import * as SecureStore from "expo-secure-store";
import { create } from "zustand";

/**
 * Theme, language, keep-awake, and the overlay-permission flag are the only
 * non-secret app preferences. SecureStore is used (not AsyncStorage) because
 * AsyncStorage isn't actually installed in this project and SecureStore already
 * backs the session — one small JSON blob stays well under its 2 KB value cap.
 */
const SETTINGS_KEY = "waseel_settings";

export type ThemeMode = "light" | "dark" | "system";
export type Lang = "en" | "ar" | "fr";

type PersistedSettings = Pick<
  SettingsState,
  "mode" | "lang" | "keepAwake" | "overlayRequested"
>;

type SettingsState = {
  /** False until hydrate() has merged SecureStore values into the store. */
  hydrated: boolean;
  mode: ThemeMode;
  lang: Lang;
  keepAwake: boolean;
  /**
   * Only records that we sent the user to the system screen — SYSTEM_ALERT_WINDOW
   * can't be queried from JS, so this is not a granted/denied signal.
   */
  overlayRequested: boolean;

  setMode: (mode: ThemeMode) => void;
  setLang: (lang: Lang) => void;
  setKeepAwake: (value: boolean) => void;
  setOverlayRequested: (value: boolean) => void;
  hydrate: () => Promise<void>;
};

const write = async (state: SettingsState) => {
  const blob: PersistedSettings = {
    mode: state.mode,
    lang: state.lang,
    keepAwake: state.keepAwake,
    overlayRequested: state.overlayRequested,
  };

  await SecureStore.setItemAsync(SETTINGS_KEY, JSON.stringify(blob));
};

export const useSettingsStore = create<SettingsState>((set, get) => ({
  hydrated: false,
  mode: "system",
  lang: "en",
  keepAwake: false,
  overlayRequested: false,

  setMode: (mode) => {
    set({ mode });
    void write(get());
  },
  setLang: (lang) => {
    set({ lang });
    void write(get());
  },
  setKeepAwake: (value) => {
    set({ keepAwake: value });
    void write(get());
  },
  setOverlayRequested: (value) => {
    set({ overlayRequested: value });
    void write(get());
  },

  hydrate: async () => {
    try {
      const stored = await SecureStore.getItemAsync(SETTINGS_KEY);

      if (stored) {
        const parsed = JSON.parse(stored) as Partial<PersistedSettings>;

        set({
          mode: parsed.mode ?? "system",
          lang: parsed.lang ?? "en",
          keepAwake: parsed.keepAwake ?? false,
          overlayRequested: parsed.overlayRequested ?? false,
          hydrated: true,
        });

        return;
      }
    } catch (error) {
      console.warn("[SETTINGS hydrate]: ", error);
    }

    set({ hydrated: true });
  },
}));