src/google2vtt.js

   1 var cheerio = require('cheerio');
   2 var https = require('https');
   3 var fs = require('fs');
   4 var path = require('path');
   5 var querystring = require('querystring');
   6 var crypto = require('crypto');
   7
   8 const LOGGER = require('@calzoneman/jsli')('google2vtt');
   9
  10 function md5(input) {
  11     var hash = crypto.createHash('md5');
  12     hash.update(input);
  13     return hash.digest('base64').replace(/\//g, ' ')
  14         .replace(/\+/g, '#')
  15         .replace(/=/g, '-');
  16 }
  17
  18 var slice = Array.prototype.slice;
  19 var subtitleDir = path.resolve(__dirname, '..', 'google-drive-subtitles');
  20 var subtitleLock = {};
  21 var ONE_HOUR = 60 * 60 * 1000;
  22 var ONE_DAY = 24 * ONE_HOUR;
  23
  24 function padZeros(n) {
  25     n = n.toString();
  26     if (n.length < 2) n = '0' + n;
  27     return n;
  28 }
  29
  30 function formatTime(time) {
  31     var hours = Math.floor(time / 3600);
  32     time = time % 3600;
  33     var minutes = Math.floor(time / 60);
  34     time = time % 60;
  35     var seconds = Math.floor(time);
  36     var ms = time - seconds;
  37
  38     var list = [minutes, seconds];
  39     if (hours) {
  40         list.unshift(hours);
  41     }
  42
  43     return list.map(padZeros).join(':') + ms.toFixed(3).substring(1);
  44 }
  45
  46 function fixText(text) {
  47     return text.replace(/&amp;/g, '&')
  48         .replace(/&lt;/g, '<')
  49         .replace(/&gt;/g, '>')
  50         .replace(/&quot;/g, '"')
  51         .replace(/&#39;/g, "'")
  52         .replace(/-->/g, '--&gt;');
  53 }
  54
  55 exports.convert = function convertSubtitles(subtitles) {
  56     var $ = cheerio.load(subtitles, { xmlMode: true });
  57     var lines = slice.call($('transcript text').map(function (index, elem) {
  58         var start = parseFloat(elem.attribs.start);
  59         var end = start + parseFloat(elem.attribs.dur);
  60         var text;
  61         if (elem.children.length) {
  62             text = elem.children[0].data;
  63         } else {
  64             text = '';
  65         }
  66
  67         var line = formatTime(start) + ' --> ' + formatTime(end);
  68         line += '\n' + fixText(text) + '\n';
  69         return line;
  70     }));
  71
  72     return 'WEBVTT\n\n' + lines.join('\n');
  73 };
  74
  75 exports.attach = function setupRoutes(app) {
  76     app.get('/gdvtt/:id/:lang/(:name)?.vtt', handleGetSubtitles);
  77 };
  78
  79 function handleGetSubtitles(req, res) {
  80     var id = req.params.id;
  81     var lang = req.params.lang;
  82     var name = req.params.name || '';
  83     var vid = req.query.vid;
  84     if (typeof vid !== 'string' || typeof id !== 'string' || typeof lang !== 'string') {
  85         return res.sendStatus(400);
  86     }
  87     var file = [id, lang, md5(name)].join('_') + '.vtt';
  88     var fileAbsolute = path.join(subtitleDir, file);
  89
  90     takeSubtitleLock(fileAbsolute, function () {
  91         fs.exists(fileAbsolute, function (exists) {
  92             if (exists) {
  93                 res.sendFile(file, { root: subtitleDir });
  94                 delete subtitleLock[fileAbsolute];
  95             } else {
  96                 fetchSubtitles(id, lang, name, vid, fileAbsolute, function (err) {
  97                     delete subtitleLock[fileAbsolute];
  98                     if (err) {
  99                         LOGGER.error(err.stack);
 100                         return res.sendStatus(500);
 101                     }
 102
 103                     res.sendFile(file, { root: subtitleDir });
 104                 });
 105             }
 106         });
 107     });
 108 }
 109
 110 function fetchSubtitles(id, lang, name, vid, file, cb) {
 111     var query = {
 112         id: id,
 113         v: id,
 114         vid: vid,
 115         lang: lang,
 116         name: name,
 117         type: 'track',
 118         kind: undefined
 119     };
 120
 121     var url = 'https://drive.google.com/timedtext?' + querystring.stringify(query);
 122     https.get(url, function (res) {
 123         if (res.statusCode !== 200) {
 124             return cb(new Error(res.statusMessage));
 125         }
 126
 127         var buf = '';
 128         res.setEncoding('utf-8');
 129         res.on('data', function (data) {
 130             buf += data;
 131         });
 132
 133         res.on('end', function () {
 134             try {
 135                 buf = exports.convert(buf);
 136             } catch (e) {
 137                 return cb(e);
 138             }
 139
 140             fs.writeFile(file, buf, function (err) {
 141                 if (err) {
 142                     cb(err);
 143                 } else {
 144                     LOGGER.info('Saved subtitle file ' + file);
 145                     cb();
 146                 }
 147             });
 148         });
 149     }).on('error', function (err) {
 150         cb(err);
 151     });
 152 }
 153
 154 function clearOldSubtitles() {
 155     fs.readdir(subtitleDir, function (err, files) {
 156         if (err) {
 157             LOGGER.error(err.stack);
 158             return;
 159         }
 160
 161         files.forEach(function (file) {
 162             fs.stat(path.join(subtitleDir, file), function (err, stats) {
 163                 if (err) {
 164                     LOGGER.error(err.stack);
 165                     return;
 166                 }
 167
 168                 if (stats.mtime.getTime() < Date.now() - ONE_DAY) {
 169                     LOGGER.info('Deleting old subtitle file: ' + file);
 170                     fs.unlink(path.join(subtitleDir, file), error => {
 171                         if (error) {
 172                             LOGGER.error(
 173                                 'Failed to remove file %s: %s',
 174                                 file,
 175                                 error.stack
 176                             );
 177                         }
 178                     });
 179                 }
 180             });
 181         });
 182     });
 183 }
 184
 185 function takeSubtitleLock(filename, cb) {
 186     if (!subtitleLock.hasOwnProperty(filename)) {
 187         subtitleLock[filename] = true;
 188         return setImmediate(cb);
 189     }
 190
 191     var tries = 1;
 192     var interval = setInterval(function () {
 193         tries++;
 194         if (!subtitleLock.hasOwnProperty(filename) || tries >= 5) {
 195             subtitleLock[filename] = true;
 196             clearInterval(interval);
 197             return setImmediate(cb);
 198         }
 199     }, 200);
 200 }
 201
 202 setInterval(clearOldSubtitles, ONE_HOUR);
 203 clearOldSubtitles();