Refactored to use MVC layout in service

src/modules/LightSwitch/LightSwitchService/LightSwitchService.cpp

@@ -11,19 +11,23 @@
 #include <logger/logger_settings.h>
 #include <logger/logger.h>
 #include <utils/logger_helper.h>
+#include "LightSwitchStateManager.h"
+#include <LightSwitchUtils.h>
 
 SERVICE_STATUS g_ServiceStatus = {};
 SERVICE_STATUS_HANDLE g_StatusHandle = nullptr;
 HANDLE g_ServiceStopEvent = nullptr;
 extern int g_lastUpdatedDay = -1;
 static ScheduleMode prevMode = ScheduleMode::Off;
-static std::wstring prevLat, prevLon;
+static std::wstring prevLat = L"0";
+static std::wstring  prevLon = L"0";
 static int prevMinutes = -1;
 static bool lastOverrideStatus = false;
 
 VOID WINAPI ServiceMain(DWORD argc, LPTSTR* argv);
 VOID WINAPI ServiceCtrlHandler(DWORD dwCtrl);
 DWORD WINAPI ServiceWorkerThread(LPVOID lpParam);
+void ApplyTheme(bool shouldBeLight);
 
 // Entry point for the executable
 int _tmain(int argc, TCHAR* argv[])
@@ -124,31 +128,66 @@ VOID WINAPI ServiceCtrlHandler(DWORD dwCtrl)
     }
 }
 
-static void update_sun_times(auto& settings)
+void ApplyTheme(bool shouldBeLight)
 {
-    double latitude = std::stod(settings.latitude);
-    double longitude = std::stod(settings.longitude);
+    const auto& s = LightSwitchSettings::settings();
+
+    if (s.changeSystem)
+    {
+        bool isSystemCurrentlyLight = GetCurrentSystemTheme();
+        if (shouldBeLight != isSystemCurrentlyLight)
+        {
+            SetSystemTheme(shouldBeLight);
+            Logger::info(L"[LightSwitchService] Changed system theme to {}.", shouldBeLight ? L"light" : L"dark");
+        }
+    }
+
+    if (s.changeApps)
+    {
+        bool isAppsCurrentlyLight = GetCurrentAppsTheme();
+        if (shouldBeLight != isAppsCurrentlyLight)
+        {
+            SetAppsTheme(shouldBeLight);
+            Logger::info(L"[LightSwitchService] Changed apps theme to {}.", shouldBeLight ? L"light" : L"dark");
+        }
+    }
+}
+
+static void DetectAndHandleExternalThemeChange(LightSwitchStateManager stateManager)
+{
+    const auto& s = LightSwitchSettings::settings();
+    if (s.scheduleMode == ScheduleMode::Off)
+        return;
 
     SYSTEMTIME st;
     GetLocalTime(&st);
+    int nowMinutes = st.wHour * 60 + st.wMinute;
 
-    SunTimes newTimes = CalculateSunriseSunset(latitude, longitude, st.wYear, st.wMonth, st.wDay);
+    // Compute effective boundaries (with offsets if needed)
+    int effectiveLight = s.lightTime;
+    int effectiveDark = s.darkTime;
 
-    int newLightTime = newTimes.sunriseHour * 60 + newTimes.sunriseMinute;
-    int newDarkTime = newTimes.sunsetHour * 60 + newTimes.sunsetMinute;
-    try
+    if (s.scheduleMode == ScheduleMode::SunsetToSunrise)
     {
-        auto values = PowerToysSettings::PowerToyValues::load_from_settings_file(L"LightSwitch");
-        values.add_property(L"lightTime", newLightTime);
-        values.add_property(L"darkTime", newDarkTime);
-        values.save_to_settings_file();
-
-        Logger::info(L"[LightSwitchService] Updated sun times and saved to config.");
+        effectiveLight = (s.lightTime + s.sunrise_offset) % 1440;
+        effectiveDark = (s.darkTime + s.sunset_offset) % 1440;
     }
-    catch (const std::exception& e)
+
+    // Use shared helper (handles wraparound logic)
+    bool shouldBeLight = ShouldBeLight(nowMinutes, effectiveLight, effectiveDark);
+
+    // Compare current system/apps theme
+    bool currentSystemLight = GetCurrentSystemTheme();
+    bool currentAppsLight = GetCurrentAppsTheme();
+
+    bool systemMismatch = s.changeSystem && (currentSystemLight != shouldBeLight);
+    bool appsMismatch = s.changeApps && (currentAppsLight != shouldBeLight);
+
+    // Trigger manual override only if mismatch and not already active
+    if ((systemMismatch || appsMismatch) && !stateManager.GetState().isManualOverride)
     {
-        std::wstring wmsg(e.what(), e.what() + strlen(e.what()));
-        Logger::error(L"[LightSwitchService] Exception during sun time update: {}", wmsg);
+        Logger::info(L"[LightSwitchService] External theme change detected (Windows Settings). Entering manual override mode.");
+        stateManager.OnManualOverride();
     }
 }
 
