ass-compiler/src/stringifier.js

Parses and compiles ASS subtitle format to easy-to-use data structure.

export function stringifyInfo(info) {
  return Object.keys(info)
    .filter((key) => info[key] !== null)
    .map((key) => `${key}: ${info[key]}`)
    .join('\n');
}

function pad00(n) {
  return `00${n}`.slice(-2);
}

export function stringifyTime(tf) {
  const t = Number.parseFloat(tf.toFixed(2));
  const ms = t.toFixed(2).slice(-2);
  const s = (t | 0) % 60;
  const m = (t / 60 | 0) % 60;
  const h = t / 3600 | 0;
  return `${h}:${pad00(m)}:${pad00(s)}.${ms}`;
}

export function stringifyEffect(eff) {
  if (!eff) return '';
  if (eff.name === 'banner') {
    return `Banner;${eff.delay};${eff.leftToRight};${eff.fadeAwayWidth}`;
  }
  if (/^scroll\s/.test(eff.name)) {
    return `${eff.name.replace(/^\w/, (x) => x.toUpperCase())};${eff.y1};${eff.y2};${eff.delay};${eff.fadeAwayHeight}`;
  }
  return eff.name;
}

export function stringifyDrawing(drawing) {
  return drawing.map((cmds) => cmds.join(' ')).join(' ');
}

export function stringifyTag(tag) {
  const [key] = Object.keys(tag);
  if (!key) return '';
  const _ = tag[key];
  if (['pos', 'org', 'move', 'fad', 'fade'].some((ft) => ft === key)) {
    return `\\${key}(${_})`;
  }
  if (/^[ac]\d$/.test(key)) {
    return `\\${key[1]}${key[0]}&H${_}&`;
  }
  if (key === 'alpha') {
    return `\\alpha&H${_}&`;
  }
  if (key === 'clip') {
    return `\\${_.inverse ? 'i' : ''}clip(${
      _.dots || `${_.scale === 1 ? '' : `${_.scale},`}${stringifyDrawing(_.drawing)}`
    })`;
  }
  if (key === 't') {
    return `\\t(${[_.t1, _.t2, _.accel, _.tags.map(stringifyTag).join('')]})`;
  }
  return `\\${key}${_}`;
}

export function stringifyText(Text) {
  return Text.parsed.map(({ tags, text, drawing }) => {
    const tagText = tags.map(stringifyTag).join('');
    const content = drawing.length ? stringifyDrawing(drawing) : text;
    return `${tagText ? `{${tagText}}` : ''}${content}`;
  }).join('');
}

export function stringifyEvent(event, format) {
  return format.map((fmt) => {
    switch (fmt) {
      case 'Start':
      case 'End':
        return stringifyTime(event[fmt]);
      case 'MarginL':
      case 'MarginR':
      case 'MarginV':
        return event[fmt] || '0000';
      case 'Effect':
        return stringifyEffect(event[fmt]);
      case 'Text':
        return stringifyText(event.Text);
      default:
        return event[fmt];
    }
  }).join();
}

export function stringify({ info, styles, events }) {
  return [
    '[Script Info]',
    stringifyInfo(info),
    '',
    '[V4+ Styles]',
    `Format: ${styles.format.join(', ')}`,
    ...styles.style.map((style) => `Style: ${styles.format.map((fmt) => style[fmt]).join()}`),
    '',
    '[Events]',
    `Format: ${events.format.join(', ')}`,
    ...[]
      .concat(...['Comment', 'Dialogue'].map((type) => (
        events[type.toLowerCase()].map((dia) => ({
          start: dia.Start,
          end: dia.End,
          string: `${type}: ${stringifyEvent(dia, events.format)}`,
        }))
      )))
      .sort((a, b) => (a.start - b.start) || (a.end - b.end))
      .map((x) => x.string),
    '',
  ].join('\n');
}