unit TestCoreFutures;

interface

uses
  DUnitX.TestFramework,
  System.SysUtils, System.Generics.Collections, // Added for TObjectList if needed, not strictly for this
  System.SyncObjs,
  Myc.Signals,    // For IMycLatch, TMycLatch, IMycState, IMycSubscriber [cite: 62, 68, 53, 45]
  Myc.Core.Tasks, // For IMycTaskFactory, TMycTaskFactory [cite: 97, 113]
  Myc.Futures, Myc.Core.Futures;    // For IMycFuture, TMycInitStateFuncFuture

type
  // Helper class to notify a latch when its Notify method is called.
  TLatchNotifierSubscriber = class(TInterfacedObject, IMycSubscriber)
  private
    FGateLatch: IMycLatch;
  public
    constructor Create(AGateLatch: IMycLatch);
    // IMycSubscriber
    function Notify: Boolean; // Implements IMycSubscriber.Notify [cite: 46, 181, 299]
  end;

  [TestFixture]
  [IgnoreMemoryLeaks(true)]
  TTestMycInitStateFuncFuture = class(TObject)
  private
    FTaskFactory: IMycTaskFactory;
    FProcExecutionCount: Integer; // Counter for side effects of AProc
    FSharedCounter: Integer; // For Fan-Out test side effects
  public
    [Setup]
    procedure Setup;
    [TearDown]
    procedure TearDown;

    [Test]
    procedure Test_BasicSuccess_WithImmediateInitState;
    [Test]
    procedure Test_ChainedExecution_WithDelayedInitState;
    [Test]
    procedure Test_ExceptionInProc_HandledAsPlanned;
    [Test]
    procedure Test_GetResult_BeforeDone_RaisesException;
    [Test]
    procedure Test_FanIn_OneFutureWaitsForMultipleOthers;
    [Test]
    procedure Test_FanOut_MultipleFuturesWaitForOneTrigger;
  end;

implementation

{ TLatchNotifierSubscriber }

constructor TLatchNotifierSubscriber.Create(AGateLatch: IMycLatch);
begin
  inherited Create;
  FGateLatch := AGateLatch;
end;

function TLatchNotifierSubscriber.Notify: Boolean;
begin
  if Assigned(FGateLatch) then
  begin
    FGateLatch.Notify; // Notify the provided gate latch [cite: 80, 215, 333]
  end;
  Result := False; // This subscriber is typically one-shot for this purpose.
end;

{ TTestMycInitStateFuncFuture }

procedure TTestMycInitStateFuncFuture.Setup;
begin
  FTaskFactory := TMycTaskFactory.Create; // Create a new task factory instance for each test [cite: 113, 235, 353]
  FProcExecutionCount := 0;
  FSharedCounter := 0;
end;

procedure TTestMycInitStateFuncFuture.TearDown;
begin
  if Assigned(FTaskFactory) then
  begin
    FTaskFactory.Teardown; // Teardown the factory, this may re-raise exceptions [cite: 107, 234, 352]
    FTaskFactory := nil;
  end;
end;

procedure TTestMycInitStateFuncFuture.Test_BasicSuccess_WithImmediateInitState;
var
  LFuture: IMycFuture<Integer>;
  LInitStateAsState: IMycState; // Parameter for Create
  LResultValue: Integer;
const
  CExpectedResult = 42;
begin
  // Use TMycLatch.Null for an already set init state [cite: 71, 81, 206, 216, 324, 334]
  LInitStateAsState := TState.Null;

  LFuture := TMycInitStateFuncFuture<Integer>.Create(FTaskFactory, LInitStateAsState,
    function: Integer
    begin
      Inc(Self.FProcExecutionCount);
      Result := CExpectedResult;
    end);

  FTaskFactory.WaitFor(LFuture.Done); // Accesses IMycFuture.GetDone [cite: 110, 234, 352]

  Assert.IsTrue(LFuture.Done.IsSet, 'Future should be marked as done.'); // Accesses IMycState.IsSet [cite: 57, 194, 312]
  Assert.AreEqual(1, FProcExecutionCount, 'AProc should have been executed once.');