@@ -162,307 +201,98 @@ DWORD WINAPI ServiceWorkerThread(LPVOID lpParam)
     Logger::info(L"[LightSwitchService] Worker thread starting...");
     Logger::info(L"[LightSwitchService] Parent PID: {}", parentPid);
 
+    // ────────────────────────────────────────────────────────────────
+    // Initialization
+    // ────────────────────────────────────────────────────────────────
+    static LightSwitchStateManager stateManager;
+
     LightSwitchSettings::instance().InitFileWatcher();
 
     HANDLE hManualOverride = OpenEventW(SYNCHRONIZE | EVENT_MODIFY_STATE, FALSE, L"POWERTOYS_LIGHTSWITCH_MANUAL_OVERRIDE");
+    HANDLE hSettingsChanged = LightSwitchSettings::instance().GetSettingsChangedEvent();
 
     LightSwitchSettings::instance().LoadSettings();
-    auto& settings = LightSwitchSettings::instance().settings();
+    const auto& settings = LightSwitchSettings::instance().settings();
 
     SYSTEMTIME st;
     GetLocalTime(&st);
     int nowMinutes = st.wHour * 60 + st.wMinute;
 
-    // Handle initial theme application if necessary
-    if (settings.scheduleMode != ScheduleMode::Off)
-    {
-        Logger::info(L"[LightSwitchService] Schedule mode is set to {}. Applying theme if necessary.", settings.scheduleMode);
-        LightSwitchSettings::instance().ApplyThemeIfNecessary();
-    }
-    else
-    {
-        Logger::info(L"[LightSwitchService] Schedule mode is set to Off.");
-    }
+    Logger::info(L"[LightSwitchService] Initialized at {:02d}:{:02d}.", st.wHour, st.wMinute);
+    stateManager.OnTick(nowMinutes);
 
