/**
 * Platform-aware geolocation.
 *
 * THE BUG THIS FIXES
 * ------------------
 * On the native Android app (ZapStore APK) the in-WebView
 * `navigator.geolocation.getCurrentPosition` returns PERMISSION_DENIED, because
 * the WebView never gets the OS location permission on its own. The app then
 * showed a "your BROWSER blocked location" help sheet — wrong and useless inside
 * a native app.
 *
 * THE FIX
 * -------
 * On native we go through Capacitor's Geolocation plugin, accessed via
 * `registerPlugin('Geolocation')` from the bundled @capacitor/core (same runtime
 * pattern used for Camera + the Amber signer — no bare `@capacitor/geolocation`
 * import in the JS bundle). We call requestPermissions() first, which triggers
 * the real Android location prompt, then getCurrentPosition().
 *
 * IMPORTANT (native build): @capacitor/geolocation must be installed (it's in
 * package.json) and synced with `npx cap sync android` so the native plugin is
 * bundled into the APK and registered. On web we just use navigator.geolocation.
 *
 * CRASH HARDENING (the "Near Me closes the app / bounces to ZapStore" bug)
 * -----------------------------------------------------------------------
 * A native plugin call that throws on the Android MAIN thread produces a
 * `FATAL EXCEPTION: main` that kills the process. No JS try/catch or Promise
 * wrapper can intercept that — it happens in Java land, off our promise chain.
 * `registerPlugin('Geolocation')` ALWAYS returns a JS proxy, even when the
 * native class isn't actually registered in the APK (e.g. after a messy plugin
 * upgrade / incomplete `cap sync`, or a missing play-services-location dep).
 * Invoking a method on such a "ghost" proxy is exactly what crashes the app.
 *
 * So before we ever touch the native plugin we verify it is GENUINELY present
 * by checking `Capacitor.isPluginAvailable('Geolocation')` and the live
 * `window.Capacitor.Plugins.Geolocation` registry. If it's not truly there we
 * DO NOT call it — we fall back to the WebView's `navigator.geolocation`
 * instead of detonating a native crash. This keeps the app alive no matter what
 * state the native project is in.
 */

import { Capacitor, registerPlugin } from '@capacitor/core';

export interface GeoCoords {
  lat: number;
  lng: number;
}

export type GeoErrorKind = 'denied' | 'unavailable' | 'timeout' | 'no_provider';

export class GeolocationError extends Error {
  kind: GeoErrorKind;
  constructor(kind: GeoErrorKind, message: string) {
    super(message);
    this.kind = kind;
    this.name = 'GeolocationError';
  }
}

// ─── Native plugin proxy ──────────────────────────────────────────────────────

interface CapPermissionStatus {
  location: 'granted' | 'denied' | 'prompt' | 'prompt-with-rationale';
  coarseLocation?: 'granted' | 'denied' | 'prompt' | 'prompt-with-rationale';
}
interface CapPosition {
  coords: { latitude: number; longitude: number };
}
/**
 * Permission methods are always safe. getCurrentPosition is attempted (safely
 * wrapped) because on GrapheneOS the WebView's navigator.geolocation is blocked
 * even after the OS permission is granted — so the native plugin is the only
 * way to actually get a fix there. Recent @capacitor/geolocation falls back to
 * Android LocationManager when Play Services is absent, so it no longer crashes.
 */
interface CapGeolocationPlugin {
  checkPermissions(): Promise<CapPermissionStatus>;
  requestPermissions(options?: { permissions?: string[] }): Promise<CapPermissionStatus>;
  getCurrentPosition(options?: {
    enableHighAccuracy?: boolean;
    timeout?: number;
    maximumAge?: number;
  }): Promise<CapPosition>;
}

/**
 * Verify the Geolocation plugin is GENUINELY registered on the native side —
 * not just that `registerPlugin` handed us a proxy (it always does). Calling a
 * method on a proxy whose native class is missing is what crashes the app, so
 * we must be certain the native implementation exists before we ever call it.
 */
function isNativeGeoAvailable(): boolean {
  try {
    if (!Capacitor?.isNativePlatform?.()) return false;

    // Capacitor's own registry check — returns false if the native plugin
    // class wasn't compiled/registered into this APK.
    if (typeof Capacitor.isPluginAvailable === 'function') {
      if (!Capacitor.isPluginAvailable('Geolocation')) return false;
    }

