/**
 * sw.js — YoTrip Service Worker
 * ─────────────────────────────────────────────────────────────────────────────
 * Strategy: Network-First with Cache-API fallback.
 *
 * Caches:
 *   1. App Shell (static assets): cached at install time
 *   2. OpenStreetMap tiles: cached dynamically on first fetch, served from
 *      cache when offline — so previously visited map areas remain navigable
 *
 * Cache names are versioned so old caches get evicted on SW update.
 */

const SHELL_CACHE   = 'yotrip-shell-v1';
const MAP_CACHE     = 'yotrip-map-tiles-v1';

// App shell files to pre-cache at install
const SHELL_URLS = [
  '/',
  '/index.html',
  '/manifest.json',
  '/favicon.ico',
];

// URL patterns for map tile providers
const MAP_TILE_ORIGINS = [
  'tile.openstreetmap.org',
  'a.tile.openstreetmap.org',
  'b.tile.openstreetmap.org',
  'c.tile.openstreetmap.org',
  'tiles.stadiamaps.com',
  'server.arcgisonline.com',
];

// ─── Install ──────────────────────────────────────────────────────────────

self.addEventListener('install', (event) => {
  console.log('[SW] Installing yotrip service worker…');
  event.waitUntil(
    caches.open(SHELL_CACHE).then((cache) => {
      return cache.addAll(SHELL_URLS).catch((err) => {
        // Non-fatal: some shell files may not exist in dev mode
        console.warn('[SW] Shell pre-cache partial failure (non-fatal):', err);
      });
    })
  );
  // Activate immediately without waiting for old tabs to close
  self.skipWaiting();
});

// ─── Activate ─────────────────────────────────────────────────────────────

self.addEventListener('activate', (event) => {
  const CURRENT_CACHES = [SHELL_CACHE, MAP_CACHE];
  event.waitUntil(
    caches.keys().then((cacheNames) =>
      Promise.all(
        cacheNames
          .filter((name) => !CURRENT_CACHES.includes(name))
          .map((name) => {
            console.log('[SW] Evicting stale cache:', name);
            return caches.delete(name);
          })
      )
    )
  );
  // Take control of all open clients immediately
  self.clients.claim();
});

// ─── Fetch ────────────────────────────────────────────────────────────────

self.addEventListener('fetch', (event) => {
  const url = new URL(event.request.url);

  // 1. Map tile requests — Network-First, fall back to cache
  const isMapTile = MAP_TILE_ORIGINS.some((origin) => url.hostname.includes(origin));
  if (isMapTile) {
    event.respondWith(
      fetch(event.request)
        .then((response) => {
          if (response && response.status === 200) {
            const clone = response.clone();
            caches.open(MAP_CACHE).then((cache) => {
              cache.put(event.request, clone);
            });
          }
          return response;
        })
        .catch(() => caches.match(event.request))
    );
    return;
  }

  // 2. API calls — Network-Only (never cache API responses)
  if (url.pathname.startsWith('/api/')) {
    return; // Let the browser handle normally
  }

  // 3. App shell navigation — Cache-First for HTML, then network
  if (event.request.mode === 'navigate') {
    event.respondWith(
      caches.match('/index.html').then((cached) => {
        return cached || fetch(event.request);
      })
    );
    return;
  }

  // 4. Static assets (JS/CSS/images) — Cache-First
  event.respondWith(
    caches.match(event.request).then((cached) => {
      return cached || fetch(event.request);
    })
  );
});