-    g_lastUpdatedDay = st.wDay;
-    Logger::info(L"[LightSwitchService] Initializing g_lastUpdatedDay to {}.", g_lastUpdatedDay);
-    ULONGLONG lastSettingsReload = 0;
-
-    // ticker loop
+    // ────────────────────────────────────────────────────────────────
+    // Worker Loop
+    // ────────────────────────────────────────────────────────────────
     for (;;)
     {
-        HANDLE waits[2] = { g_ServiceStopEvent, hParent };
-        DWORD count = hParent ? 2 : 1;
-        bool skipRest = false;
-
-        const auto& settings = LightSwitchSettings::instance().settings();
-
-        // If the mode is set to Off, suspend the scheduler and avoid extra work
-        if (settings.scheduleMode == ScheduleMode::Off)
-        {
-            Logger::info(L"[LightSwitchService] Schedule mode is OFF - suspending scheduler but keeping service alive.");
-
-            if (!hManualOverride)
-                hManualOverride = OpenEventW(SYNCHRONIZE | EVENT_MODIFY_STATE, FALSE, L"POWERTOYS_LIGHTSWITCH_MANUAL_OVERRIDE");
-
-            HANDLE waitsOff[4];
-            DWORD countOff = 0;
-            waitsOff[countOff++] = g_ServiceStopEvent;
-            if (hParent)
-                waitsOff[countOff++] = hParent;
-            if (hManualOverride)
-                waitsOff[countOff++] = hManualOverride;
-            waitsOff[countOff++] = LightSwitchSettings::instance().GetSettingsChangedEvent();
-
-            for (;;)
-            {
-                DWORD wait = WaitForMultipleObjects(countOff, waitsOff, FALSE, INFINITE);
-
-                if (wait == WAIT_OBJECT_0)
-                {
-                    Logger::info(L"[LightSwitchService] Stop event triggered - exiting worker loop.");
-                    goto cleanup;
-                }
-                if (hParent && wait == WAIT_OBJECT_0 + 1)
-                {
-                    Logger::info(L"[LightSwitchService] Parent exited - stopping service.");
-                    goto cleanup;
-                }
-
-                if (wait == WAIT_OBJECT_0 + (hParent ? 2 : 1))
-                {
-                    Logger::info(L"[LightSwitchService] Manual override received while schedule OFF.");
-                    ResetEvent(hManualOverride);
-                    continue;
-                }
-
-                if (wait == WAIT_OBJECT_0 + (hParent ? 3 : 2))
-                {
-                    Logger::trace(L"[LightSwitchService] Settings change event triggered, reloading settings...");
-                    ResetEvent(LightSwitchSettings::instance().GetSettingsChangedEvent());
-                    const auto& newSettings = LightSwitchSettings::instance().settings();
-                    lastSettingsReload = GetTickCount64();
-
-                    if (newSettings.scheduleMode != ScheduleMode::Off)
-                    {
-                        Logger::info(L"[LightSwitchService] Schedule re-enabled, resuming normal loop.");
-                        break;
-                    }
-                }
-            }
-
-            continue;
-        }
-
-        bool scheduleJustEnabled = (prevMode == ScheduleMode::Off && settings.scheduleMode != ScheduleMode::Off);
-        prevMode = settings.scheduleMode;
-
-        ULONGLONG nowTick = GetTickCount64();
-        bool recentSettingsReload = (nowTick - lastSettingsReload < 2000);
-
-        Logger::debug(L"[LightSwitchService] Current g_lastUpdatedDay value = {}.", g_lastUpdatedDay);
-
-        // Manual Override Detection Logic
-        bool manualOverrideActive = (hManualOverride && WaitForSingleObject(hManualOverride, 0) == WAIT_OBJECT_0);
-
-        if (manualOverrideActive != lastOverrideStatus)
-        {
-            Logger::debug(L"[LightSwitchService] Manual override active = {}", manualOverrideActive);
-            lastOverrideStatus = manualOverrideActive;
-        }
-
-        if (settings.scheduleMode != ScheduleMode::Off && !recentSettingsReload && !scheduleJustEnabled && !manualOverrideActive)
-        {
-            bool currentSystemTheme = GetCurrentSystemTheme();
-            bool currentAppsTheme = GetCurrentAppsTheme();
-
-            SYSTEMTIME st;
-            GetLocalTime(&st);
-            int nowMinutes = st.wHour * 60 + st.wMinute;
-
-            int lightBoundary = 0;
-            int darkBoundary = 0;
-
-            if (settings.scheduleMode == ScheduleMode::SunsetToSunrise)
-            {
-                lightBoundary = (settings.lightTime + settings.sunrise_offset) % 1440;
-                darkBoundary = (settings.darkTime + settings.sunset_offset) % 1440;
-            }
-            else
-            {
-                lightBoundary = settings.lightTime;
-                darkBoundary = settings.darkTime;
-            }
-
-            bool shouldBeLight = (lightBoundary < darkBoundary) ? (nowMinutes >= lightBoundary && nowMinutes < darkBoundary) : (nowMinutes >= lightBoundary || nowMinutes < darkBoundary);
-
-            Logger::debug(L"[LightSwitchService] shouldBeLight = {}", shouldBeLight);
-
-            bool systemMismatch = settings.changeSystem && (currentSystemTheme != shouldBeLight);
-            bool appsMismatch = settings.changeApps && (currentAppsTheme != shouldBeLight);
-
-            if (systemMismatch || appsMismatch)
-            {
-              // Make sure this is not because we crossed a boundary
-              bool crossedBoundary = false;
-              if (prevMinutes != -1)
-              {
-                  if (nowMinutes < prevMinutes)
-                  {
-                      // wrapped around midnight
-                      crossedBoundary = (prevMinutes <= lightBoundary || nowMinutes >= lightBoundary) ||
-                                        (prevMinutes <= darkBoundary || nowMinutes >= darkBoundary);
-                  }
-                  else
-                  {
-                      crossedBoundary = (prevMinutes < lightBoundary && nowMinutes >= lightBoundary) ||
-                                        (prevMinutes < darkBoundary && nowMinutes >= darkBoundary);
-                  }
-              }
-
-              if (crossedBoundary)
-              {
-                  Logger::info(L"[LightSwitchService] Missed boundary detected. Applying theme instead of triggering manual override.");
-                  LightSwitchSettings::instance().ApplyThemeIfNecessary();
-              }
-              else
-              {
-                  Logger::info(L"[LightSwitchService] External {} theme change detected, enabling manual override.",
-                               systemMismatch && appsMismatch ? L"system/app" :
-                               systemMismatch                 ? L"system" :
-                                                                L"app");
-                  SetEvent(hManualOverride);
-                  skipRest = true;
-              }
-            }
-        }
-        else
-        {
-            Logger::debug(L"[LightSwitchService] Skipping external-change detection (schedule off, recent reload, or just enabled).");
-        }
-        
+        HANDLE waits[4];
+        DWORD count = 0;
+        waits[count++] = g_ServiceStopEvent;
+        if (hParent)
+            waits[count++] = hParent;
         if (hManualOverride)
-            manualOverrideActive = (WaitForSingleObject(hManualOverride, 0) == WAIT_OBJECT_0);
+            waits[count++] = hManualOverride;
+        waits[count++] = hSettingsChanged;
 
