refactor(controller): separate storeInitialFanState and storeCurrentFanState

Update storeCurrentFanState to unconditionally capture and overwrite the current fan state snapshot.
Introduce storeInitialFanState to preserve the initial snapshot on subsequent calls, and clearInitialFanState to reset it.
Add unit tests for storeInitialFanState, storeCurrentFanState, and clearInitialFanState.

Author: epicfail

internal/controller/controller.go

@@ -188,11 +188,9 @@ func (f *DefaultFanController) prepareController() (err error) {
 	return err
 }
 
+// storeCurrentFanState captures the current fan control mode and PWM value,
+// overwriting any previously saved snapshot in originalFanState.
 func (f *DefaultFanController) storeCurrentFanState() error {
-	if f.originalFanState != nil {
-		return nil
-	}
-
 	fan := f.fan
 	// store original pwm value
 	pwm, err := f.getPwm()
@@ -215,6 +213,20 @@ func (f *DefaultFanController) storeCurrentFanState() error {
 	return nil
 }
 
+// storeInitialFanState stores the initial fan state snapshot if it hasn't been captured yet.
+// Subsequent calls are no-ops to preserve the state before any controller actions.
+func (f *DefaultFanController) storeInitialFanState() error {
+	if f.originalFanState != nil {
+		return nil
+	}
+	return f.storeCurrentFanState()
+}
+
+// clearInitialFanState resets the captured initial fan state snapshot.
+func (f *DefaultFanController) clearInitialFanState() {
+	f.originalFanState = nil
+}
+
 func (f *DefaultFanController) Run(ctx context.Context) error {
 	// prepare the controller by initializing persistence and checking the fan
 	err := f.prepareController()
@@ -223,7 +235,7 @@ func (f *DefaultFanController) Run(ctx context.Context) error {
 	}
 
 	// store the current fan state to restore it when stopping the controller
-	err = f.storeCurrentFanState()
+	err = f.storeInitialFanState()
 	if err != nil {
 		return err
 	}
@@ -372,7 +384,7 @@ func (f *DefaultFanController) runInitializationIfNeeded(ctx context.Context) (m
 }
 
 func (f *DefaultFanController) RunInitialization(ctx context.Context) (map[int]float64, error) {
-	err := f.storeCurrentFanState()
+	err := f.storeInitialFanState()
 	if err != nil {
 		return nil, err
 	}

internal/controller/controller_test.go

@@ -2350,3 +2350,68 @@ func TestGetPwmSetDelay_FallsBackToGlobal(t *testing.T) {
 	// THEN
 	assert.Equal(t, globalDelay, result)
 }
+
+func TestStoreInitialFanState_OnlyCapturesOnce(t *testing.T) {
+	fan := &mockFanForRestore{
+		MockFan: MockFan{
+			ID:          "fan",
+			PWM:         100,
+			ControlMode: fans.ControlModePWM,
+		},
+		supportsControlMode: true,
+	}
+	controller := DefaultFanController{
+		fan: fan,
+	}
+
+	err := controller.storeInitialFanState()
+	assert.NoError(t, err)
+	assert.NotNil(t, controller.originalFanState)
+	assert.Equal(t, 100, controller.originalFanState.PwmValue)
+
+	// Change fan PWM to 200
+	fan.PWM = 200
+
+	// Subsequent storeInitialFanState call should not overwrite existing snapshot
+	err = controller.storeInitialFanState()
+	assert.NoError(t, err)
+	assert.Equal(t, 100, controller.originalFanState.PwmValue)
+}
+
+func TestStoreCurrentFanState_OverwritesSnapshot(t *testing.T) {
+	fan := &mockFanForRestore{
+		MockFan: MockFan{
+			ID:          "fan",
+			PWM:         100,
+			ControlMode: fans.ControlModePWM,
+		},
+		supportsControlMode: true,
+	}
+	controller := DefaultFanController{
+		fan: fan,
+	}
+
+	err := controller.storeInitialFanState()
+	assert.NoError(t, err)
+	assert.Equal(t, 100, controller.originalFanState.PwmValue)
+
+	// Change fan PWM to 200
+	fan.PWM = 200
+
+	// storeCurrentFanState should overwrite snapshot with new value
+	err = controller.storeCurrentFanState()
+	assert.NoError(t, err)
+	assert.Equal(t, 200, controller.originalFanState.PwmValue)
+}
+
+func TestClearInitialFanState_ResetsSnapshot(t *testing.T) {
+	controller := DefaultFanController{
+		originalFanState: &FanStateSnapshot{
+			PwmValue:    100,
+			ControlMode: fans.ControlModePWM,
+		},
+	}
+
+	controller.clearInitialFanState()
+	assert.Nil(t, controller.originalFanState)
+}