// sw.js  (use this as your vite-plugin-pwa worker source)
// - Tees streaming responses matching TARGET_SUBSTRING
// - Continuously overwrites "last thread" in localForage backing DB (key=threads_v1)
// - No importScripts required (uses native IndexedDB)
// - Exposes debug commands via postMessage: PING, PING_STATUS, TEST_WRITE, READ_KEY, LIST_SW_SAVED

const TARGET_SUBSTRING = 'openrouter.ai/api/v1/chat/completions'; // adjust if necessary
const THREADS_KEY = 'threads_v1';
const SAVE_BYTES_THRESHOLD = 6 * 1024;
const SAVE_TIME_THRESHOLD = 800;
const BROADCAST_THROTTLE_MS = 600;

const DB_NAME = 'localforage';
const STORE_NAME = 'keyvaluepairs';

const gid = () => Math.random().toString(36).slice(2,9) + '-' + Date.now().toString(36);
const now = () => Date.now();

function openLFDB() {
  return new Promise((resolve, reject) => {
    const req = indexedDB.open(DB_NAME);
    req.onsuccess = (e) => resolve(e.target.result);
    req.onerror = (e) => reject(e.target.error || new Error('open error'));
  });
}

async function idbGetRaw(key) {
  const db = await openLFDB();
  const tx = db.transaction(STORE_NAME, 'readonly');
  const store = tx.objectStore(STORE_NAME);
  return await new Promise((res, rej) => {
    const r = store.get(key);
    r.onsuccess = ev => res(ev.target.result);
    r.onerror = ev => rej(ev.target.error || new Error('get error'));
  });
}

async function idbPutRaw(key, value) {
  const db = await openLFDB();
  const tx = db.transaction(STORE_NAME, 'readwrite');
  const store = tx.objectStore(STORE_NAME);
  return await new Promise((res, rej) => {
    const r = store.put({ key, value });
    r.onsuccess = () => res(true);
    r.onerror = ev => rej(ev.target.error || new Error('put error'));
  });
}

async function idbGetThreads() {
  const rec = await idbGetRaw(THREADS_KEY).catch(err => { throw err; });
  if (!rec) return [];
  return Array.isArray(rec.value) ? rec.value : [];
}
async function idbWriteThreads(arr) {
  await idbPutRaw(THREADS_KEY, arr);
}

function pickLastThread(threads) {
  if (!threads || threads.length === 0) return null;
  const sorted = [...threads].sort((a,b) => (b.updatedAt||0) - (a.updatedAt||0));
  return sorted[0];
}

function upsertAssistantInThreadObj(threadObj, streamId, text) {
  threadObj.updatedAt = now();
  for (let i = threadObj.messages.length - 1; i >= 0; i--) {
    const m = threadObj.messages[i];
    if (m && m.sw_streamId === streamId) {
      m.content = text;
      m.contentParts = [{ type:'text', text }];
      m.updatedAt = now();
      m._sw_savedAt = now();
      return threadObj;
    }
  }
  const msg = {
    id: 'swmsg-' + gid(),
    role: 'assistant',
    content: text,
    contentParts: [{ type:'text', text }],
    kind: 'assistant',
    sw_saved: true,
    sw_streamId: streamId,
    createdAt: now(),
    updatedAt: now(),
    _sw_savedAt: now()
  };
  threadObj.messages.push(msg);
  return threadObj;
}

async function safeFlushLastThread(streamId, accumulated, meta = {}) {
  const threads = await idbGetThreads();
  let thread = pickLastThread(threads);
  const ts = now();
  if (!thread) {
    thread = { id: 'sw-thread-' + gid(), title: 'Missed while backgrounded', pinned:false, updatedAt: ts, messages: [] };
    threads.unshift(thread);
  }
  upsertAssistantInThreadObj(thread, streamId, accumulated);
  await idbWriteThreads(threads);
  return { ok:true, threadId: thread.id };
}

async function broadcast(msg) {
  try {
    const cl = await self.clients.matchAll({ includeUncontrolled: true, type: 'window' });
    for (const c of cl) {
      try { c.postMessage(msg); } catch(_) {}
    }
  } catch(_) {}
}

/* lifecycle */
self.addEventListener('install', ev => self.skipWaiting());
self.addEventListener('activate', ev => ev.waitUntil(self.clients.claim()));

/* fetch handler: tee + continuous overwrite */
self.addEventListener('fetch', event => {
  try {
    const url = String(event.request.url || '');
    if (!url.includes(TARGET_SUBSTRING)) return;
    event.respondWith((async () => {
      const upstream = await fetch(event.request);
      if (!upstream || !upstream.body) return upstream;

      const streamId = 'sw-' + gid();
      const meta = { url, startedAt: now(), bytes: 0, status: 'started' };
      broadcast({ type: 'sw-intercept-start', streamId, meta });

      const [clientStream, swStream] = upstream.body.tee();

      const savePromise = (async () => {
        const reader = swStream.getReader();
        const decoder = new TextDecoder('utf-8');
        let accumulated = '';
        let sinceSaveBytes = 0;
        let lastSaveAt = 0;
        let lastBroadcastAt = 0;

