);
         _cancelInstaller = new CancelInstaller(cancel);
 
-        _optionSelector.SetupSelector(moduleName ?? string.Empty);
+        // TODO: consider passing moduleName along
+        _guidedInstaller.SetupInstaller();
     }
 
     public void EndDialog()
@@ -68,7 +69,7 @@ public void EndDialog()
         _selectOptions = DummySelectOptions;
         _continueToNextStep = DummyContinueToNextStep;
 
-        _optionSelector.CleanupSelector();
+        _guidedInstaller.CleanupInstaller();
     }
 
     public void ReportError(
@@ -79,92 +80,131 @@ public void ReportError(
         _logger.LogError("Reporting an error: {Title}: {Message}\n{Details}", title, message, details);
     }
 
-    public void UpdateState(InstallerStep[] installSteps, int currentStepId)
+    public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps, int currentStepId)
     {
         var currentStep = installSteps[currentStepId];
-        var choices = ToChoices(currentStep.optionalFileGroups).ToArray();
+        var groupIdMappings = new List<KeyValuePair<int, GroupId>>();
+        var optionIdMappings = new List<KeyValuePair<int, OptionId>>();
 
-        _optionSelector
-            .RequestMultipleChoices(choices)
+        var guidedInstallationStep = ToGuidedInstallationStep(
+            currentStep.optionalFileGroups,
+            groupIdMappings,
+            optionIdMappings
+        );
+
+        _guidedInstaller
+            .RequestUserChoice(guidedInstallationStep, new CancellationToken())
             .ContinueWith(task =>
             {
-                var result = task.Result;
                 _logger.LogDebug("Status: {TaskStatus}", task.Status);
+                var result = task.Result;
 
-                // TODO: figure out how to go backwards. Our internal API doesn't support this concept.
-                if (result is null)
+                if (result.IsCancelInstallation)
                 {
-                    // Result is null, the user wants to cancel installation.
+                    // TODO: verify that this calls EndDialog
                     _cancelInstaller();
-                    return;
-                }
-
-                // NOTE(erri120): This _selectOptions delegate we got from the executor is
-                // fucking weird. It only accepts the selected options from a single group.
-                // Vortex: https://github.com/Nexus-Mods/Vortex/blob/82e8ad3e051ab4ad41df43d11803ee43d399a85f/src/extensions/installer_fomod/views/InstallerDialog.tsx#L450-L461
-                // This is "supposed" to be called whenever the user clicks on a button in the UI.
-                // However, this explicit relationship doesn't work in our case and is generally
-                // pretty stupid. As such, we get the "final" result from the implementation
-                // and push those all at once to the executor.
-
-                foreach (var kv in result)
+                } else if (result.IsGoToPreviousStep)
                 {
-                    var (selectedGroupId, selectedOptionIds) = kv;
-                    _selectOptions(currentStepId, selectedGroupId, selectedOptionIds);
+                    _continueToNextStep(forward: false, currentStepId);
+                } else if (result.IsGoToNextStep)
+                {
+                    var selectedOptions = result.AsT2.SelectedOptions;
+
+                    // NOTE(erri120): This _selectOptions delegate we got from the executor is
+                    // fucking weird. It only accepts the selected options from a single group.
+                    // Vortex: https://github.com/Nexus-Mods/Vortex/blob/82e8ad3e051ab4ad41df43d11803ee43d399a85f/src/extensions/installer_fomod/views/InstallerDialog.tsx#L450-L461
+                    // This is "supposed" to be called whenever the user clicks on a button in the UI.
+                    // However, this explicit relationship doesn't work in our case and is generally
+                    // pretty stupid. As such, we get the "final" result from the implementation
+                    // and push those all at once to the executor.
+
+                    var groupings = selectedOptions.GroupBy(x => x.GroupId);
+
+                    foreach (var grouping in groupings)
+                    {
+                        var selectedGroupId = groupIdMappings.First(kv => kv.Value == grouping.Key).Key;
+                        var selectedOptionIds = grouping
+                            .Select(x => optionIdMappings.FirstOrDefault(kv => kv.Value == x.OptionId).Key)
+                            .ToArray();
+
+                        _selectOptions(currentStepId, selectedGroupId, selectedOptionIds);
+                    }
+
+                    // We need to explicitly call this, since our implementations
+                    // return from RequestMultipleChoices when the user wants to go
+                    // to the next step. Once again, the API is ass.
+                    _continueToNextStep(forward: true, currentStepId);
                 }
-
-                // We need to explicitly call this, since our implementations
-                // return from RequestMultipleChoices when the user wants to go
-                // to the next step. Once again, the API is ass.
-                _continueToNextStep(forward: true, currentStepId);
             });
     }
 
-    private static IEnumerable<ChoiceGroup<int, int>> ToChoices(GroupList groups)
+    private static GuidedInstallationStep ToGuidedInstallationStep(
+        FomodInstaller.Interface.ui.GroupList groups,
+        ICollection<KeyValuePair<int, GroupId>> groupIdMapping,
+        ICollection<KeyValuePair<int, OptionId>> optionIdMappings)
     {
-        return groups.group.Select(group => new ChoiceGroup<int, int>
+        var stepGroups = groups.group.Select(group =>
         {
-            Id = group.id,
-            Type = ConvertChoiceType(group.type),
-            Query = group.name,
-            Options = ToOptions(group.options).ToArray(),
+            var groupId = GroupId.From(Guid.NewGuid());
+            groupIdMapping.Add(new KeyValuePair<int, GroupId>(group.id, groupId));
+
+            return new OptionGroup
+            {
+                Id = groupId,
+                OptionGroupType = ConvertOptionGroupType(group.type),
+                Description = group.name,
+                Options = ToOptions(group.options, optionIdMappings).ToArray(),
+            };
         });
+
+        return new GuidedInstallationStep
+        {
+            Id = StepId.From(Guid.NewGuid()),
+            Groups = stepGroups.ToArray()
+        };
     }
 
-    private static IEnumerable<Option<int>> ToOptions(IEnumerable<Option> options)
+    private static IEnumerable<Option> ToOptions(
+        IEnumerable<FomodInstaller.Interface.ui.Option> options,
+        ICollection<KeyValuePair<int, OptionId>> optionIdMappings)
     {
-        return options.Select(option => new Option<int>
+        return options.Select(option =>
         {
-            Id = option.id,
-            Name = option.name,
-            Description = option.description,
-            ImageUrl = option.image != null ? AssetUrl.From(option.image) : null,
-            Type = MakeOptionState(option),
+            var optionId = OptionId.From(Guid.NewGuid());
+            optionIdMappings.Add(new KeyValuePair<int, OptionId>(option.id, optionId));
+
+            return new Option
+            {
+                Id = optionId,
+                Name = option.name,
+                Description = option.description,
+                ImageUrl = option.image != null ? AssetUrl.From(option.image) : null,
+                OptionType = MakeOptionType(option),
+            };
         });
     }
 
-    private static OptionState MakeOptionState(Option option)
+    private static OptionType MakeOptionType(FomodInstaller.Interface.ui.Option option)
     {
         var state = option.type switch
         {
-            "Required" => OptionState.Required,
-            "NotUsable" => OptionState.Disabled,
-            "Recommended" => OptionState.Selected,
-            _ => OptionState.Available
+            "Required" => OptionType.Required,
+            "NotUsable" => OptionType.Disabled,
+            "Recommended" => OptionType.PreSelected,
+            _ => OptionType.Available
         };
 
-        if (state == OptionState.Available && option.selected) state = OptionState.Selected;
         return state;
     }
 
