/**
* GNU LibreJS - A browser add-on to block nonfree nontrivial JavaScript.
* *
* Copyright (C) 2017, 2018 Nathan Nichols
* Copyright (C) 2018 Ruben Rodriguez <ruben@gnu.org>
*
* This file is part of GNU LibreJS.
*
* GNU LibreJS is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GNU LibreJS is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU LibreJS.  If not, see <http://www.gnu.org/licenses/>.
*/

const acorn = require('acorn');
const legacy_license_lib = require('./legacy_license_check.js');
const { ResponseProcessor } = require('./bg/ResponseProcessor');
const { Storage, ListStore, hash } = require('./common/Storage');
const { ListManager } = require('./bg/ListManager');
const { ExternalLicenses } = require('./bg/ExternalLicenses');
const { licenses } = require('./license_definitions');
const { patternUtils } = require('./pattern_utils');

console.log('main_background.js');
/**
*	If this is true, it evaluates entire scripts instead of returning as soon as it encounters a violation.
*
*	Also, it controls whether or not this part of the code logs to the console.
*
*/
var DEBUG = false; // debug the JS evaluation
var PRINT_DEBUG = false; // Everything else
var time = Date.now();

function dbg_print(a, b) {
  if (PRINT_DEBUG == true) {
    console.log('Time spent so far: ' + (Date.now() - time) / 1000 + ' seconds');
    if (b === undefined) {
      console.log(a);
    } else {
      console.log(a, b);
    }
  }
}

/*
  NONTRIVIAL THINGS:
  - Fetch
  - XMLhttpRequest
  - eval()
  - ?
  JAVASCRIPT CAN BE FOUND IN:
  - Event handlers (onclick, onload, onsubmit, etc.)
  - <script>JS</script>
  - <script src="/JS.js"></script>
  WAYS TO DETERMINE PASS/FAIL:
  - "// @license [magnet link] [identifier]" then "// @license-end" (may also use /* comments)
  - Automatic whitelist: (http://bzr.savannah.gnu.org/lh/librejs/dev/annotate/head:/data/script_libraries/script-libraries.json_
*/

// These are objects that it will search for in an initial regex pass over non-free scripts.
const RESERVED_OBJECTS = [
  //"document",
  //"window",
  'fetch',
  'XMLHttpRequest',
  'chrome', // only on chrome
  'browser', // only on firefox
  'eval'
];
const LOOPKEYS = new Set(['for', 'if', 'while', 'switch']);
const OPERATORS = new Set(['||', '&&', '=', '==', '++', '--', '+=', '-=', '*']);
// @license match, second and third capture groups are canonicalUrl
// and license name
const OPENING_LICENSE_RE = /\/[/*]\s*?(@license)\s+(\S+)\s+(\S+).*$/mi;
const CLOSING_LICENSE_RE = /\/([*/])\s*@license-end\s*(\*\/)?/mi;

/*
*
*	Called when something changes the persistent data of the add-on.
*
*	The only things that should need to change this data are:
*	a) The "Whitelist this page" button
*	b) The options screen
*
*	When the actual blocking is implemented, this will need to comminicate
*	with its code to update accordingly
*
*/
function options_listener(changes, area) {
  dbg_print('Items updated in area' + area + ': ');

  var changedItems = Object.keys(changes);
  var changed_items = '';
  for (var i = 0; i < changedItems.length; i++) {
    var item = changedItems[i];
    changed_items += item + ',';
  }
  dbg_print(changed_items);

}


var activeMessagePorts = {};
var activityReports = {};
async function createReport(initializer) {
  if (!(initializer && (initializer.url || initializer.tabId))) {
    throw new Error('createReport() needs an URL or a tabId at least');
  }
  let template = {
    'accepted': [],
    'blocked': [],
    'blacklisted': [],
    'whitelisted': [],
    'unknown': [],
  };
  template = Object.assign(template, initializer);
  let [url] = (template.url || (await browser.tabs.get(initializer.tabId)).url).split('#');
  template.url = url;
  template.site = ListStore.siteItem(url);
  template.siteStatus = listManager.getStatus(template.site);
  let list = { 'whitelisted': whitelist, 'blacklisted': blacklist }[template.siteStatus];
  if (list) {
    template.listedSite = ListManager.siteMatch(template.site, list);
  }
  return template;
}

/**
*	Executes the "Display this report in new tab" function
*	by opening a new tab with whatever HTML is in the popup
*	at the moment.
*/
async function openReportInTab(data) {
  let popupURL = await browser.browserAction.getPopup({});
  let tab = await browser.tabs.create({ url: `${popupURL}#fromTab=${data.tabId}` });
  activityReports[tab.id] = await createReport(data);
}

/**
*
*	Clears local storage (the persistent data)
*
*/
function debug_delete_local() {
  browser.storage.local.clear();
  dbg_print('Local storage cleared');
}

/**
*
*	Prints local storage (the persistent data) as well as the temporary popup object
*
*/
function debug_print_local() {
  function storage_got(items) {
    console.log('%c Local storage: ', 'color: red;');
    for (var i in items) {
      console.log('%c ' + i + ' = ' + items[i], 'color: blue;');
    }
  }
  console.log('%c Variable \'activityReports\': ', 'color: red;');
  console.log(activityReports);
  browser.storage.local.get(storage_got);
}