        async function maybeFlush(force=false) {
          try {
            const nowMs = now();
            if (!force && sinceSaveBytes < SAVE_BYTES_THRESHOLD && (nowMs - lastSaveAt) < SAVE_TIME_THRESHOLD) return;
            await safeFlushLastThread(streamId, accumulated, { bytes: meta.bytes });
            sinceSaveBytes = 0;
            lastSaveAt = nowMs;
            if (nowMs - lastBroadcastAt > BROADCAST_THROTTLE_MS) {
              lastBroadcastAt = nowMs;
              broadcast({ type: 'sw-intercept-progress', streamId, meta: { bytes: meta.bytes, savedAt: lastSaveAt, snippet: accumulated.slice(-1024) }});
            }
          } catch (err) {
            broadcast({ type: 'sw-intercept-error', streamId, meta: { error: String(err && err.message ? err.message : err) }});
          }
        }

        try {
          while (true) {
            const { value, done } = await reader.read();
            if (done) break;
            let chunk = '';
            try { chunk = decoder.decode(value, { stream: true }); } catch (e) { chunk = ''; }
            accumulated += chunk;
            const bytes = value ? (value.byteLength || 0) : chunk.length;
            meta.bytes += bytes;
            sinceSaveBytes += bytes;
            await maybeFlush(false);
          }
          await maybeFlush(true);
          meta.status = 'finished';
          meta.endedAt = now();
          broadcast({ type: 'sw-intercept-end', streamId, meta: { totalBytes: meta.bytes, endedAt: meta.endedAt }});
        } catch (err) {
          meta.status = 'error';
          meta.error = String(err && err.message ? err.message : err);
          broadcast({ type: 'sw-intercept-error', streamId, meta: { error: meta.error }});
        }
      })();

      event.waitUntil(savePromise);

      return new Response(clientStream, { status: upstream.status, statusText: upstream.statusText, headers: upstream.headers });
    })());
  } catch (err) {
    broadcast({ type: 'sw-debug', text: 'fetch handler error: ' + String(err && err.message ? err.message : err) });
  }
});

/* messages: PING, PING_STATUS, TEST_WRITE, READ_KEY, LIST_SW_SAVED */
self.addEventListener('message', (event) => {
  const data = event.data || {};
  (async () => {
    try {
      if (data.type === 'PING') {
        if (event.ports && event.ports[0]) event.ports[0].postMessage({ type:'PONG', ts: now(), ok:true });
        else broadcast({ type:'PONG', ts: now(), ok:true });
        return;
      }

      if (data.type === 'PING_STATUS') {
        const reply = { type:'PONG_STATUS', ts: now() };
        if (event.ports && event.ports[0]) event.ports[0].postMessage(reply);
        else broadcast(reply);
        return;
      }

      if (data.type === 'TEST_WRITE') {
        try {
          const threads = await idbGetThreads();
          const tid = 'sw-test-' + gid();
          const nowMs = now();
          const testThread = { id: tid, title: 'SW test ' + new Date(nowMs).toISOString(), pinned:false, updatedAt: nowMs, messages: [ { id:'swtest-'+gid(),role:'assistant',content:'sw test write @'+new Date(nowMs).toISOString(), contentParts:[{type:'text',text:'sw test write'}], createdAt: nowMs, updatedAt: nowMs } ]};
          threads.unshift(testThread);
          await idbWriteThreads(threads);
          const res = { type:'TEST_WRITE_RESULT', ok:true, tid };
          if (event.ports && event.ports[0]) event.ports[0].postMessage(res);
          else broadcast(res);
        } catch (err) {
          const res = { type:'TEST_WRITE_RESULT', ok:false, error: String(err && err.message ? err.message : err) };
          if (event.ports && event.ports[0]) event.ports[0].postMessage(res);
          else broadcast(res);
        }
        return;
      }

      if (data.type === 'READ_KEY') {
        const key = data.key || THREADS_KEY;
        try {
          const rec = await idbGetRaw(key);
          const val = rec ? rec.value : null;
          const res = { type:'READ_KEY_RESULT', ok:true, key, value: val };
          if (event.ports && event.ports[0]) event.ports[0].postMessage(res);
          else broadcast(res);
        } catch (err) {
          const res = { type:'READ_KEY_RESULT', ok:false, key, error: String(err && err.message ? err.message : err) };
          if (event.ports && event.ports[0]) event.ports[0].postMessage(res);
          else broadcast(res);
        }
        return;
      }

      if (data.type === 'LIST_SW_SAVED') {
        try {
          const threads = await idbGetThreads();
          const found = [];
          for (const t of (threads||[])) {
            for (const m of (t.messages||[])) {
              if (m && m.sw_streamId) found.push({ threadId: t.id, messageId: m.id, sw_streamId: m.sw_streamId, snippet: (m.content||'').slice(0,200) });
            }
          }
          const res = { type:'LIST_SW_SAVED_RESULT', ok:true, found };
          if (event.ports && event.ports[0]) event.ports[0].postMessage(res);
          else broadcast(res);
        } catch (err) {
          const res = { type:'LIST_SW_SAVED_RESULT', ok:false, error: String(err && err.message ? err.message : err) };
          if (event.ports && event.ports[0]) event.ports[0].postMessage(res);
          else broadcast(res);
        }
        return;
      }

    } catch (err) {
      const r = { type:'SW_ERROR', error: String(err && err.message ? err.message : err) };
      if (event.ports && event.ports[0]) event.ports[0].postMessage(r);
      else broadcast(r);
    }
  })();
});