'use client';

import { useEffect, useState } from 'react';
import { RefreshCw } from 'lucide-react';

const BUILD_ID = process.env.NEXT_PUBLIC_BUILD_ID ?? '';
const RELOADED_FOR = '1driver_reloaded_for';
const CHECK_EVERY_MS = 10 * 60 * 1000;

/** The build the server is serving now, or '' when unknown (offline, dev). */
async function liveBuildId(): Promise<string> {
  try {
    const res = await fetch(`/version.json?t=${Date.now()}`, { cache: 'no-store' });
    if (!res.ok) return '';
    const body = (await res.json()) as { id?: unknown };
    return typeof body.id === 'string' ? body.id : '';
  } catch {
    return '';
  }
}

/**
 * Drop the cached pages (not the hashed /_next/static files) so the service
 * worker fetches the new HTML, then reload. Without this the first reload
 * after a deploy still shows the old cached page.
 */
async function loadNewVersion(): Promise<void> {
  try {
    for (const name of await caches.keys()) {
      const cache = await caches.open(name);
      for (const req of await cache.keys()) {
        const url = new URL(req.url);
        if (url.origin === location.origin && !url.pathname.startsWith('/_next/static/')) {
          await cache.delete(req);
        }
      }
    }
    const reg = await navigator.serviceWorker?.getRegistration();
    await reg?.update();
  } catch {
    // Reload anyway; the worst case is one more stale open.
  }
  location.reload();
}

// Keeps drivers on the latest build. On launch a new build loads straight
// away (once per build, so a stale server can't cause a reload loop). While
// the app stays open it only shows an Update banner: a reload then could cut
// off a camera photo or an upload in progress.
export default function UpdateWatcher() {
  const [ready, setReady] = useState(false);
  const [busy, setBusy] = useState(false);

  useEffect(() => {
    if (process.env.NODE_ENV !== 'production' || !BUILD_ID) return;
    let stopped = false;

    const check = async (onLaunch: boolean) => {
      const live = await liveBuildId();
      if (stopped || !live || live === BUILD_ID) return;
      let alreadyTried = false;
      try {
        alreadyTried = sessionStorage.getItem(RELOADED_FOR) === live;
        if (onLaunch && !alreadyTried) sessionStorage.setItem(RELOADED_FOR, live);
      } catch {
        alreadyTried = true; // no storage: never auto-reload, the banner is enough
      }
      if (onLaunch && !alreadyTried) void loadNewVersion();
      else setReady(true);
    };

    void check(true);
    const onVisible = () => {
      if (document.visibilityState === 'visible') void check(false);
    };
    document.addEventListener('visibilitychange', onVisible);
    const timer = setInterval(() => void check(false), CHECK_EVERY_MS);
    return () => {
      stopped = true;
      document.removeEventListener('visibilitychange', onVisible);
      clearInterval(timer);
    };
  }, []);

  if (!ready) return null;

  return (
    <div className="fixed bottom-[76px] left-3 right-3 z-[85] safe-bottom" role="status" aria-live="polite">
      <div
        className="flex items-center gap-3 rounded-2xl bg-[#26251e] text-white px-4 py-3"
        style={{ boxShadow: '0 14px 32px rgba(0,0,0,0.25)' }}
      >
        <p className="flex-1 text-[14px] leading-snug">A new version of the app is ready.</p>
        <button
          type="button"
          disabled={busy}
          onClick={() => {
            setBusy(true);
            void loadNewVersion();
          }}
          className="h-10 px-4 rounded-xl bg-[#f54e00] text-[14px] font-semibold flex items-center gap-1.5 disabled:opacity-60 touch-manipulation"
        >
          <RefreshCw size={15} className={busy ? 'animate-spin' : ''} aria-hidden="true" />
          Update
        </button>
      </div>
    </div>
  );
}