-        if (manualOverrideActive)
-        {
-            int lightBoundary = (settings.lightTime + settings.sunrise_offset) % 1440;
-            int darkBoundary = (settings.darkTime + settings.sunset_offset) % 1440;
-
-            SYSTEMTIME st;
-            GetLocalTime(&st);
-            nowMinutes = st.wHour * 60 + st.wMinute;
-
-            bool crossedLight = false;
-            bool crossedDark = false;
-
-            if (prevMinutes != -1)
-            {
-                // this means we are in a new day cycle
-                if (nowMinutes < prevMinutes)
-                {
-                    crossedLight = (prevMinutes <= lightBoundary || nowMinutes >= lightBoundary);
-                    crossedDark = (prevMinutes <= darkBoundary || nowMinutes >= darkBoundary);
-                }
-                else
-                {
-                    crossedLight = (prevMinutes < lightBoundary && nowMinutes >= lightBoundary);
-                    crossedDark = (prevMinutes < darkBoundary && nowMinutes >= darkBoundary);
-                }
-            }
-
-            if (crossedLight || crossedDark)
-            {
-                ResetEvent(hManualOverride);
-                Logger::info(L"[LightSwitchService] Manual override cleared after crossing schedule boundary.");
-            }
-            else
-            {
-                Logger::debug(L"[LightSwitchService] Skipping schedule due to manual override");
-                skipRest = true;
-            }
-        }
-
-        // Apply theme if nothing has made us skip
-        if (!skipRest)
-        {
-            // Next two conditionals check for any updates necessary to the sun times.
-            bool modeChangedToSunset = (prevMode != settings.scheduleMode &&
-                                        settings.scheduleMode == ScheduleMode::SunsetToSunrise);
-            bool coordsChanged = (prevLat != settings.latitude || prevLon != settings.longitude);
-
-            if ((modeChangedToSunset || coordsChanged) && settings.scheduleMode == ScheduleMode::SunsetToSunrise)
-            {
-                SYSTEMTIME st;
-                GetLocalTime(&st);
-
-                Logger::info(L"[LightSwitchService] Mode or coordinates changed, recalculating sun times.");
-                update_sun_times(settings);
-                g_lastUpdatedDay = st.wDay;
-                prevMode = settings.scheduleMode;
-                prevLat = settings.latitude;
-                prevLon = settings.longitude;
-            }
-
-            SYSTEMTIME st;
-            GetLocalTime(&st);
-            int nowMinutes = st.wHour * 60 + st.wMinute;
-
-            if ((g_lastUpdatedDay != st.wDay) && (settings.scheduleMode == ScheduleMode::SunsetToSunrise))
-            {
-                update_sun_times(settings);
-                g_lastUpdatedDay = st.wDay;
-                prevMinutes = -1;
-                Logger::info(L"[LightSwitchService] Recalculated sun times at new day boundary.");
-            }
-
-            // settings after any necessary updates.
-            LightSwitchSettings::instance().LoadSettings();
-            const auto& currentSettings = LightSwitchSettings::instance().settings();
-
-            wchar_t msg[160];
-            swprintf_s(msg,
-                       L"[LightSwitchService] now=%02d:%02d | light=%02d:%02d | dark=%02d:%02d | mode=%s",
-                       st.wHour,
-                       st.wMinute,
-                       currentSettings.lightTime / 60,
-                       currentSettings.lightTime % 60,
-                       currentSettings.darkTime / 60,
-                       currentSettings.darkTime % 60,
-                       ToString(currentSettings.scheduleMode).c_str());
-            Logger::info(msg);
-
-            LightSwitchSettings::instance().ApplyThemeIfNecessary();
-        }
-
-        // ─── Wait For Next Minute Tick Or Stop Event ────────────────────────────────
+        // Wait for one of these to trigger or for a new minute tick
         SYSTEMTIME st;
         GetLocalTime(&st);
         int msToNextMinute = (60 - st.wSecond) * 1000 - st.wMilliseconds;
         if (msToNextMinute < 50)
             msToNextMinute = 50;
 