  LResultValue := LFuture.GetResult; // Accesses IMycFuture.GetResult
  Assert.AreEqual(CExpectedResult, LResultValue, 'GetResult returned an unexpected value.');
end;

procedure TTestMycInitStateFuncFuture.Test_ChainedExecution_WithDelayedInitState;
var
  LFuture: IMycFuture<string>;
  LInitLatch: IMycLatch;
  LResultValue: string;
const
  CExpectedResult = 'ChainCompleted';
begin
  LInitLatch := TState.CreateLatch(1); // Create an init state that is not yet set [cite: 77, 212, 330]

  LFuture := TMycInitStateFuncFuture<string>.Create(FTaskFactory, LInitLatch.State,
    function: string
    begin
      Inc(Self.FProcExecutionCount);
      Result := CExpectedResult;
    end);

  Assert.AreEqual(0, FProcExecutionCount, 'AProc should not have executed yet.');
  Assert.IsFalse(LFuture.Done.IsSet, 'Future should not be done yet.');

  LInitLatch.Notify; // Trigger the initial state [cite: 80, 215, 333]

  FTaskFactory.WaitFor(LFuture.Done);

  Assert.IsTrue(LFuture.Done.IsSet, 'Future should be marked as done after init state trigger.');
  Assert.AreEqual(1, FProcExecutionCount, 'AProc should have been executed once after init state.');

  LResultValue := LFuture.GetResult;
  Assert.AreEqual(CExpectedResult, LResultValue, 'GetResult returned an unexpected value after delayed init.');
end;

procedure TTestMycInitStateFuncFuture.Test_ExceptionInProc_HandledAsPlanned;
var
  LFuture: IMycFuture<Integer>;
  LLocalTaskFactory: IMycTaskFactory;
  LInitStateAsState: IMycState;
  LResultValue: Integer;
  LExpectedExceptionRaisedByFactory: Boolean;
const
  CExceptionMessage = 'Test exception from AProc';
begin
  LExpectedExceptionRaisedByFactory := False;
  LLocalTaskFactory := TMycTaskFactory.Create;
  LInitStateAsState := TState.Null; // Immediate execution

  LFuture := TMycInitStateFuncFuture<Integer>.Create(LLocalTaskFactory, LInitStateAsState,
    function: Integer
    begin
      Inc(Self.FProcExecutionCount);
      raise Exception.Create(CExceptionMessage);
    end);

  try
    LLocalTaskFactory.WaitFor(LFuture.Done);
  except
    on E: Exception do
    begin
      if E.Message = CExceptionMessage then
        LExpectedExceptionRaisedByFactory := True;
    end;
  end;

  Assert.IsTrue(LFuture.Done.IsSet, 'Future should be done even if AProc raised an exception.');
  Assert.AreEqual(1, FProcExecutionCount, 'AProc (which raised) should have been executed once.');

  LResultValue := LFuture.GetResult;
  Assert.AreEqual(Default(Integer), LResultValue, 'GetResult should return Default(T) when AProc raises an exception.');

  if not LExpectedExceptionRaisedByFactory then
  begin
    try
      LLocalTaskFactory.Teardown; // This should re-raise the exception [cite: 108, 234, 352]
    except
      on E: Exception do
      begin
        Assert.AreEqual(CExceptionMessage, E.Message, 'TaskFactory did not re-raise the correct exception message on Teardown.');
        LExpectedExceptionRaisedByFactory := True;
      end;
    end;
    Assert.IsTrue(LExpectedExceptionRaisedByFactory, 'TaskFactory Teardown did not raise any exception as expected.');
  end;

  if LExpectedExceptionRaisedByFactory then // Factory was torn down (implicitly or explicitly) and did its job
      LLocalTaskFactory := nil
  else if Assigned(LLocalTaskFactory) then // Teardown didn't raise as expected, or wasn't called due to earlier exception path
  begin
      LLocalTaskFactory.Teardown; // Ensure it's torn down if test logic failed to confirm exception
      LLocalTaskFactory := nil;
  end;
end;

procedure TTestMycInitStateFuncFuture.Test_GetResult_BeforeDone_RaisesException;
var
  LFuture: IMycFuture<Integer>;
  LInitLatch: IMycLatch;
begin
  LInitLatch := TState.CreateLatch(1);