/**
*
*
*	Sends a message to the content script that sets the popup entries for a tab.
*
*	var example_blocked_info = {
*		"accepted": [["REASON 1","SOURCE 1"],["REASON 2","SOURCE 2"]],
*		"blocked": [["REASON 1","SOURCE 1"],["REASON 2","SOURCE 2"]],
*		"url": "example.com"
*	}
*
*	NOTE: This WILL break if you provide inconsistent URLs to it.
*	Make sure it will use the right URL when refering to a certain script.
*
*/
async function updateReport(tabId, oldReport, updateUI = false) {
  let { url } = oldReport;
  let newReport = await createReport({ url, tabId });
  for (let property of Object.keys(oldReport)) {
    let entries = oldReport[property];
    if (!Array.isArray(entries)) continue;
    let defValue = property === 'accepted' || property === 'blocked' ? property : 'unknown';
    for (let script of entries) {
      let status = listManager.getStatus(script[0], defValue);
      if (Array.isArray(newReport[status])) newReport[status].push(script);
    }
  }
  activityReports[tabId] = newReport;
  if (browser.sessions) browser.sessions.setTabValue(tabId, url, newReport);
  dbg_print(newReport);
  if (updateUI && activeMessagePorts[tabId]) {
    dbg_print(`[TABID: ${tabId}] Sending script blocking report directly to browser action.`);
    activeMessagePorts[tabId].postMessage({ show_info: newReport });
  }
}

/** Updates the report for tab with tabId with action.
 *
 *	This is what you call when a page gets changed to update the info
 *	box.
 * 
 *	Sends a message to the content script that adds a popup entry for
 *	a tab.
 *
 *	The action argument is an object with two properties: one named of
 * "accepted","blocked", "whitelisted", "blacklisted", whose value is
 * the array [scriptName, reason], and another named "url". Example:
 * action =
 *   {
 *     "accepted": ["jquery.js (someHash)", "Whitelisted by user"],
 *     "url": "https://example.com/js/jquery.js"
 *   }
 *
 *  Overrides the action type with the white/blacklist status for
 *  scriptName, if any.  Then add the entry if scriptName is not
 *  already in the entries associated with the action type.
 *
 *	Returns one of "whitelisted", "blacklisted", "blocked", "accepted"
 *	or "unknown"
 *
 *	NOTE: This WILL break if you provide inconsistent URLs to it.
 *	Make sure it will use the right URL when refering to a certain
 *	script.
 *
 */
async function addReportEntry(tabId, action) {

  const actionPair = Object.entries(action).find(
    ([k, _]) => ['accepted', 'blocked', 'whitelisted', 'blacklisted'].indexOf(k) != -1);
  if (!actionPair) {
    console.debug('Wrong action', action);
    return 'unknown';
  }
  const [actionType, actionValue] = actionPair;
  const scriptName = actionValue[0];

  const report = activityReports[tabId] || (activityReports[tabId] = await createReport({ tabId }));
  let entryType;
  // Update the report if the scriptName is new for the entryType.
  try {
    entryType = listManager.getStatus(scriptName, actionType);
    const entries = report[entryType];
    if (!entries.find(e => e[0] === scriptName)) {
      dbg_print(activityReports);
      dbg_print(activityReports[tabId]);
      dbg_print(entryType);
      entries.push(actionValue);
    }
  } catch (e) {
    console.error('action %o, type %s, entryType %s', action, actionType, entryType, e);
    entryType = 'unknown';
  }

  // Refresh the main panel script list.
  if (activeMessagePorts[tabId]) {
    activeMessagePorts[tabId].postMessage({ show_info: report });
  }

  if (browser.sessions) browser.sessions.setTabValue(tabId, report.url, report);
  updateBadge(tabId, report);
  return entryType;
}


function getDomain(url) {
  let domain = url.replace('http://', '').replace('https://', '').split(/[/?#]/)[0];
  if (url.indexOf('http://') == 0) {
    domain = 'http://' + domain;
  }
  else if (url.indexOf('https://') == 0) {
    domain = 'https://' + domain;
  }
  domain = domain + '/';
  domain = domain.replace(/ /g, '');
  return domain;
}

/**
*
*	This is the callback where the content scripts of the browser action will contact the background script.
*
*/
async function connected(p) {
  if (p.name === 'contact_finder') {
    // style the contact finder panel
    await browser.tabs.insertCSS(p.sender.tab.id, {
      file: '/content/dialog.css',
      cssOrigin: 'user',
      matchAboutBlank: true,
      allFrames: true
    });