-       prevMinutes = nowMinutes;
-
         DWORD wait = WaitForMultipleObjects(count, waits, FALSE, msToNextMinute);
+
+        if (wait == WAIT_TIMEOUT)
+        {
+            // regular minute tick
+            GetLocalTime(&st);
+            nowMinutes = st.wHour * 60 + st.wMinute;
+            DetectAndHandleExternalThemeChange(stateManager);
+            stateManager.OnTick(nowMinutes);
+            continue;
+        }
+
         if (wait == WAIT_OBJECT_0)
         {
-            Logger::info(L"[LightSwitchService] Stop event triggered - exiting worker loop.");
+            Logger::info(L"[LightSwitchService] Stop event triggered — exiting.");
             break;
         }
+
         if (hParent && wait == WAIT_OBJECT_0 + 1)
         {
-            Logger::info(L"[LightSwitchService] Parent process exited - stopping service.");
+            Logger::info(L"[LightSwitchService] Parent process exited — stopping service.");
             break;
         }
+
+        if (hManualOverride && wait == WAIT_OBJECT_0 + (hParent ? 2 : 1))
+        {
+            Logger::info(L"[LightSwitchService] Manual override event detected.");
+            stateManager.OnManualOverride();
+            ResetEvent(hManualOverride);
+            continue;
+        }
+
+        if (wait == WAIT_OBJECT_0 + (hParent ? (hManualOverride ? 3 : 2) : 2))
+        {
+            Logger::info(L"[LightSwitchService] Settings file changed event detected.");
+            ResetEvent(hSettingsChanged);
+            LightSwitchSettings::instance().LoadSettings();
+            stateManager.OnSettingsChanged();
+            continue;
+        }
     }
 
-cleanup:
+    // ────────────────────────────────────────────────────────────────
+    // Cleanup
+    // ────────────────────────────────────────────────────────────────
     if (hManualOverride)
         CloseHandle(hManualOverride);
     if (hParent)
         CloseHandle(hParent);
 
+    Logger::info(L"[LightSwitchService] Worker thread exiting cleanly.");
     return 0;
 }
 

src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj

@@ -75,6 +75,7 @@
   <ItemGroup>
     <ClCompile Include="LightSwitchService.cpp" />
     <ClCompile Include="LightSwitchSettings.cpp" />
+    <ClCompile Include="LightSwitchStateManager.cpp" />
     <ClCompile Include="SettingsConstants.cpp" />
     <ClCompile Include="ThemeHelper.cpp" />
     <ClCompile Include="ThemeScheduler.cpp" />
@@ -85,6 +86,8 @@
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="LightSwitchSettings.h" />
+    <ClInclude Include="LightSwitchStateManager.h" />
+    <ClInclude Include="LightSwitchUtils.h" />
     <ClInclude Include="SettingsConstants.h" />
     <ClInclude Include="SettingsObserver.h" />
     <ClInclude Include="ThemeHelper.h" />

src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj.filters

@@ -33,6 +33,9 @@
     <ClCompile Include="WinHookEventIDs.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="LightSwitchStateManager.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="ThemeScheduler.h">
@@ -53,6 +56,12 @@
     <ClInclude Include="WinHookEventIDs.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="LightSwitchStateManager.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="LightSwitchUtils.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <Natvis Include="$(MSBuildThisFileDirectory)..\..\natvis\wil.natvis" />

src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.cpp

@@ -2,10 +2,8 @@
 #include <common/utils/json.h>
 #include <common/SettingsAPI/settings_helpers.h>
 #include "SettingsObserver.h"
-#include "ThemeHelper.h"
 #include <filesystem>
 #include <fstream>
-#include <WinHookEventIDs.h>
 #include <logger.h>
 
