ad-block/lib/filtering.js

Ad block engine used in the Brave browser for ABP filter syntax based lists like EasyList.

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

const I = (x) => x

/**
 * Same as filterPredicate but will log if there is a LOG_OUTPUT env variable
 */
const filterPredicateWithPossibleLogging = (rule, filterPredicate = I) => {
  const result = filterPredicate(rule)
  if (process.env['LOG_OUTPUT'] && !result) {
    console.log('Filtering out rule: ', rule)
  }
  return result
}

/**
 * Mapping rule which reformats rules
 */
const mapRule = (rule) => {
  if (rule === '||imasdk.googleapis.com^$third-party') {
    return '||imasdk.googleapis.com^$third-party,explicitcancel'
  }
  if (rule === '/ima3.js') {
    return '/ima3.js$explicitcancel'
  }
  return rule
}

/**
 * Given a list of inputs returns a filtered list of rules that should be used.
 *
 * @param input {string} - ABP filter syntax to filter
 * @return A better filter list
 */
const sanitizeABPInput = (input, filterPredicate = I) =>
  input.split('\n')
    .filter((rule) =>
      filterPredicateWithPossibleLogging(rule, filterPredicate))
    .map(mapRule)
    // TODO: This can be removed a few versions after 0.62.x.
    // It was just added to be backwards compatible with 0.61.x.
    .concat(extraConcatRules)
    .join('\n')

/**
 * Extra rules that should be appended when sanitizing ABP input
 */
const extraConcatRules = [
  '||imasdk.googleapis.com/$third-party',
  '^ima3.js'
]

module.exports = {
  sanitizeABPInput,
  extraConcatRules
}