    // Send a message back with the relevant settings
    p.postMessage(await browser.storage.local.get(['pref_subject', 'pref_body']));
    return;
  }
  p.onMessage.addListener(async function(m) {
    var update = false;
    var contact_finder = false;

    for (let action of ['whitelist', 'blacklist', 'forget']) {
      if (m[action]) {
        let [key] = m[action];
        if (m.site) {
          key = ListStore.siteItem(m.site);
        } else {
          key = ListStore.inlineItem(key) || key;
        }
        await listManager[action](key);
        update = true;
      }
    }

    if (m.report_tab) {
      openReportInTab(m.report_tab);
    }
    // a debug feature
    if (m['printlocalstorage'] !== undefined) {
      console.log('Print local storage');
      debug_print_local();
    }
    // invoke_contact_finder
    if (m['invoke_contact_finder'] !== undefined) {
      contact_finder = true;
      await injectContactFinder();
    }
    // a debug feature (maybe give the user an option to do this?)
    if (m['deletelocalstorage'] !== undefined) {
      console.log('Delete local storage');
      debug_delete_local();
    }

    let tabs = await browser.tabs.query({ active: true, currentWindow: true });

    if (contact_finder) {
      let tab = tabs.pop();
      dbg_print(`[TABID:${tab.id}] Injecting contact finder`);
      //inject_contact_finder(tabs[0]["id"]);
    }
    if (update || m.update && activityReports[m.tabId]) {
      let tabId = 'tabId' in m ? m.tabId : tabs.pop().id;
      dbg_print(`%c updating tab ${tabId}`, 'color: red;');
      activeMessagePorts[tabId] = p;
      await updateReport(tabId, activityReports[tabId], true);
    } else {
      for (let tab of tabs) {
        if (activityReports[tab.id]) {
          // If we have some data stored here for this tabID, send it
          dbg_print(`[TABID: ${tab.id}] Sending stored data associated with browser action'`);
          p.postMessage({ 'show_info': activityReports[tab.id] });
        } else {
          // create a new entry
          let report = activityReports[tab.id] = await createReport({ 'url': tab.url, tabId: tab.id });
          p.postMessage({ show_info: report });
          dbg_print(`[TABID: ${tab.id}] No data found, creating a new entry for this window.`);
        }
      }
    }
  });
}

/**
*	The callback for tab closings.
*
*	Delete the info we are storing about this tab if there is any.
*
*/
function delete_removed_tab_info(tab_id, _) {
  dbg_print('[TABID:' + tab_id + ']' + 'Deleting stored info about closed tab');
  if (activityReports[tab_id] !== undefined) {
    delete activityReports[tab_id];
  }
  if (activeMessagePorts[tab_id] !== undefined) {
    delete activeMessagePorts[tab_id];
  }
  ExternalLicenses.purgeCache(tab_id);
}

/**
*	Called when the tab gets updated / activated
*
*	Here we check if  new tab's url matches activityReports[tabId].url, and if
* it doesn't we use the session cached value (if any).
*
*/

async function onTabUpdated(tabId, _, tab) {
  let [url] = tab.url.split('#');
  let report = activityReports[tabId];
  if (!(report && report.url === url)) {
    let cache = browser.sessions &&
      await browser.sessions.getTabValue(tabId, url) || null;
    // on session restore tabIds may change
    if (cache && cache.tabId !== tabId) cache.tabId = tabId;
    updateBadge(tabId, activityReports[tabId] = cache);
  }
}

async function onTabActivated({ tabId }) {
  await onTabUpdated(tabId, {}, await browser.tabs.get(tabId));
}

/* *********************************************************************************************** */

const fnameData = require('./fname_data.json').fname_data;

//************************this part can be tested in the HTML file index.html's script test.js****************************

/**
 * Checks whether script is trivial by analysing its tokens.
 *
 * Returns an array of
 * [flag (boolean, true if trivial), reason (string, human readable report)].
 */
function fullEvaluate(script) {
  if (script === undefined || script == '') {
    return [true, 'Harmless null script'];
  }

  let tokens;

  try {
    tokens = acorn.tokenizer(script);
  } catch (e) {
    console.warn('Tokenizer could not be initiated (probably invalid code)');
    return [false, 'Tokenizer could not be initiated (probably invalid code)'];
  }
  try {
    var toke = tokens.getToken();
  } catch (e) {
    console.log(script);
    console.log(e);
    console.warn('couldn\'t get first token (probably invalid code)');
    console.warn('Continuing evaluation');
  }

  let amtloops = 0;
  let definesFunctions = false;

  /**
  * Given the end of an identifer token, it tests for parentheses
  */
  function is_bsn(end) {
    let i = 0;
    while (script.charAt(end + i).match(/\s/g) !== null) {
      i++;
      if (i >= script.length - 1) {
        return false;
      }
    }
    return script.charAt(end + i) == '[';
  }

  function evaluateByTokenValue(toke) {
    const value = toke.value;
    if (OPERATORS.has(value)) {
      // It's just an operator. Javascript doesn't have operator overloading so it must be some
      // kind of primitive (I.e. a number)
    } else {
      const status = fnameData[value];
      if (status === true) { // is the identifier banned?
        dbg_print('%c NONTRIVIAL: nontrivial token: \'' + value + '\'', 'color:red');
        if (DEBUG == false) {
          return [false, 'NONTRIVIAL: nontrivial token: \'' + value + '\''];
        }
      } else if (status === false || status === undefined) {// is the identifier not banned or user defined?
        // Is there bracket suffix notation?
        if (is_bsn(toke.end)) {
          dbg_print('%c NONTRIVIAL: Bracket suffix notation on variable \'' + value + '\'', 'color:red');
          if (DEBUG == false) {
            return [false, '%c NONTRIVIAL: Bracket suffix notation on variable \'' + value + '\''];
          }
        }
      } else {
        dbg_print('trivial token:' + value);
      }
    }
    return [true, ''];
  }

