Atmos Air Grenades (#37531)

Content.Server/Explosion/EntitySystems/ReleaseGasOnTriggerSystem.cs

@@ -0,0 +1,92 @@
+using Content.Server.Atmos.EntitySystems;
+using Content.Shared.Explosion.Components.OnTrigger;
+using Content.Shared.Explosion.EntitySystems;
+using Robust.Shared.Timing;
+
+namespace Content.Server.Explosion.EntitySystems;
+
+/// <summary>
+/// Releases a gas mixture to the atmosphere when triggered.
+/// Can also release gas over a set timespan to prevent trolling people
+/// with the instant-wall-of-pressure-inator.
+/// </summary>
+public sealed partial class ReleaseGasOnTriggerSystem : SharedReleaseGasOnTriggerSystem
+{
+    [Dependency] private readonly SharedAppearanceSystem _appearance = default!;
+    [Dependency] private readonly AtmosphereSystem _atmosphereSystem = default!;
+    [Dependency] private readonly IGameTiming _timing = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<ReleaseGasOnTriggerComponent, TriggerEvent>(OnTrigger);
+    }
+
+    /// <summary>
+    /// Shrimply sets the component to active when triggered, allowing it to release over time.
+    /// </summary>
+    private void OnTrigger(Entity<ReleaseGasOnTriggerComponent> ent, ref TriggerEvent args)
+    {
+        ent.Comp.Active = true;
+        ent.Comp.NextReleaseTime = _timing.CurTime;
+        ent.Comp.StartingTotalMoles = ent.Comp.Air.TotalMoles;
+        UpdateAppearance(ent.Owner, true);
+    }
+
+    public override void Update(float frameTime)
+    {
+        base.Update(frameTime);
+
+        var curTime = _timing.CurTime;
+        var query = EntityQueryEnumerator<ReleaseGasOnTriggerComponent>();
+
+        while (query.MoveNext(out var uid, out var comp))
+        {
+            if (!comp.Active || comp.NextReleaseTime > curTime)
+                continue;
+
+            var giverGasMix = comp.Air.Remove(comp.StartingTotalMoles * comp.RemoveFraction);
+            var environment = _atmosphereSystem.GetContainingMixture(uid, false, true);
+
+            if (environment == null)
+            {
+                UpdateAppearance(uid, false);
+                RemCompDeferred<ReleaseGasOnTriggerComponent>(uid);
+                continue;
+            }
+
+            _atmosphereSystem.Merge(environment, giverGasMix);
+            comp.NextReleaseTime += comp.ReleaseInterval;
+
+            if (comp.PressureLimit != 0 && environment.Pressure >= comp.PressureLimit ||
+                comp.Air.TotalMoles <= 0)
+            {
+                UpdateAppearance(uid, false);
+                RemCompDeferred<ReleaseGasOnTriggerComponent>(uid);
+                continue;
+            }
+
+            if (comp.ExponentialRise)
+                UpdateExponentialRise(comp, comp.RemoveFraction);
+        }
+    }
+
+    /// <summary>
+    /// Updates the RemoveFraction for exponential rise.
+    /// </summary>
+    /// <remarks>See https://www.desmos.com/calculator/fx9gfrhoim</remarks>
+    private static void UpdateExponentialRise(ReleaseGasOnTriggerComponent comp, float baseFraction)
+    {
+        comp.TimesReleased++;
+        comp.RemoveFraction = 1f - MathF.Pow(1f - baseFraction, comp.TimesReleased);
+    }
+
+    private void UpdateAppearance(Entity<AppearanceComponent?> entity, bool state)
+    {
+        if (!Resolve(entity, ref entity.Comp, false))
+            return;
+
+        _appearance.SetData(entity, ReleaseGasOnTriggerComponent.ReleaseGasOnTriggerVisuals.Key, state);
+    }
+}