Add mob retaliation (#19901)

Content.Server/NPC/Systems/NPCRetaliationSystem.cs

@@ -0,0 +1,90 @@
+using Content.Server.NPC.Components;
+using Content.Shared.CombatMode;
+using Content.Shared.Damage;
+using Content.Shared.Mobs.Components;
+using Robust.Shared.Collections;
+using Robust.Shared.Timing;
+
+namespace Content.Server.NPC.Systems;
+
+/// <summary>
+/// Handles NPC which become aggressive after being attacked.
+/// </summary>
+public sealed class NPCRetaliationSystem : EntitySystem
+{
+    [Dependency] private readonly IGameTiming _timing = default!;
+    [Dependency] private readonly NpcFactionSystem _npcFaction = default!;
+
+    private readonly HashSet<EntityUid> _deAggroQueue = new();
+
+    /// <inheritdoc/>
+    public override void Initialize()
+    {
+        SubscribeLocalEvent<NPCRetaliationComponent, DamageChangedEvent>(OnDamageChanged);
+        SubscribeLocalEvent<NPCRetaliationComponent, DisarmedEvent>(OnDisarmed);
+    }
+
+    private void OnDamageChanged(EntityUid uid, NPCRetaliationComponent component, DamageChangedEvent args)
+    {
+        if (!args.DamageIncreased)
+            return;
+
+        if (args.Origin is not { } origin)
+            return;
+
+        TryRetaliate(uid, origin, component);
+    }
+
+    private void OnDisarmed(EntityUid uid, NPCRetaliationComponent component, DisarmedEvent args)
+    {
+        TryRetaliate(uid, args.Source, component);
+    }
+
+    public bool TryRetaliate(EntityUid uid, EntityUid target, NPCRetaliationComponent? component = null)
+    {
+        if (!Resolve(uid, ref component))
+            return false;
+
+        // don't retaliate against inanimate objects.
+        if (!HasComp<MobStateComponent>(target))
+            return false;
+
+        if (_npcFaction.IsEntityFriendly(uid, target))
+            return false;
+
+        _npcFaction.AggroEntity(uid, target);
+        if (component.AttackMemoryLength is { } memoryLength)
+        {
+            component.AttackMemories[target] = _timing.CurTime + memoryLength;
+        }
+
+        return true;
+    }
+
+    public override void Update(float frameTime)
+    {
+        base.Update(frameTime);
+
+        var query = EntityQueryEnumerator<NPCRetaliationComponent, FactionExceptionComponent, MetaDataComponent>();
+        while (query.MoveNext(out var uid, out var comp, out var factionException, out var metaData))
+        {
+            _deAggroQueue.Clear();
+
+            foreach (var ent in new ValueList<EntityUid>(comp.AttackMemories.Keys))
+            {
+                if (_timing.CurTime < comp.AttackMemories[ent])
+                    continue;
+
+                if (TerminatingOrDeleted(ent, metaData))
+                    _deAggroQueue.Add(ent);
+
+                _deAggroQueue.Add(ent);
+            }
+
+            foreach (var ent in _deAggroQueue)
+            {
+                _npcFaction.DeAggroEntity(uid, ent, factionException);
+            }
+        }
+    }
+}