  function evaluateByTokenTypeKeyword(keyword) {
    if (toke.type.keyword == 'function') {
      dbg_print('%c NOTICE: Function declaration.', 'color:green');
      definesFunctions = true;
    }

    if (LOOPKEYS.has(keyword)) {
      amtloops++;
      if (amtloops > 3) {
        dbg_print('%c NONTRIVIAL: Too many loops/conditionals.', 'color:red');
        if (DEBUG == false) {
          return [false, 'NONTRIVIAL: Too many loops/conditionals.'];
        }
      }
    }
    return [true, ''];
  }

  while (toke !== undefined && toke.type != acorn.tokTypes.eof) {
    if (toke.type.keyword !== undefined) {
      //dbg_print("Keyword:");
      //dbg_print(toke);

      // This type of loop detection ignores functional loop alternatives and ternary operators
      const tokeTypeRes = evaluateByTokenTypeKeyword(toke.type.keyword);
      if (tokeTypeRes[0] === false) {
        return tokeTypeRes;
      }
    } else if (toke.value !== undefined) {
      const tokeValRes = evaluateByTokenValue(toke);
      if (tokeValRes[0] === false) {
        return tokeValRes;
      }
    }
    // If not a keyword or an identifier it's some kind of operator, field parenthesis, brackets
    try {
      toke = tokens.getToken();
    } catch (e) {
      dbg_print('Denied script because it cannot be parsed.');
      return [false, 'NONTRIVIAL: Cannot be parsed. This could mean it is a 404 error.'];
    }
  }

  dbg_print('%cAppears to be trivial.', 'color:green;');
  if (definesFunctions === true)
    return [true, 'Script appears to be trivial but defines functions.'];
  else
    return [true, 'Script appears to be trivial.'];
}


//****************************************************************************************************
/**
*	This is the entry point for full code evaluation for triviality.
*
*	Performs the initial pass on code to see if it needs to be completely parsed
*
*	This can only determine if a script is bad, not if it's good
*
*	If it passes the intitial pass, it runs the full pass and returns the result

*	It returns an array of [flag (boolean, false if "bad"), reason (string, human readable report)]
*
*/
function evaluate(script, name) {
  const reservedResult = evaluateForReservedObj(script, name);
  if (reservedResult[0] === true) {
    dbg_print('%c pass', 'color:green;');
  } else {
    return reservedResult;
  }

  return fullEvaluate(script);
}

function evaluateForReservedObj(script, name) {
  function reservedObjectRegex(object) {
    const arithOperators = '\\+\\-\\*\\/\\%\\=';
    return new RegExp('(?:[^\\w\\d]|^|(?:' + arithOperators + '))' + object + '(?:\\s*?(?:[\\;\\,\\.\\(\\[])\\s*?)', 'g');
  }
  const mlComment = /\/\*([\s\S]+?)\*\//g;
  const ilComment = /\/\/.+/gm;
  const temp = script.replace(/'.+?'+/gm, '\'string\'').replace(/".+?"+/gm, '"string"').replace(mlComment, '').replace(ilComment, '');
  dbg_print('%c ------evaluation results for ' + name + '------', 'color:white');
  dbg_print('Script accesses reserved objects?');

  // 	This is where individual "passes" are made over the code
  for (const reserved of RESERVED_OBJECTS) {
    if (reservedObjectRegex(reserved).exec(temp) != null) {
      dbg_print('%c fail', 'color:red;');
      return [false, 'Script uses a reserved object (' + reserved + ')'];
    }
  }
  return [true, 'Reserved object not found.'];
}

// checks license in an OPENING_LICENSE_RE match
function checkLicenseInMatch(match) {
  if (!(Array.isArray(match) && match.length >= 4)) {
    return [false, 'Malformed or unrecognized license tag.'];
  }

  const [all, first] = [match[0], match[2].replace('&amp;', '&')];

  for (const key in licenses) {
    // Match by canonicalUrl
    for (const url of licenses[key].canonicalUrl) {
      if (first === url || first === url.replace('^http://', 'https://')) {
        return [true, `Recognized license: "${licenses[key].licenseName}".`];
      }
    }
  }
  return [false, `Unrecognized license tag: "${all}"`];
}


/**
 *
 *	Evaluates the content of a script for licenses and triviality
 * scriptSrc: content of the script; name: script name; external:
 * whether the script is external
 *
 *	Returns
 *	[
 *		true (accepted) or false (denied),
 *		edited content,
 *		reason text
 *	]
 */
function licenseRead(scriptSrc, name, external = false) {
  let inSrc = scriptSrc.trim();
  if (!inSrc) return [true, scriptSrc, 'Empty source.'];

  // Check for @licstart .. @licend method
  const license = legacy_license_lib.check(scriptSrc);
  if (license) {
    return [true, scriptSrc, `Licensed under: ${license}`];
  }
  if (listManager.builtInHashes.has(hash(scriptSrc))) {
    return [true, scriptSrc, 'Common script known to be free software.'];
  }

  let outSrc = '';
  let reason = '';
  let partsDenied = false;
  let partsAccepted = false;

  function checkTriviality(s) {
    if (!patternUtils.removeJsComments(s).trim()) {
      return true; // empty, ignore it
    }
    const [trivial, message] = external ?
      [false, 'External script with no known license']
      : evaluate(s, name);
    if (trivial) {
      partsAccepted = true;
      outSrc += s;
    } else {
      partsDenied = true;
      if (s.startsWith('javascript:'))
        outSrc += `# LIBREJS BLOCKED: ${message}`;
      else
        outSrc += `/*\nLIBREJS BLOCKED: ${message}\n*/`;
    }
    reason += `\n${message}`;
  }

