// parses VTT timestamp (mm:ss.ms or hh:mm:ss.ms) to seconds
export const parseVttTime = (raw: string): number => {
  const parts = raw.trim().split(":");
  if (parts.length < 2) {
    return 0;
  }
  const secPart = parts.at(-1);
  const minPart = parts.at(-2);
  const hourPart = parts.length > 2 ? parts.at(-3) : "0";
  if (!secPart || !minPart) {
    return 0;
  }
  const hour = Number(hourPart);
  const minute = Number(minPart);
  const second = Number(secPart.replace(",", "."));
  if (!Number.isFinite(hour) || !Number.isFinite(minute) || !Number.isFinite(second)) {
    return 0;
  }
  return hour * 3600 + minute * 60 + second;
};

// parses a single VTT cue: timestamp line + text lines
const parseVttCue = (line: string, lines: string[], i: number) => {
  if (!line.includes("-->")) {
    return null;
  }
  const [startRaw, endRaw] = line.split("-->");
  const payload: string[] = [];
  let j = i + 1;
  // collect text until blank line
  while (j < lines.length && lines[j].trim() !== "") {
    payload.push(lines[j]);
    j++;
  }
  // strip tags, join lines
  const text = payload
    .join("\n")
    .replaceAll(/<[^>]+>/g, "")
    .trim();
  if (!text) {
    return null;
  }
  const endTime = endRaw.trim().split(/\s+/)[0] ?? "";
  return { start: parseVttTime(startRaw), end: parseVttTime(endTime), text };
};

/**
 * Parses full VTT file into cue array. Handles both compact (timestamp on separate line) and
 * standard formats.
 */
export const parseVtt = (text: string) => {
  const lines = text.replaceAll(/\r/g, "").split("\n");
  const cues = [];
  for (let i = 0; i < lines.length; i++) {
    const line = lines[i].trim();
    if (!line) {
      continue;
    }
    // compact: cue id on line i, timestamp on i+1
    if (i + 1 < lines.length && !line.includes("-->") && lines[i + 1].includes("-->")) {
      const cue = parseVttCue(lines[i + 1].trim(), lines, i + 1);
      if (cue) {
        cues.push(cue);
      }
      i++;
    } else if (line.includes("-->")) {
      // standard: timestamp on same line
      const cue = parseVttCue(line, lines, i);
      if (cue) {
        cues.push(cue);
      }
    }
  }
  return cues;
};