export interface EdlImportRow {
  outputName: string;
  sourceClip: string;
  timecodeStart: string;
  timecodeEnd: string;
  clipDuration: string;
  // Derived
  shotCode: string;
  exrOutput: string;
  // Action decided during preview
  action: "create" | "update" | "skip";
  existingShotId?: string;
}

/**
 * Parse a VFX pull CSV into import rows.
 * Output Name format: {showId}_{episode}_{scene}_{shot}_BG01_TT_v001
 * shotCode = first 4 underscore-separated segments
 * exrOutput = {shotCode}_{sourceClip}
 */
export function parseEdlCsv(csvText: string): { rows: EdlImportRow[]; errors: string[] } {
  const lines = csvText.split(/\r?\n/).map((l) => l.trim()).filter(Boolean);
  if (lines.length < 2) return { rows: [], errors: ["CSV must have a header row and at least one data row"] };

  const unquote = (s: string) => s.replace(/^"|"$/g, "").trim();

  const rawHeaders = lines[0].split(",").map(unquote).map((h) => h.toLowerCase());
  const col = (name: string) => rawHeaders.indexOf(name);

  const outNameIdx = col("output name");
  const srcClipIdx = col("source clip");
  const tcStartIdx = col("timecode start");
  const tcEndIdx   = col("timecode end");
  const durIdx     = col("duration");

  if (outNameIdx === -1 || srcClipIdx === -1) {
    return { rows: [], errors: ['CSV must contain "Output Name" and "Source Clip" columns'] };
  }

  const rows: EdlImportRow[] = [];
  const errors: string[] = [];

  for (let i = 1; i < lines.length; i++) {
    const cells = lines[i].match(/("(?:[^"]|"")*"|[^,]*)/g)?.map(unquote) ?? [];
    const get = (idx: number) => (idx !== -1 ? cells[idx] ?? "" : "");

    const outputName = get(outNameIdx);
    const sourceClip = get(srcClipIdx);
    if (!outputName) { errors.push(`Row ${i + 1}: empty Output Name — skipped`); continue; }

    const parts = outputName.split("_");
    if (parts.length < 4) {
      errors.push(`Row ${i + 1}: "${outputName}" — cannot parse shot code (need at least 4 segments)`);
      continue;
    }
    const shotCode = parts.slice(0, 4).join("_");
    const exrOutput = sourceClip ? `${shotCode}_${sourceClip}` : shotCode;

    rows.push({
      outputName,
      sourceClip,
      timecodeStart: get(tcStartIdx),
      timecodeEnd:   get(tcEndIdx),
      clipDuration:  get(durIdx),
      shotCode,
      exrOutput,
      action: "create",
    });
  }

  return { rows, errors };
}