#include "flutter_window.h"

#include <optional>
#include <dwmapi.h>
#include <winreg.h>

#include "flutter/generated_plugin_registrant.h"

// Helper: Read AppsUseLightTheme from registry (0 = dark mode, 1 = light mode)
static BOOL IsDarkMode() {
  HKEY hKey;
  DWORD value = 1;  // default: light
  DWORD size = sizeof(value);
  if (RegOpenKeyExW(HKEY_CURRENT_USER,
                    L"Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
                    0, KEY_READ, &hKey) == ERROR_SUCCESS) {
    RegQueryValueExW(hKey, L"AppsUseLightTheme", nullptr, nullptr,
                     reinterpret_cast<LPBYTE>(&value), &size);
    RegCloseKey(hKey);
  }
  return (value == 0) ? TRUE : FALSE;
}

// Apply dark/light title bar based on current system setting
static void ApplyDarkTitleBar(HWND hwnd) {
  BOOL dark = IsDarkMode();
  DwmSetWindowAttribute(hwnd, DWMWA_USE_IMMERSIVE_DARK_MODE, &dark, sizeof(dark));
}

FlutterWindow::FlutterWindow(const flutter::DartProject& project)
    : project_(project) {}

FlutterWindow::~FlutterWindow() {}

bool FlutterWindow::OnCreate() {
  if (!Win32Window::OnCreate()) {
    return false;
  }

  RECT frame = GetClientArea();

  // The size here must match the window dimensions to avoid unnecessary surface
  // creation / destruction in the startup path.
  flutter_controller_ = std::make_unique<flutter::FlutterViewController>(
      frame.right - frame.left, frame.bottom - frame.top, project_);
  // Ensure that basic setup of the controller was successful.
  if (!flutter_controller_->engine() || !flutter_controller_->view()) {
    return false;
  }
  RegisterPlugins(flutter_controller_->engine());
  SetChildContent(flutter_controller_->view()->GetNativeWindow());

  // Apply dark/light title bar to match system theme
  ApplyDarkTitleBar(GetHandle());

  return true;
}

void FlutterWindow::OnDestroy() {
  if (flutter_controller_) {
    flutter_controller_ = nullptr;
  }

  Win32Window::OnDestroy();
}

LRESULT
FlutterWindow::MessageHandler(HWND hwnd, UINT const message,
                              WPARAM const wparam,
                              LPARAM const lparam) noexcept {
  // Give Flutter, including plugins, an opportunity to handle window messages.
  if (flutter_controller_) {
    std::optional<LRESULT> result =
        flutter_controller_->HandleTopLevelWindowProc(hwnd, message, wparam,
                                                      lparam);
    if (result) {
      return *result;
    }
  }

  switch (message) {
    case WM_FONTCHANGE:
      flutter_controller_->engine()->ReloadSystemFonts();
      break;
    case WM_SETTINGCHANGE:
      if (lparam &&
          wcscmp(reinterpret_cast<LPCWSTR>(lparam), L"ImmersiveColorSet") == 0) {
        ApplyDarkTitleBar(hwnd);
      }
      break;
  }

  return Win32Window::MessageHandler(hwnd, message, wparam, lparam);
}