  // Consume inSrc by checking licenses in all @license / @license-end
  // blocks and triviality outside these blocks
  while (inSrc) {
    const openingMatch = OPENING_LICENSE_RE.exec(inSrc);
    const openingIndex = openingMatch ? openingMatch.index : inSrc.length;
    // checks the triviality of the code before the license tag, if any
    checkTriviality(inSrc.substring(0, openingIndex));
    inSrc = inSrc.substring(openingIndex);
    if (!inSrc) break;

    // checks the remaining part, that starts with an @license
    const closureMatch = CLOSING_LICENSE_RE.exec(inSrc);
    if (!closureMatch) {
      const msg = 'ERROR: @license with no @license-end';
      return [false, `\n/*\n ${msg} \n*/\n`, msg];
    }
    let closureEndIndex = closureMatch.index + closureMatch[0].length;
    const commentEndOffset = inSrc.substring(closureEndIndex).indexOf(closureMatch[1] === '*' ? '*/' : '\n');
    if (commentEndOffset !== -1) {
      closureEndIndex += commentEndOffset;
    }

    const [licenseOK, message] = checkLicenseInMatch(openingMatch);
    if (licenseOK) {
      outSrc += inSrc.substr(0, closureEndIndex);
      partsAccepted = true;
    } else {
      outSrc += `\n/*\n${message}\n*/\n`;
      partsDenied = true;
    }
    reason += `\n${message}`;

    // trim off everything we just evaluated
    inSrc = inSrc.substring(closureEndIndex).trim();
  }

  if (partsDenied) {
    if (partsAccepted) {
      reason = `Some parts of the script have been disabled (check the source for details).\n^--- ${reason}`;
    }
    return [false, outSrc, reason];
  }

  return [true, scriptSrc, reason];
}

/* *********************************************************************************************** */
// TODO: Test if this script is being loaded from another domain compared to activityReports[tabid]["url"]

/**
*	Asynchronous function, returns the final edited script as a string,
* or an array containing it -1, if returnsPair is true
*/
async function getScript(scriptSrc, url, tabId = -1, whitelisted = false, returnsPair = true, isExternal = false) {
  function result(scriptSource) {
    return returnsPair ? scriptSource : [scriptSource, -1];
  }

  const scriptName = url.split('/').pop();
  if (whitelisted) {
    if (tabId !== -1) {
      const site = ListManager.siteMatch(url, whitelist);
      // Accept without reading script, it was explicitly whitelisted
      const reason = site
        ? `All ${site} whitelisted by user`
        : 'Address whitelisted by user';
      addReportEntry(tabId, { 'whitelisted': [site || url, reason], url });
    }
    if (scriptSrc.startsWith('javascript:'))
      return result(scriptSrc);
    else
      return result(`/* LibreJS: script whitelisted by user preference. */\n${scriptSrc}`);
  }

  let [accepted, editedSource, reason] = licenseRead(scriptSrc, scriptName, isExternal);

  if (tabId < 0) {
    return result(editedSource);
  }

  const domain = getDomain(url);
  const report = activityReports[tabId] || (activityReports[tabId] = await createReport({ tabId }));
  updateBadge(tabId, report, !accepted);
  const category = await addReportEntry(tabId, { 'url': domain, [accepted ? 'accepted' : 'blocked']: [url, reason] });
  switch (category) {
    case 'blacklisted': {
      const edited = `/* LibreJS: script ${category} by user. */`;
      return result(scriptSrc.startsWith('javascript:')
        ? `javascript:void(${encodeURIComponent(edited)})` : edited);
    }
    case 'whitelisted': {
      return result(scriptSrc.startsWith('javascript:')
        ? scriptSrc : `/* LibreJS: script ${category} by user. */\n${scriptSrc}`);
    }
    default: {
      const scriptSource = accepted ? scriptSrc : editedSource;
      return result(scriptSrc.startsWith('javascript:')
        ? (accepted ? scriptSource : `javascript:void(/* ${scriptSource} */)`)
        : `/* LibreJS: script ${category}. */\n${scriptSource}`
      );
    }
  }
}

