native-lyrics-tools/src/lrc.js

A JavaScript library for parsing and generating various lyric formats.

function parseTime(str) {
  const match = str.match(/^\[(\d+):(\d+)[.:](\d{1,3})]/);
  if (!match) throw new Error(`Invalid timestamp: ${str}`);

  const minutes = parseInt(match[1], 10);
  const seconds = parseInt(match[2], 10);
  let milliseconds = match[3].padEnd(3, '0'); // Normalize to 3 digits
  milliseconds = parseInt(milliseconds, 10);

  const totalMs = minutes * 60000 + seconds * 1000 + milliseconds;
  const remaining = str.slice(match[0].length);
  return { remaining, time: totalMs };
}

function parseLine(line) {
  const timeRegex = /\[\d+:\d+[.:]\d{1,3}]/g;
  const matches = [...line.matchAll(timeRegex)];

  if (matches.length === 0) return [];

  const times = matches.map(match => parseTime(match[0]).time);
  const textStart = matches[matches.length - 1].index + matches[matches.length - 1][0].length;
  const lyricText = line.slice(textStart).trim();
  if (!lyricText) return [];

  return times.map(t => ({
    start_time: t,
    end_time: 0,
    words: [{
      start_time: t,
      end_time: 0,
      word: lyricText
    }]
  }));
}

function parseLRC(src) {
  const result = [];
  const lines = src.split(/\r?\n/);
  for (const line of lines) {
    try {
      const parsed = parseLine(line);
      if (parsed.length > 0) {
        result.push(...parsed);
      }
    } catch (e) {
      continue;
    }
  }

  result.sort((a, b) => a.start_time - b.start_time);

  let lastEndTime = Number.MAX_SAFE_INTEGER;
  for (let i = result.length - 1; i >= 0; i--) {
    const line = result[i];
    line.end_time = lastEndTime;
    if (line.words.length > 0) {
      line.words[0].end_time = lastEndTime;
    }
    lastEndTime = line.start_time;
  }

  // Optional: insert timing adjustments with a separate `processLyrics()` if needed
  return result;
}

function writeTimestamp(time) {
  const ms = time % 1000;
  const sec = Math.floor(time / 1000) % 60;
  const min = Math.floor(time / 60000);
  return `[${String(min).padStart(2, '0')}:${String(sec).padStart(2, '0')}.${String(ms).padStart(3, '0')}]`;
}

function stringifyLRC(lines) {
  let result = '';
  for (const line of lines) {
    if (!line.words.length) continue;
    result += writeTimestamp(line.words[0].start_time);
    for (const word of line.words) {
      result += word.word;
    }
    result += '\n';
  }
  return result;
}

// Exported ES module API
export {
  parseTime,
  parseLine,
  parseLRC,
  stringifyLRC,
  writeTimestamp
};