postMessageRelay.js

/* eslint-env browser, webextensions */
var postMessageRelay; // eslint-disable-line no-var, no-unused-vars
(() => {
'use strict';

const port = browser.runtime.connect({name: 'webappfind-postMessage-content-script'});

function l (...msgs) {
  console.log(...msgs);
}

function sameOriginAndHasType (data) {
  return origin === location.origin && // Security
    data && data.webappfind && data.webappfind.type; // === type;
}
window.addEventListener('unload', () => {
  port.postMessage({type: 'unload'});
});

// Listen for subsequent requests to read the file (necessary also for
//  cases where the 'view' listener cannot be added immediately,
//  e.g., within our SVG-edit extension which is loaded by the main page
//  doing a script tag injection)
window.addEventListener('message', function ({origin, data}) {
  if (!sameOriginAndHasType(data)) {
    return;
  }
  const {type, pathID, content} = data.webappfind;
  // console.log('type', type, origin, data);
  switch (type) {
  case 'read':
    port.postMessage({type: 'read', pathID});
    break;
  case 'save':
    if (!pathID) { // User may be attempting edit with view-only access
      console.log('No path ID provided');
      return;
    }
    // l(content.length);
    l('saving... pathID:', pathID, 'length: ', content.length);
    port.postMessage({type: 'save', pathID, content});
    break;
  default:
    throw new TypeError('Unexpected type: ' + type);
  }
});

async function webappfindStart (result) {
  // l(JSON.stringify(result));
  const {pathID, content, site, mode, binary} = result;
  let {args, error} = result;
  /* if (site !== location.href) { // Not matching with about:newtab, but not needed
    console.log('Mismatch for ' + site + ' and ' + location.href);
    return;
  } */
  l('made it past site check', site);
  try {
    args = JSON.parse(args);
  } catch (err) {
    error = err;
  }

  const message = {
    webappfind: {
      type: 'view',
      pathID: mode === 'edit' ? pathID : null,
      args,
      binary,
      content,
      error: Boolean(error)
    }
  };
  console.log('sending', JSON.stringify(message));

  // Todo: make option to enable but indicate this is a major
  //  privacy leak! (at least until such time as a null
  //  origin is allowed)
  // This should work but
  //   [tabs.create](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/tabs/create)
  //   does not work with the `file:` protocol
  if (0 && site.startsWith('file:')) {
    l('file protocol');
    // Todo: We could (and should) set this message to the
    //  relevant URL if `file:` support is added
    try {
      window.postMessage(message, '*'); // location.href); // Gives security error while location.origin is `null` for file:
    } catch (e) {
      l('file protocol err: ' + e);
    }
  } else {
    l('pathID', pathID, 'contentlen', content.length || (content.data && content.data.length), 'location.origin', location.origin);
    window.postMessage(message, location.origin);
  }
}

port.onMessage.addListener(function ({type, result, pathID, error}) {
  switch (type) {
  case 'saveEnd':
    window.postMessage({
      webappfind: {
        type: 'save-end',
        pathID,
        // result,
        error: Boolean(error)
      }
    }, location.origin);
    break;
  case 'start':
    webappfindStart(result);
    break;
  default:
    throw new TypeError('Unexpected type: ' + type);
  }
});
})();