// Updates the extension icon in the toolbar.
function updateBadge(tabId, report = null, forceRed = false) {
  const blockedCount = report ? report.blocked.length + report.blacklisted.length : 0;
  const [text, color] = blockedCount > 0 || forceRed
    ? [blockedCount && blockedCount.toString() || '!', 'red'] : ['✓', 'green']
  const { browserAction } = browser;
  if ('setBadgeText' in browserAction) {
    browserAction.setBadgeText({ text, tabId });
    browserAction.setBadgeBackgroundColor({ color, tabId });
  } else {
    // Mobile
    browserAction.setTitle({ title: `LibreJS (${text})`, tabId });
  }
}

function blockGoogleAnalytics(request) {
  let { url } = request;
  let res = {};
  if (url === 'https://www.google-analytics.com/analytics.js' ||
    /^https:\/\/www\.google\.com\/analytics\/[^#]/.test(url)
  ) {
    res.cancel = true;
  }
  return res;
}

async function blockBlacklistedScripts(request) {
  let { url, tabId, documentUrl } = request;
  url = ListStore.urlItem(url);
  let status = listManager.getStatus(url);
  if (status !== 'blacklisted') return {};
  let blacklistedSite = ListManager.siteMatch(url, blacklist);
  await addReportEntry(tabId, {
    url: documentUrl,
    'blacklisted': [url, /\*/.test(blacklistedSite) ? `User blacklisted ${blacklistedSite}` : 'Blacklisted by user']
  });
  return { cancel: true };
}

/**
*	This listener gets called as soon as we've got all the HTTP headers, can guess
* content type and encoding, and therefore correctly parse HTML documents
* and external script inclusions in search of non-free JavaScript
*/

var ResponseHandler = {
  /**
  *	Enforce white/black lists for url/site early (hashes will be handled later)
  */
  async pre(response) {
    let { request } = response;
    let { url, type, tabId, frameId, documentUrl } = request;

    let fullUrl = url;
    url = ListStore.urlItem(url);
    let site = ListStore.siteItem(url);

    let blacklistedSite = ListManager.siteMatch(site, blacklist);
    let blacklisted = blacklistedSite || blacklist.contains(url);
    let topUrl = type === 'sub_frame' && request.frameAncestors && request.frameAncestors.pop() || documentUrl;

    if (blacklisted) {
      if (type === 'script') {
        // this shouldn't happen, because we intercept earlier in blockBlacklistedScripts()
        return ResponseProcessor.REJECT;
      }
      if (type === 'main_frame') { // we handle the page change here too, since we won't call edit_html()
        activityReports[tabId] = await createReport({ url: fullUrl, tabId });
        // Go on without parsing the page: it was explicitly blacklisted
        let reason = blacklistedSite
          ? `All ${blacklistedSite} blacklisted by user`
          : 'Address blacklisted by user';
        await addReportEntry(tabId, { 'blacklisted': [blacklistedSite || url, reason], url: fullUrl });
      }
      // use CSP to restrict JavaScript execution in the page
      request.responseHeaders.unshift({
        name: 'Content-security-policy',
        value: 'script-src \'none\';'
      });
      return { responseHeaders: request.responseHeaders }; // let's skip the inline script parsing, since we block by CSP
    } else {
      let whitelistedSite = ListManager.siteMatch(site, whitelist);
      let whitelisted = response.whitelisted = whitelistedSite || whitelist.contains(url);
      if (type === 'script') {
        if (whitelisted) {
          // accept the script and stop processing
          addReportEntry(tabId, {
            url: topUrl,
            'whitelisted': [url, whitelistedSite ? `User whitelisted ${whitelistedSite}` : 'Whitelisted by user']
          });
          return ResponseProcessor.ACCEPT;
        } else {
          // Check for the weblabel method
          const scriptInfo = await ExternalLicenses.check({ url: fullUrl, tabId, frameId, documentUrl });
          if (scriptInfo) {
            const [verdict, ret] = scriptInfo.free ? ['accepted', ResponseProcessor.ACCEPT] : ['blocked', ResponseProcessor.REJECT];
            const msg = scriptInfo.toString();
            addReportEntry(tabId, { url, [verdict]: [url, msg] });
            return ret;
          }
        }
      }
    }
    // it's a page (it's too early to report) or an unknown script:
    //  let's keep processing
    return ResponseProcessor.CONTINUE;
  },

  /**
  *	Here we do the heavylifting, analyzing unknown scripts
  */
  async post(response) {
    const { type } = response.request;
    const handle_it = type === 'script' ? handle_script : handle_html;
    return await handle_it(response, response.whitelisted);
  }
}

/**
* Here we handle external script requests
*/
async function handle_script(response, whitelisted) {
  let { text, request } = response;
  let { url, tabId } = request;
  url = ListStore.urlItem(url);
  let edited = await getScript(text, url, tabId, whitelisted, returnsPair = false, isExternal = true);
  return Array.isArray(edited) ? edited[0] : edited;
}

/**
* Serializes HTMLDocument objects including the root element and
*	the DOCTYPE declaration
*/
function doc2HTML(doc) {
  let s = doc.documentElement.outerHTML;
  if (doc.doctype) {
    let dt = doc.doctype;
    let sDoctype = `<!DOCTYPE ${dt.name || 'html'}`;
    if (dt.publicId) sDoctype += ` PUBLIC "${dt.publicId}"`;
    if (dt.systemId) sDoctype += ` "${dt.systemId}"`;
    s = `${sDoctype}>\n${s}`;
  }
  return s;
}

/**
* Shortcut to create a correctly namespaced DOM HTML elements
*/
function createHTMLElement(doc, name) {
  return doc.createElementNS('http://www.w3.org/1999/xhtml', name);
}

/**
* Replace any element with a span having the same content (useful to force
* NOSCRIPT elements to visible the same way as NoScript and uBlock do)
*/
function forceElement(doc, element) {
  let replacement = createHTMLElement(doc, 'span');
  replacement.innerHTML = element.innerHTML;
  element.replaceWith(replacement);
  return replacement;
}

