flow-extension/background.js

// Background service worker.
//  * Trusted input via the Chrome DevTools Protocol — Flow's editor ignores synthetic
//    DOM events (isTrusted=false); CDP Input.* events are trusted so it registers them.
//  * Asset download — fetches the harvested media URL with the page's session cookies
//    (host_permission covers labs.google) and hands the bytes to the local server. Runs
//    in the worker, so it's not blocked by the page's CSP.

const attached = new Set();

function attach(tabId) {
  return new Promise((res, rej) =>
    chrome.debugger.attach({ tabId }, '1.3', () =>
      chrome.runtime.lastError ? rej(chrome.runtime.lastError) : res()));
}
function cmd(tabId, method, params) {
  return new Promise((res, rej) =>
    chrome.debugger.sendCommand({ tabId }, method, params || {}, (r) =>
      chrome.runtime.lastError ? rej(chrome.runtime.lastError) : res(r)));
}
async function ensure(tabId) {
  if (attached.has(tabId)) return;
  try { await attach(tabId); attached.add(tabId); }
  catch (e) {
    if (/already attached/i.test(String(e.message || e))) attached.add(tabId);
    else throw e;
  }
}

const ENTER = { key: 'Enter', code: 'Enter', windowsVirtualKeyCode: 13, nativeVirtualKeyCode: 13 };
const ESC = { key: 'Escape', code: 'Escape', windowsVirtualKeyCode: 27, nativeVirtualKeyCode: 27 };

// While a harvest pass runs, route every browser download into flowrinse/harvest/.
let harvestRouting = false;
chrome.downloads.onDeterminingFilename.addListener((item, suggest) => {
  if (!harvestRouting) return;
  suggest({ filename: `flowrinse/harvest/${(item.filename || 'asset').split(/[\\/]/).pop()}`, conflictAction: 'uniquify' });
});

chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
  const tabId = sender.tab && sender.tab.id;
  (async () => {
    try {
      if (msg.type === 'insertText') {
        await ensure(tabId);
        await cmd(tabId, 'Input.insertText', { text: msg.text });
        sendResponse({ ok: true });
      } else if (msg.type === 'pressEnter') {
        await ensure(tabId);
        await cmd(tabId, 'Input.dispatchKeyEvent', { type: 'keyDown', ...ENTER });
        await cmd(tabId, 'Input.dispatchKeyEvent', { type: 'keyUp', ...ENTER });
        sendResponse({ ok: true });
      } else if (msg.type === 'download') {
        // Browser-native download: uses the page's session cookies, follows the media
        // redirect, no CSP/CORS/base64. Lands under the browser's Downloads dir.
        const dlId = await new Promise((res, rej) => chrome.downloads.download(
          { url: msg.url, filename: msg.filename, conflictAction: 'uniquify', saveAs: false },
          (id) => chrome.runtime.lastError ? rej(chrome.runtime.lastError) : res(id)));
        sendResponse({ ok: dlId != null, id: dlId });
      } else if (msg.type === 'hoverAt') {
        await ensure(tabId);
        await cmd(tabId, 'Input.dispatchMouseEvent', { type: 'mouseMoved', x: msg.x, y: msg.y });
        sendResponse({ ok: true });
      } else if (msg.type === 'clickAt') {
        // Trusted click at viewport coords — Flow's menus ignore synthetic .click().
        await ensure(tabId);
        await cmd(tabId, 'Input.dispatchMouseEvent', { type: 'mouseMoved', x: msg.x, y: msg.y });
        await cmd(tabId, 'Input.dispatchMouseEvent', { type: 'mousePressed', x: msg.x, y: msg.y, button: 'left', clickCount: 1 });
        await cmd(tabId, 'Input.dispatchMouseEvent', { type: 'mouseReleased', x: msg.x, y: msg.y, button: 'left', clickCount: 1 });
        sendResponse({ ok: true });
      } else if (msg.type === 'pressEscape') {
        await ensure(tabId);
        await cmd(tabId, 'Input.dispatchKeyEvent', { type: 'keyDown', ...ESC });
        await cmd(tabId, 'Input.dispatchKeyEvent', { type: 'keyUp', ...ESC });
        sendResponse({ ok: true });
      } else if (msg.type === 'harvestRouting') {
        harvestRouting = !!msg.on;
        sendResponse({ ok: true });
      } else if (msg.type === 'hardReload') {
        // Cache-bypass reload — the by-hand fix for a wedged Flow session.
        if (attached.has(tabId)) { chrome.debugger.detach({ tabId }, () => {}); attached.delete(tabId); }
        chrome.tabs.reload(tabId, { bypassCache: true });
        sendResponse({ ok: true });
      } else if (msg.type === 'detach') {
        if (attached.has(tabId)) { chrome.debugger.detach({ tabId }, () => {}); attached.delete(tabId); }
        sendResponse({ ok: true });
      } else {
        sendResponse({ ok: false, error: 'unknown message' });
      }
    } catch (e) {
      sendResponse({ ok: false, error: String(e.message || e) });
    }
  })();
  return true; // async response
});

chrome.debugger.onDetach.addListener((src) => { if (src.tabId) attached.delete(src.tabId); });