-    private static ChoiceType ConvertChoiceType(string input)
+    private static OptionGroupType ConvertOptionGroupType(string input)
     {
         return input switch
         {
-            "SelectAtLeastOne" => ChoiceType.AtLeastOne,
-            "SelectAtMostOne" => ChoiceType.AtMostOne,
-            "SelectExactlyOne" => ChoiceType.ExactlyOne,
-            _ => ChoiceType.Any
+            "SelectAtLeastOne" => OptionGroupType.AtLeastOne,
+            "SelectAtMostOne" => OptionGroupType.AtMostOne,
+            "SelectExactlyOne" => OptionGroupType.ExactlyOne,
+            _ => OptionGroupType.Any
         };
     }
 }
diff --git a/src/Games/NexusMods.Games.TestHarness/Verbs/StressTest.cs b/src/Games/NexusMods.Games.TestHarness/Verbs/StressTest.cs
index 4999fa529a..b784482f1a 100644
--- a/src/Games/NexusMods.Games.TestHarness/Verbs/StressTest.cs
+++ b/src/Games/NexusMods.Games.TestHarness/Verbs/StressTest.cs
@@ -2,7 +2,7 @@
 using NexusMods.Abstractions.CLI;
 using NexusMods.Abstractions.CLI.DataOutputs;
 using NexusMods.CLI;
-using NexusMods.Common.UserInput;
+using NexusMods.Common.GuidedInstaller;
 using NexusMods.DataModel.Abstractions;
 using NexusMods.DataModel.Games;
 using NexusMods.DataModel.Loadouts;
@@ -39,9 +39,9 @@ public StressTest(ILogger<StressTest> logger,
         IArchiveAnalyzer archiveAnalyzer,
         IArchiveInstaller archiveInstaller,
         IEnumerable<IGameLocator> gameLocators,
-        IOptionSelector optionSelector)
+        IGuidedInstaller optionSelector)
     {
-        ((CliOptionSelector)optionSelector).AutoFail = true;
+        ((CliGuidedInstaller)optionSelector).SkipAll = true;
         _archiveAnalyzer = archiveAnalyzer;
         _archiveInstaller = archiveInstaller;
         _downloader = downloader;
diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
new file mode 100644
index 0000000000..33920c5bad
--- /dev/null
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -0,0 +1,212 @@
+using System.Diagnostics;
+using JetBrains.Annotations;
+using NexusMods.Abstractions.CLI;
+using NexusMods.Abstractions.CLI.DataOutputs;
+using NexusMods.Common;
+using NexusMods.Common.GuidedInstaller;
+
+namespace NexusMods.CLI;
+
+/// <summary>
+/// Implementation of an option selector for the CLI.
+/// </summary>
+[UsedImplicitly]
+public class CliGuidedInstaller : IGuidedInstaller
+{
+    private const string ReturnInput = "x";
+    private static readonly string[] TableOfOptionsHeaders = { "Key", "State", "Name", "Description" };
+    private static readonly object[] TableOfOptionsFooter = { ReturnInput, "", "Back", "" };
+    private static readonly string[] TableOfGroupsHeaders = { "Key", "Group" };
+    private static readonly object[] TableOfGroupsFooter = { ReturnInput, "Continue" };
+
+    /// <summary>
+    /// The renderer to use for rendering the options.
+    /// </summary>
+    private IRenderer Renderer { get; set; } = null!;
+
+    /// <summary>
+    /// If true, all option selection will select the first choice.
+    /// </summary>
+    public bool SkipAll { get; set; }
+
+    /// <inheritdoc/>
+    public void SetupInstaller() { }
+
+    /// <inheritdoc/>
+    public void CleanupInstaller() { }
+
+    /// <inheritdoc />
+    public Task<UserChoice> RequestUserChoice(GuidedInstallationStep installationStep, CancellationToken cancellationToken)
+    {
+        var currentGroup = installationStep.Groups.Length == 1
+            ? installationStep.Groups[0]
+            : null;
+
+        var selectedOptions = new List<SelectedOption>();
+
+        while (true)
+        {
+            RenderStep(installationStep, currentGroup, selectedOptions);
+            var input = SkipAll ? "0" : GetUserInput();
+
+            // TODO: the current implementation doesn't support selecting many options from many groups
+            // see https://github.com/Nexus-Mods/NexusMods.App/issues/544
+
+            // if the installation step has multiple groups
+            // the user has to select which group they want to use
+            if (currentGroup is null)
+            {
+                var groupIndex = ParseNumericalUserInput(input, installationStep.Groups.Length) ?? -1;
+                if (groupIndex >= 0)
+                {
+                    currentGroup = installationStep.Groups[groupIndex];
+                    selectedOptions = currentGroup.Options
+                        .Where(x => x.OptionType == OptionType.PreSelected)
+                        .Select(x => new SelectedOption
+                        {
+                            GroupId = currentGroup.Id,
+                            OptionId = x.Id
+                        })
+                        .ToList();
+                }
+            }
+            else
+            {
+                // if the user has selected a group, the input will be for the options they want to use
+                if (input == ReturnInput)
+                {
+                    var requiredOptions = currentGroup.Options
+                        .Where(x => x.OptionType == OptionType.Required)
+                        .Select(x => new SelectedOption
+                        {
+                            GroupId = currentGroup.Id,
+                            OptionId = x.Id
+                        });
+
+                    selectedOptions.AddRange(requiredOptions);
+
+                    // proceed to the next step
+                    return Task.FromResult(new UserChoice(new UserChoice.GoToNextStep(selectedOptions.ToArray())));
+                }
+
+                UpdatedSelectedGroup(currentGroup, selectedOptions, input);
+            }
+
+            if (input == ReturnInput) break;
+        }
+
+        // The user aborted the installation
+        return Task.FromResult(new UserChoice(new UserChoice.CancelInstallation()));
+    }
+
+    private void RenderStep(
+        GuidedInstallationStep installationStep,
+        OptionGroup? currentGroup,
+        IReadOnlyCollection<SelectedOption> selectedOptions)
+    {
+        Renderer.Render(currentGroup is null
+            ? TableOfGroups(installationStep.Groups)
+            : TableOfOptions(currentGroup, selectedOptions));
+    }
+
+    private static Table TableOfOptions(
+        OptionGroup group,
+        IReadOnlyCollection<SelectedOption> selectedOptions)
+    {
+        var key = 1;
+        var row = group.Options
+            .Select(option =>
+            {
+                var hasSelected = selectedOptions.Any(x => x.OptionId == option.Id);
+
+                return new object[]
+                {
+                    key++,
+                    RenderOptionState(hasSelected, option.OptionType),
+                    option.Name,
+                    option.Description
+                };
+            })
+            .Append(TableOfOptionsFooter)
+            .ToArray();
+
+        return new Table(TableOfOptionsHeaders, row, group.Description);
+    }
+
+    private static string RenderOptionState(bool hasSelected, OptionType type)
+    {
+        if (hasSelected) return "Selected";
+
+        Debug.Assert(Enum.IsDefined(typeof(OptionType), type));
+
+        return type switch
+        {
+            OptionType.Disabled => "Disabled",
+            OptionType.Available => "Off",
+            OptionType.Required => "Required",
+            _ => throw new UnreachableException()
+        };
+    }
+
+    private static Table TableOfGroups(IEnumerable<OptionGroup> groups)
+    {
+        var key = 1;
+        var row = groups
+            .Select(group => new object[] { key++, group.Description })
+            .Append(TableOfGroupsFooter)
+            .ToArray();
+
+        return new Table(TableOfGroupsHeaders, row, "Select a Group");
+    }
+
+    private static void UpdatedSelectedGroup(
+        OptionGroup currentGroup,
+        ICollection<SelectedOption> selectedOptions,
+        string input)
+    {
+        var optionIndex = ParseNumericalUserInput(input, currentGroup.Options.Length) ?? -1;
+        if (optionIndex < 0) return;
+
+        var targetOption = currentGroup.Options[optionIndex];
+
+        var hasSelected = selectedOptions.TryGetFirst(x => x.OptionId == targetOption.Id, out var selectedOption);
+        if (hasSelected)
+        {
+            // the target option is already selected, the user wants to "toggle" it
+            selectedOptions.Remove(selectedOption);
+            return;
+        }
+
+        // the target option is not selected, the user wants to select it
+        if (currentGroup.OptionGroupType is OptionGroupType.ExactlyOne or OptionGroupType.AtMostOne)
+        {
+            // "deselect" everything
+            selectedOptions.Clear();
+        }
+
+        selectedOptions.Add(new SelectedOption
+        {
+            GroupId = currentGroup.Id,
+            OptionId = targetOption.Id
+        });
+    }
+
+    private static string GetUserInput()
+    {
+        return (Console.ReadLine() ?? "").Trim();
+    }
+
+    private static int? ParseNumericalUserInput(string input, int upperLimit)
+    {
+        try
+        {
+            var idx = int.Parse(input) - 1;
+            if (idx >= 0 && idx < upperLimit)
+                return idx;
+        }
+        catch (FormatException) { /* ignored */ }
+
+        // input invalid or out of range
+        return null;
+    }
+}
diff --git a/src/NexusMods.CLI/CliOptionSelector.cs b/src/NexusMods.CLI/CliOptionSelector.cs
deleted file mode 100644
index 46d1e4082b..0000000000
--- a/src/NexusMods.CLI/CliOptionSelector.cs
+++ /dev/null
@@ -1,249 +0,0 @@
-using System.Diagnostics;
-using JetBrains.Annotations;
-using NexusMods.Abstractions.CLI;
-using NexusMods.Abstractions.CLI.DataOutputs;
-using NexusMods.Common.UserInput;
-
-namespace NexusMods.CLI;
-
-/// <summary>
-/// Implementation of an option selector for the CLI.
-/// </summary>
-[UsedImplicitly]
-public class CliOptionSelector : IOptionSelector
-{
-    private const string ReturnInput = "x";
-    private static readonly string[] TableOfOptionsHeaders = { "Key", "State", "Name", "Description" };
-    private static readonly object[] TableOfOptionsFooter = { ReturnInput, "", "Back", "" };
-    private static readonly string[] TableOfGroupsHeaders = { "Key", "Group" };
-    private static readonly object[] TableOfGroupsFooter = { ReturnInput, "Continue" };
-
-    /// <summary>
-    /// The renderer to use for rendering the options.
-    /// </summary>
-    private IRenderer Renderer { get; set; } = null!;
-
-    /// <summary>
-    /// If true, all option selection will throw an error, useful for automated installers and tests
-    /// </summary>
-    public bool AutoFail { get; set; }
-
-    /// <inheritdoc/>
-    public void SetupSelector(string name) { }
-
-    /// <inheritdoc/>
-    public void CleanupSelector() { }
-
-    /// <summary>
-    /// Request a choice from the user.
-    /// </summary>
-    /// <param name="query"></param>
-    /// <param name="type"></param>
-    /// <param name="options"></param>
-    /// <typeparam name="TOptionId"></typeparam>
-    /// <returns></returns>
-    public Task<TOptionId[]> RequestChoice<TOptionId>(string query, ChoiceType type, Option<TOptionId>[] options)
-    {
-        var done = false;
-        var current = options;
-        while (!done)
-        {
-            var input = GetUserInput();
-            if (input == ReturnInput)
-            {
-                done = true;
-            }
-            else
-            {
-                var idx = ParseNumericalUserInput(input, current.Count());
-                if (idx != null)
-                    current[idx.Value].Type = ToggleState(current[idx.Value].Type);
-
-                Renderer.Render(TableOfOptions(current, query));
-            }
-        }
-
-        var res = current
-            .Where(x => x.Type is OptionState.Selected or OptionState.Required)
-            .Select(x => x.Id)
-            .ToArray();
-
-        return Task.FromResult(res);
-    }
-
-    /// <inheritdoc />
-    public Task<KeyValuePair<TGroupId, TOptionId[]>[]?> RequestMultipleChoices<TGroupId, TOptionId>(ChoiceGroup<TGroupId, TOptionId>[] groups)
-    {
-        if (AutoFail) throw new Exception("AutoFail is enabled for this option selector.");
-
-        var selectedGroupIdx = -1;
-        KeyValuePair<TGroupId, TOptionId[]>[]? result = null;
-        IList<Option<TOptionId>>? selectedGroup = null;
-        var selectedGroupName = "";
-
-        // TODO: update this to support selecting options from multiple groups
-        while (true)
-        {
-            RenderOptions(groups, selectedGroup, selectedGroupName);
-            var input = GetUserInput();
-
-            if (selectedGroupIdx < 0)
-            {
-                selectedGroupIdx = ParseNumericalUserInput(input, groups.Length) ?? selectedGroupIdx;
-                if (selectedGroupIdx >= 0)
-                {
-                    var group = groups.ElementAt(selectedGroupIdx);
-                    selectedGroup = group.Options;
-                    selectedGroupName = group.Query;
-                }
-            }
-            else
-            {
-                if (input == ReturnInput)
-                    result = new[] { CreateResult(groups, selectedGroupIdx, selectedGroup!) };
-                else
-                    UpdatedSelectedGroup(ref selectedGroup, groups, selectedGroupIdx, input);
-            }
-
-            if (input == ReturnInput)
-                break;
-        }
-
-        return Task.FromResult(result);
-    }
-
-    private static void UpdatedSelectedGroup<TGroupId, TOptionId>(ref IList<Option<TOptionId>>? selectedGroup,
-                                                           IEnumerable<ChoiceGroup<TGroupId, TOptionId>> groups,
-                                                           int selectedGroupIdx,
-                                                           string input)
-    {
-        var idx = ParseNumericalUserInput(input, selectedGroup!.Count) ?? -1;
-        if (idx < 0)
-            return;
-
-        var oldState = selectedGroup[idx].Type;
-        selectedGroup[idx].Type = ToggleState(selectedGroup[idx].Type);
-        if (oldState == selectedGroup[idx].Type)
-            return;
-
-        var groupType = groups.ElementAt(selectedGroupIdx).Type;
-        FixSelection(ref selectedGroup, groupType, idx);
-    }
-
-    private static string GetUserInput()
-    {
-        return (Console.ReadLine() ?? "").Trim();
-    }
-
-    private static KeyValuePair<TGroupId, TOptionId[]> CreateResult<TGroupId, TOptionId>(
-        IEnumerable<ChoiceGroup<TGroupId, TOptionId>> groups,
-        int selectedGroupIdx,
-        IEnumerable<Option<TOptionId>> selectedGroup)
-    {
-        var updatedOptions = selectedGroup
-            .Where(x => x.Type is OptionState.Selected or OptionState.Required)
-            .Select(x => x.Id);
-
-        return new KeyValuePair<TGroupId, TOptionId[]>(groups.ElementAt(selectedGroupIdx).Id, updatedOptions.ToArray());
-    }
-
-    private static void FixSelection<TOptionId>(ref IList<Option<TOptionId>> list, ChoiceType groupType, int lastChangeIdx)
-    {
-        switch (groupType)
-        {
-            case ChoiceType.ExactlyOne or ChoiceType.AtMostOne
-            when list[lastChangeIdx].Type == OptionState.Selected:
-                DeselectAllBut(ref list, lastChangeIdx);
-                return;
-
-            case ChoiceType.ExactlyOne or ChoiceType.AtLeastOne
-            when list.All(x => x.Type != OptionState.Selected):
-                list[lastChangeIdx].Type = OptionState.Selected;
-                break;
-        }
-    }
-
-    private static void DeselectAllBut<TOptionId>(ref IList<Option<TOptionId>> list, int lastChangeIdx)
-    {
-        for (var i = 0; i < list.Count; ++i)
-        {
-            if (i != lastChangeIdx && list[lastChangeIdx].Type == OptionState.Selected)
-            {
-                list[i].Type = OptionState.Available;
-            }
-        }
-    }
-
-    private static int? ParseNumericalUserInput(string input, int upperLimit)
-    {
-        try
-        {
-            var idx = int.Parse(input) - 1;
-            if (idx >= 0 && idx < upperLimit)
-                return idx;
-        }
-        catch (FormatException) { /* ignored */ }
-
-        // input invalid or out of range
-        return null;
-    }
-
-    private void RenderOptions<TGroupId, TOptionId>(
-        IEnumerable<ChoiceGroup<TGroupId, TOptionId>> groups,
-        IList<Option<TOptionId>>? selectedGroup, string selectedGroupName)
-    {
-        Renderer.Render(selectedGroup == null
-            ? TableOfGroups(groups)
-            : TableOfOptions(selectedGroup, selectedGroupName));
-    }
-
-    private Table TableOfOptions<TOptionId>(
-        IEnumerable<Option<TOptionId>> current, string selectedGroupName)
-    {
-        var key = 1;
-        var row = current
-            .Select(item => new object[] { key++, RenderOptionState(item.Type), item.Name, item.Description ?? "" })
-            .ToList();
-
-        row.Add(TableOfOptionsFooter);
-        return new Table(TableOfOptionsHeaders, row, selectedGroupName);
-    }
-
-    private static Table TableOfGroups<TGroupId, TOptionId>(IEnumerable<ChoiceGroup<TGroupId, TOptionId>> groups)
-    {
-        var key = 1;
-        var row = groups
-            .Select(item => new object[] { key++, item.Query })
-            .ToList();
-
-        row.Add(TableOfGroupsFooter);
-        return new Table(TableOfGroupsHeaders, row, "Select a Group");
-    }
-
-    private static OptionState ToggleState(OptionState old)
-    {
-        Debug.Assert(Enum.IsDefined(typeof(OptionState), old));
-
-        return old switch
-        {
-            OptionState.Available => OptionState.Selected,
-            OptionState.Selected => OptionState.Available,
-            _ => old
-        };
-    }
-
-    private static string RenderOptionState(OptionState state)
-    {
-        Debug.Assert(Enum.IsDefined(typeof(OptionState), state));
-
-        return state switch
-        {
-            OptionState.Disabled => "Disabled",
-            OptionState.Available => "Off",
-            OptionState.Required => "Required",
-            OptionState.Selected => "On",
-            _ => throw new UnreachableException()
-        };
-    }
-}
-
diff --git a/src/NexusMods.CLI/CommandLineConfigurator.cs b/src/NexusMods.CLI/CommandLineConfigurator.cs
index 54db21cf96..29c26b11fc 100644
--- a/src/NexusMods.CLI/CommandLineConfigurator.cs
+++ b/src/NexusMods.CLI/CommandLineConfigurator.cs
@@ -28,7 +28,7 @@ public class CommandLineConfigurator
     /// <param name="provider">Instance of dependency injection container.</param>
     /// <param name="selector"></param>
     /// <param name="renderers"></param>
-    public CommandLineConfigurator(IEnumerable<RegisteredVerb> verbs, IServiceProvider provider, CliOptionSelector selector, IEnumerable<IRenderer> renderers)
+    public CommandLineConfigurator(IEnumerable<RegisteredVerb> verbs, IServiceProvider provider, CliGuidedInstaller selector, IEnumerable<IRenderer> renderers)
     {
         _renderers = renderers.ToArray();
         _defaultConsoleRenderer = _renderers.FirstOrDefault(r => r.Name == "console") ?? _renderers.First();
diff --git a/src/NexusMods.CLI/Services.cs b/src/NexusMods.CLI/Services.cs
index 3df4263960..2b4ed9894a 100644
--- a/src/NexusMods.CLI/Services.cs
+++ b/src/NexusMods.CLI/Services.cs
@@ -13,8 +13,8 @@
 using NexusMods.CLI.Types;
 using NexusMods.CLI.Types.DownloadHandlers;
 using NexusMods.CLI.Types.IpcHandlers;
+using NexusMods.Common.GuidedInstaller;
 using NexusMods.Common.ProtocolRegistration;
-using NexusMods.Common.UserInput;
 
 namespace NexusMods.CLI;
 