/**
*	Forces displaying any element having the "data-librejs-display" attribute and
* <noscript> elements on pages where LibreJS disabled inline scripts (unless
* they have the "data-librejs-nodisplay" attribute).
*/
function forceNoscriptElements(doc) {
  let shown = 0;
  // inspired by NoScript's onScriptDisabled.js
  for (let noscript of doc.querySelectorAll('noscript:not([data-librejs-nodisplay])')) {
    let replacement = forceElement(doc, noscript);
    // emulate meta-refresh
    let meta = replacement.querySelector('meta[http-equiv="refresh"]');
    if (meta) {
      doc.head.appendChild(meta);
    }
    shown++;
  }
  return shown;
}
/**
*	Forces displaying any element having the "data-librejs-display" attribute and
* <noscript> elements on pages where LibreJS disabled inline scripts (unless
* they have the "data-librejs-nodisplay" attribute).
*/
function showConditionalElements(doc) {
  let shown = 0;
  for (let element of document.querySelectorAll('[data-librejs-display]')) {
    forceElement(doc, element);
    shown++;
  }
  return shown;
}

/**
*	Tests to see if the intrinsic events on the page are free or not.
*	returns true if they are, false if they're not
*/
function read_metadata(meta_element) {

  if (meta_element === undefined || meta_element === null) {
    return;
  }

  console.log('metadata found');

  var metadata = {};

  try {
    metadata = JSON.parse(meta_element.innerHTML);
  } catch (error) {
    console.log('Could not parse metadata on page.')
    return false;
  }

  var license_str = metadata['intrinsic-events'];
  if (license_str === undefined) {
    console.log('No intrinsic events license');
    return false;
  }
  console.log(license_str);

  var parts = license_str.split(' ');
  if (parts.length != 2) {
    console.log('invalid (>2 tokens)');
    return false;
  }

  // this should be adequete to escape the HTML escaping
  parts[0] = parts[0].replace(/&amp;/g, '&');

  try {
    for (const url of licenses[parts[1]].canonicalUrl) {
      if (url.startsWith('magnet:') && url == parts[0]) {
        return true;
      }
    }
    console.log('invalid (doesn\'t match licenses)');
    return false;
  } catch (error) {
    console.log('invalid (threw error, key didn\'t exist)');
    return false;
  }
}
/**

* 	Reads/changes the HTML of a page and the scripts within it.
*/
async function editHtml(html, documentUrl, tabId, frameId, whitelisted) {

  var parser = new DOMParser();
  var html_doc = parser.parseFromString(html, 'text/html');

  // moves external licenses reference, if any, before any <SCRIPT> element
  ExternalLicenses.optimizeDocument(html_doc, { tabId, frameId, documentUrl });

  let url = ListStore.urlItem(documentUrl);

  if (whitelisted) { // don't bother rewriting
    await getScript(html, url, tabId, whitelisted); // generates whitelisted report
    return null;
  }

  var scripts = html_doc.scripts;

  var meta_element = html_doc.getElementById('LibreJS-info');
  var first_script_src = '';

  // get the potential inline source that can contain a license
  for (let script of scripts) {
    // The script must be in-line and exist
    if (script && !script.src) {
      first_script_src = script.textContent;
      break;
    }
  }

  let license = null;
  if (first_script_src != '') {
    license = legacy_license_lib.check(first_script_src);
  }

  let findLine = finder => finder.test(html) && html.substring(0, finder.lastIndex).split(/\n/).length || 0;
  if (read_metadata(meta_element) || license) {
    console.log('Valid license for intrinsic events found');
    let line, extras;
    if (meta_element) {
      line = findLine(/id\s*=\s*['"]?LibreJS-info\b/gi);
      extras = '(0)';
    } else if (license) {
      line = html.substring(0, html.indexOf(first_script_src)).split(/\n/).length;
      extras = '\n' + first_script_src;
    }
    let viewUrl = line ? `view-source:${documentUrl}#line${line}(<${meta_element ? meta_element.tagName : 'SCRIPT'}>)${extras}` : url;
    addReportEntry(tabId, { url, 'accepted': [viewUrl, `Global license for the page: ${license}`] });
    // Do not process inline scripts
    scripts = [];
  } else {
    let dejaVu = new Map(); // deduplication map & edited script cache
    let modified = false;
    // Deal with intrinsic events
    let intrinsicFinder = /<[a-z][^>]*\b(on\w+|href\s*=\s*['"]?javascript:)/gi;
    for (let element of html_doc.querySelectorAll('*')) {
      let line = -1;
      for (let attr of element.attributes) {
        let { name, value } = attr;
        value = value.trim();
        if (name.startsWith('on') || (name === 'href' && value.toLowerCase().startsWith('javascript:'))) {
          if (line === -1) {
            line = findLine(intrinsicFinder);
          }
          try {
            let key = `<${element.tagName} ${name}="${value}">`;
            let edited;
            if (dejaVu.has(key)) {
              edited = dejaVu.get(key);
            } else {
              let url = `view-source:${documentUrl}#line${line}(<${element.tagName} ${name}>)\n${value.trim()}`;
              if (name === 'href') value = decodeURIComponent(value);
              edited = await getScript(value, url, tabId, whitelist.contains(url));
              dejaVu.set(key, edited);
            }
            if (edited && edited !== value) {
              modified = true;
              attr.value = edited;
            }
          } catch (e) {
            console.error(e);
          }
        }
      }
    }

