text: #!/usr/bin/env node
  /**
   * Copyright 2017 Google Inc. All rights reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  const assert = require('assert');
  const https = require('https');
  
  const packageJSON = require('../package.json');
  const BrowserFetcher = require('../lib/BrowserFetcher').BrowserFetcher;
  
  const SUPPORTER_PLATFORMS = ['linux', 'mac', 'win32', 'win64'];
  const fetchers = SUPPORTER_PLATFORMS.map(
    (platform) => new BrowserFetcher('', { platform })
  );
  
  const colors = {
    reset: '\x1b[0m',
    red: '\x1b[31m',
    green: '\x1b[32m',
    yellow: '\x1b[33m',
  };
  
  class Table {
    /**
     * @param {!Array<number>} columnWidths
     */
    constructor(columnWidths) {
      this.widths = columnWidths;
    }
  
    /**
     * @param {!Array<string>} values
     */
    drawRow(values) {
      assert(values.length === this.widths.length);
      let row = '';
      for (let i = 0; i < values.length; ++i)
        row += padCenter(values[i], this.widths[i]);
      console.log(row);
    }
  }
  
  const helpMessage = `
  This script checks availability of prebuilt Chromium snapshots.
  
  Usage: node check_availability.js [<options>] [<browser version(s)>]
  
  options
      -f          full mode checks availability of all the platforms, default mode
      -r          roll mode checks for the most recent Chromium roll candidate
      -h          show this help
  
  browser version(s)
      <revision>  single revision number means checking for this specific revision
      <from> <to> checks all the revisions within a given range, inclusively
  
  Examples
    To check Chromium availability of a certain revision
      node check_availability.js [revision]
  
    To find a Chromium roll candidate for current Stable Linux version
      node check_availability.js -r
  
    To check Chromium availability from the latest revision in a descending order
      node check_availability.js
  `;
  
  function main() {
    const args = process.argv.slice(2);
  
    if (args.length > 3) {
      console.log(helpMessage);
      return;
    }
  
    if (args.length === 0) {
      checkOmahaProxyAvailability();
      return;
    }
  
    if (args[0].startsWith('-')) {
      const option = args[0].substring(1);
      switch (option) {
        case 'f':
          break;
        case 'r':
          checkRollCandidate();
          return;
        default:
          console.log(helpMessage);
          return;
      }
      args.splice(0, 1); // remove options arg since we are done with options
    }
  
    if (args.length === 1) {
      const revision = parseInt(args[0], 10);
      checkRangeAvailability({
        fromRevision: revision,
        toRevision: revision,
        stopWhenAllAvailable: false,
      });
    } else {
      const fromRevision = parseInt(args[0], 10);
      const toRevision = parseInt(args[1], 10);
      checkRangeAvailability({
        fromRevision,
        toRevision,
        stopWhenAllAvailable: false,
      });
    }
  }
  
  async function checkOmahaProxyAvailability() {
    const latestRevisions = (
      await Promise.all([
        fetch(
          'https://storage.googleapis.com/chromium-browser-snapshots/Mac/LAST_CHANGE'
        ),
        fetch(
          'https://storage.googleapis.com/chromium-browser-snapshots/Linux_x64/LAST_CHANGE'
        ),
        fetch(
          'https://storage.googleapis.com/chromium-browser-snapshots/Win/LAST_CHANGE'
        ),
        fetch(
          'https://storage.googleapis.com/chromium-browser-snapshots/Win_x64/LAST_CHANGE'
        ),
      ])
    ).map((s) => parseInt(s, 10));
    const from = Math.max(...latestRevisions);
    checkRangeAvailability({
      fromRevision: from,
      toRevision: 0,
      stopWhenAllAvailable: false,
    });
  }
  
  async function checkRollCandidate() {
    const omahaResponse = await fetch(
      'https://omahaproxy.appspot.com/all.json?channel=stable&os=linux'
    );
    const stableLinuxInfo = JSON.parse(omahaResponse)[0];
    if (!stableLinuxInfo) {
      console.error('no stable linux information available from omahaproxy');
      return;
    }
  
    const stableLinuxRevision = parseInt(
      stableLinuxInfo.versions[0].branch_base_position,
      10
    );
    const currentRevision = parseInt(packageJSON.puppeteer.chromium_revision, 10);
  
    checkRangeAvailability({
      fromRevision: stableLinuxRevision,
      toRevision: currentRevision,
      stopWhenAllAvailable: true,
    });
  }
  
  /**
   * @param {*} options
   */
  async function checkRangeAvailability({
    fromRevision,
    toRevision,
    stopWhenAllAvailable,
  }) {
    const table = new Table([10, 7, 7, 7, 7]);
    table.drawRow([''].concat(SUPPORTER_PLATFORMS));
  
    const inc = fromRevision < toRevision ? 1 : -1;
    const revisionToStop = toRevision + inc; // +inc so the range is fully inclusive
    for (
      let revision = fromRevision;
      revision !== revisionToStop;
      revision += inc
    ) {
      const allAvailable = await checkAndDrawRevisionAvailability(
        table,
        '',
        revision
      );
      if (allAvailable && stopWhenAllAvailable) break;
    }
  }
  
  /**
   * @param {!Table} table
   * @param {string} name
   * @param {number} revision
   * @return {boolean}
   */
  async function checkAndDrawRevisionAvailability(table, name, revision) {
    const promises = fetchers.map((fetcher) => fetcher.canDownload(revision));
    const availability = await Promise.all(promises);
    const allAvailable = availability.every((e) => !!e);
    const values = [
      name +
        ' ' +
        (allAvailable ? colors.green + revision + colors.reset : revision),
    ];
    for (let i = 0; i < availability.length; ++i) {
      const decoration = availability[i] ? '+' : '-';
      const color = availability[i] ? colors.green : colors.red;
      values.push(color + decoration + colors.reset);
    }
    table.drawRow(values);
    return allAvailable;
  }
  
  /**
   * @param {string} url
   * @return {!Promise<?string>}
   */
  function fetch(url) {
    let resolve;
    const promise = new Promise((x) => (resolve = x));
    https
      .get(url, (response) => {
        if (response.statusCode !== 200) {
          resolve(null);
          return;
        }
        let body = '';
        response.on('data', function (chunk) {
          body += chunk;
        });
        response.on('end', function () {
          resolve(body);
        });
      })
      .on('error', function (e) {
        console.error('Error fetching json: ' + e);
        resolve(null);
      });
    return promise;
  }
  
  /**
   * @param {number} size
   * @return {string}
   */
  function spaceString(size) {
    return new Array(size).fill(' ').join('');
  }
  
  /**
   * @param {string} text
   * @return {string}
   */
  function filterOutColors(text) {
    for (const colorName in colors) {
      const color = colors[colorName];
      text = text.replace(color, '');
    }
    return text;
  }
  
  /**
   * @param {string} text
   * @param {number} length
   * @return {string}
   */
  function padCenter(text, length) {
    const printableCharacters = filterOutColors(text);
    if (printableCharacters.length >= length) return text;
    const left = Math.floor((length - printableCharacters.length) / 2);
    const right = Math.ceil((length - printableCharacters.length) / 2);
    return spaceString(left) + text + spaceString(right);
  }
  
  main();
  