 using namespace std;
@@ -69,7 +67,6 @@ void LightSwitchSettings::InitFileWatcher()
                     try
                     {
                         LoadSettings();
-                        ApplyThemeIfNecessary();
                         SetEvent(m_settingsChangedEvent);
                     }
                     catch (const std::exception& e)
@@ -250,48 +247,3 @@ void LightSwitchSettings::LoadSettings()
         // Keeps defaults if load fails
     }
 }
-
-void LightSwitchSettings::ApplyThemeIfNecessary()
-{
-    std::lock_guard<std::mutex> guard(m_settingsMutex);
-
-    SYSTEMTIME st;
-    GetLocalTime(&st);
-    int nowMinutes = st.wHour * 60 + st.wMinute;
-
-    bool shouldBeLight = false;
-    if (m_settings.lightTime < m_settings.darkTime)
-        shouldBeLight = (nowMinutes >= m_settings.lightTime && nowMinutes < m_settings.darkTime);
-    else
-        shouldBeLight = (nowMinutes >= m_settings.lightTime || nowMinutes < m_settings.darkTime);
-
-    bool isSystemCurrentlyLight = GetCurrentSystemTheme();
-    bool isAppsCurrentlyLight = GetCurrentAppsTheme();
-
-    if (shouldBeLight)
-    {
-        if (m_settings.changeSystem && !isSystemCurrentlyLight)
-        {
-            SetSystemTheme(true);
-            Logger::info(L"[LightSwitchService] Changing system theme to light mode.");
-        }
-        if (m_settings.changeApps && !isAppsCurrentlyLight)
-        {
-            SetAppsTheme(true);
-            Logger::info(L"[LightSwitchService] Changing apps theme to light mode.");
-        }
-    }
-    else
-    {
-        if (m_settings.changeSystem && isSystemCurrentlyLight)
-        {
-            SetSystemTheme(false);
-            Logger::info(L"[LightSwitchService] Changing system theme to dark mode.");
-        }
-        if (m_settings.changeApps && isAppsCurrentlyLight)
-        {
-            SetAppsTheme(false);
-            Logger::info(L"[LightSwitchService] Changing apps theme to dark mode.");
-        }
-    }
-}

src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.h

@@ -81,7 +81,6 @@ public:
     void RemoveObserver(SettingsObserver& observer);
 
     void LoadSettings();
-    void ApplyThemeIfNecessary();
 
     HANDLE GetSettingsChangedEvent() const;
 

