background.js

import { createEngine } from './engine.js';

// Restrict the store before reading secrets. Content scripts receive a redacted snapshot.
const storageReady = chrome.storage.local.setAccessLevel({ accessLevel: 'TRUSTED_CONTEXTS' });
const engine = createEngine({
  storage: {
    get: async key => { await storageReady; return chrome.storage.local.get(key); },
    set: async value => { await storageReady; return chrome.storage.local.set(value); },
  },
  onChange: async state => {
    const text = !state.settings.enabled ? 'Ⅱ' : state.lastError ? '!' : state.stats.hidden ? String(Math.min(state.stats.hidden, 999)) : '';
    await Promise.allSettled([
      chrome.action.setBadgeText({ text }),
      chrome.action.setBadgeBackgroundColor({ color: state.lastError ? '#a75232' : !state.settings.enabled ? '#69716b' : '#365b43' }),
      (async () => {
        const tabs = await chrome.tabs.query({ url: ['https://x.com/*', 'https://twitter.com/*'] });
        await Promise.allSettled(tabs.map(tab => chrome.tabs.sendMessage(tab.id, { type: 'STATE_UPDATED', revision: state.revision })));
      })(),
    ]);
  },
});

export function authorize(message, sender) {
  if (sender.id !== chrome.runtime.id) throw new Error('Unrecognized sender.');
  const trusted = typeof sender.url === 'string' && sender.url.startsWith(chrome.runtime.getURL(''));
  let isFeed = false;
  try { const url = new URL(sender.url); isFeed = url.protocol === 'https:' && ['x.com', 'twitter.com'].includes(url.hostname) && sender.frameId === 0; } catch { /* Deny unknown contexts. */ }
  if (!trusted && !isFeed) throw new Error('Sift only handles requests from its settings or X feed.');
  if (!trusted) {
    const allowed = ['GET_STATE', 'CLASSIFY_POSTS', 'SAVE_FEEDBACK', 'OPEN_APP', 'SAVE_SETTINGS'];
    if (!allowed.includes(message?.type)) throw new Error('Open Sift settings to perform this action.');
    if (message.type === 'SAVE_SETTINGS' && (!message.settings || Object.keys(message.settings).some(key => key !== 'enabled'))) throw new Error('Only filtering can be toggled from the feed.');
  }
  return trusted;
}

chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  (async () => {
    const trusted = authorize(message, sender);
    if (message.type === 'OPEN_APP') {
      const tab = ['preferences', 'review', 'connection'].includes(message.tab) ? message.tab : 'preferences';
      await chrome.tabs.create({ url: chrome.runtime.getURL(`app.html#${tab}`) });
      return { ok: true };
    }
    if (message.type === 'OPEN_X') {
      await chrome.tabs.create({ url: 'https://x.com/home' });
      return { ok: true };
    }
    return engine.handle(message, trusted);
  })().then(sendResponse, error => sendResponse({ ok: false, error: error.message || 'Sift could not complete that action.' }));
  return true;
});

chrome.runtime.onInstalled.addListener(async ({ reason }) => {
  try {
    await engine.handle({ type: 'SAVE_SETTINGS', settings: {} });
    if (reason === 'install') await chrome.tabs.create({ url: chrome.runtime.getURL('app.html#connection') });
  } catch (error) { console.error('Sift could not initialize:', error.message); }
});