@@ -38,7 +38,7 @@ public static IServiceCollection AddCLI(this IServiceCollection services)
         services.AddSingleton<IOptionParser<Version>, VersionParser>();
         services.AddSingleton<IOptionParser<Loadout>, LoadoutParser>();
         services.AddSingleton<IOptionParser<ITool>, ToolParser>();
-        services.AddAllSingleton<IOptionSelector, CliOptionSelector>();
+        services.AddAllSingleton<IGuidedInstaller, CliGuidedInstaller>();
 
         OSInformation.Shared.SwitchPlatform(
             ref services,
diff --git a/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs b/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs
new file mode 100644
index 0000000000..05d636eed5
--- /dev/null
+++ b/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs
@@ -0,0 +1,12 @@
+using JetBrains.Annotations;
+using NexusMods.Common.GuidedInstaller.ValueObjects;
+
+namespace NexusMods.Common.GuidedInstaller;
+
+[PublicAPI]
+public record GuidedInstallationStep
+{
+    public required StepId Id { get; init; }
+
+    public required OptionGroup[] Groups { get; init; }
+}
diff --git a/src/NexusMods.Common/GuidedInstaller/IGuidedInstaller.cs b/src/NexusMods.Common/GuidedInstaller/IGuidedInstaller.cs
new file mode 100644
index 0000000000..40d3f71c9d
--- /dev/null
+++ b/src/NexusMods.Common/GuidedInstaller/IGuidedInstaller.cs
@@ -0,0 +1,28 @@
+using JetBrains.Annotations;
+
+namespace NexusMods.Common.GuidedInstaller;
+
+/// <summary>
+/// Interface for a guided installer.
+/// </summary>
+[PublicAPI]
+public interface IGuidedInstaller
+{
+    /// <summary>
+    /// Sets up the installer.
+    /// </summary>
+    public void SetupInstaller();
+
+    /// <summary>
+    /// Cleans up the installer.
+    /// </summary>
+    public void CleanupInstaller();
+
+    /// <summary>
+    /// Requests the user for a choice.
+    /// </summary>
+    /// <param name="installationStep"></param>
+    /// <param name="cancellationToken"></param>
+    /// <returns></returns>
+    public Task<UserChoice> RequestUserChoice(GuidedInstallationStep installationStep, CancellationToken cancellationToken);
+}
diff --git a/src/NexusMods.Common/GuidedInstaller/Option.cs b/src/NexusMods.Common/GuidedInstaller/Option.cs
new file mode 100644
index 0000000000..dec6d6bdd5
--- /dev/null
+++ b/src/NexusMods.Common/GuidedInstaller/Option.cs
@@ -0,0 +1,20 @@
+using JetBrains.Annotations;
+using NexusMods.Common.GuidedInstaller.ValueObjects;
+
+namespace NexusMods.Common.GuidedInstaller;
+
+[PublicAPI]
+public record Option
+{
+    public required OptionId Id { get; init; }
+
+    public required OptionType OptionType { get; init; }
+
+    public required string Name { get; init; }
+
+    public string Description { get; init; } = string.Empty;
+
+    public AssetUrl? ImageUrl { get; init; }
+
+    public string HoverText { get; init; } = string.Empty;
+}
diff --git a/src/NexusMods.Common/GuidedInstaller/OptionGroup.cs b/src/NexusMods.Common/GuidedInstaller/OptionGroup.cs
new file mode 100644
index 0000000000..2726161bc5
--- /dev/null
+++ b/src/NexusMods.Common/GuidedInstaller/OptionGroup.cs
@@ -0,0 +1,15 @@
+using JetBrains.Annotations;
+
+namespace NexusMods.Common.GuidedInstaller;
+
+[PublicAPI]
+public record OptionGroup
+{
+    public required ValueObjects.GroupId Id { get; init; }
+
+    public required string Description { get; init; }
+
+    public required OptionGroupType OptionGroupType { get; init; }
+
+    public required Option[] Options { get; init; }
+}
diff --git a/src/NexusMods.Common/UserInput/ChoiceType.cs b/src/NexusMods.Common/GuidedInstaller/OptionGroupType.cs
similarity index 86%
rename from src/NexusMods.Common/UserInput/ChoiceType.cs
rename to src/NexusMods.Common/GuidedInstaller/OptionGroupType.cs
index 0d8de1b004..319dab0987 100644
--- a/src/NexusMods.Common/UserInput/ChoiceType.cs
+++ b/src/NexusMods.Common/GuidedInstaller/OptionGroupType.cs
@@ -1,9 +1,9 @@
-namespace NexusMods.Common.UserInput;
+namespace NexusMods.Common.GuidedInstaller;
 
 /// <summary>
 /// The rules used with regards to making a choice among multiple possibilities.
 /// </summary>
-public enum ChoiceType
+public enum OptionGroupType
 {
     /// <summary>
     /// Select 1 from the group.
diff --git a/src/NexusMods.Common/GuidedInstaller/OptionType.cs b/src/NexusMods.Common/GuidedInstaller/OptionType.cs
new file mode 100644
index 0000000000..3566ca94f9
--- /dev/null
+++ b/src/NexusMods.Common/GuidedInstaller/OptionType.cs
@@ -0,0 +1,27 @@
+namespace NexusMods.Common.GuidedInstaller;
+
+/// <summary>
+/// Describes the type of an option.
+/// </summary>
+public enum OptionType
+{
+    /// <summary>
+    /// The option can be selected.
+    /// </summary>
+    Available,
+
+    /// <summary>
+    /// The option can't be selected.
+    /// </summary>
+    Disabled,
+
+    /// <summary>
+    /// This option is selected by default.
+    /// </summary>
+    PreSelected,
+
+    /// <summary>
+    /// The option is always selected.
+    /// </summary>
+    Required,
+}
diff --git a/src/NexusMods.Common/GuidedInstaller/SelectedOption.cs b/src/NexusMods.Common/GuidedInstaller/SelectedOption.cs
new file mode 100644
index 0000000000..e0be7a7c2c
--- /dev/null
+++ b/src/NexusMods.Common/GuidedInstaller/SelectedOption.cs
@@ -0,0 +1,18 @@
+using JetBrains.Annotations;
+using NexusMods.Common.GuidedInstaller.ValueObjects;
+
+namespace NexusMods.Common.GuidedInstaller;
+
+[PublicAPI]
+public readonly struct SelectedOption
+{
+    public readonly GroupId GroupId { get; init; }
+
+    public readonly OptionId OptionId { get; init; }
+
+    public SelectedOption(GroupId groupId, OptionId optionId)
+    {
+        GroupId = groupId;
+        OptionId = optionId;
+    }
+}
diff --git a/src/NexusMods.Common/GuidedInstaller/UserChoice.cs b/src/NexusMods.Common/GuidedInstaller/UserChoice.cs
new file mode 100644
index 0000000000..223a31510c
--- /dev/null
+++ b/src/NexusMods.Common/GuidedInstaller/UserChoice.cs
@@ -0,0 +1,50 @@
+using JetBrains.Annotations;
+using OneOf;
+
+namespace NexusMods.Common.GuidedInstaller;
+
+/// <summary>
+/// Represents the user's choice in a guided installer.
+/// </summary>
+[PublicAPI]
+public sealed class UserChoice : OneOfBase<
+    UserChoice.CancelInstallation,
+    UserChoice.GoToPreviousStep,
+    UserChoice.GoToNextStep>
+{
+    /// <summary>
+    /// The user wants to cancel the installation.
+    /// </summary>
+    public sealed record CancelInstallation;
+
+    /// <summary>
+    /// The user wants to go to the previous installation step.
+    /// </summary>
+    public sealed record GoToPreviousStep;
+
+    /// <summary>
+    /// The user wants to go to the next installation step.
+    /// </summary>
+    /// <param name="SelectedOptions">The options the user has selected.</param>
+    public sealed record GoToNextStep(SelectedOption[] SelectedOptions);
+
+    /// <summary>
+    /// Constructor.
+    /// </summary>
+    public UserChoice(OneOf<CancelInstallation, GoToPreviousStep, GoToNextStep> input) : base(input) { }
+
+    /// <summary>
+    /// <see cref="IsCancelInstallation"/>
+    /// </summary>
+    public bool IsCancelInstallation => IsT0;
+
+    /// <summary>
+    /// <see cref="IsGoToPreviousStep"/>
+    /// </summary>
+    public bool IsGoToPreviousStep => IsT1;
+
+    /// <summary>
+    /// <see cref="IsGoToNextStep"/>
+    /// </summary>
+    public bool IsGoToNextStep => IsT2;
+}
diff --git a/src/NexusMods.Common/UserInput/AssetUrl.cs b/src/NexusMods.Common/GuidedInstaller/ValueObjects/AssetUrl.cs
similarity index 69%
rename from src/NexusMods.Common/UserInput/AssetUrl.cs
rename to src/NexusMods.Common/GuidedInstaller/ValueObjects/AssetUrl.cs
index 56e3e1f98f..3ba923c012 100644
--- a/src/NexusMods.Common/UserInput/AssetUrl.cs
+++ b/src/NexusMods.Common/GuidedInstaller/ValueObjects/AssetUrl.cs
@@ -1,10 +1,12 @@
+using JetBrains.Annotations;
 using Vogen;
 
-namespace NexusMods.Common.UserInput;
+namespace NexusMods.Common.GuidedInstaller.ValueObjects;
 
 /// <summary>
 /// URL of an asset that's tied to an option. This can be a relative path, or
 /// a URL to a remote resource.
 /// </summary>
+[PublicAPI]
 [ValueObject<string>]
 public readonly partial struct AssetUrl { }
diff --git a/src/NexusMods.Common/GuidedInstaller/ValueObjects/GroupId.cs b/src/NexusMods.Common/GuidedInstaller/ValueObjects/GroupId.cs
new file mode 100644
index 0000000000..fb8a384ea5
--- /dev/null
+++ b/src/NexusMods.Common/GuidedInstaller/ValueObjects/GroupId.cs
@@ -0,0 +1,8 @@
+using JetBrains.Annotations;
+using Vogen;
+
+namespace NexusMods.Common.GuidedInstaller.ValueObjects;
+
+[PublicAPI]
+[ValueObject<Guid>]
+public readonly partial struct GroupId { }
diff --git a/src/NexusMods.Common/GuidedInstaller/ValueObjects/OptionId.cs b/src/NexusMods.Common/GuidedInstaller/ValueObjects/OptionId.cs
new file mode 100644
index 0000000000..2191e2b941
--- /dev/null
+++ b/src/NexusMods.Common/GuidedInstaller/ValueObjects/OptionId.cs
@@ -0,0 +1,8 @@
+using JetBrains.Annotations;
+using Vogen;
+
+namespace NexusMods.Common.GuidedInstaller.ValueObjects;
+
+[PublicAPI]
+[ValueObject<Guid>]
+public readonly partial struct OptionId { }
diff --git a/src/NexusMods.Common/GuidedInstaller/ValueObjects/StepId.cs b/src/NexusMods.Common/GuidedInstaller/ValueObjects/StepId.cs
new file mode 100644
index 0000000000..6842f739b4
--- /dev/null
+++ b/src/NexusMods.Common/GuidedInstaller/ValueObjects/StepId.cs
@@ -0,0 +1,8 @@
+using JetBrains.Annotations;
+using Vogen;
+
+namespace NexusMods.Common.GuidedInstaller.ValueObjects;
+
+[PublicAPI]
+[ValueObject<Guid>]
+public readonly partial struct StepId { }
diff --git a/src/NexusMods.Common/NexusMods.Common.csproj b/src/NexusMods.Common/NexusMods.Common.csproj
index 3a47f54ac0..d2a42ccbb8 100644
--- a/src/NexusMods.Common/NexusMods.Common.csproj
+++ b/src/NexusMods.Common/NexusMods.Common.csproj
@@ -6,6 +6,7 @@
         <PackageReference Include="NexusMods.Paths" />
         <PackageReference Include="CliWrap" />
         <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" />
+        <PackageReference Include="OneOf" />
     </ItemGroup>
 
