Add TurnSignalLight function block

.github/workflows/ci.yml

@@ -28,6 +28,7 @@ jobs:
             src/Functions/TimingUtils.st \
             src/FunctionBlocks/TrafficLight.st \
             src/FunctionBlocks/PedestrianLight.st \
+            src/FunctionBlocks/TurnSignalLight.st \
             src/FunctionBlocks/VehicleDetector.st \
             src/FunctionBlocks/TrafficLogger.st \
             src/Programs/IntersectionController.st \
@@ -92,3 +93,12 @@ jobs:
             src/Interfaces/IControllable.st \
             src/FunctionBlocks/TrafficLight.st \
             --test tests/test_interface.st
+
+      - name: Run turn signal tests
+        run: |
+          strucpp \
+            src/DataTypes/TrafficTypes.st \
+            src/Interfaces/IControllable.st \
+            src/FunctionBlocks/TrafficLight.st \
+            src/FunctionBlocks/TurnSignalLight.st \
+            --test tests/test_turn_signal.st

src/FunctionBlocks/TurnSignalLight.st

@@ -0,0 +1,60 @@
+(* TurnSignalLight Function Block
+   Extends TrafficLight with a dedicated turn signal arrow.
+   The turn arrow activates during the RED-to-GREEN transition. *)
+
+FUNCTION_BLOCK TurnSignalLight EXTENDS TrafficLight
+  VAR_INPUT
+    turnEnabled   : BOOL := TRUE;
+    turnDuration  : TIME := T#10s;
+  END_VAR
+
+  VAR_OUTPUT
+    turnArrowOn   : BOOL := FALSE;
+    turnDirection : INT := 0;   (* 0=none, 1=left, 2=right *)
+  END_VAR
+
+  VAR
+    turnTimer    : TON;
+    turnActive   : BOOL := FALSE;
+    prevState    : TrafficState := TrafficState.RED;
+  END_VAR
+
+  METHOD PUBLIC SetLeftTurn : BOOL
+    turnDirection := 1;
+    SetLeftTurn := TRUE;
+  END_METHOD
+
+  METHOD PUBLIC SetRightTurn : BOOL
+    turnDirection := 2;
+    SetRightTurn := TRUE;
+  END_METHOD
+
+  METHOD PUBLIC IsTurnActive : BOOL
+    IsTurnActive := turnArrowOn;
+  END_METHOD
+
+  (* Run parent TrafficLight state machine first *)
+  SUPER^();
+
+  (* Detect RED-to-GREEN transition to activate turn signal *)
+  IF prevState = TrafficState.RED AND currentState = TrafficState.GREEN THEN
+    IF turnEnabled AND turnDirection > 0 THEN
+      turnActive := TRUE;
+    END_IF;
+  END_IF;
+
+  (* Run turn signal timer *)
+  turnTimer(IN := turnActive, PT := turnDuration);
+  IF turnTimer.Q THEN
+    turnActive := FALSE;
+    turnTimer(IN := FALSE, PT := turnDuration);
+  END_IF;
+
+  (* Turn off arrow when not in GREEN phase *)
+  IF currentState <> TrafficState.GREEN THEN
+    turnActive := FALSE;
+  END_IF;
+
+  turnArrowOn := turnActive;
+  prevState := currentState;
+END_FUNCTION_BLOCK

tests/test_turn_signal.st

@@ -0,0 +1,86 @@
+(* Tests for the TurnSignalLight function block *)
+
+TEST 'TurnSignalLight starts with arrow off'
+  VAR ts : TurnSignalLight; END_VAR
+
+  ts();
+  ASSERT_FALSE(ts.turnArrowOn, 'Arrow should be off initially');
+  ASSERT_EQ(ts.turnDirection, 0, 'No direction set');
+END_TEST
+
+TEST 'TurnSignalLight SetLeftTurn sets direction'
+  VAR ts : TurnSignalLight; END_VAR
+
+  ts.SetLeftTurn();
+  ASSERT_EQ(ts.turnDirection, 1, 'Should be left turn');
+END_TEST
+
+TEST 'TurnSignalLight SetRightTurn sets direction'
+  VAR ts : TurnSignalLight; END_VAR
+
+  ts.SetRightTurn();
+  ASSERT_EQ(ts.turnDirection, 2, 'Should be right turn');
+END_TEST
+
+TEST 'TurnSignalLight activates on RED to GREEN transition'
+  VAR
+    ts     : TurnSignalLight;
+    timing : PhaseTiming;
+  END_VAR
+
+  timing.redDuration := T#100ms;
+  timing.greenDuration := T#200ms;
+  timing.yellowDuration := T#50ms;
+  ts.timing := timing;
+  ts.turnDuration := T#80ms;
+  ts.SetLeftTurn();
+
+  (* Start in RED *)
+  ts();
+  ASSERT_EQ(ts.currentState, TrafficState.RED, 'Start in RED');
+  ASSERT_FALSE(ts.turnArrowOn, 'Arrow off during RED');
+
+  (* Transition to GREEN *)
+  ADVANCE_TIME(T#50ms);
+  ts();
+  ADVANCE_TIME(T#50ms);
+  ts();
+  ASSERT_EQ(ts.currentState, TrafficState.GREEN, 'Now GREEN');
+  ASSERT_TRUE(ts.turnArrowOn, 'Arrow on during GREEN after RED');
+END_TEST
+
+TEST 'TurnSignalLight arrow turns off after duration'
+  VAR
+    ts     : TurnSignalLight;
+    timing : PhaseTiming;
+  END_VAR
+
+  timing.redDuration := T#100ms;
+  timing.greenDuration := T#300ms;
+  timing.yellowDuration := T#50ms;
+  ts.timing := timing;
+  ts.turnDuration := T#80ms;
+  ts.SetLeftTurn();
+
+  (* Get to GREEN *)
+  ts();
+  ADVANCE_TIME(T#50ms);
+  ts();
+  ADVANCE_TIME(T#50ms);
+  ts();
+  ASSERT_TRUE(ts.turnArrowOn, 'Arrow should be on');
+
+  (* Wait for turn duration to expire *)
+  ADVANCE_TIME(T#40ms);
+  ts();
+  ADVANCE_TIME(T#40ms);
+  ts();
+  ASSERT_FALSE(ts.turnArrowOn, 'Arrow should be off after duration');
+END_TEST
+
+TEST 'TurnSignalLight IsTurnActive method'
+  VAR ts : TurnSignalLight; END_VAR
+
+  ts();
+  ASSERT_FALSE(ts.IsTurnActive(), 'Not active initially');
+END_TEST