  LFuture := TMycInitStateFuncFuture<Integer>.Create(FTaskFactory, LInitLatch.State,
    function: Integer
    begin
      Inc(Self.FProcExecutionCount);
      Result := 123;
    end);

  Assert.IsFalse(LFuture.Done.IsSet, 'Future should not be marked as done initially.');

  Assert.WillRaise(
    procedure
    begin
        LFuture.GetResult;
    end );

  LInitLatch.Notify;

  FTaskFactory.WaitFor(LFuture.Done);

  Assert.WillNotRaise(
    procedure
    begin
        LFuture.GetResult;
    end );
end;

procedure TTestMycInitStateFuncFuture.Test_FanIn_OneFutureWaitsForMultipleOthers;
var
  LPrerequisiteFuture1, LPrerequisiteFuture2: IMycFuture<Integer>;
  LMainFuture: IMycFuture<string>;
  LGateLatch: IMycLatch;
  LSub1, LSub2: IMycSubscriber; // To hold the TLatchNotifierSubscriber instances
  LInitStateP1, LInitStateP2: IMycLatch;
  Subscriptions: array[1..2] of TMycSubscription; // To manage subscriptions
const
  CMainFutureResult = 'AllPrerequisitesCompleted';
begin
  FProcExecutionCount := 0; // Reset for this test

  // Gate Latch: MainFuture waits for this latch, which needs 2 notifications.
  LGateLatch := TState.CreateLatch(2); // [cite: 77, 212, 330]

  // Create MainFuture, AInitState is the GateLatch's state.
  LMainFuture := TMycInitStateFuncFuture<string>.Create(FTaskFactory, LGateLatch.State,
    function: string
    begin
      Inc(Self.FProcExecutionCount, 10); // Indicate MainFuture's proc ran
      Result := CMainFutureResult;
    end);

  // Setup Prerequisite Futures
  // PrerequisiteFuture1
  LInitStateP1 := TState.CreateLatch(1); // Controllable init state for PF1
  LPrerequisiteFuture1 := TMycInitStateFuncFuture<Integer>.Create(FTaskFactory, LInitStateP1.State,
    function: Integer
    begin
      Inc(Self.FProcExecutionCount, 1); // PF1 ran
      Result := 1;
    end);
  LSub1 := TLatchNotifierSubscriber.Create(LGateLatch);
  Subscriptions[1] := LPrerequisiteFuture1.Done.Subscribe(LSub1); // Subscribe to PF1's completion [cite: 56, 188, 306]

  // PrerequisiteFuture2
  LInitStateP2 := TState.CreateLatch(1); // Controllable init state for PF2
  LPrerequisiteFuture2 := TMycInitStateFuncFuture<Integer>.Create(FTaskFactory, LInitStateP2.State,
    function: Integer
    begin
      Inc(Self.FProcExecutionCount, 1); // PF2 ran
      Result := 2;
    end);
  LSub2 := TLatchNotifierSubscriber.Create(LGateLatch);
  Subscriptions[2] := LPrerequisiteFuture2.Done.Subscribe(LSub2); // Subscribe to PF2's completion

  // --- Execution & Verification ---
  Assert.IsFalse(LMainFuture.Done.IsSet, 'MainFuture should not be done yet.');
  Assert.AreEqual(0, FProcExecutionCount, 'No AProc should have executed yet.');

