From a6cb156e683327372fe2843a82d1cc8cc1464cca Mon Sep 17 00:00:00 2001
From: Martin <mautner@vrvis.at>
Date: Mon, 19 Aug 2024 17:05:23 +0200
Subject: [PATCH] [FSharp] Rework LookupTable utilities

---
 .../Utilities/Interop/FSLibExtensions.fs      | 54 +++++++++++++------
 .../PixImage/ImageTrafo.fs                    |  4 +-
 .../PixImage/PixImageErrorMetric.fs           |  2 +-
 .../Tensors/PixTests.fs                       |  2 +-
 4 files changed, 41 insertions(+), 21 deletions(-)

diff --git a/src/Aardvark.Base.FSharp/Utilities/Interop/FSLibExtensions.fs b/src/Aardvark.Base.FSharp/Utilities/Interop/FSLibExtensions.fs
index 1d484020..b63e5c13 100644
--- a/src/Aardvark.Base.FSharp/Utilities/Interop/FSLibExtensions.fs
+++ b/src/Aardvark.Base.FSharp/Utilities/Interop/FSLibExtensions.fs
@@ -367,35 +367,55 @@ module NiceUtilities =
     module LookupTable =
         open System.Collections.Generic
 
-        let lookupTable (l : list<'a * 'b>) =
+        let private build (entries: #seq<'Key * 'Value>) =
             let d = Dictionary()
-            for (k,v) in l do
 
+            for k, v in entries do
                 match d.TryGetValue k with
-                    | (true, vo) -> failwithf "duplicated lookup-entry: %A (%A vs %A)" k vo v
-                    | _ -> ()
+                | (true, vo) -> raise <| ArgumentException($"Duplicate lookup table entry {k}: {v} and {vo}.")
+                | _ -> ()
 
                 d.[k] <- v
 
-            fun (key : 'a) ->
+            d
+
+        /// Builds a lookup table from the given entries and returns a function that retrieves the value associated with a key.
+        /// Fails if a key occurs more than once in the input collection.
+        let lookup (entries: #seq<'Key * 'Value>) =
+            let d = build entries
+
+            fun (key : 'Key) ->
                 match d.TryGetValue key with
-                    | (true, v) -> v
-                    | _ -> failwithf "unsupported %A: %A" typeof<'a> key
+                | (true, v) -> v
+                | _ -> raise <| KeyNotFoundException($"Key {key} of type {typeof<'Key>} not found in lookup table.")
 
+        /// Builds a lookup table from the given entries and returns a function that retrieves the value associated with a key if it exists.
+        /// Fails if a key occurs more than once in the input collection.
+        let tryLookup (entries: #seq<'Key * 'Value>) =
+            let d = build entries
 
-        let lookupTable' (l : list<'a * 'b>) =
-            let d = Dictionary()
-            for (k,v) in l do
-                match d.TryGetValue k with
-                    | (true, vo) -> failwithf "duplicated lookup-entry: %A (%A vs %A)" k vo v
-                    | _ -> ()
+            fun (key : 'Key) ->
+                match d.TryGetValue key with
+                | (true, v) -> Some v
+                | _ -> None
 
-                d.[k] <- v
+        /// Builds a lookup table from the given entries and returns a function that retrieves the value associated with a key if it exists.
+        /// Fails if a key occurs more than once in the input collection.
+        let tryLookupV (entries: #seq<'Key * 'Value>) =
+            let d = build entries
 
-            fun (key : 'a) ->
+            fun (key : 'Key) ->
                 match d.TryGetValue key with
-                    | (true, v) -> Some v
-                    | _ -> None
+                | (true, v) -> ValueSome v
+                | _ -> ValueNone
+
+        [<Obsolete("Use LookupTable.lookup instead.")>]
+        let lookupTable (l : list<'a * 'b>) =
+            lookup l
+
+        [<Obsolete("Use LookupTable.tryLookup instead.")>]
+        let lookupTable' (l : list<'a * 'b>) =
+            tryLookup l
 
 [<AutoOpen>]
 module EnumExtensions =
diff --git a/src/Aardvark.Base.Tensors/PixImage/ImageTrafo.fs b/src/Aardvark.Base.Tensors/PixImage/ImageTrafo.fs
index 71a210d0..0b55b103 100644
--- a/src/Aardvark.Base.Tensors/PixImage/ImageTrafo.fs
+++ b/src/Aardvark.Base.Tensors/PixImage/ImageTrafo.fs
@@ -3,7 +3,7 @@
 [<CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
 module ImageTrafo =
     let private composeTable =
-        LookupTable.lookupTable [
+        LookupTable.lookup [
             struct (ImageTrafo.Identity, ImageTrafo.Identity), ImageTrafo.Identity
             struct (ImageTrafo.Identity, ImageTrafo.Rot90), ImageTrafo.Rot90
             struct (ImageTrafo.Identity, ImageTrafo.Rot180), ImageTrafo.Rot180
@@ -74,7 +74,7 @@ module ImageTrafo =
         composeTable (struct (l, r))
 
     let inverse =
-        LookupTable.lookupTable [
+        LookupTable.lookup [
             ImageTrafo.MirrorX, ImageTrafo.MirrorX
             ImageTrafo.MirrorY, ImageTrafo.MirrorY
             ImageTrafo.Identity, ImageTrafo.Identity
diff --git a/src/Aardvark.Base.Tensors/PixImage/PixImageErrorMetric.fs b/src/Aardvark.Base.Tensors/PixImage/PixImageErrorMetric.fs
index 99e7ba6d..a113eae1 100644
--- a/src/Aardvark.Base.Tensors/PixImage/PixImageErrorMetric.fs
+++ b/src/Aardvark.Base.Tensors/PixImage/PixImageErrorMetric.fs
@@ -13,7 +13,7 @@ module FSharpPixImageErrorMetricExtensions =
         module ErrorMetricHelpers =
 
             let maxValues =
-                LookupTable.lookupTable [
+                LookupTable.lookup [
                     typeof<uint8>,   255.0
                     typeof<int8>,    255.0
                     typeof<uint16>,  65535.0
diff --git a/src/Tests/Aardvark.Base.FSharp.Tests/Tensors/PixTests.fs b/src/Tests/Aardvark.Base.FSharp.Tests/Tensors/PixTests.fs
index 6efc38b6..52c357a1 100644
--- a/src/Tests/Aardvark.Base.FSharp.Tests/Tensors/PixTests.fs
+++ b/src/Tests/Aardvark.Base.FSharp.Tests/Tensors/PixTests.fs
@@ -258,7 +258,7 @@ module PixTests =
 
     let computePSNR =
         let table : Type -> (PixImage -> PixImage -> float) =
-            LookupTable.lookupTable [
+            LookupTable.lookup [
                 typeof<uint8>,   fun src dst -> PixImage.peakSignalToNoiseRatio (src.AsPixImage<uint8>()) (dst.AsPixImage<uint8>())
                 typeof<uint16>,  fun src dst -> PixImage.peakSignalToNoiseRatio (src.AsPixImage<uint16>()) (dst.AsPixImage<uint16>())
                 typeof<uint32>,  fun src dst -> PixImage.peakSignalToNoiseRatio (src.AsPixImage<uint32>()) (dst.AsPixImage<uint32>())