FSM now takes a type parameter so that we can use FSM with other classes.

Shared/FSM.cs

@@ -2,17 +2,17 @@
 using System.Collections.Generic;
 
 namespace SemiColinGames {
-  public interface IState {
+  public interface IState<T> {
     public void Enter();
-    public string? Update(NPC npc, float modelTime, AABB[] collisionTargets);
+    public string? Update(T obj, float modelTime, AABB[] collisionTargets);
   }
 
-  public class FSM {
+  public class FSM<T> {
     float timeInState = 0f;
-    Dictionary<string, IState> states;
-    IState state;
+    Dictionary<string, IState<T>> states;
+    IState<T> state;
 
-    public FSM(Dictionary<string, IState> states, string initial) {
+    public FSM(Dictionary<string, IState<T>> states, string initial) {
       this.states = states;
       StateName = initial;
       Transition(StateName);
@@ -20,9 +20,9 @@ namespace SemiColinGames {
 
     public string StateName { get; private set; }
 
-    public void Update(NPC npc, float modelTime, AABB[] collisionTargets) {
+    public void Update(T obj, float modelTime, AABB[] collisionTargets) {
       timeInState += modelTime;
-      string? newState = state.Update(npc, modelTime, collisionTargets);
+      string? newState = state.Update(obj, modelTime, collisionTargets);
       if (newState != null) {
         Transition(newState);
       }
@@ -32,7 +32,7 @@ namespace SemiColinGames {
       Debug.WriteLine("{0} -> {1} @ {2}", StateName, state, timeInState);
       timeInState = 0f;
       StateName = state;
-      IState newState = states[state];
+      IState<T> newState = states[state];
       this.state = newState;
       this.state.Enter();
     }

Shared/NPC.cs

@@ -3,7 +3,7 @@ using Microsoft.Xna.Framework.Graphics;
 using System.Collections.Generic;
 
 namespace SemiColinGames {
-  class IdleState : IState {
+  class IdleState : IState<NPC> {
     float timeInState = 0;
 
     public void Enter() {
@@ -20,7 +20,7 @@ namespace SemiColinGames {
     }
   }
 
-  class RunState : IState {
+  class RunState : IState<NPC> {
     public void Enter() {}
 
     public string? Update(NPC npc, float modelTime, AABB[] collisionTargets) {
@@ -50,11 +50,11 @@ namespace SemiColinGames {
     private const int spriteHeight = 81;
     private const int spriteCenterYOffset = 2;
 
-    private FSM fsm;
+    private FSM<NPC> fsm;
 
     public NPC(Point position) {
       Position = position;
-      fsm = new FSM(new Dictionary<string, IState> {
+      fsm = new FSM<NPC>(new Dictionary<string, IState<NPC>> {
         { "idle", new IdleState() },
         { "run", new RunState() }
       }, "run");