  // Trigger PrerequisiteFuture1
  LInitStateP1.Notify; //
  FTaskFactory.WaitFor(LPrerequisiteFuture1.Done); // Ensure PF1 completes and notifies GateLatch
  Assert.IsFalse(LGateLatch.State.IsSet, 'GateLatch should not be set after only one prerequisite.');
  Assert.IsFalse(LMainFuture.Done.IsSet, 'MainFuture should still not be done.');
  Assert.AreEqual(1, FProcExecutionCount mod 10, 'Only PF1 AProc should have run.');


  // Trigger PrerequisiteFuture2
  LInitStateP2.Notify; //
  FTaskFactory.WaitFor(LPrerequisiteFuture2.Done); // Ensure PF2 completes and notifies GateLatch

  // Now GateLatch should be set, and MainFuture should execute
  FTaskFactory.WaitFor(LMainFuture.Done);

  Assert.IsTrue(LGateLatch.State.IsSet, 'GateLatch should be set after both prerequisites.');
  Assert.IsTrue(LMainFuture.Done.IsSet, 'MainFuture should be done now.');
  Assert.AreEqual(12, FProcExecutionCount, 'All AProcs (PF1, PF2, Main) should have run.'); // 1+1+10
  Assert.AreEqual(CMainFutureResult, LMainFuture.GetResult, 'MainFuture returned an unexpected result.');

  // Clean up subscriptions explicitly, though ARC + managed records handle much
  Subscriptions[1].Unsubscribe; // [cite: 52, 186, 304]
  Subscriptions[2].Unsubscribe; //
end;

procedure TTestMycInitStateFuncFuture.Test_FanOut_MultipleFuturesWaitForOneTrigger;
var
  LTriggerLatch: IMycLatch;
  LFutureA, LFutureB: IMycFuture<Integer>;
  LFlagFutureARan, LFlagFutureBRan: Boolean;
begin
  LFlagFutureARan := False;
  LFlagFutureBRan := False;
  Self.FSharedCounter := 0; // Reset shared counter for this test

  LTriggerLatch := TState.CreateLatch(1); // Single trigger [cite: 77, 212, 330]

  // Future A
  LFutureA := TMycInitStateFuncFuture<Integer>.Create(FTaskFactory, LTriggerLatch.State,
    function: Integer
    begin
      LFlagFutureARan := True;
      System.SyncObjs.TInterlocked.Increment(Self.FSharedCounter); // Thread-safe increment
      Result := 100;
    end);

  // Future B
  LFutureB := TMycInitStateFuncFuture<Integer>.Create(FTaskFactory, LTriggerLatch.State,
    function: Integer
    begin
      LFlagFutureBRan := True;
      System.SyncObjs.TInterlocked.Increment(Self.FSharedCounter); // Thread-safe increment
      Result := 200;
    end);

  Assert.IsFalse(LFutureA.Done.IsSet, 'FutureA should not be done yet.');
  Assert.IsFalse(LFutureB.Done.IsSet, 'FutureB should not be done yet.');
  Assert.AreEqual(0, Self.FSharedCounter, 'No future AProcs should have executed yet.');

  // Trigger the common latch
  LTriggerLatch.Notify; // [cite: 80, 215, 333]

  // Wait for both futures to complete
  FTaskFactory.WaitFor(LFutureA.Done);
  FTaskFactory.WaitFor(LFutureB.Done);

  Assert.IsTrue(LFutureA.Done.IsSet, 'FutureA should be done.');
  Assert.IsTrue(LFutureB.Done.IsSet, 'FutureB should be done.');
  Assert.IsTrue(LFlagFutureARan, 'FutureA AProc should have run.');
  Assert.IsTrue(LFlagFutureBRan, 'FutureB AProc should have run.');
  Assert.AreEqual(2, Self.FSharedCounter, 'Both future AProcs should have incremented the counter.');
  Assert.AreEqual(100, LFutureA.GetResult, 'FutureA GetResult value mismatch.');
  Assert.AreEqual(200, LFutureB.GetResult, 'FutureB GetResult value mismatch.');
end;

initialization
  // For DUnitX, attributes typically handle registration.
  // If needed for older DUnit: RegisterTest(TTestMycInitStateFuncFuture.Suite);
end.