     <ItemGroup>
diff --git a/src/NexusMods.Common/UserInput/ChoiceGroup.cs b/src/NexusMods.Common/UserInput/ChoiceGroup.cs
deleted file mode 100644
index 7a6784c258..0000000000
--- a/src/NexusMods.Common/UserInput/ChoiceGroup.cs
+++ /dev/null
@@ -1,30 +0,0 @@
-namespace NexusMods.Common.UserInput;
-
-/// <summary>
-/// Represents a group of items from which the user has to pick, one, at least one or many.
-/// </summary>
-/// <typeparam name="TId">Type of unique identifier for this option.</typeparam>
-/// <typeparam name="TOptionId">Type of unique identifier for each option.</typeparam>
-public record ChoiceGroup<TId, TOptionId>
-{
-    /// <summary>
-    /// Unique identifier for this item.
-    /// </summary>
-    public required TId Id { get; init; }
-
-    /// <summary>
-    /// Name of the group displayed to the user.
-    /// For example 'Pick a Texture'.
-    /// </summary>
-    public required string Query { get; init; }
-
-    /// <summary>
-    /// The logic to use for picking this option, such as one, multiple etc.
-    /// </summary>
-    public required ChoiceType Type { get; init; }
-
-    /// <summary>
-    /// Contains all the items the user can select from.
-    /// </summary>
-    public required Option<TOptionId>[] Options { get; init; }
-}
diff --git a/src/NexusMods.Common/UserInput/IOptionSelector.cs b/src/NexusMods.Common/UserInput/IOptionSelector.cs
deleted file mode 100644
index c1c7eaa79d..0000000000
--- a/src/NexusMods.Common/UserInput/IOptionSelector.cs
+++ /dev/null
@@ -1,41 +0,0 @@
-namespace NexusMods.Common.UserInput;
-
-/// <summary>
-/// An interface for selecting item(s) from a group.
-/// </summary>
-/// <remarks>
-///     This implementation is inspired by FOMOD but has been slightly generalised out;
-///     so theoretically could be reused.
-/// </remarks>
-public interface IOptionSelector
-{
-    /// <summary>
-    /// Sets up the selector.
-    /// </summary>
-    /// <param name="name">Name of the new selection.</param>
-    public void SetupSelector(string name);
-
-    /// <summary>
-    /// Cleans up the selector.
-    /// </summary>
-    public void CleanupSelector();
-
-    /// <summary>
-    /// Requests the user to make a choice from an individual group of choices.
-    /// </summary>
-    /// <param name="query">The prompt displayed to the user for this choice.</param>
-    /// <param name="type">The kind of choice the user has to make.</param>
-    /// <param name="options">The items the user can select from.</param>
-    /// <typeparam name="TOptionId">Unique ID for each option.</typeparam>
-    /// <returns>Number of picked options by the user.</returns>
-    public Task<TOptionId[]> RequestChoice<TOptionId>(string query, ChoiceType type, Option<TOptionId>[] options);
-
-    /// <summary>
-    /// Requests the user to make a series of choices from multiple groups of choices.
-    /// </summary>
-    /// <param name="choices">Number of individual groups the user will make choices from.</param>
-    /// <typeparam name="TGroupId">Unique ID for each group.</typeparam>
-    /// <typeparam name="TOptionId">Unique ID for each option.</typeparam>
-    /// <returns></returns>
-    public Task<KeyValuePair<TGroupId, TOptionId[]>[]?> RequestMultipleChoices<TGroupId, TOptionId>(ChoiceGroup<TGroupId, TOptionId>[] choices);
-}
diff --git a/src/NexusMods.Common/UserInput/Option.cs b/src/NexusMods.Common/UserInput/Option.cs
deleted file mode 100644
index d9c4373dc7..0000000000
--- a/src/NexusMods.Common/UserInput/Option.cs
+++ /dev/null
@@ -1,41 +0,0 @@
-namespace NexusMods.Common.UserInput;
-
-/// <summary>
-/// Represents an individual selectable item presented to the user.
-/// </summary>
-/// <typeparam name="TId">Type of unique identifier for the item.</typeparam>
-public record Option<TId>
-{
-    /// <summary>
-    /// Uniquely identifies this option.
-    /// </summary>
-    public required TId Id { get; init; }
-
-    /// <summary>
-    /// Name of the individual selectable option, e.g.
-    /// 'Checked Suit', 'Purple Suit'
-    /// </summary>
-    public required string Name { get; init; }
-
-    /// <summary>
-    /// Short description of this item, e.g.
-    /// 'Equips Joker with a Blue Suit'
-    /// </summary>
-    public string? Description { get; init; }
-
-    /// <summary>
-    /// URL to the image associated with this selection.
-    /// This can be the path to a file or to a remote resource.
-    /// </summary>
-    public AssetUrl? ImageUrl { get; init; }
-
-    /// <summary>
-    /// Text displayed to the user when they hover over the option with the mouse.
-    /// </summary>
-    public string? HoverText { get; init; }
-
-    /// <summary>
-    /// The logic to use for picking this option, such as one, multiple etc.
-    /// </summary>
-    public OptionState Type { get; set; } = OptionState.Available;
-}
diff --git a/src/NexusMods.Common/UserInput/OptionState.cs b/src/NexusMods.Common/UserInput/OptionState.cs
deleted file mode 100644
index 7f1d6766b7..0000000000
--- a/src/NexusMods.Common/UserInput/OptionState.cs
+++ /dev/null
@@ -1,27 +0,0 @@
-namespace NexusMods.Common.UserInput;
-
-/// <summary>
-/// Describes the state of a selectable option.
-/// </summary>
-public enum OptionState
-{
-    /// <summary>
-    /// Not selected but could be.
-    /// </summary>
-    Available,
-
-    /// <summary>
-    /// Selected, could be deselected.
-    /// </summary>
-    Selected,
-
-    /// <summary>
-    /// Not selected and can't be.
-    /// </summary>
-    Disabled,
-
-    /// <summary>
-    /// Selected and can't be deselected.
-    /// </summary>
-    Required,
-}

From c292fe009c3b29822d56bbf8052674e16810b20e Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Thu, 10 Aug 2023 16:19:12 +0200
Subject: [PATCH 05/19] Add installer name

---
 src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs      | 4 ++--
 src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs | 3 +--
 src/NexusMods.App/Services.cs                               | 2 +-
 src/NexusMods.CLI/CliGuidedInstaller.cs                     | 2 +-
 src/NexusMods.Common/GuidedInstaller/IGuidedInstaller.cs    | 3 ++-
 5 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs b/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
index 23dd5d82ba..4041ae8b68 100644
--- a/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
+++ b/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
@@ -18,14 +18,14 @@ public UiOptionSelector(IServiceProvider serviceProvider)
         _serviceProvider = serviceProvider;
     }
 
-    public void SetupInstaller()
+    public void SetupInstaller(string windowName)
     {
         Debug.Assert(_currentScope is null);
         _currentScope = _serviceProvider.CreateScope();
 
         // TODO: create/show window?
         _windowViewModel = _currentScope.ServiceProvider.GetRequiredService<IGuidedInstallerWindowViewModel>();
-        // _windowViewModel.WindowName = windowName;
+        _windowViewModel.WindowName = windowName;
     }
 
     public void CleanupInstaller()
diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index 055b923730..af851ce614 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -60,8 +60,7 @@ public void StartDialog(
         _continueToNextStep = new ContinueToNextStep(cont);
         _cancelInstaller = new CancelInstaller(cancel);
 
-        // TODO: consider passing moduleName along
-        _guidedInstaller.SetupInstaller();
+        _guidedInstaller.SetupInstaller(moduleName ?? "FOMOD Installer");
     }
 
     public void EndDialog()
diff --git a/src/NexusMods.App/Services.cs b/src/NexusMods.App/Services.cs
index 4edb7e9ef7..26add228b7 100644
--- a/src/NexusMods.App/Services.cs
+++ b/src/NexusMods.App/Services.cs
@@ -49,7 +49,7 @@ public static IServiceCollection AddApp(this IServiceCollection services,
         services.AddCLI()
             .AddFileSystem()
             .AddUI()
-            .AddFomodInstallerUi()
+            // .AddFomodInstallerUi()
             .AddFileExtractors(config.FileExtractorSettings)
             .AddDataModel(config.DataModelSettings)
             .AddBethesdaGameStudios()
diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
index 33920c5bad..ab4537ebf4 100644
--- a/src/NexusMods.CLI/CliGuidedInstaller.cs
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -30,7 +30,7 @@ public class CliGuidedInstaller : IGuidedInstaller
     public bool SkipAll { get; set; }
 
     /// <inheritdoc/>
-    public void SetupInstaller() { }
+    public void SetupInstaller(string name) { }
 
     /// <inheritdoc/>
     public void CleanupInstaller() { }
diff --git a/src/NexusMods.Common/GuidedInstaller/IGuidedInstaller.cs b/src/NexusMods.Common/GuidedInstaller/IGuidedInstaller.cs
index 40d3f71c9d..4ab7ac1ddf 100644
--- a/src/NexusMods.Common/GuidedInstaller/IGuidedInstaller.cs
+++ b/src/NexusMods.Common/GuidedInstaller/IGuidedInstaller.cs
@@ -11,7 +11,8 @@ public interface IGuidedInstaller
     /// <summary>
     /// Sets up the installer.
     /// </summary>
-    public void SetupInstaller();
+    /// <param name="name">Name of the installer.</param>
+    public void SetupInstaller(string name);
 
     /// <summary>
     /// Cleans up the installer.

From e198f593de1ce930493dfe19e2bb3af3d5eaf8cd Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Thu, 10 Aug 2023 16:37:06 +0200
Subject: [PATCH 06/19] Update docs

---
 .../CoreDelegates/UiDelegate.cs               |  4 +--
 src/NexusMods.CLI/CliGuidedInstaller.cs       | 29 +++++++------------
 .../GuidedInstaller/GuidedInstallationStep.cs |  9 ++++++
 .../GuidedInstaller/Option.cs                 | 23 ++++++++++++++-
 .../GuidedInstaller/OptionGroup.cs            | 20 +++++++++++--
 .../GuidedInstaller/SelectedOption.cs         | 16 ++++++++--
 .../GuidedInstaller/ValueObjects/AssetUrl.cs  |  2 ++
 .../GuidedInstaller/ValueObjects/GroupId.cs   |  3 ++
 .../GuidedInstaller/ValueObjects/OptionId.cs  |  3 ++
 .../GuidedInstaller/ValueObjects/StepId.cs    |  3 ++
 10 files changed, 86 insertions(+), 26 deletions(-)

diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index af851ce614..f2728a04c1 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -150,7 +150,7 @@ private static GuidedInstallationStep ToGuidedInstallationStep(
             return new OptionGroup
             {
                 Id = groupId,
-                OptionGroupType = ConvertOptionGroupType(group.type),
+                Type = ConvertOptionGroupType(group.type),
                 Description = group.name,
                 Options = ToOptions(group.options, optionIdMappings).ToArray(),
             };
@@ -178,7 +178,7 @@ private static IEnumerable<Option> ToOptions(
                 Name = option.name,
                 Description = option.description,
                 ImageUrl = option.image != null ? AssetUrl.From(option.image) : null,
-                OptionType = MakeOptionType(option),
+                Type = MakeOptionType(option),
             };
         });
     }
diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
index ab4537ebf4..e7df10ddf2 100644
--- a/src/NexusMods.CLI/CliGuidedInstaller.cs
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -61,12 +61,8 @@ public Task<UserChoice> RequestUserChoice(GuidedInstallationStep installationSte
                 {
                     currentGroup = installationStep.Groups[groupIndex];
                     selectedOptions = currentGroup.Options
-                        .Where(x => x.OptionType == OptionType.PreSelected)
-                        .Select(x => new SelectedOption
-                        {
-                            GroupId = currentGroup.Id,
-                            OptionId = x.Id
-                        })
+                        .Where(x => x.Type == OptionType.PreSelected)
+                        .Select(x => new SelectedOption(currentGroup.Id, x.Id))
                         .ToList();
                 }
             }
@@ -76,12 +72,8 @@ public Task<UserChoice> RequestUserChoice(GuidedInstallationStep installationSte
                 if (input == ReturnInput)
                 {
                     var requiredOptions = currentGroup.Options
-                        .Where(x => x.OptionType == OptionType.Required)
-                        .Select(x => new SelectedOption
-                        {
-                            GroupId = currentGroup.Id,
-                            OptionId = x.Id
-                        });
+                        .Where(x => x.Type == OptionType.Required)
+                        .Select(x => new SelectedOption(currentGroup.Id, x.Id));
 
                     selectedOptions.AddRange(requiredOptions);
 
@@ -122,7 +114,7 @@ private static Table TableOfOptions(
                 return new object[]
                 {
                     key++,
-                    RenderOptionState(hasSelected, option.OptionType),
+                    RenderOptionState(hasSelected, option.Type),
                     option.Name,
                     option.Description
                 };
@@ -169,6 +161,9 @@ private static void UpdatedSelectedGroup(
 
         var targetOption = currentGroup.Options[optionIndex];
 
+        // can't toggle disabled or required options
+        if (targetOption.Type is OptionType.Disabled or OptionType.Required) return;
+
         var hasSelected = selectedOptions.TryGetFirst(x => x.OptionId == targetOption.Id, out var selectedOption);
         if (hasSelected)
         {
@@ -178,17 +173,13 @@ private static void UpdatedSelectedGroup(
         }
 
         // the target option is not selected, the user wants to select it
-        if (currentGroup.OptionGroupType is OptionGroupType.ExactlyOne or OptionGroupType.AtMostOne)
+        if (currentGroup.Type is OptionGroupType.ExactlyOne or OptionGroupType.AtMostOne)
         {
             // "deselect" everything
             selectedOptions.Clear();
         }
 
-        selectedOptions.Add(new SelectedOption
-        {
-            GroupId = currentGroup.Id,
-            OptionId = targetOption.Id
-        });
+        selectedOptions.Add(new SelectedOption(currentGroup.Id, targetOption.Id));
     }
 
     private static string GetUserInput()
diff --git a/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs b/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs
index 05d636eed5..780746c748 100644
--- a/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs
+++ b/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs
@@ -3,10 +3,19 @@
 
 namespace NexusMods.Common.GuidedInstaller;
 
+/// <summary>
+/// Represents a single step during installation.
+/// </summary>
 [PublicAPI]
 public record GuidedInstallationStep
 {
+    /// <summary>
+    /// Gets the unique identifier of the step.
+    /// </summary>
     public required StepId Id { get; init; }
 
+    /// <summary>
+    /// Gets one or multiple option groups.
+    /// </summary>
     public required OptionGroup[] Groups { get; init; }
 }
diff --git a/src/NexusMods.Common/GuidedInstaller/Option.cs b/src/NexusMods.Common/GuidedInstaller/Option.cs
index dec6d6bdd5..b0476e5e0d 100644
--- a/src/NexusMods.Common/GuidedInstaller/Option.cs
+++ b/src/NexusMods.Common/GuidedInstaller/Option.cs
@@ -3,18 +3,39 @@
 
 namespace NexusMods.Common.GuidedInstaller;
 
