ArtPlayer/packages/artplayer/src/utils/subtitle.ts

function fixSrt(srt: string): string {
  return srt.replace(/(\d\d:\d\d:\d\d)[,.](\d+)/g, (_match: string, $1: string, $2: string) => {
    let ms = $2.slice(0, 3)
    if ($2.length === 1) {
      ms = `${$2}00`
    }
    if ($2.length === 2) {
      ms = `${$2}0`
    }
    return `${$1},${ms}`
  })
}

export function srtToVtt(srtText: string): string {
  return 'WEBVTT \r\n\r\n'.concat(
    fixSrt(srtText)
      .replace(/\{\\([ibu])\}/g, '</$1>')
      .replace(/\{\\([ibu])1\}/g, '<$1>')
      .replace(/\{([ibu])\}/g, '<$1>')
      .replace(/\{\/([ibu])\}/g, '</$1>')
      .replace(/(\d\d:\d\d:\d\d),(\d\d\d)/g, '$1.$2')
      .replace(/\{[\s\S]*?\}/g, '')
      .concat('\r\n\r\n'),
  )
}

export function vttToBlob(vttText: string): string {
  return URL.createObjectURL(
    new Blob([vttText], {
      type: 'text/vtt',
    }),
  )
}

export function assToVtt(ass: string): string {
  const reAss = new RegExp(
    'Dialogue:\\s\\d,'
    + '(\\d+:\\d\\d:\\d\\d.\\d\\d),'
    + '(\\d+:\\d\\d:\\d\\d.\\d\\d),'
    + '([^,]*),'
    + '([^,]*),'
    + '(?:[^,]*,){4}'
    + '([\\s\\S]*)$',
    'i',
  )

  function fixTime(time = '') {
    return time
      .split(/[:.]/)
      .map((item, index, arr) => {
        if (index === arr.length - 1) {
          if (item.length === 1) {
            return `.${item}00`
          }

          if (item.length === 2) {
            return `.${item}0`
          }
        }
        else if (item.length === 1) {
          return (index === 0 ? '0' : ':0') + item
        }

        return index === 0 ? item : index === arr.length - 1 ? `.${item}` : `:${item}`
      })
      .join('')
  }

  return (
    `WEBVTT`
    + `\n`
    + `\n${
      ass
        .split(/\r?\n/)
        .map((line) => {
          const m = line.match(reAss)
          if (!m)
            return null
          const [, start = '', end = '', , , text = ''] = m
          return {
            start: fixTime(start.trim()),
            end: fixTime(end.trim()),
            text: text
              .replace(/\{[\s\S]*?\}/g, '')
              .replace(/(\\N)/g, '\n')
              .trim()
              .split(/\r?\n/)
              .map(item => item.trim())
              .join('\n'),
          }
        })
        .filter(line => line)
        .map((line, index) => {
          if (line) {
            return `${index + 1}\n` + `${line.start} --> ${line.end}` + `\n` + `${line.text}`
          }
          return ''
        })
        .filter(line => line.trim())
        .join('\n\n')}`
  )
}