Mobstate Refactor (#13389)

Refactors mobstate and moves mob health thresholds to their own component

Co-authored-by: DrSmugleaf <drsmugleaf@gmail.com>

Content.Shared/Mobs/Systems/MobStateSystem.StateMachine.cs

@@ -0,0 +1,130 @@
+using Content.Shared.Database;
+using Content.Shared.Mobs.Components;
+
+namespace Content.Shared.Mobs.Systems;
+
+public partial class MobStateSystem
+{
+    #region Public API
+
+    /// <summary>
+    /// Check if an Entity can be set to a particular MobState
+    /// </summary>
+    /// <param name="entity">Target Entity</param>
+    /// <param name="mobState">MobState to check</param>
+    /// <param name="component">MobState Component owned by the target</param>
+    /// <returns>If the entity can be set to that MobState</returns>
+    public bool HasState(EntityUid entity, MobState mobState, MobStateComponent? component = null)
+    {
+        return Resolve(entity, ref component, false) && component.AllowedStates.Contains(mobState);
+    }
+
+    /// <summary>
+    /// Run a MobState update check. This will trigger update events if the state has been changed.
+    /// </summary>
+    /// <param name="entity">Target Entity we want to change the MobState of</param>
+    /// <param name="component">MobState Component attached to the entity</param>
+    /// <param name="origin">Entity that caused the state update (if applicable)</param>
+    public void UpdateMobState(EntityUid entity, MobStateComponent? component = null, EntityUid? origin = null)
+    {
+        if (!Resolve(entity, ref component))
+            return;
+
+        var ev = new UpdateMobStateEvent {Target = entity, Component = component, Origin = origin};
+        RaiseLocalEvent(entity, ref ev);
+        ChangeState(entity, component, ev.State);
+    }
+
+    /// <summary>
+    /// Change the MobState and trigger MobState update events
+    /// </summary>
+    /// <param name="entity">Target Entity we want to change the MobState of</param>
+    /// <param name="mobState">The new MobState we want to set</param>
+    /// <param name="component">MobState Component attached to the entity</param>
+    /// <param name="origin">Entity that caused the state update (if applicable)</param>
+    public void ChangeMobState(EntityUid entity, MobState mobState, MobStateComponent? component = null,
+        EntityUid? origin = null)
+    {
+        if (!Resolve(entity, ref component))
+            return;
+
+        var ev = new UpdateMobStateEvent {Target = entity, Component = component, Origin = origin};
+        RaiseLocalEvent(entity, ref ev);
+        ChangeState(entity, component, ev.State);
+    }
+
+    #endregion
+
+    #region Virtual API
+
+    /// <summary>
+    /// Called when a new MobState is entered.
+    /// </summary>
+    /// <param name="entity">The owner of the MobState Component</param>
+    /// <param name="component">MobState Component owned by the target</param>
+    /// <param name="state">The new MobState</param>
+    protected virtual void OnEnterState(EntityUid entity, MobStateComponent component, MobState state)
+    {
+        OnStateEnteredSubscribers(entity, component, state);
+    }
+
+    /// <summary>
+    ///  Called when this entity changes MobState
+    /// </summary>
+    /// <param name="entity">The owner of the MobState Component</param>
+    /// <param name="component">MobState Component owned by the target</param>
+    /// <param name="oldState">The previous MobState</param>
+    /// <param name="newState">The new MobState</param>
+    protected virtual void OnStateChanged(EntityUid entity, MobStateComponent component, MobState oldState,
+        MobState newState)
+    {
+    }
+
+    /// <summary>
+    /// Called when a new MobState is exited.
+    /// </summary>
+    /// <param name="entity">The owner of the MobState Component</param>
+    /// <param name="component">MobState Component owned by the target</param>
+    /// <param name="state">The old MobState</param>
+    protected virtual void OnExitState(EntityUid entity, MobStateComponent component, MobState state)
+    {
+        OnStateExitSubscribers(entity, component, state);
+    }
+
+    #endregion
+
+    #region Private Implementation
+
+    //Actually change the MobState
+    private void ChangeState(EntityUid target, MobStateComponent component, MobState newState, EntityUid? origin = null)
+    {
+        var oldState = component.CurrentState;
+        //make sure we are allowed to enter the new state
+        if (oldState == newState || !component.AllowedStates.Contains(newState))
+            return;
+
+        OnExitState(target, component, oldState);
+        component.CurrentState = newState;
+        OnEnterState(target, component, newState);
+
+        var ev = new MobStateChangedEvent(target, component, oldState, newState, origin);
+        OnStateChanged(target, component, oldState, newState);
+        RaiseLocalEvent(target, ev, true);
+        _adminLogger.Add(LogType.Damaged, oldState == MobState.Alive ? LogImpact.Low : LogImpact.Medium,
+            $"{ToPrettyString(component.Owner):user} state changed from {oldState} to {newState}");
+        Dirty(component);
+    }
+
+    #endregion
+}
+
+/// <summary>
+/// Event that gets triggered when we want to update the mobstate. This allows for systems to override MobState changes
+/// </summary>
+/// <param name="Target">The Entity whose MobState is changing</param>
+/// <param name="Component">The MobState Component owned by the Target</param>
+/// <param name="State">The new MobState we want to set</param>
+/// <param name="Origin">Entity that caused the state update (if applicable)</param>
+[ByRefEvent]
+public record struct UpdateMobStateEvent(EntityUid Target, MobStateComponent Component, MobState State,
+    EntityUid? Origin = null);