+/// <summary>
+/// Represents a single option inside an <see cref="OptionGroup"/>.
+/// </summary>
 [PublicAPI]
 public record Option
 {
+    /// <summary>
+    /// Gets the unique identifier of the option.
+    /// </summary>
     public required OptionId Id { get; init; }
 
-    public required OptionType OptionType { get; init; }
+    /// <summary>
+    /// Gets the type of the option.
+    /// </summary>
+    public required OptionType Type { get; init; }
 
+    /// <summary>
+    /// Gets the name of the option.
+    /// </summary>
     public required string Name { get; init; }
 
+    /// <summary>
+    /// Gets the description of the option.
+    /// </summary>
     public string Description { get; init; } = string.Empty;
 
+    /// <summary>
+    /// Gets the <see cref="AssetUrl"/> of the image.
+    /// </summary>
     public AssetUrl? ImageUrl { get; init; }
 
+    /// <summary>
+    /// Gets the hover text of the option.
+    /// </summary>
     public string HoverText { get; init; } = string.Empty;
 }
diff --git a/src/NexusMods.Common/GuidedInstaller/OptionGroup.cs b/src/NexusMods.Common/GuidedInstaller/OptionGroup.cs
index 2726161bc5..52ecff40ec 100644
--- a/src/NexusMods.Common/GuidedInstaller/OptionGroup.cs
+++ b/src/NexusMods.Common/GuidedInstaller/OptionGroup.cs
@@ -1,15 +1,31 @@
 using JetBrains.Annotations;
+using NexusMods.Common.GuidedInstaller.ValueObjects;
 
 namespace NexusMods.Common.GuidedInstaller;
 
+/// <summary>
+/// Represents group of <see cref="Option"/> inside a <see cref="GuidedInstallationStep"/>.
+/// </summary>
 [PublicAPI]
 public record OptionGroup
 {
-    public required ValueObjects.GroupId Id { get; init; }
+    /// <summary>
+    /// Gets the unique identifier of the group.
+    /// </summary>
+    public required GroupId Id { get; init; }
 
+    /// <summary>
+    /// Gets the description of the group.
+    /// </summary>
     public required string Description { get; init; }
 
-    public required OptionGroupType OptionGroupType { get; init; }
+    /// <summary>
+    /// Gets the type of the group.
+    /// </summary>
+    public required OptionGroupType Type { get; init; }
 
+    /// <summary>
+    /// Gets one or more options inside the group.
+    /// </summary>
     public required Option[] Options { get; init; }
 }
diff --git a/src/NexusMods.Common/GuidedInstaller/SelectedOption.cs b/src/NexusMods.Common/GuidedInstaller/SelectedOption.cs
index e0be7a7c2c..b97e8c84d2 100644
--- a/src/NexusMods.Common/GuidedInstaller/SelectedOption.cs
+++ b/src/NexusMods.Common/GuidedInstaller/SelectedOption.cs
@@ -3,13 +3,25 @@
 
 namespace NexusMods.Common.GuidedInstaller;
 
+/// <summary>
+/// Represents a selected option.
+/// </summary>
 [PublicAPI]
 public readonly struct SelectedOption
 {
-    public readonly GroupId GroupId { get; init; }
+    /// <summary>
+    /// Gets the unique identifier of the group that contains the selected option.
+    /// </summary>
+    public readonly GroupId GroupId;
 
-    public readonly OptionId OptionId { get; init; }
+    /// <summary>
+    /// Gets the unique identifier of the selected option.
+    /// </summary>
+    public readonly OptionId OptionId;
 
+    /// <summary>
+    /// Constructor.
+    /// </summary>
     public SelectedOption(GroupId groupId, OptionId optionId)
     {
         GroupId = groupId;
diff --git a/src/NexusMods.Common/GuidedInstaller/ValueObjects/AssetUrl.cs b/src/NexusMods.Common/GuidedInstaller/ValueObjects/AssetUrl.cs
index 3ba923c012..57f36baad7 100644
--- a/src/NexusMods.Common/GuidedInstaller/ValueObjects/AssetUrl.cs
+++ b/src/NexusMods.Common/GuidedInstaller/ValueObjects/AssetUrl.cs
@@ -3,6 +3,8 @@
 
 namespace NexusMods.Common.GuidedInstaller.ValueObjects;
 
+// TODO: convert this into a discriminated union using OneOf
+
 /// <summary>
 /// URL of an asset that's tied to an option. This can be a relative path, or
 /// a URL to a remote resource.
diff --git a/src/NexusMods.Common/GuidedInstaller/ValueObjects/GroupId.cs b/src/NexusMods.Common/GuidedInstaller/ValueObjects/GroupId.cs
index fb8a384ea5..6df64b1382 100644
--- a/src/NexusMods.Common/GuidedInstaller/ValueObjects/GroupId.cs
+++ b/src/NexusMods.Common/GuidedInstaller/ValueObjects/GroupId.cs
@@ -3,6 +3,9 @@
 
 namespace NexusMods.Common.GuidedInstaller.ValueObjects;
 
+/// <summary>
+/// Represents a unique identifier of an <see cref="OptionGroup"/>.
+/// </summary>
 [PublicAPI]
 [ValueObject<Guid>]
 public readonly partial struct GroupId { }
diff --git a/src/NexusMods.Common/GuidedInstaller/ValueObjects/OptionId.cs b/src/NexusMods.Common/GuidedInstaller/ValueObjects/OptionId.cs
index 2191e2b941..2f381dca85 100644
--- a/src/NexusMods.Common/GuidedInstaller/ValueObjects/OptionId.cs
+++ b/src/NexusMods.Common/GuidedInstaller/ValueObjects/OptionId.cs
@@ -3,6 +3,9 @@
 
 namespace NexusMods.Common.GuidedInstaller.ValueObjects;
 
+/// <summary>
+/// Represents a unique identifier of an <see cref="Option"/>.
+/// </summary>
 [PublicAPI]
 [ValueObject<Guid>]
 public readonly partial struct OptionId { }
diff --git a/src/NexusMods.Common/GuidedInstaller/ValueObjects/StepId.cs b/src/NexusMods.Common/GuidedInstaller/ValueObjects/StepId.cs
index 6842f739b4..3c1a3fe942 100644
--- a/src/NexusMods.Common/GuidedInstaller/ValueObjects/StepId.cs
+++ b/src/NexusMods.Common/GuidedInstaller/ValueObjects/StepId.cs
@@ -3,6 +3,9 @@
 
 namespace NexusMods.Common.GuidedInstaller.ValueObjects;
 
+/// <summary>
+/// Represents a unique identifier of an <see cref="GuidedInstallationStep"/>.
+/// </summary>
 [PublicAPI]
 [ValueObject<Guid>]
 public readonly partial struct StepId { }

From 4269aa68cd1a258877af99be6a64de0dce34dd30 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Thu, 10 Aug 2023 16:39:39 +0200
Subject: [PATCH 07/19] Rename

---
 .../{UiOptionSelector.cs => GuidedInstallerUi.cs}             | 4 ++--
 src/Games/NexusMods.Games.FOMOD.UI/Services.cs                | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)
 rename src/Games/NexusMods.Games.FOMOD.UI/{UiOptionSelector.cs => GuidedInstallerUi.cs} (93%)

diff --git a/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs b/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerUi.cs
similarity index 93%
rename from src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
rename to src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerUi.cs
index 4041ae8b68..6b7eec6331 100644
--- a/src/Games/NexusMods.Games.FOMOD.UI/UiOptionSelector.cs
+++ b/src/Games/NexusMods.Games.FOMOD.UI/GuidedInstallerUi.cs
@@ -6,14 +6,14 @@
 namespace NexusMods.Games.FOMOD.UI;
 
 [UsedImplicitly]
-public sealed class UiOptionSelector : IGuidedInstaller, IDisposable
+public sealed class GuidedInstallerUi : IGuidedInstaller, IDisposable
 {
     private readonly IServiceProvider _serviceProvider;
 
     private IServiceScope? _currentScope;
     private IGuidedInstallerWindowViewModel? _windowViewModel;
 
-    public UiOptionSelector(IServiceProvider serviceProvider)
+    public GuidedInstallerUi(IServiceProvider serviceProvider)
     {
         _serviceProvider = serviceProvider;
     }
diff --git a/src/Games/NexusMods.Games.FOMOD.UI/Services.cs b/src/Games/NexusMods.Games.FOMOD.UI/Services.cs
index 7e7c3c34b3..6241e2a795 100644
--- a/src/Games/NexusMods.Games.FOMOD.UI/Services.cs
+++ b/src/Games/NexusMods.Games.FOMOD.UI/Services.cs
@@ -9,7 +9,7 @@ public static class Services
     public static IServiceCollection AddFomodInstallerUi(this IServiceCollection serviceCollection)
     {
         return serviceCollection
-            .AddTransient<IGuidedInstaller, UiOptionSelector>()
+            .AddTransient<IGuidedInstaller, GuidedInstallerUi>()
             .AddViewModel<GuidedInstallerStepViewModel, IGuidedInstallerStepViewModel>()
             .AddViewModel<GuidedInstallerWindowViewModel, IGuidedInstallerWindowViewModel>();
     }

From f2b0326f8e632a7ccad167a35802e339cd37526a Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Mon, 14 Aug 2023 10:07:00 +0200
Subject: [PATCH 08/19] Rebase fixes

---
 src/NexusMods.App/Program.cs            | 4 ++--
 src/NexusMods.CLI/CliGuidedInstaller.cs | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/NexusMods.App/Program.cs b/src/NexusMods.App/Program.cs
index d0e94b2a33..cf4211d3fc 100644
--- a/src/NexusMods.App/Program.cs
+++ b/src/NexusMods.App/Program.cs
@@ -52,8 +52,8 @@ public static async Task<int> Main(string[] args)
         }
         else
         {
-            var selector = host.Services.GetRequiredService<CliOptionSelector>();
-            var renderers = host.Services.GetServices<IRenderer>();
+            var selector = host.Services.GetRequiredService<CliGuidedInstaller>();
+            var renderers = host.Services.GetServices<IRenderer>().ToArray();
             selector.Renderer = renderers.FirstOrDefault(r => r.Name == "console") ?? renderers.First();
         }
 
diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
index e7df10ddf2..82d030a747 100644
--- a/src/NexusMods.CLI/CliGuidedInstaller.cs
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -22,7 +22,7 @@ public class CliGuidedInstaller : IGuidedInstaller
     /// <summary>
     /// The renderer to use for rendering the options.
     /// </summary>
-    private IRenderer Renderer { get; set; } = null!;
+    public IRenderer Renderer { get; set; } = null!;
 
     /// <summary>
     /// If true, all option selection will select the first choice.

From 9772fb50d1d112c29c8fb9baa09e64d0eb15b929 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Mon, 14 Aug 2023 10:44:37 +0200
Subject: [PATCH 09/19] Fix OptionType PreSelected when toggling an option

---
 src/NexusMods.CLI/CliGuidedInstaller.cs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
index 82d030a747..3e964a445a 100644
--- a/src/NexusMods.CLI/CliGuidedInstaller.cs
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -134,9 +134,12 @@ private static string RenderOptionState(bool hasSelected, OptionType type)
         return type switch
         {
             OptionType.Disabled => "Disabled",
-            OptionType.Available => "Off",
+            // NOTE (erri120): These are the "initial" states.
+            // The user can toggle a pre-selected option, which
+            // won't change the type but the "hasSelected" value.
+            OptionType.Available or OptionType.PreSelected => "Off",
             OptionType.Required => "Required",
-            _ => throw new UnreachableException()
+            _ => throw new UnreachableException($"hasSelected: {hasSelected}, type: {type}")
         };
     }
 

From 24645c6d509af5434c3feaa61916dbe49e779c5c Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Mon, 14 Aug 2023 11:02:09 +0200
Subject: [PATCH 10/19] Fix continue

---
 .../CoreDelegates/UiDelegate.cs               |  1 -
 src/NexusMods.CLI/CliGuidedInstaller.cs       | 29 +++++++++++--------
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index f2728a04c1..af330181dc 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -95,7 +95,6 @@ public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps
             .RequestUserChoice(guidedInstallationStep, new CancellationToken())
             .ContinueWith(task =>
             {
-                _logger.LogDebug("Status: {TaskStatus}", task.Status);
                 var result = task.Result;
 
                 if (result.IsCancelInstallation)
diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
index 3e964a445a..595f101549 100644
--- a/src/NexusMods.CLI/CliGuidedInstaller.cs
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -56,15 +56,18 @@ public Task<UserChoice> RequestUserChoice(GuidedInstallationStep installationSte
             // the user has to select which group they want to use
             if (currentGroup is null)
             {
-                var groupIndex = ParseNumericalUserInput(input, installationStep.Groups.Length) ?? -1;
-                if (groupIndex >= 0)
+                var groupIndex = ParseNumericalUserInput(input, installationStep.Groups.Length);
+                if (groupIndex < 0)
                 {
-                    currentGroup = installationStep.Groups[groupIndex];
-                    selectedOptions = currentGroup.Options
-                        .Where(x => x.Type == OptionType.PreSelected)
-                        .Select(x => new SelectedOption(currentGroup.Id, x.Id))
-                        .ToList();
+                    // "Continue" with nothing selected.
+                    return Task.FromResult(new UserChoice(new UserChoice.GoToNextStep(Array.Empty<SelectedOption>())));
                 }
+
+                currentGroup = installationStep.Groups[groupIndex];
+                selectedOptions = currentGroup.Options
+                    .Where(x => x.Type == OptionType.PreSelected)
+                    .Select(x => new SelectedOption(currentGroup.Id, x.Id))
+                    .ToList();
             }
             else
             {
@@ -159,7 +162,7 @@ private static void UpdatedSelectedGroup(
         ICollection<SelectedOption> selectedOptions,
         string input)
     {
-        var optionIndex = ParseNumericalUserInput(input, currentGroup.Options.Length) ?? -1;
+        var optionIndex = ParseNumericalUserInput(input, currentGroup.Options.Length);
         if (optionIndex < 0) return;
 
         var targetOption = currentGroup.Options[optionIndex];
@@ -190,7 +193,7 @@ private static string GetUserInput()
         return (Console.ReadLine() ?? "").Trim();
     }
 