src/modules/LightSwitch/LightSwitchService/LightSwitchStateManager.cpp

@@ -0,0 +1,195 @@
+#include "pch.h"
+#include "LightSwitchStateManager.h"
+#include <logger.h>
+#include <LightSwitchUtils.h>
+#include "ThemeScheduler.h"
+#include <ThemeHelper.h>
+
+void ApplyTheme(bool shouldBeLight);
+
+// Constructor
+LightSwitchStateManager::LightSwitchStateManager()
+{
+    Logger::info(L"[LightSwitchStateManager] Initialized");
+}
+
+// Called when settings.json changes
+void LightSwitchStateManager::OnSettingsChanged()
+{
+    Logger::info(L"[LightSwitchStateManager] Settings changed event received");
+
+    // If manual override was active, clear it so new settings take effect
+    if (_state.isManualOverride)
+    {
+        Logger::info(L"[LightSwitchStateManager] Clearing manual override due to settings update.");
+        _state.isManualOverride = false;
+    }
+
+    EvaluateAndApplyIfNeeded();
+}
+
+
+// Called once per minute
+void LightSwitchStateManager::OnTick(int currentMinutes)
+{
+    Logger::debug(L"[LightSwitchStateManager] Tick received: {}", currentMinutes);
+    EvaluateAndApplyIfNeeded();
+}
+
+// Called when manual override is triggered
+void LightSwitchStateManager::OnManualOverride()
+{
+    Logger::info(L"[LightSwitchStateManager] Manual override triggered");
+    _state.isManualOverride = !_state.isManualOverride;
+
+    // When entering manual override, sync internal theme state to match the current system
+    if (_state.isManualOverride)
+    {
+        bool systemLight = GetCurrentSystemTheme();
+        _state.isLightThemeActive = systemLight;
+        Logger::info(L"[LightSwitchStateManager] Synced internal theme state to current system theme ({})",
+                     systemLight ? L"light" : L"dark");
+    }
+
+    EvaluateAndApplyIfNeeded();
+}
+
+// Helpers
+bool LightSwitchStateManager::CoordinatesAreValid(const std::wstring& lat, const std::wstring& lon)
+{
+    try
+    {
+        double latVal = std::stod(lat);
+        double lonVal = std::stod(lon);
+        return !(latVal == 0 && lonVal == 0);
+    }
+    catch (...)
+    {
+        return false;
+    }
+}
+
+static std::pair<int, int> update_sun_times(auto& settings)
+{
+    double latitude = std::stod(settings.latitude);
+    double longitude = std::stod(settings.longitude);
+
+    SYSTEMTIME st;
+    GetLocalTime(&st);
+
+    SunTimes newTimes = CalculateSunriseSunset(latitude, longitude, st.wYear, st.wMonth, st.wDay);
+
+    int newLightTime = newTimes.sunriseHour * 60 + newTimes.sunriseMinute;
+    int newDarkTime = newTimes.sunsetHour * 60 + newTimes.sunsetMinute;
+
+    try
+    {
+        auto values = PowerToysSettings::PowerToyValues::load_from_settings_file(L"LightSwitch");
+        values.add_property(L"lightTime", newLightTime);
+        values.add_property(L"darkTime", newDarkTime);
+        values.save_to_settings_file();
+
+        Logger::info(L"[LightSwitchService] Updated sun times and saved to config.");
+    }
+    catch (const std::exception& e)
+    {
+        std::wstring wmsg(e.what(), e.what() + strlen(e.what()));
+        Logger::error(L"[LightSwitchService] Exception during sun time update: {}", wmsg);
+    }
+
+    return { newLightTime, newDarkTime };
+}
+
+// Internal: decide what should happen now
+void LightSwitchStateManager::EvaluateAndApplyIfNeeded()
+{
+    const auto& _currentSettings = LightSwitchSettings::settings();
+    auto now = GetNowMinutes();
+
+    // Early exit: OFF mode just pauses activity
+    if (_currentSettings.scheduleMode == ScheduleMode::Off)
+    {
+        Logger::debug(L"[LightSwitchStateManager] Mode is OFF — pausing service logic.");
+        _state.lastTickMinutes = now;
+        return;
+    }
+
+    bool coordsValid = CoordinatesAreValid(_currentSettings.latitude, _currentSettings.longitude);
+
+    // Handle Sun Mode recalculation
+    if (_currentSettings.scheduleMode == ScheduleMode::SunsetToSunrise && coordsValid)
+    {
+        SYSTEMTIME st;
+        GetLocalTime(&st);
+        bool newDay = (_state.lastEvaluatedDay != st.wDay);
+        bool modeChangedToSun = (_state.lastAppliedMode != ScheduleMode::SunsetToSunrise &&
+                                 _currentSettings.scheduleMode == ScheduleMode::SunsetToSunrise);
+
+        if (newDay || modeChangedToSun)
+        {
+            Logger::info(L"[LightSwitchStateManager] Recalculating sun times (mode/day change).");
+            auto [newLightTime, newDarkTime] = update_sun_times(_currentSettings);
+            _state.lastEvaluatedDay = st.wDay;
+            _state.effectiveLightMinutes = newLightTime + _currentSettings.sunrise_offset;
+            _state.effectiveDarkMinutes = newDarkTime + _currentSettings.sunset_offset;
+        }
+    }
+    else if (_currentSettings.scheduleMode == ScheduleMode::FixedHours)
+    {
+        _state.effectiveLightMinutes = _currentSettings.lightTime;
+        _state.effectiveDarkMinutes = _currentSettings.darkTime;
+    }
+
+    // Handle manual override logic
+    if (_state.isManualOverride)
+    {
+        bool crossedBoundary = false;
+        if (_state.lastTickMinutes != -1)
+        {
+            int prev = _state.lastTickMinutes;
+
+            // Handle midnight wraparound safely
+            if (now < prev)
+            {
+                crossedBoundary =
+                    (prev <= _state.effectiveLightMinutes || now >= _state.effectiveLightMinutes) ||
+                    (prev <= _state.effectiveDarkMinutes || now >= _state.effectiveDarkMinutes);
+            }
+            else
+            {
+                crossedBoundary =
+                    (prev < _state.effectiveLightMinutes && now >= _state.effectiveLightMinutes) ||
+                    (prev < _state.effectiveDarkMinutes && now >= _state.effectiveDarkMinutes);
+            }
+        }
+
+        if (crossedBoundary)
+        {
+            Logger::info(L"[LightSwitchStateManager] Manual override cleared after crossing boundary.");
+            _state.isManualOverride = false;
+        }
+        else
+        {
+            Logger::debug(L"[LightSwitchStateManager] Manual override active — skipping auto apply.");
+            _state.lastTickMinutes = now;
+            return;
+        }
+    }
+
+    _state.lastAppliedMode = _currentSettings.scheduleMode;
+
+    bool shouldBeLight = ShouldBeLight(now, _state.effectiveLightMinutes, _state.effectiveDarkMinutes);
+
+    // Only apply theme if there's a change or no override active
+    if (!_state.isManualOverride && _state.isLightThemeActive != shouldBeLight)
+    {
+        Logger::info(L"[LightSwitchStateManager] Applying {} theme", shouldBeLight ? L"light" : L"dark");
+        ApplyTheme(shouldBeLight);
+        _state.isLightThemeActive = shouldBeLight;
+    }
+
+    _state.lastTickMinutes = now;
+}
+
+
+