    // Belt-and-braces: confirm the live plugin registry actually holds a
    // Geolocation entry with the methods we intend to call.
    const w = globalThis as unknown as {
      Capacitor?: { Plugins?: Record<string, unknown> };
    };
    const registered = w.Capacitor?.Plugins?.Geolocation as
      | { getCurrentPosition?: unknown }
      | undefined;
    if (!registered || typeof registered.getCurrentPosition !== 'function') {
      return false;
    }

    return true;
  } catch {
    return false;
  }
}

let geoPlugin: CapGeolocationPlugin | null = null;
function getNativeGeo(): CapGeolocationPlugin | null {
  if (!isNativeGeoAvailable()) return null;

  if (!geoPlugin) {
    try {
      geoPlugin = registerPlugin<CapGeolocationPlugin>('Geolocation');
    } catch {
      return null;
    }
  }
  return geoPlugin;
}

/**
 * True when running inside the native app AND the Geolocation plugin is
 * genuinely registered — i.e. the native permission path is the one in use.
 * The UI uses this to tailor error copy ("open device Settings" vs. "browser
 * settings"). When the native plugin is a ghost proxy we fall back to the web
 * path, so this returns false and the UI shows the browser-appropriate help.
 */
export function isNativeGeolocation(): boolean {
  return isNativeGeoAvailable();
}

/** True when running inside the native Capacitor app, regardless of plugins. */
export function isNativePlatform(): boolean {
  try {
    return Capacitor?.isNativePlatform?.() ?? false;
  } catch {
    return false;
  }
}

// ─── Public API ───────────────────────────────────────────────────────────────

/**
 * Get the device's current position. Uses the native Geolocation plugin on the
 * app (with a proper OS permission prompt) and navigator.geolocation on web.
 * Throws a GeolocationError with a `kind` the UI can branch on.
 */
export async function getCurrentPosition(): Promise<GeoCoords> {
  const native = getNativeGeo();

  if (native) {
    return getNativePosition(native);
  }

  return getWebPosition();
}

/**
 * Native path.
 *
 * CRITICAL — GrapheneOS / de-Googled devices
 * ------------------------------------------
 * Capacitor Geolocation v8 fetches the position through Google Play Services
 * (`play-services-location` / Ionic's `iongeolocation-android`). On a phone
 * WITHOUT Play Services (GrapheneOS, /e/OS, most de-Googled ROMs) the plugin's
 * `getCurrentPosition`/`watchPosition` touch Google classes that don't exist on
 * the device → `NoClassDefFoundError` on the Android MAIN thread → the whole
 * app is killed ("Near Me closes the app"). No JS try/catch can stop that.
 *
 * THE FIX: we use the native plugin ONLY to request the OS location permission
 * (that path is pure Android, no Play Services). For the actual position we use
 * the WebView's `navigator.geolocation`, which talks to Android's own
 * LocationManager (GPS/network) directly and works fine without Google. This
 * keeps a proper native permission prompt while never invoking the
 * Play-Services position code that crashes de-Googled devices.
 */
async function getNativePosition(native: CapGeolocationPlugin): Promise<GeoCoords> {
  // Wrap EVERY bridge call in Promise.resolve().then(...) so that even a
  // SYNCHRONOUS throw from the native proxy becomes a rejected promise we can
  // catch here — a sync throw is what can otherwise crash the whole app.
  const safeCall = <T>(fn: () => Promise<T>): Promise<T> =>
    Promise.resolve().then(fn);

  try {
    // Ask the OS for permission first — this shows the Android prompt.
    // checkPermissions/requestPermissions do NOT use Play Services, so they are
    // safe to call on de-Googled devices. Guard each step independently.
    let status = await safeCall(() => native.checkPermissions()).catch(() => null);
    if (!status || (status.location !== 'granted' && status.coarseLocation !== 'granted')) {
      status = await safeCall(() =>
        native.requestPermissions({ permissions: ['location', 'coarseLocation'] }),
      ).catch((permErr) => {
        console.warn('[geolocation] requestPermissions failed:', permErr);
        return null;
      });
    }
    if (status && status.location !== 'granted' && status.coarseLocation !== 'granted') {
      throw new GeolocationError('denied', 'Location permission denied.');
    }

    // Permission granted natively. Now get the actual position.
    //
    // On GrapheneOS the WebView's navigator.geolocation is BLOCKED even after the
    // OS-level permission is granted (the WebView has its own geolocation gate
    // that Capacitor doesn't open) → navigator.geolocation returns
    // PERMISSION_DENIED, which is the "granted but still denied" bug users hit.
    //
    // So we ask the NATIVE plugin for the position first — it talks to Android's
    // LocationManager directly and honours the permission we just granted.
    // Modern @capacitor/geolocation degrades to LocationManager when Play
    // Services is absent, so this no longer crashes de-Googled devices. We wrap
    // it defensively and fall back to navigator.geolocation only if it fails.
    try {
      const pos = await safeCall(() =>
        native.getCurrentPosition({ enableHighAccuracy: false, timeout: 15000, maximumAge: 60000 }),
      );
      const lat = pos?.coords?.latitude;
      const lng = pos?.coords?.longitude;
      if (typeof lat === 'number' && typeof lng === 'number' && !(lat === 0 && lng === 0)) {
        return { lat, lng };
      }
      // Bad/empty reading — fall through to the web path.
    } catch (nativePosErr) {
      console.warn('[geolocation] native getCurrentPosition failed, falling back to WebView:', nativePosErr);
    }