-    private static int? ParseNumericalUserInput(string input, int upperLimit)
+    private static int ParseNumericalUserInput(string input, int upperLimit)
     {
         try
         {
@@ -198,9 +201,11 @@ private static string GetUserInput()
             if (idx >= 0 && idx < upperLimit)
                 return idx;
         }
-        catch (FormatException) { /* ignored */ }
+        catch (FormatException)
+        {
+            return -1;
+        }
 
-        // input invalid or out of range
-        return null;
+        return -1;
     }
 }

From f43978983721a235ac8610ececcad66ba28b3174 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Mon, 14 Aug 2023 14:36:20 +0200
Subject: [PATCH 11/19] Fix typo

---
 src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index af330181dc..d08b413394 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -31,7 +31,7 @@ private static void DummyContinueToNextStep(bool forward, int currentStepId) { }
 
     /// <summary>
     /// Created by the executor, this delegate notifies the executor that the installer
-    /// should exist.
+    /// should exit.
     /// </summary>
     private delegate void CancelInstaller();
     private static void DummyCancelInstaller() { }

From b84484b922ee491ceb2f8ec694db83245c0c0de2 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Mon, 14 Aug 2023 15:23:02 +0200
Subject: [PATCH 12/19] Add HasPreviousStep and HasNextStep

---
 .../CoreDelegates/UiDelegate.cs               | 17 +++++++++--
 src/NexusMods.CLI/CliGuidedInstaller.cs       | 28 +++++++++++--------
 .../GuidedInstaller/GuidedInstallationStep.cs | 10 +++++++
 3 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index d08b413394..b3cdb8c03c 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -1,7 +1,10 @@
+using System.Diagnostics;
 using FomodInstaller.Interface;
+using FomodInstaller.Interface.ui;
 using Microsoft.Extensions.Logging;
 using NexusMods.Common.GuidedInstaller;
 using NexusMods.Common.GuidedInstaller.ValueObjects;
+using Option = NexusMods.Common.GuidedInstaller.Option;
 
 namespace NexusMods.Games.FOMOD.CoreDelegates;
 
@@ -81,12 +84,15 @@ public void ReportError(
 
     public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps, int currentStepId)
     {
+        Debug.Assert(currentStepId >= 0 && currentStepId < installSteps.Length);
+
         var currentStep = installSteps[currentStepId];
         var groupIdMappings = new List<KeyValuePair<int, GroupId>>();
         var optionIdMappings = new List<KeyValuePair<int, OptionId>>();
 
         var guidedInstallationStep = ToGuidedInstallationStep(
-            currentStep.optionalFileGroups,
+            installSteps,
+            currentStepId,
             groupIdMappings,
             optionIdMappings
         );
@@ -137,10 +143,13 @@ public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps
     }
 
     private static GuidedInstallationStep ToGuidedInstallationStep(
-        FomodInstaller.Interface.ui.GroupList groups,
+        IList<InstallerStep> installSteps,
+        int currentStepId,
         ICollection<KeyValuePair<int, GroupId>> groupIdMapping,
         ICollection<KeyValuePair<int, OptionId>> optionIdMappings)
     {
+        var groups = installSteps[currentStepId].optionalFileGroups;
+
         var stepGroups = groups.group.Select(group =>
         {
             var groupId = GroupId.From(Guid.NewGuid());
@@ -158,7 +167,9 @@ private static GuidedInstallationStep ToGuidedInstallationStep(
         return new GuidedInstallationStep
         {
             Id = StepId.From(Guid.NewGuid()),
-            Groups = stepGroups.ToArray()
+            Groups = stepGroups.ToArray(),
+            HasPreviousStep = currentStepId != 0,
+            HasNextStep = currentStepId != installSteps.Count - 1,
         };
     }
 
diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
index 595f101549..84e069d96e 100644
--- a/src/NexusMods.CLI/CliGuidedInstaller.cs
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -15,9 +15,10 @@ public class CliGuidedInstaller : IGuidedInstaller
 {
     private const string ReturnInput = "x";
     private static readonly string[] TableOfOptionsHeaders = { "Key", "State", "Name", "Description" };
-    private static readonly object[] TableOfOptionsFooter = { ReturnInput, "", "Back", "" };
+    private static readonly object[] TableOfOptionsFooterBack = { ReturnInput, "", "Back", "" };
     private static readonly string[] TableOfGroupsHeaders = { "Key", "Group" };
-    private static readonly object[] TableOfGroupsFooter = { ReturnInput, "Continue" };
+    private static readonly object[] TableOfGroupsFooterContinue = { ReturnInput, "Continue" };
+    private static readonly object[] TableOfGroupsFooterFinish = { ReturnInput, "Finish" };
 
     /// <summary>
     /// The renderer to use for rendering the options.
@@ -100,11 +101,12 @@ private void RenderStep(
         IReadOnlyCollection<SelectedOption> selectedOptions)
     {
         Renderer.Render(currentGroup is null
-            ? TableOfGroups(installationStep.Groups)
-            : TableOfOptions(currentGroup, selectedOptions));
+            ? TableOfGroups(installationStep)
+            : TableOfOptions(installationStep, currentGroup, selectedOptions));
     }
 
     private static Table TableOfOptions(
+        GuidedInstallationStep installationStep,
         OptionGroup group,
         IReadOnlyCollection<SelectedOption> selectedOptions)
     {
@@ -121,11 +123,11 @@ private static Table TableOfOptions(
                     option.Name,
                     option.Description
                 };
-            })
-            .Append(TableOfOptionsFooter)
-            .ToArray();
+            });
+
+        if (installationStep.HasPreviousStep) row = row.Append(TableOfOptionsFooterBack);
 
-        return new Table(TableOfOptionsHeaders, row, group.Description);
+        return new Table(TableOfOptionsHeaders, row.ToArray(), group.Description);
     }
 
     private static string RenderOptionState(bool hasSelected, OptionType type)
@@ -146,13 +148,15 @@ private static string RenderOptionState(bool hasSelected, OptionType type)
         };
     }
 
-    private static Table TableOfGroups(IEnumerable<OptionGroup> groups)
+    private static Table TableOfGroups(GuidedInstallationStep installationStep)
     {
         var key = 1;
-        var row = groups
+        var row = installationStep.Groups
             .Select(group => new object[] { key++, group.Description })
-            .Append(TableOfGroupsFooter)
-            .ToArray();
+            .Append(installationStep.HasNextStep
+                ? TableOfGroupsFooterContinue
+                : TableOfGroupsFooterFinish
+            ).ToArray();
 
         return new Table(TableOfGroupsHeaders, row, "Select a Group");
     }
diff --git a/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs b/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs
index 780746c748..8c3203fd09 100644
--- a/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs
+++ b/src/NexusMods.Common/GuidedInstaller/GuidedInstallationStep.cs
@@ -18,4 +18,14 @@ public record GuidedInstallationStep
     /// Gets one or multiple option groups.
     /// </summary>
     public required OptionGroup[] Groups { get; init; }
+
+    /// <summary>
+    /// Gets whether or not there is a previous step.
+    /// </summary>
+    public bool HasPreviousStep { get; init; }
+
+    /// <summary>
+    /// Gets whether or not there is a next step.
+    /// </summary>
+    public bool HasNextStep { get; init; }
 }

From 9f1346621bde30ae457ee398bc3c0c34d3e3adf1 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Tue, 15 Aug 2023 12:36:19 +0200
Subject: [PATCH 13/19] Rework FOMOD CLI

---
 .../CoreDelegates/UiDelegate.cs               |   7 +-
 src/NexusMods.CLI/CliGuidedInstaller.cs       | 147 ++++++++++--------
 2 files changed, 83 insertions(+), 71 deletions(-)

diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index b3cdb8c03c..4dd8db3627 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -1,6 +1,4 @@
 using System.Diagnostics;
-using FomodInstaller.Interface;
-using FomodInstaller.Interface.ui;
 using Microsoft.Extensions.Logging;
 using NexusMods.Common.GuidedInstaller;
 using NexusMods.Common.GuidedInstaller.ValueObjects;
@@ -54,7 +52,7 @@ public UiDelegates(ILogger<UiDelegates> logger, IGuidedInstaller guidedInstaller
 
     public void StartDialog(
         string? moduleName,
-        HeaderImage image,
+        FomodInstaller.Interface.HeaderImage image,
         Action<int, int, int[]> select,
         Action<bool, int> cont,
         Action cancel)
@@ -86,7 +84,6 @@ public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps
     {
         Debug.Assert(currentStepId >= 0 && currentStepId < installSteps.Length);
 
-        var currentStep = installSteps[currentStepId];
         var groupIdMappings = new List<KeyValuePair<int, GroupId>>();
         var optionIdMappings = new List<KeyValuePair<int, OptionId>>();
 
@@ -143,7 +140,7 @@ public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps
     }
 
     private static GuidedInstallationStep ToGuidedInstallationStep(
-        IList<InstallerStep> installSteps,
+        IList<FomodInstaller.Interface.ui.InstallerStep> installSteps,
         int currentStepId,
         ICollection<KeyValuePair<int, GroupId>> groupIdMapping,
         ICollection<KeyValuePair<int, OptionId>> optionIdMappings)
diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
index 84e069d96e..6a6389c1a0 100644
--- a/src/NexusMods.CLI/CliGuidedInstaller.cs
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -13,12 +13,19 @@ namespace NexusMods.CLI;
 [UsedImplicitly]
 public class CliGuidedInstaller : IGuidedInstaller
 {
-    private const string ReturnInput = "x";
-    private static readonly string[] TableOfOptionsHeaders = { "Key", "State", "Name", "Description" };
-    private static readonly object[] TableOfOptionsFooterBack = { ReturnInput, "", "Back", "" };
+    private const string CancelInput = "x";
+    private const string BackInput = "b";
+    private const string NextInput = "n";
+
     private static readonly string[] TableOfGroupsHeaders = { "Key", "Group" };
-    private static readonly object[] TableOfGroupsFooterContinue = { ReturnInput, "Continue" };
-    private static readonly object[] TableOfGroupsFooterFinish = { ReturnInput, "Finish" };
+    private static readonly object[] TableOfGroupsFooterNextGroup = { NextInput, "Next" };
+    private static readonly object[] TableOfGroupsFooterFinish = { NextInput, "Finish" };
+    private static readonly object[] TableOfGroupsFooterGoBack = { BackInput, "Back" };
+    private static readonly object[] TableOfGroupsFooterCancel = { CancelInput, "Cancel" };
+
+    private static readonly string[] TableOfOptionsHeaders = { "Key", "State", "Name", "Description" };
+    private static readonly object[] TableOfOptionsFooterBackToGroupSelection = { BackInput, "", "Back", "Back to group selection" };
+    private static readonly object[] TableOfOptionsFooterCancel = { CancelInput, "", "Cancel", "Cancel the installation" };
 
     /// <summary>
     /// The renderer to use for rendering the options.
@@ -39,74 +46,94 @@ public void CleanupInstaller() { }
     /// <inheritdoc />
     public Task<UserChoice> RequestUserChoice(GuidedInstallationStep installationStep, CancellationToken cancellationToken)
     {
-        var currentGroup = installationStep.Groups.Length == 1
-            ? installationStep.Groups[0]
-            : null;
+        OptionGroup? currentGroup = null;
 
-        var selectedOptions = new List<SelectedOption>();
+        var selectedOptions = installationStep.Groups
+            .SelectMany(group => group.Options
+                .Where(option => option.Type == OptionType.PreSelected)
+                .Select(option => new SelectedOption(group.Id, option.Id))
+            ).ToList();
 
         while (true)
         {
-            RenderStep(installationStep, currentGroup, selectedOptions);
-            var input = SkipAll ? "0" : GetUserInput();
-
-            // TODO: the current implementation doesn't support selecting many options from many groups
-            // see https://github.com/Nexus-Mods/NexusMods.App/issues/544
-
-            // if the installation step has multiple groups
-            // the user has to select which group they want to use
             if (currentGroup is null)
             {
-                var groupIndex = ParseNumericalUserInput(input, installationStep.Groups.Length);
-                if (groupIndex < 0)
+                // if the installation step has multiple groups
+                // the user has to select which group they want to use
+
+                RenderTableOfGroups(installationStep);
+
+                var input = SkipAll ? NextInput : GetUserInput();
+
+                switch (input)
                 {
-                    // "Continue" with nothing selected.
-                    return Task.FromResult(new UserChoice(new UserChoice.GoToNextStep(Array.Empty<SelectedOption>())));
+                    case CancelInput:
+                        return Task.FromResult(new UserChoice(new UserChoice.CancelInstallation()));
+                    case BackInput:
+                        return Task.FromResult(new UserChoice(new UserChoice.GoToPreviousStep()));
+                    case NextInput:
+                    {
+                        var requiredOptions = installationStep.Groups
+                            .SelectMany(group => group.Options
+                                .Where(option => option.Type == OptionType.Required)
+                                .Select(option => new SelectedOption(group.Id, option.Id))
+                            );
+
+                        selectedOptions.AddRange(requiredOptions);
+
+                        // proceed to the next step
+                        return Task.FromResult(new UserChoice(new UserChoice.GoToNextStep(selectedOptions.ToArray())));
+                    }
                 }
 
