import { computed, reactive } from "vue";

type ThemeMode = "light" | "dark" | "system";
type DensityMode = "comfortable" | "compact";

const STORAGE_KEYS = {
  themeMode: "live-recorder-ui-theme",
  density: "live-recorder-ui-density",
  sidebarCollapsed: "live-recorder-ui-sidebar-collapsed"
} as const;

const state = reactive({
  themeMode: "system" as ThemeMode,
  density: "comfortable" as DensityMode,
  sidebarCollapsed: false,
  systemTheme: "light" as "light" | "dark",
  initialized: false
});

let mediaQueryList: MediaQueryList | null = null;

function readStoredThemeMode(): ThemeMode {
  const stored = window.localStorage.getItem(STORAGE_KEYS.themeMode);
  return stored === "light" || stored === "dark" || stored === "system" ? stored : "system";
}

function readStoredDensity(): DensityMode {
  return window.localStorage.getItem(STORAGE_KEYS.density) === "compact" ? "compact" : "comfortable";
}

function readStoredSidebarCollapsed() {
  return window.localStorage.getItem(STORAGE_KEYS.sidebarCollapsed) === "true";
}

function resolveTheme(): "light" | "dark" {
  return state.themeMode === "system" ? state.systemTheme : state.themeMode;
}

function applyDocumentPreferences() {
  if (typeof document === "undefined") {
    return;
  }

  const resolvedTheme = resolveTheme();
  document.documentElement.dataset.theme = resolvedTheme;
  document.documentElement.dataset.themeMode = state.themeMode;
  document.documentElement.dataset.density = state.density;
}

function syncSystemTheme() {
  state.systemTheme = mediaQueryList?.matches ? "dark" : "light";
  applyDocumentPreferences();
}

function ensureInitialized() {
  if (state.initialized || typeof window === "undefined") {
    return;
  }

  state.themeMode = readStoredThemeMode();
  state.density = readStoredDensity();
  state.sidebarCollapsed = readStoredSidebarCollapsed();
  mediaQueryList = window.matchMedia("(prefers-color-scheme: dark)");

  if (typeof mediaQueryList.addEventListener === "function") {
    mediaQueryList.addEventListener("change", syncSystemTheme);
  } else {
    mediaQueryList.addListener(syncSystemTheme);
  }

  syncSystemTheme();
  state.initialized = true;
}

function persistPreferences() {
  if (typeof window === "undefined") {
    return;
  }

  window.localStorage.setItem(STORAGE_KEYS.themeMode, state.themeMode);
  window.localStorage.setItem(STORAGE_KEYS.density, state.density);
  window.localStorage.setItem(STORAGE_KEYS.sidebarCollapsed, String(state.sidebarCollapsed));
}

export function useUiPreferences() {
  ensureInitialized();

  const resolvedTheme = computed(() => resolveTheme());

  function setThemeMode(value: ThemeMode) {
    state.themeMode = value;
    persistPreferences();
    applyDocumentPreferences();
  }

  function cycleThemeMode() {
    const nextValue =
      state.themeMode === "light" ? "dark" : state.themeMode === "dark" ? "system" : "light";
    setThemeMode(nextValue);
  }

  function setDensity(value: DensityMode) {
    state.density = value;
    persistPreferences();
    applyDocumentPreferences();
  }

  function setSidebarCollapsed(value: boolean) {
    state.sidebarCollapsed = value;
    persistPreferences();
  }

  function toggleSidebarCollapsed() {
    setSidebarCollapsed(!state.sidebarCollapsed);
  }

  return {
    themeMode: computed({
      get: () => state.themeMode,
      set: (value: ThemeMode) => setThemeMode(value)
    }),
    resolvedTheme,
    density: computed({
      get: () => state.density,
      set: (value: DensityMode) => setDensity(value)
    }),
    sidebarCollapsed: computed({
      get: () => state.sidebarCollapsed,
      set: (value: boolean) => setSidebarCollapsed(value)
    }),
    cycleThemeMode,
    toggleSidebarCollapsed
  };
}