src/lib/export-formats.ts

import { buildCaptionWords, buildCaptionLines, type CaptionLine } from "./captions";
import type { EDLItem, Word } from "./timeline-model";

const pad = (n: number, w = 2) => String(n).padStart(w, "0");
// HH:MM:SS,mmm (SRT, comma) or HH:MM:SS.mmm (VTT, dot)
const clock = (ms: number, sep: "," | ".") => {
  const t = Math.max(0, Math.round(ms));
  const h = Math.floor(t / 3600000), m = Math.floor((t % 3600000) / 60000), s = Math.floor((t % 60000) / 1000);
  return `${pad(h)}:${pad(m)}:${pad(s)}${sep}${pad(t % 1000, 3)}`;
};

export const captionLinesFor = (edl: EDLItem[], wordsById: Record<string, Word>): CaptionLine[] =>
  buildCaptionLines(buildCaptionWords(edl, wordsById));

const lineText = (l: CaptionLine) => l.words.map((w) => w.text).join(" ").trim();

export function toSRT(lines: CaptionLine[]): string {
  return lines.filter(lineText).map((l, i) =>
    `${i + 1}\n${clock(l.startMs, ",")} --> ${clock(l.endMs, ",")}\n${lineText(l)}`
  ).join("\n\n") + "\n";
}

export function toVTT(lines: CaptionLine[]): string {
  return "WEBVTT\n\n" + lines.filter(lineText).map((l) =>
    `${clock(l.startMs, ".")} --> ${clock(l.endMs, ".")}\n${lineText(l)}`
  ).join("\n\n") + "\n";
}

export function downloadFile(name: string, content: BlobPart, type: string) {
  const url = URL.createObjectURL(new Blob([content], { type }));
  const a = document.createElement("a");
  a.href = url; a.download = name;
  document.body.appendChild(a); a.click(); a.remove();
  setTimeout(() => URL.revokeObjectURL(url), 1000);
}