Filter list preprocessor

Readme.md

Filter list preprocessor

Use to remove unsupported filters from a list

Usage

npx -- node ./preprocessor.js <path-to-list>

preprocessor.js

import { readFileSync, existsSync } from "node:fs";
import path from "node:path";
import { FiltersEngine } from "@cliqz/adblocker";

function preprocess(list, env) {
  const engine = FiltersEngine.parse(list, {
    loadPreprocessors: true,
    debug: true,
  });

  engine.updateEnv(env);

  const { networkFilters, cosmeticFilters } = engine.getFilters();

  return [...networkFilters, ...cosmeticFilters]
    .filter((filter) => !engine.preprocessors.isFilterExcluded(filter))
    .map((filter) => filter.rawLine)
    .sort();
}

const args = process.argv.slice(2);

// list of common envs https://github.com/ghostery/adblocker/blob/ca11ec5269d5657890c7195d11d5c06df0651c82/packages/adblocker/src/preprocessor.ts#L3
// by default all filters are accepted
// please specify ones that are meant to be expluded
const env = new Map([
  ['cap_html_filtering', false],
  ['env_firefox', false],
]);

const listPath = path.resolve(args[0]);

if (!existsSync(listPath)) {
  throw new Error("Cannot find a filter list at location:", listPath);
}

const list =  readFileSync(listPath, { encoding: 'utf-8' });

const filters = preprocess(list, env);

process.stdout.write(filters.join('\n'));