    // Fallback: WebView navigator.geolocation (works on stock Android, shares
    // the app's granted permission).
    return await getWebPosition();
  } catch (err) {
    if (err instanceof GeolocationError) throw err;
    const msg = (err instanceof Error ? err.message : String(err)).toLowerCase();
    if (msg.includes('denied') || msg.includes('permission')) {
      throw new GeolocationError('denied', 'Location permission denied.');
    }
    // "location disabled" / "provider" → the OS has NO usable location provider.
    // On GrapheneOS (no Google Play Services) there's often no network/fused
    // provider, so only GPS satellites work — which fail indoors. Surface this
    // as its own kind so the UI can give accurate advice.
    if (
      msg.includes('disabled') ||
      msg.includes('provider') ||
      msg.includes('settings') ||
      msg.includes('unavailable')
    ) {
      throw new GeolocationError(
        'no_provider',
        err instanceof Error ? err.message : String(err) || 'No location provider available.',
      );
    }
    if (msg.includes('timeout') || msg.includes('timed out')) {
      throw new GeolocationError('timeout', 'Location request timed out.');
    }
    // Anything else — pass the real native message through so it shows in the
    // on-screen toast and we can see what actually failed without needing adb.
    throw new GeolocationError(
      'unavailable',
      err instanceof Error ? err.message : String(err) || 'Location unavailable.',
    );
  }
}

/**
 * Web path (also used as a safe fallback when the native plugin isn't genuinely
 * registered). Uses the WebView/browser `navigator.geolocation`.
 *
 * Same fast-fix idea as native: start a low-accuracy watchPosition and resolve
 * on the FIRST update (the quick network/wifi fix), racing it against a cheap
 * getCurrentPosition. Whichever returns first wins.
 */
function getWebPosition(): Promise<GeoCoords> {
  if (!('geolocation' in navigator)) {
    return Promise.reject(
      new GeolocationError('unavailable', 'Geolocation is not supported by this browser.'),
    );
  }

  return new Promise<GeoCoords>((resolve, reject) => {
    let settled = false;
    let watchId: number | null = null;
    let deadline: ReturnType<typeof setTimeout> | null = null;

    const cleanup = () => {
      if (deadline) clearTimeout(deadline);
      if (watchId !== null) {
        try {
          navigator.geolocation.clearWatch(watchId);
        } catch {
          // ignore
        }
        watchId = null;
      }
    };

    const succeed = (pos: GeolocationPosition) => {
      if (settled) return;
      settled = true;
      cleanup();
      resolve({ lat: pos.coords.latitude, lng: pos.coords.longitude });
    };

    const mapError = (err: GeolocationPositionError): GeolocationError => {
      if (err.code === err.PERMISSION_DENIED) {
        return new GeolocationError('denied', 'Location permission denied.');
      }
      if (err.code === err.TIMEOUT) {
        return new GeolocationError('timeout', 'Location request timed out.');
      }
      return new GeolocationError('unavailable', 'Location unavailable.');
    };

    const fail = (err: GeolocationPositionError) => {
      if (settled) return;
      // Permission denial is terminal; other errors let the watch/deadline decide.
      if (err.code === err.PERMISSION_DENIED) {
        settled = true;
        cleanup();
        reject(mapError(err));
      }
    };

    deadline = setTimeout(() => {
      if (settled) return;
      settled = true;
      cleanup();
      reject(new GeolocationError('timeout', 'Location request timed out.'));
    }, 25000);

    // 1) watchPosition — first update wins (fast network fix).
    try {
      watchId = navigator.geolocation.watchPosition(
        (pos) => succeed(pos),
        (err) => fail(err),
        { enableHighAccuracy: false, timeout: 20000, maximumAge: 60000 },
      );
    } catch {
      // ignore — getCurrentPosition below still runs
    }

    // 2) getCurrentPosition — instant if a recent fix is cached.
    navigator.geolocation.getCurrentPosition(
      (pos) => succeed(pos),
      (err) => fail(err),
      { enableHighAccuracy: false, timeout: 15000, maximumAge: 120000 },
    );
  });
}