Crawling Part 1: The Knockdownening (#36881)

Co-authored-by: slarticodefast <161409025+slarticodefast@users.noreply.github.com>
Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>
Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>
Co-authored-by: Princess Cheeseballs <66055347+Pronana@users.noreply.github.com>
Co-authored-by: ScarKy0 <scarky0@onet.eu>

Content.Shared/Movement/Systems/MovementModStatusSystem.cs

@@ -0,0 +1,100 @@
+using Content.Shared.Movement.Components;
+using Content.Shared.Movement.Events;
+using Content.Shared.StatusEffectNew;
+using Robust.Shared.Prototypes;
+
+namespace Content.Shared.Movement.Systems;
+
+/// <summary>
+/// This handles the application of movement and friction modifiers to an entity as status effects.
+/// </summary>
+public sealed class MovementModStatusSystem : EntitySystem
+{
+    public static readonly EntProtoId StatusEffectFriction = "StatusEffectFriction";
+
+    [Dependency] private readonly MovementSpeedModifierSystem _movementSpeedModifier = default!;
+    [Dependency] private readonly StatusEffectsSystem _status = default!;
+
+    /// <inheritdoc/>
+    public override void Initialize()
+    {
+        SubscribeLocalEvent<FrictionStatusEffectComponent, StatusEffectRemovedEvent>(OnFrictionStatusEffectRemoved);
+        SubscribeLocalEvent<FrictionStatusEffectComponent, StatusEffectRelayedEvent<RefreshFrictionModifiersEvent>>(OnRefreshFrictionStatus);
+        SubscribeLocalEvent<FrictionStatusEffectComponent, StatusEffectRelayedEvent<TileFrictionEvent>>(OnRefreshTileFrictionStatus);
+    }
+
+    private void OnRefreshFrictionStatus(Entity<FrictionStatusEffectComponent> ent, ref StatusEffectRelayedEvent<RefreshFrictionModifiersEvent> args)
+    {
+        var ev = args.Args;
+        ev.ModifyFriction(ent.Comp.FrictionModifier);
+        ev.ModifyAcceleration(ent.Comp.AccelerationModifier);
+        args.Args = ev;
+    }
+
+    private void OnRefreshTileFrictionStatus(Entity<FrictionStatusEffectComponent> ent, ref StatusEffectRelayedEvent<TileFrictionEvent> args)
+    {
+        var ev = args.Args;
+        ev.Modifier *= ent.Comp.FrictionModifier;
+        args.Args = ev;
+    }
+
+    /// <summary>
+    ///     Applies a friction de-buff to the player.
+    /// </summary>
+    public bool TryFriction(EntityUid uid,
+        TimeSpan time,
+        bool refresh,
+        float friction,
+        float acceleration)
+    {
+        if (time <= TimeSpan.Zero)
+            return false;
+
+        if (refresh)
+        {
+            return _status.TryUpdateStatusEffectDuration(uid, StatusEffectFriction, out var status, time)
+                   && TrySetFrictionStatus(status.Value, friction, acceleration, uid);
+        }
+        else
+        {
+            return _status.TryAddStatusEffectDuration(uid, StatusEffectFriction, out var status, time)
+                   && TrySetFrictionStatus(status.Value, friction, acceleration, uid);
+        }
+    }
+
+    /// <summary>
+    /// Sets the friction status modifiers for a status effect.
+    /// </summary>
+    /// <param name="status">The status effect entity we're modifying.</param>
+    /// <param name="friction">The friction modifier we're applying.</param>
+    /// <param name="entity">The entity the status effect is attached to that we need to refresh.</param>
+    private bool TrySetFrictionStatus(Entity<FrictionStatusEffectComponent?> status, float friction, EntityUid entity)
+    {
+        return TrySetFrictionStatus(status, friction, friction, entity);
+    }
+
+    /// <summary>
+    /// Sets the friction status modifiers for a status effect.
+    /// </summary>
+    /// <param name="status">The status effect entity we're modifying.</param>
+    /// <param name="friction">The friction modifier we're applying.</param>
+    /// <param name="acceleration">The acceleration modifier we're applying</param>
+    /// <param name="entity">The entity the status effect is attached to that we need to refresh.</param>
+    private bool TrySetFrictionStatus(Entity<FrictionStatusEffectComponent?> status, float friction, float acceleration, EntityUid entity)
+    {
+        if (!Resolve(status, ref status.Comp, false))
+            return false;
+
+        status.Comp.FrictionModifier = friction;
+        status.Comp.AccelerationModifier = acceleration;
+        Dirty(status);
+
+        _movementSpeedModifier.RefreshFrictionModifiers(entity);
+        return true;
+    }
+
+    private void OnFrictionStatusEffectRemoved(Entity<FrictionStatusEffectComponent> entity, ref StatusEffectRemovedEvent args)
+    {
+        TrySetFrictionStatus(entity!, 1f, args.Target);
+    }
+}