Convert Harpy Singing Into a Trait (#714)

# Description
Adds a new trait that lets characters play midi without needing an
instrument.

Singer a 1-point positive trait. For now it's only available for vulps
and felinids as they are naturally more vocal than other species.

Also refactored harpy singing system a bit.

# TODO

- [X] Find out whatever causes this. Not critical, but probably should
be fixed...
<details><p>


![image](https://github.com/user-attachments/assets/8e0a6bf5-5fa3-4a0a-8937-2931dfe4ee62)

</p></details>

<details><summary><h1>Media</h1></summary>
<p>

Outdated


![image](https://github.com/user-attachments/assets/018b6cf3-d510-46e2-8c38-4bd49e1929bd)


![image](https://github.com/user-attachments/assets/f27bd451-b3c2-4a22-ab50-35c2f4ecbcb3)

</p>
</details>

# Changelog
:cl:
- add: Added a new positive trait - singer. It allows you to play midi
songs without an instrument, similarly to harpies.

---------

Signed-off-by: Mnemotechnican <[email protected]>
Co-authored-by: Danger Revolution! <[email protected]>
Co-authored-by: VMSolidus <[email protected]>

Content.Client/Traits/SingerSystem.cs

@@ -0,0 +1,13 @@
+using Content.Client.Instruments;
+using Content.Shared.Instruments;
+using Content.Shared.Traits.Assorted.Systems;
+
+namespace Content.Client.Traits;
+
+public sealed class SingerSystem : SharedSingerSystem
+{
+    protected override SharedInstrumentComponent EnsureInstrumentComp(EntityUid uid)
+    {
+        return EnsureComp<InstrumentComponent>(uid); // I hate this, but it's the only way.
+    }
+}