    let modifiedInline = false;
    let scriptFinder = /<script\b/ig;
    for (let i = 0, len = scripts.length; i < len; i++) {
      let script = scripts[i];
      let line = findLine(scriptFinder);
      if (!script.src && !(script.type && script.type !== 'text/javascript')) {
        let source = script.textContent.trim();
        let editedSource;
        if (dejaVu.has(source)) {
          editedSource = dejaVu.get(source);
        } else {
          let url = `view-source:${documentUrl}#line${line}(<SCRIPT>)\n${source}`;
          let edited = await getScript(source, url, tabId, whitelisted, returnsPair = false);
          editedSource = edited && edited[0].trim();
          dejaVu.set(url, editedSource);
        }
        if (editedSource) {
          if (source !== editedSource) {
            script.textContent = editedSource;
            modified = modifiedInline = true;
          }
        }
      }
    }

    modified = showConditionalElements(html_doc) > 0 || modified;
    if (modified) {
      if (modifiedInline) {
        forceNoscriptElements(html_doc);
      }
      return doc2HTML(html_doc);
    }
  }
  return null;
}

/**
* Here we handle html document responses
*/
async function handle_html(response, whitelisted) {
  let { text, request } = response;
  let { url, tabId, frameId, type } = request;
  if (type === 'main_frame') {
    activityReports[tabId] = await createReport({ url, tabId });
    updateBadge(tabId);
  }
  return await editHtml(text, url, tabId, frameId, whitelisted);
}

var whitelist = new ListStore('pref_whitelist', Storage.CSV);
var blacklist = new ListStore('pref_blacklist', Storage.CSV);
var listManager = new ListManager(whitelist, blacklist,
  // built-in whitelist of script hashes, e.g. jQuery
  Object.values(require('./utilities/hash_script/whitelist').whitelist)
    .reduce((a, b) => a.concat(b)) // as a flat array
    .map(script => script.hash)
);


async function initDefaults() {
  let defaults = {
    pref_subject: 'Issues with Javascript on your website',
    pref_body: `Please consider using a free license for the Javascript on your website.

[Message generated by LibreJS. See https://www.gnu.org/software/librejs/ for more information]
`
  };
  let keys = Object.keys(defaults);
  let prefs = await browser.storage.local.get(keys);
  let changed = false;
  for (let k of keys) {
    if (!(k in prefs)) {
      prefs[k] = defaults[k];
      changed = true;
    }
  }
  if (changed) {
    await browser.storage.local.set(prefs);
  }
}

/**
*	Initializes various add-on functions
*	only meant to be called once when the script starts
*/
async function init_addon() {
  await initDefaults();
  await whitelist.load();
  browser.runtime.onConnect.addListener(connected);
  browser.storage.onChanged.addListener(options_listener);
  browser.tabs.onRemoved.addListener(delete_removed_tab_info);
  browser.tabs.onUpdated.addListener(onTabUpdated);
  browser.tabs.onActivated.addListener(onTabActivated);
  // Prevents Google Analytics from being loaded from Google servers
  let all_types = [
    'beacon', 'csp_report', 'font', 'image', 'imageset', 'main_frame', 'media',
    'object', 'object_subrequest', 'ping', 'script', 'stylesheet', 'sub_frame',
    'web_manifest', 'websocket', 'xbl', 'xml_dtd', 'xmlhttprequest', 'xslt',
    'other'
  ];
  browser.webRequest.onBeforeRequest.addListener(blockGoogleAnalytics,
    { urls: ['<all_urls>'], types: all_types },
    ['blocking']
  );
  browser.webRequest.onBeforeRequest.addListener(blockBlacklistedScripts,
    { urls: ['<all_urls>'], types: ['script'] },
    ['blocking']
  );
  browser.webRequest.onResponseStarted.addListener(request => {
    let { tabId } = request;
    let report = activityReports[tabId];
    if (report) {
      updateBadge(tabId, activityReports[tabId]);
    }
  }, { urls: ['<all_urls>'], types: ['main_frame'] });

  // Analyzes all the html documents and external scripts as they're loaded
  ResponseProcessor.install(ResponseHandler);

  legacy_license_lib.init();

  const Test = require('./common/Test');
  if (Test.getURL()) {
    // export testable functions to the global scope
    this.LibreJS = {
      editHtml,
      handle_script,
      ExternalLicenses,
      ListManager, ListStore, Storage,
    };
    // create or focus the autotest tab if it's a debugging session
    if ((await browser.management.getSelf()).installType === 'development') {
      Test.getTab(true);
    }
  }
}


/**
*	Loads the contact finder on the given tab ID.
*/
async function injectContactFinder(tabId) {
  await Promise.all([
    browser.tabs.insertCSS(tabId, { file: '/content/overlay.css', cssOrigin: 'user' }),
    browser.tabs.executeScript(tabId, { file: '/content/contactFinder.js' }),
  ]);
}

init_addon();