+                var groupIndex = ParseNumericalUserInput(input, installationStep.Groups.Length);
+                if (groupIndex < 0) continue;
+
                 currentGroup = installationStep.Groups[groupIndex];
-                selectedOptions = currentGroup.Options
-                    .Where(x => x.Type == OptionType.PreSelected)
-                    .Select(x => new SelectedOption(currentGroup.Id, x.Id))
-                    .ToList();
             }
             else
             {
                 // if the user has selected a group, the input will be for the options they want to use
-                if (input == ReturnInput)
-                {
-                    var requiredOptions = currentGroup.Options
-                        .Where(x => x.Type == OptionType.Required)
-                        .Select(x => new SelectedOption(currentGroup.Id, x.Id));
+                RenderTableOfOptions(
+                    currentGroup,
+                    selectedOptions
+                );
 
-                    selectedOptions.AddRange(requiredOptions);
+                var input = GetUserInput();
 
-                    // proceed to the next step
-                    return Task.FromResult(new UserChoice(new UserChoice.GoToNextStep(selectedOptions.ToArray())));
+                switch (input)
+                {
+                    case CancelInput:
+                        return Task.FromResult(new UserChoice(new UserChoice.CancelInstallation()));
+                    case BackInput:
+                        currentGroup = null;
+                        continue;
+                    default:
+                        UpdatedSelectedGroup(currentGroup, selectedOptions, input);
+                        break;
                 }
-
-                UpdatedSelectedGroup(currentGroup, selectedOptions, input);
             }
-
-            if (input == ReturnInput) break;
         }
-
-        // The user aborted the installation
-        return Task.FromResult(new UserChoice(new UserChoice.CancelInstallation()));
     }
 
-    private void RenderStep(
-        GuidedInstallationStep installationStep,
-        OptionGroup? currentGroup,
-        IReadOnlyCollection<SelectedOption> selectedOptions)
+    private void RenderTableOfGroups(GuidedInstallationStep installationStep)
     {
-        Renderer.Render(currentGroup is null
-            ? TableOfGroups(installationStep)
-            : TableOfOptions(installationStep, currentGroup, selectedOptions));
+        var key = 1;
+        var row = installationStep.Groups
+            .Select(group => new object[] { key++, group.Description })
+            .Append(installationStep.HasNextStep
+                ? TableOfGroupsFooterNextGroup
+                : TableOfGroupsFooterFinish
+            );
+
+        if (installationStep.HasPreviousStep) row = row.Append(TableOfGroupsFooterGoBack);
+        row = row.Append(TableOfGroupsFooterCancel);
+
+        var table = new Table(TableOfGroupsHeaders, row.ToArray(), "Select a Group");
+        Renderer.Render(table);
     }
 
-    private static Table TableOfOptions(
-        GuidedInstallationStep installationStep,
+    private void RenderTableOfOptions(
         OptionGroup group,
         IReadOnlyCollection<SelectedOption> selectedOptions)
     {
@@ -123,11 +150,12 @@ private static Table TableOfOptions(
                     option.Name,
                     option.Description
                 };
-            });
+            })
+            .Append(TableOfOptionsFooterBackToGroupSelection)
+            .Append(TableOfOptionsFooterCancel);
 
-        if (installationStep.HasPreviousStep) row = row.Append(TableOfOptionsFooterBack);
-
-        return new Table(TableOfOptionsHeaders, row.ToArray(), group.Description);
+        var table = new Table(TableOfOptionsHeaders, row.ToArray(), group.Description);
+        Renderer.Render(table);
     }
 
     private static string RenderOptionState(bool hasSelected, OptionType type)
@@ -148,19 +176,6 @@ private static string RenderOptionState(bool hasSelected, OptionType type)
         };
     }
 
-    private static Table TableOfGroups(GuidedInstallationStep installationStep)
-    {
-        var key = 1;
-        var row = installationStep.Groups
-            .Select(group => new object[] { key++, group.Description })
-            .Append(installationStep.HasNextStep
-                ? TableOfGroupsFooterContinue
-                : TableOfGroupsFooterFinish
-            ).ToArray();
-
-        return new Table(TableOfGroupsHeaders, row, "Select a Group");
-    }
-
     private static void UpdatedSelectedGroup(
         OptionGroup currentGroup,
         ICollection<SelectedOption> selectedOptions,

From e2681db5a31e4cadafcacde588a9d49e8c65c213 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Tue, 15 Aug 2023 12:37:32 +0200
Subject: [PATCH 14/19] Update descriptions

---
 src/NexusMods.CLI/CliGuidedInstaller.cs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
index 6a6389c1a0..72c4dabf8a 100644
--- a/src/NexusMods.CLI/CliGuidedInstaller.cs
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -18,13 +18,13 @@ public class CliGuidedInstaller : IGuidedInstaller
     private const string NextInput = "n";
 
     private static readonly string[] TableOfGroupsHeaders = { "Key", "Group" };
-    private static readonly object[] TableOfGroupsFooterNextGroup = { NextInput, "Next" };
-    private static readonly object[] TableOfGroupsFooterFinish = { NextInput, "Finish" };
-    private static readonly object[] TableOfGroupsFooterGoBack = { BackInput, "Back" };
-    private static readonly object[] TableOfGroupsFooterCancel = { CancelInput, "Cancel" };
+    private static readonly object[] TableOfGroupsFooterNextGroup = { NextInput, "Next Step" };
+    private static readonly object[] TableOfGroupsFooterFinish = { NextInput, "Finish Installation" };
+    private static readonly object[] TableOfGroupsFooterGoBack = { BackInput, "Previous Step" };
+    private static readonly object[] TableOfGroupsFooterCancel = { CancelInput, "Cancel Installation" };
 
     private static readonly string[] TableOfOptionsHeaders = { "Key", "State", "Name", "Description" };
-    private static readonly object[] TableOfOptionsFooterBackToGroupSelection = { BackInput, "", "Back", "Back to group selection" };
+    private static readonly object[] TableOfOptionsFooterBackToGroupSelection = { BackInput, "", "Back", "Back to the group selection" };
     private static readonly object[] TableOfOptionsFooterCancel = { CancelInput, "", "Cancel", "Cancel the installation" };
 
     /// <summary>

From bccd88c0ae16652289a73de55aef14fdb7bd3dee Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Tue, 15 Aug 2023 14:03:47 +0200
Subject: [PATCH 15/19] move SemaphoreSlimWaiter to Common

---
 .../SemaphoreSlimWaiter.cs                    | 24 ++++++++++++++++---
 .../Interprocess/SqliteIPC.cs                 |  1 +
 2 files changed, 22 insertions(+), 3 deletions(-)
 rename src/{NexusMods.DataModel/Interprocess => NexusMods.Common}/SemaphoreSlimWaiter.cs (51%)

diff --git a/src/NexusMods.DataModel/Interprocess/SemaphoreSlimWaiter.cs b/src/NexusMods.Common/SemaphoreSlimWaiter.cs
similarity index 51%
rename from src/NexusMods.DataModel/Interprocess/SemaphoreSlimWaiter.cs
rename to src/NexusMods.Common/SemaphoreSlimWaiter.cs
index 4f39638828..532e443bbf 100644
--- a/src/NexusMods.DataModel/Interprocess/SemaphoreSlimWaiter.cs
+++ b/src/NexusMods.Common/SemaphoreSlimWaiter.cs
@@ -1,9 +1,19 @@
-namespace NexusMods.DataModel.Interprocess;
+using JetBrains.Annotations;
 
-internal readonly struct SemaphoreSlimWaiter : IDisposable
+namespace NexusMods.Common;
+
+/// <summary>
+/// Wrapper around <see cref="SemaphoreSlim"/> that releases it afterwards.
+/// </summary>
+[PublicAPI]
+public readonly struct SemaphoreSlimWaiter : IDisposable
 {
     private readonly SemaphoreSlim _semaphoreSlim;
 
+    /// <summary>
+    /// Whether or not the current thread entered the semaphore and needs to
+    /// release it afterwards.
+    /// </summary>
     public bool HasEntered { get; }
 
     internal SemaphoreSlimWaiter(SemaphoreSlim semaphoreSlim, bool entered)
@@ -12,6 +22,7 @@ internal SemaphoreSlimWaiter(SemaphoreSlim semaphoreSlim, bool entered)
         HasEntered = entered;
     }
 
+    /// <inheritdoc/>
     public void Dispose()
     {
         if (!HasEntered) return;
@@ -19,8 +30,15 @@ public void Dispose()
     }
 }
 
-internal static class SemaphoreExtensions
+/// <summary>
+/// Extension methods for <see cref="SemaphoreSlim"/>.
+/// </summary>
+[PublicAPI]
+public static class SemaphoreExtensions
 {
+    /// <summary>
+    /// Custom wait using <see cref="SemaphoreSlimWaiter"/>.
+    /// </summary>
     public static SemaphoreSlimWaiter CustomWait(
         this SemaphoreSlim semaphoreSlim,
         TimeSpan timeout,
diff --git a/src/NexusMods.DataModel/Interprocess/SqliteIPC.cs b/src/NexusMods.DataModel/Interprocess/SqliteIPC.cs
index 6af169528b..de9421c395 100644
--- a/src/NexusMods.DataModel/Interprocess/SqliteIPC.cs
+++ b/src/NexusMods.DataModel/Interprocess/SqliteIPC.cs
@@ -4,6 +4,7 @@
 using DynamicData;
 using Microsoft.Data.Sqlite;
 using Microsoft.Extensions.Logging;
+using NexusMods.Common;
 using NexusMods.DataModel.Abstractions;
 using NexusMods.DataModel.Extensions;
 using NexusMods.DataModel.Interprocess.Jobs;

From 58712021e1406702f47e3220dc9a29aafee9973d Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Tue, 15 Aug 2023 14:06:00 +0200
Subject: [PATCH 16/19] Force single threaded execution

---
 .../NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs | 10 ++++++++++
 src/NexusMods.CLI/CliGuidedInstaller.cs               | 11 +++++++++++
 2 files changed, 21 insertions(+)

diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index 4dd8db3627..590b98b2ec 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -1,5 +1,6 @@
 using System.Diagnostics;
 using Microsoft.Extensions.Logging;
+using NexusMods.Common;
 using NexusMods.Common.GuidedInstaller;
 using NexusMods.Common.GuidedInstaller.ValueObjects;
 using Option = NexusMods.Common.GuidedInstaller.Option;
@@ -44,6 +45,8 @@ private static void DummyCancelInstaller() { }
     private ContinueToNextStep _continueToNextStep = DummyContinueToNextStep;
     private CancelInstaller _cancelInstaller = DummyCancelInstaller;
 
+    private readonly SemaphoreSlim _semaphoreSlim = new (1, 1);
+
     public UiDelegates(ILogger<UiDelegates> logger, IGuidedInstaller guidedInstaller)
     {
         _logger = logger;
@@ -82,6 +85,13 @@ public void ReportError(
 
     public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps, int currentStepId)
     {
+        // NOTE (erri120): The FOMOD library we're using was designed for threading in JavaScript.
+        // A semaphore is required because the library can spawn multiple tasks on different threads
+        // that will call this method multiple times. This can lead to double-state and it's
+        // just a complete mess. This is what you get when you write a .NET library for JavaScript...
+        using var waiter = _semaphoreSlim.CustomWait(TimeSpan.Zero);
+        if (!waiter.HasEntered) return;
+
         Debug.Assert(currentStepId >= 0 && currentStepId < installSteps.Length);
 
         var groupIdMappings = new List<KeyValuePair<int, GroupId>>();
diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
index 72c4dabf8a..910f599673 100644
--- a/src/NexusMods.CLI/CliGuidedInstaller.cs
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -1,5 +1,6 @@
 using System.Diagnostics;
 using JetBrains.Annotations;
+using Microsoft.Extensions.Logging;
 using NexusMods.Abstractions.CLI;
 using NexusMods.Abstractions.CLI.DataOutputs;
 using NexusMods.Common;
@@ -27,6 +28,16 @@ public class CliGuidedInstaller : IGuidedInstaller
     private static readonly object[] TableOfOptionsFooterBackToGroupSelection = { BackInput, "", "Back", "Back to the group selection" };
     private static readonly object[] TableOfOptionsFooterCancel = { CancelInput, "", "Cancel", "Cancel the installation" };
 
+    private readonly ILogger<CliGuidedInstaller> _logger;
+
+    /// <summary>
+    /// Constructor.
+    /// </summary>
+    public CliGuidedInstaller(ILogger<CliGuidedInstaller> logger)
+    {
+        _logger = logger;
+    }
+
     /// <summary>
     /// The renderer to use for rendering the options.
     /// </summary>

From c03e3af4248f4ba1dc53d99832b74a6b62198a93 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Tue, 15 Aug 2023 14:25:53 +0200
Subject: [PATCH 17/19] Guard against stupid inputs