src/modules/LightSwitch/LightSwitchService/LightSwitchStateManager.h

@@ -0,0 +1,42 @@
+#pragma once
+#include "LightSwitchSettings.h"
+#include <optional>
+
+// Represents runtime-only information (not saved in settings.json)
+struct LightSwitchState
+{
+    ScheduleMode lastAppliedMode = ScheduleMode::Off;
+    bool isManualOverride = false;
+    bool isLightThemeActive = false;
+    int lastEvaluatedDay = -1;
+    int lastTickMinutes = -1;
+
+    // Derived, runtime-resolved times
+    int effectiveLightMinutes = 0; // the boundary we actually act on
+    int effectiveDarkMinutes = 0; // includes offsets if needed
+};
+
+// The controller that reacts to settings changes, time ticks, and manual overrides.
+class LightSwitchStateManager
+{
+public:
+    LightSwitchStateManager();
+
+    // Called when settings.json changes or stabilizes.
+    void OnSettingsChanged();
+
+    // Called every minute (from service worker tick).
+    void OnTick(int currentMinutes);
+
+    // Called when manual override is toggled (via shortcut or system change).
+    void OnManualOverride();
+
+    // Accessor for current state (optional, for debugging or telemetry)
+    const LightSwitchState& GetState() const { return _state; }
+
+private:
+    LightSwitchState _state;
+
+    void EvaluateAndApplyIfNeeded();
+    bool CoordinatesAreValid(const std::wstring& lat, const std::wstring& lon);
+};

src/modules/LightSwitch/LightSwitchService/LightSwitchUtils.h

@@ -0,0 +1,25 @@
+#pragma once
+#include <windows.h>
+
+constexpr bool ShouldBeLight(int nowMinutes, int lightTime, int darkTime)
+{
+    // Normalize values into [0, 1439]
+    lightTime = (lightTime % 1440 + 1440) % 1440;
+    darkTime = (darkTime % 1440 + 1440) % 1440;
+    nowMinutes = (nowMinutes % 1440 + 1440) % 1440;
+
+    // Case 1: Normal range, e.g. light mode comes before dark mode in the same day
+    if (lightTime < darkTime)
+        return nowMinutes >= lightTime && nowMinutes < darkTime;
+
+    // Case 2: Wrap-around range, e.g. light mode starts in the evening and dark mode starts in the morning
+    return nowMinutes >= lightTime || nowMinutes < darkTime;
+}
+
+
+inline int GetNowMinutes()
+{
+    SYSTEMTIME st;
+    GetLocalTime(&st);
+    return st.wHour * 60 + st.wMinute;
+}

src/settings-ui/Settings.UI/SettingsXAML/Views/LightSwitchPage.xaml.cs

@@ -37,7 +37,7 @@ namespace Microsoft.PowerToys.Settings.UI.Views
         private readonly IFileSystemWatcher _fileSystemWatcher;
         private readonly DispatcherQueue _dispatcherQueue;
         private bool _suppressViewModelUpdates;
-        private bool _suppressLatLonChange;
+        private bool _suppressLatLonChange = true;
 
         private LightSwitchViewModel ViewModel { get; set; }