Merge pull request #130 from xodial/xodial/on-start-stop

feat: add OnStart/OnStop to LogicBlock

Chickensoft.LogicBlocks.Tests/test/fixtures/FakeLogicBlock.cs

@@ -156,6 +156,10 @@ public static class Output {
 public partial class FakeLogicBlock : LogicBlock<FakeLogicBlock.State> {
   public Func<Transition>? InitialState { get; set; }
 
+  public Action? OnStartCalled { get; set; }
+
+  public Action? OnStopCalled { get; set; }
+
   public List<Exception> Exceptions { get; } = new();
 
   public override Transition GetInitialState() =>
@@ -167,6 +171,10 @@ public FakeLogicBlock(Action<Exception>? onError = null) {
     _onError = onError;
   }
 
+  public override void OnStart() => OnStartCalled?.Invoke();
+
+  public override void OnStop() => OnStopCalled?.Invoke();
+
   ~FakeLogicBlock() { }
 
   protected override void HandleError(Exception e) {

Chickensoft.LogicBlocks.Tests/test/src/LogicBlockTest.cs

@@ -327,20 +327,24 @@ public void StartsManuallyAndIgnoresStartWhenProcessing() {
   [Fact]
   public void StartEntersState() {
     var enterCalled = false;
+    var onStartCalled = false;
     var context = new FakeContext();
     var block = new FakeLogicBlock() {
       InitialState = () =>
         new FakeLogicBlock.Transition(new FakeLogicBlock.State.OnEnterState() {
           Callback = (previous) => enterCalled = true
-        })
+        }),
+      OnStartCalled = () => onStartCalled = true
     };
 
     enterCalled.ShouldBeFalse();
+    onStartCalled.ShouldBeFalse();
 
     block.Start();
     block.Start(); // Should do nothing.
 
     enterCalled.ShouldBeTrue();
+    onStartCalled.ShouldBeTrue();
   }
 
   [Fact]
@@ -357,31 +361,50 @@ public void StartDoesNothingIfProcessing() {
     logic.Value.ShouldBeOfType<FakeLogicBlock.State.StateA>();
   }
 
+  [Fact]
+  public void ImplicitStartCallsOnStart() {
+    var onStartCalled = false;
+    var logic = new FakeLogicBlock() {
+      OnStartCalled = () => onStartCalled = true
+    };
+
+    logic.Input(new FakeLogicBlock.Input.InputOne(2, 3));
+
+    onStartCalled.ShouldBeTrue();
+  }
+
   [Fact]
   public void StopExitsState() {
     var exitCalled = false;
+    var onStopCalled = false;
     var context = new FakeContext();
     var block = new FakeLogicBlock() {
       InitialState = () => new FakeLogicBlock.Transition(
         new FakeLogicBlock.State.OnExitState() {
           Callback = (previous) => exitCalled = true
         }
-      )
+      ),
+      OnStopCalled = () => onStopCalled = true
     };
 
     exitCalled.ShouldBeFalse();
+    onStopCalled.ShouldBeFalse();
 
     block.Start();
     block.Stop();
     block.Stop(); // Should do nothing.
 
     exitCalled.ShouldBeTrue();
+    onStopCalled.ShouldBeTrue();
   }
 
   [Fact]
   public void StopDoesNothingIfProcessing() {
+    var onStopCalled = false;
     var context = new FakeContext();
-    var logic = new FakeLogicBlock();
+    var logic = new FakeLogicBlock() {
+      OnStopCalled = () => onStopCalled = true
+    };
     logic.InitialState = () => new FakeLogicBlock.Transition(
       new FakeLogicBlock.State.OnExitState() {
         Callback = (previous) => logic.Stop()
@@ -390,6 +413,8 @@ public void StopDoesNothingIfProcessing() {
 
     logic.Input(new FakeLogicBlock.Input.InputOne(2, 3));
     logic.IsStarted.ShouldBeTrue();
+
+    onStopCalled.ShouldBeFalse();
   }
 
   [Fact]

Chickensoft.LogicBlocks/src/LogicBlock.cs

@@ -226,10 +226,18 @@ public void Start() {
     Flush();
   }
 
+  /// <summary>
+  /// Called when the logic block is started. Override this method to
+  /// perform any initialization logic.
+  /// </summary>
+  public virtual void OnStart() { }
+
   /// <inheritdoc />
   public void Stop() {
     if (IsProcessing || _value is null) { return; }
 
+    OnStop();
+
     // Repeatedly exit and detach the current state until there is none.
     ChangeState(null);
 
@@ -239,6 +247,12 @@ public void Stop() {
     _value = null;
   }
 
+  /// <summary>
+  /// Called when the logic block is stopped. Override this method to
+  /// perform any cleanup logic.
+  /// </summary>
+  public virtual void OnStop() { }
+
   /// <inheritdoc />
   public TState ForceReset(TState state) {
     if (IsProcessing) {
@@ -386,6 +400,8 @@ internal TState ProcessInputs<TInputType>(
 
     if (_value is null) {
       // No state yet. Let's get the first state going!
+      OnStart();
+      Blackboard.InstantiateAnyMissingSavedData();
       ChangeState(RestoredState as TState ?? GetInitialState().State);
       RestoredState = null;
     }
@@ -500,13 +516,7 @@ TState fallback
   /// </summary>
   /// <returns>The resting state.</returns>
   [MethodImpl(MethodImplOptions.AggressiveInlining)]
-  private TState Flush() {
-    if (_value is null) {
-      Blackboard.InstantiateAnyMissingSavedData();
-    }
-
-    return ProcessInputs<int>();
-  }
+  private TState Flush() => ProcessInputs<int>();
 
   /// <summary>
   /// Determines if two logic blocks are equivalent. Logic blocks are equivalent