// tslint:disable-next-line:max-line-length
const timestampRegex = /^(?:(\d{2,})(:))?([0-5][0-9])(:)([0-5][0-9])([,.])(\d{3})( --> )(?:(\d{2,})(:))?([0-5][0-9])(:)([0-5][0-9])([,.])(\d{3})/;
 
function fixSrt(input) {
    const trim = (str) => str.trim()
      .replace(/^[^\S\n]+/gm, '')
      .replace(/\u0000/g, '\uFFFD')
      .replace(/\r\n/g, '\n')
      .replace(/\r/g, '\n')
      .replace(/\n{3,}/g, '\n\n');
    const origin = trim(input)
      .split('\n');
    let id = 0;
    let idCache = '';
    let state = 'root';
    const processLine = line => {
      switch (state) {
        case 'note':
          /* falls through */
        case 'title':
          if (line === '') {
            state = 'root';
          }
          return [];
        case 'root':
          if (line.match(/^WEBVTT/)) {
            state = 'title';
            return [];
          } else if (line.match(/^NOTE/)) {
            state = 'note';
            return [];
          } else if (line === '') return [line];
          else if (!line.match(/-->/)) {
            state = 'timeline';
            idCache = line;
            return [];
          }
          /* falls through */
        case 'timeline':
          const match = timestampRegex.exec(line);
          if (match) {
            idCache = '';
            id++;
            state = 'text';
            return [
              id + '',
              // tslint:disable-next-line:max-line-length
              `${match[1] || '00'}:${match[3]}:${match[5]},${match[7]} --> ${match[9] || '00'}:${match[11]}:${match[13]},${match[15]}`
            ];
          } else {
            // 坏的字幕块
            state = 'root';
            // 原样输出
            const lastLine = idCache;
            idCache = '';
            return lastLine ? [lastLine, line] : [line];
            // 忽略这个字幕块
            // return [];
          }
        case 'text':
          if (line === '') {
            state = 'root';
          }
          return [line];
      }
    };
    const result = [];
    origin.forEach(line => result.push(...processLine(line)));
    // 没写完的字幕块
    // 原样输出
    if (idCache) result.push(idCache);
    return trim(result.join('\n')) + '\n';
  }