Content.Server/Traits/Assorted/SingerSystem.cs

@@ -0,0 +1,161 @@
+using Content.Server.Instruments;
+using Content.Server.Speech.Components;
+using Content.Server.UserInterface;
+using Content.Shared.ActionBlocker;
+using Content.Shared.Damage;
+using Content.Shared.Damage.ForceSay;
+using Content.Shared.FixedPoint;
+using Content.Shared.Instruments;
+using Content.Shared.Inventory;
+using Content.Shared.Inventory.Events;
+using Content.Shared.Mobs;
+using Content.Shared.Popups;
+using Content.Shared.StatusEffect;
+using Content.Shared.Stunnable;
+using Content.Shared.Traits.Assorted.Components;
+using Content.Shared.Traits.Assorted.Prototypes;
+using Content.Shared.Traits.Assorted.Systems;
+using Content.Shared.UserInterface;
+using Content.Shared.Zombies;
+using Robust.Shared.Player;
+using Robust.Shared.Prototypes;
+
+namespace Content.Server.Traits.Assorted;
+
+public sealed class SingerSystem : SharedSingerSystem
+{
+    [Dependency] private readonly ActionBlockerSystem _actionBlocker = default!;
+    [Dependency] private readonly InventorySystem _inventory = default!;
+    [Dependency] private readonly SharedPopupSystem _popup = default!;
+    [Dependency] private readonly InstrumentSystem _instrument = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<GotEquippedEvent>(OnEquip);
+        SubscribeLocalEvent<InstrumentComponent, MobStateChangedEvent>(OnMobStateChangedEvent);
+        SubscribeLocalEvent<InstrumentComponent, KnockedDownEvent>(OnKnockedDown);
+        SubscribeLocalEvent<InstrumentComponent, StunnedEvent>(OnStunned);
+        SubscribeLocalEvent<InstrumentComponent, SleepStateChangedEvent>(OnSleep);
+        SubscribeLocalEvent<InstrumentComponent, StatusEffectAddedEvent>(OnStatusEffect);
+        SubscribeLocalEvent<InstrumentComponent, DamageChangedEvent>(OnDamageChanged);
+        // This is intended to intercept and cancel the UI event before it reaches ActivatableUISystem.
+        SubscribeLocalEvent<SingerComponent, OpenUiActionEvent>(OnInstrumentOpen, before: [typeof(ActivatableUISystem)]);
+    }
+
+    protected override SharedInstrumentComponent EnsureInstrumentComp(EntityUid uid)
+    {
+        return EnsureComp<InstrumentComponent>(uid);
+    }
+
+    protected override void SetUpSwappableInstrument(EntityUid uid, SingerInstrumentPrototype singer)
+    {
+        if (singer.InstrumentList.Count <= 1)
+            return;
+
+        var swappableComp = EnsureComp<SwappableInstrumentComponent>(uid);
+        swappableComp.InstrumentList = singer.InstrumentList;
+    }
+
+    private void OnEquip(GotEquippedEvent args)
+    {
+        // Check if an item that makes the singer mumble is equipped to their face
+        // (not their pockets!). As of writing, this should just be the muzzle.
+        if (TryComp<AddAccentClothingComponent>(args.Equipment, out var accent) &&
+            accent.ReplacementPrototype == "mumble" &&
+            args.Slot == "mask")
+        {
+            CloseMidiUi(args.Equipee);
+        }
+    }
+
+    private void OnMobStateChangedEvent(EntityUid uid, SharedInstrumentComponent component, MobStateChangedEvent args)
+    {
+        if (args.NewMobState is MobState.Critical or MobState.Dead)
+            CloseMidiUi(args.Target);
+    }
+
+    private void OnKnockedDown(EntityUid uid, SharedInstrumentComponent component, ref KnockedDownEvent args)
+    {
+        CloseMidiUi(uid);
+    }
+
+    private void OnStunned(EntityUid uid, SharedInstrumentComponent component, ref StunnedEvent args)
+    {
+        CloseMidiUi(uid);
+    }
+
+    private void OnSleep(EntityUid uid, SharedInstrumentComponent component, ref SleepStateChangedEvent args)
+    {
+        if (args.FellAsleep)
+            CloseMidiUi(uid);
+    }
+
+    private void OnStatusEffect(EntityUid uid, SharedInstrumentComponent component, StatusEffectAddedEvent args)
+    {
+        if (args.Key == "Muted")
+            CloseMidiUi(uid);
+    }
+
+    /// <summary>
+    /// Almost a copy of Content.Server.Damage.ForceSay.DamageForceSaySystem.OnDamageChanged.
+    /// Done so because DamageForceSaySystem doesn't output an event, and my understanding is
+    /// that we don't want to change upstream code more than necessary to avoid merge conflicts
+    /// and maintenance overhead. It still reuses the values from DamageForceSayComponent, so
+    /// any tweaks to that will keep ForceSay consistent with singing interruptions.
+    /// </summary>
+    private void OnDamageChanged(EntityUid uid, SharedInstrumentComponent instrumentComponent, DamageChangedEvent args)
+    {
+        if (!TryComp<DamageForceSayComponent>(uid, out var component) ||
+            args.DamageDelta == null ||
+            !args.DamageIncreased ||
+            args.DamageDelta.GetTotal() < component.DamageThreshold ||
+            component.ValidDamageGroups == null)
+            return;
+
+        var totalApplicableDamage = FixedPoint2.Zero;
+        foreach (var (group, value) in args.DamageDelta.GetDamagePerGroup(ProtoMan))
+        {
+            if (!component.ValidDamageGroups.Contains(group))
+                continue;
+
+            totalApplicableDamage += value;
+        }
+
+        if (totalApplicableDamage >= component.DamageThreshold)
+            CloseMidiUi(uid);
+    }
+
+    /// <summary>
+    /// Prevent the player from opening the MIDI UI under some circumstances.
+    /// </summary>
+    private void OnInstrumentOpen(EntityUid uid, SingerComponent component, OpenUiActionEvent args)
+    {
+        // CanSpeak covers all reasons you can't talk, including being incapacitated
+        // (crit/dead), asleep, or for any reason mute inclding glimmer or a mime's vow.
+        // TODO why the fuck is any of this hardcoded?
+        var canNotSpeak = !_actionBlocker.CanSpeak(uid);
+        var zombified = TryComp<ZombieComponent>(uid, out var _);
+        var muzzled = _inventory.TryGetSlotEntity(uid, "mask", out var maskUid) &&
+                      TryComp<AddAccentClothingComponent>(maskUid, out var accent) &&
+                      accent.ReplacementPrototype == "mumble";
+
+        // Set this event as handled when the singer should be incapable of singing in order
+        // to stop the ActivatableUISystem event from opening the MIDI UI.
+        args.Handled = canNotSpeak || muzzled || zombified;
+
+        // Tell the user that they can not sing.
+        if (args.Handled)
+            _popup.PopupEntity(Loc.GetString("no-sing-while-no-speak"), uid, uid, PopupType.Medium);
+    }
+
+    public override void CloseMidiUi(EntityUid uid)
+    {
+        if (HasComp<ActiveInstrumentComponent>(uid) &&
+            TryComp<ActorComponent>(uid, out var actor))
+        {
+            _instrument.ToggleInstrumentUi(uid, actor.PlayerSession);
+        }
+    }
+}