---
 src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index 590b98b2ec..89c0ee35b3 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -85,6 +85,9 @@ public void ReportError(
 
     public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps, int currentStepId)
     {
+        // NOTE (erri120): The FOMOD library we're using can send us stupid inputs.
+        if (currentStepId < 0 || currentStepId >= installSteps.Length) return;
+
         // NOTE (erri120): The FOMOD library we're using was designed for threading in JavaScript.
         // A semaphore is required because the library can spawn multiple tasks on different threads
         // that will call this method multiple times. This can lead to double-state and it's
@@ -92,8 +95,6 @@ public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps
         using var waiter = _semaphoreSlim.CustomWait(TimeSpan.Zero);
         if (!waiter.HasEntered) return;
 
-        Debug.Assert(currentStepId >= 0 && currentStepId < installSteps.Length);
-
         var groupIdMappings = new List<KeyValuePair<int, GroupId>>();
         var optionIdMappings = new List<KeyValuePair<int, OptionId>>();
 

From 1c3cddba96e1850774a93095b12eaac088a7d20a Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Tue, 15 Aug 2023 15:18:17 +0200
Subject: [PATCH 18/19] More task fuckery

---
 .../CoreDelegates/UiDelegate.cs               | 59 ++++++++++++++++---
 1 file changed, 52 insertions(+), 7 deletions(-)

diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index 89c0ee35b3..c8514b8236 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -1,13 +1,11 @@
-using System.Diagnostics;
 using Microsoft.Extensions.Logging;
 using NexusMods.Common;
 using NexusMods.Common.GuidedInstaller;
 using NexusMods.Common.GuidedInstaller.ValueObjects;
-using Option = NexusMods.Common.GuidedInstaller.Option;
 
 namespace NexusMods.Games.FOMOD.CoreDelegates;
 
-public class UiDelegates : FomodInstaller.Interface.ui.IUIDelegates
+public sealed class UiDelegates : FomodInstaller.Interface.ui.IUIDelegates, IDisposable
 {
     /// <summary>
     /// Created by the executor, this delegate notifies the executor about which options the
@@ -46,6 +44,11 @@ private static void DummyCancelInstaller() { }
     private CancelInstaller _cancelInstaller = DummyCancelInstaller;
 
     private readonly SemaphoreSlim _semaphoreSlim = new (1, 1);
+    private readonly EventWaitHandle _waitHandle = new ManualResetEvent(initialState: false);
+    private long _taskFuckeryState;
+
+    private const long Ready = 0;
+    private const long WaitingForCallback = 1;
 
     public UiDelegates(ILogger<UiDelegates> logger, IGuidedInstaller guidedInstaller)
     {
@@ -85,10 +88,21 @@ public void ReportError(
 
     public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps, int currentStepId)
     {
-        // NOTE (erri120): The FOMOD library we're using can send us stupid inputs.
+        // NOTE(erri120): The FOMOD library we're using can send us stupid inputs.
         if (currentStepId < 0 || currentStepId >= installSteps.Length) return;
 
-        // NOTE (erri120): The FOMOD library we're using was designed for threading in JavaScript.
+        // NOTE(erri120): This fuckery is explained further below when we call _selectOptions()
+        if (Interlocked.Read(ref _taskFuckeryState) == WaitingForCallback)
+        {
+            if (!_waitHandle.Set())
+            {
+                _logger.LogWarning("Unable to signal completion!");
+            }
+
+            return;
+        }
+
+        // NOTE(erri120): The FOMOD library we're using was designed for threading in JavaScript.
         // A semaphore is required because the library can spawn multiple tasks on different threads
         // that will call this method multiple times. This can lead to double-state and it's
         // just a complete mess. This is what you get when you write a .NET library for JavaScript...
@@ -113,8 +127,10 @@ public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps
 
                 if (result.IsCancelInstallation)
                 {
-                    // TODO: verify that this calls EndDialog
                     _cancelInstaller();
+
+                    // NOTE(erri120): We have to manually call this method.
+                    EndDialog();
                 } else if (result.IsGoToPreviousStep)
                 {
                     _continueToNextStep(forward: false, currentStepId);
@@ -139,10 +155,33 @@ public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps
                             .Select(x => optionIdMappings.FirstOrDefault(kv => kv.Value == x.OptionId).Key)
                             .ToArray();
 
+                        // NOTE(erri120): Once again, the FOMOD library we're using is complete ass and expects
+                        // to be used in a JavaScript environment. However, this isn't JavaScript this is C#.
+                        // When calling _selectOptions, the library spawns a new Task that runs in the background.
+                        // This means that after calling _selectOptions, we state hasn't been updated YET.
+                        // Inside _selectOptions, the library wants to get the next step, however, if we
+                        // call _continueToNextStep, then the next step variable has already been updated.
+                        // The library doesn't do any checks to prevent this and can throw an exception
+                        // if we're at the last step and continue. In that case, the step variable will be set to -1
+                        // and steps[-1] will throw an exception.
+                        // As such, we're required to use our own synchronization. Thankfully, we can abuse the stupid
+                        // behavior of the library. As explained earlier, the library expects us to call _selectOptions
+                        // when the user clicks on a button. The method _selectOptions will call us back, once it has
+                        // updated its internal state. This behavior allows us to use an EventWaitHandle to "wait" for
+                        // the library to call us back.
+                        // We're also using CAS to set our state into "waiting" mode.
+                        if (Interlocked.CompareExchange(ref _taskFuckeryState, WaitingForCallback, Ready) != Ready)
+                            _logger.LogWarning("Unable to CAS!");
+
                         _selectOptions(currentStepId, selectedGroupId, selectedOptionIds);
+                        _waitHandle.WaitOne(TimeSpan.FromMilliseconds(200), exitContext: false);
+                        _waitHandle.Reset();
+
+                        if (Interlocked.CompareExchange(ref _taskFuckeryState, Ready, WaitingForCallback) != WaitingForCallback)
+                            _logger.LogWarning("Unable to CAS!");
                     }
 
-                    // We need to explicitly call this, since our implementations
+                    // NOTE(erri120): We need to explicitly call this, since our implementations
                     // return from RequestMultipleChoices when the user wants to go
                     // to the next step. Once again, the API is ass.
                     _continueToNextStep(forward: true, currentStepId);
@@ -224,4 +263,10 @@ private static OptionGroupType ConvertOptionGroupType(string input)
             _ => OptionGroupType.Any
         };
     }
+
+    public void Dispose()
+    {
+        _semaphoreSlim.Dispose();
+        _waitHandle.Dispose();
+    }
 }

From c81b9d15d00fa4940b3b21ca6b044ef88627d8f9 Mon Sep 17 00:00:00 2001
From: erri120 <erri120@protonmail.com>
Date: Tue, 15 Aug 2023 17:54:56 +0200
Subject: [PATCH 19/19] Cleanup

---
 .../CoreDelegates/UiDelegate.cs               | 10 +++----
 src/NexusMods.CLI/CliGuidedInstaller.cs       | 29 +++++++++++--------
 2 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
index c8514b8236..4183cb7b7a 100644
--- a/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
+++ b/src/Games/NexusMods.Games.FOMOD/CoreDelegates/UiDelegate.cs
@@ -45,7 +45,7 @@ private static void DummyCancelInstaller() { }
 
     private readonly SemaphoreSlim _semaphoreSlim = new (1, 1);
     private readonly EventWaitHandle _waitHandle = new ManualResetEvent(initialState: false);
-    private long _taskFuckeryState;
+    private long _taskWaitingState;
 
     private const long Ready = 0;
     private const long WaitingForCallback = 1;
@@ -92,7 +92,7 @@ public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps
         if (currentStepId < 0 || currentStepId >= installSteps.Length) return;
 
         // NOTE(erri120): This fuckery is explained further below when we call _selectOptions()
-        if (Interlocked.Read(ref _taskFuckeryState) == WaitingForCallback)
+        if (Interlocked.Read(ref _taskWaitingState) == WaitingForCallback)
         {
             if (!_waitHandle.Set())
             {
@@ -158,7 +158,7 @@ public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps
                         // NOTE(erri120): Once again, the FOMOD library we're using is complete ass and expects
                         // to be used in a JavaScript environment. However, this isn't JavaScript this is C#.
                         // When calling _selectOptions, the library spawns a new Task that runs in the background.
-                        // This means that after calling _selectOptions, we state hasn't been updated YET.
+                        // This means that after calling _selectOptions, the state hasn't been updated YET.
                         // Inside _selectOptions, the library wants to get the next step, however, if we
                         // call _continueToNextStep, then the next step variable has already been updated.
                         // The library doesn't do any checks to prevent this and can throw an exception
@@ -170,14 +170,14 @@ public void UpdateState(FomodInstaller.Interface.ui.InstallerStep[] installSteps
                         // updated its internal state. This behavior allows us to use an EventWaitHandle to "wait" for
                         // the library to call us back.
                         // We're also using CAS to set our state into "waiting" mode.
-                        if (Interlocked.CompareExchange(ref _taskFuckeryState, WaitingForCallback, Ready) != Ready)
+                        if (Interlocked.CompareExchange(ref _taskWaitingState, WaitingForCallback, Ready) != Ready)
                             _logger.LogWarning("Unable to CAS!");
 
                         _selectOptions(currentStepId, selectedGroupId, selectedOptionIds);
                         _waitHandle.WaitOne(TimeSpan.FromMilliseconds(200), exitContext: false);
                         _waitHandle.Reset();
 
-                        if (Interlocked.CompareExchange(ref _taskFuckeryState, Ready, WaitingForCallback) != WaitingForCallback)
+                        if (Interlocked.CompareExchange(ref _taskWaitingState, Ready, WaitingForCallback) != WaitingForCallback)
                             _logger.LogWarning("Unable to CAS!");
                     }
 
diff --git a/src/NexusMods.CLI/CliGuidedInstaller.cs b/src/NexusMods.CLI/CliGuidedInstaller.cs
index 910f599673..e5c2a29a23 100644
--- a/src/NexusMods.CLI/CliGuidedInstaller.cs
+++ b/src/NexusMods.CLI/CliGuidedInstaller.cs
@@ -15,13 +15,14 @@ namespace NexusMods.CLI;
 public class CliGuidedInstaller : IGuidedInstaller
 {
     private const string CancelInput = "x";
+    private const string PreviousInput = "p";
     private const string BackInput = "b";
     private const string NextInput = "n";
 
     private static readonly string[] TableOfGroupsHeaders = { "Key", "Group" };
-    private static readonly object[] TableOfGroupsFooterNextGroup = { NextInput, "Next Step" };
+    private static readonly object[] TableOfGroupsFooterNextStep = { NextInput, "Next Step" };
     private static readonly object[] TableOfGroupsFooterFinish = { NextInput, "Finish Installation" };
-    private static readonly object[] TableOfGroupsFooterGoBack = { BackInput, "Previous Step" };
+    private static readonly object[] TableOfGroupsFooterPreviousStep = { PreviousInput, "Previous Step" };
     private static readonly object[] TableOfGroupsFooterCancel = { CancelInput, "Cancel Installation" };
 
     private static readonly string[] TableOfOptionsHeaders = { "Key", "State", "Name", "Description" };
@@ -69,9 +70,7 @@ public Task<UserChoice> RequestUserChoice(GuidedInstallationStep installationSte
         {
             if (currentGroup is null)
             {
-                // if the installation step has multiple groups
-                // the user has to select which group they want to use
-
+                // the user hasn't selected a group yet
                 RenderTableOfGroups(installationStep);
 
                 var input = SkipAll ? NextInput : GetUserInput();
@@ -80,7 +79,7 @@ public Task<UserChoice> RequestUserChoice(GuidedInstallationStep installationSte
                 {
                     case CancelInput:
                         return Task.FromResult(new UserChoice(new UserChoice.CancelInstallation()));
-                    case BackInput:
+                    case PreviousInput:
                         return Task.FromResult(new UserChoice(new UserChoice.GoToPreviousStep()));
                     case NextInput:
                     {
@@ -95,12 +94,16 @@ public Task<UserChoice> RequestUserChoice(GuidedInstallationStep installationSte
                         // proceed to the next step
                         return Task.FromResult(new UserChoice(new UserChoice.GoToNextStep(selectedOptions.ToArray())));
                     }
-                }
+                    default:
+                    {
+                        var groupIndex = ParseNumericalUserInput(input, installationStep.Groups.Length);
+                        if (groupIndex < 0) continue;
 
-                var groupIndex = ParseNumericalUserInput(input, installationStep.Groups.Length);
-                if (groupIndex < 0) continue;
+                        currentGroup = installationStep.Groups[groupIndex];
+                        break;
+                    }
+                }
 
-                currentGroup = installationStep.Groups[groupIndex];
             }
             else
             {
@@ -133,11 +136,11 @@ private void RenderTableOfGroups(GuidedInstallationStep installationStep)
         var row = installationStep.Groups
             .Select(group => new object[] { key++, group.Description })
             .Append(installationStep.HasNextStep
-                ? TableOfGroupsFooterNextGroup
+                ? TableOfGroupsFooterNextStep
                 : TableOfGroupsFooterFinish
             );
 
-        if (installationStep.HasPreviousStep) row = row.Append(TableOfGroupsFooterGoBack);
+        if (installationStep.HasPreviousStep) row = row.Append(TableOfGroupsFooterPreviousStep);
         row = row.Append(TableOfGroupsFooterCancel);
 
         var table = new Table(TableOfGroupsHeaders, row.ToArray(), "Select a Group");
@@ -227,6 +230,8 @@ private static int ParseNumericalUserInput(string input, int upperLimit)
     {
         try
         {
+            // method returns a zero-based index for use as the option index
+            // the user inputs a one-based index, as it's easier to understand
             var idx = int.Parse(input) - 1;
             if (idx >= 0 && idx < upperLimit)
                 return idx;