tools-app/extension/background.js

// background.js
// Listen for messages from content scripts or offscreen document

let isSniffing = false;
let lastClipboardContent = '';
let creatingOffscreenDocument;

// Hot-reconnect: Inject content script into existing tabs upon installation/update/restart
const injectContentScriptIfNeeded = async () => {
  const tabs = await chrome.tabs.query({ url: ['http://localhost/*', 'http://localhost:*/*', 'https://tools.7u.pl/*'] });
  for (const tab of tabs) {
    try {
      // Try to ping the tab first
      try {
        await chrome.tabs.sendMessage(tab.id, { action: 'ping' });
        // console.log('Content script already active in tab:', tab.id);
      } catch (e) {
        // If ping fails (no listener), inject script
        await chrome.scripting.executeScript({
          target: { tabId: tab.id },
          files: ['content.js']
        });
        // console.log('Injected content script into existing tab:', tab.id);
      }
    } catch (err) {
      // console.error('Failed to handle tab:', tab.id, err);
    }
  }
};

chrome.runtime.onInstalled.addListener(injectContentScriptIfNeeded);
// Also run on startup (when extension is enabled/reloaded)
injectContentScriptIfNeeded();

// Listen for alarms
try {
  if (chrome.alarms) {
    chrome.alarms.onAlarm.addListener((alarm) => {
      if (alarm.name === 'keepAlive') {
        refreshOffscreenDocument();
      }
    });
  } else {
    // console.warn('chrome.alarms API is not available.');
  }
} catch (e) {
  // console.error('Error initializing alarms:', e);
}

// Setup offscreen document
async function setupOffscreenDocument(path) {
  // Check if an offscreen document already exists
  const existingContexts = await chrome.runtime.getContexts({
    contextTypes: ['OFFSCREEN_DOCUMENT'],
  });

  if (existingContexts.length > 0) {
    return;
  }

  // Create an offscreen document
  if (creatingOffscreenDocument) {
    await creatingOffscreenDocument;
  } else {
    creatingOffscreenDocument = chrome.offscreen.createDocument({
      url: path,
      reasons: ['CLIPBOARD', 'AUDIO_PLAYBACK'],
      justification: 'To read clipboard content in the background and play notification sounds',
    });
    await creatingOffscreenDocument;
    creatingOffscreenDocument = null;
  }
}

// Lifecycle management: Refresh offscreen document every 25s to avoid 30s timeout
async function refreshOffscreenDocument() {
  if (isSniffing) {
    await chrome.offscreen.closeDocument();
    await setupOffscreenDocument('offscreen.html');
  }
}

// Start sniffing when requested
chrome.runtime.onMessage.addListener(async (request, sender, sendResponse) => {
  if (request.action === 'startSniffing') {
    if (isSniffing) {
       sendResponse({ status: 'already_started' });
       return true;
    }

    isSniffing = true;
    // console.log('Starting sniffing process...');
    await setupOffscreenDocument('offscreen.html');

    // Setup interval to keep offscreen alive - more aggressive
    chrome.alarms.create('keepAlive', { periodInMinutes: 0.1 }); // every 6 seconds

    sendResponse({ status: 'started' });
    return true;
  }

  if (request.action === 'stopSniffing') {
    if (!isSniffing) {
      sendResponse({ status: 'not_running' });
      return true;
    }

    isSniffing = false;
    // console.log('Stopping sniffing process...');

    // Stop alarm
    chrome.alarms.clear('keepAlive');

    // Close offscreen document
    if (creatingOffscreenDocument) {
      await creatingOffscreenDocument;
    }
    await chrome.offscreen.closeDocument().catch(() => {});
    creatingOffscreenDocument = null;

    sendResponse({ status: 'stopped' });
    return true;
  }

  if (request.type === 'clipboard-data' && request.target === 'background') {
    // Received data from offscreen document
    if (isSniffing && request.data && request.data !== lastClipboardContent) {
      lastClipboardContent = request.data;
      // console.log('Clipboard changed:', request.data.substring(0, 20) + '...');

      // Check if sound should be played
      chrome.storage.local.get(['playSound'], (result) => {
        if (result.playSound !== false) {
          // Send message to offscreen document to play sound
          chrome.runtime.sendMessage({
            target: 'offscreen',
            type: 'play-sound'
          });
        }
      });

      // Broadcast to all active tabs (content scripts)
      // We could filter by sender.tab.id if we knew which tab started sniffing,
      // but broadcasting is simpler for now and covers multiple open tabs of the app.
      const tabs = await chrome.tabs.query({ url: ['http://localhost/*', 'http://localhost:*/*', 'https://tools.7u.pl/*'] });
      for (const tab of tabs) {
        chrome.tabs.sendMessage(tab.id, {
          action: 'clipboardUpdate',
          content: request.data
        }).catch(() => {
          // Tab might be closed or content script not injected yet
        });
      }
    }
  }
});