/** Parse a CSV string into { headers, rows } */
export function parseCSV(text) {
  const lines = text.replace(/\r\n/g, '\n').replace(/\r/g, '\n').split('\n').filter(l => l.trim());
  if (!lines.length) return { headers: [], rows: [] };

  function splitLine(l) {
    const r = []; let c = '', q = false;
    for (let i = 0; i < l.length; i++) {
      const ch = l[i];
      if (ch === '"') { q = !q; }
      else if (ch === ',' && !q) { r.push(c.trim()); c = ''; }
      else { c += ch; }
    }
    r.push(c.trim());
    return r;
  }

  const headers = splitLine(lines[0]).map(h => h.replace(/^"|"$/g, '').trim());
  const rows = lines.slice(1).map((ln, i) => {
    const vals = splitLine(ln);
    const o = { __id: i + 1 };
    headers.forEach((h, j) => { o[h] = (vals[j] || '').replace(/^"|"$/g, '').trim(); });
    return o;
  });
  return { headers, rows };
}

/** Parse with progress callback — calls cb(pct 0-100) periodically, then cb(100, result) */
export function parseCSVWithProgress(text, onProgress) {
  return new Promise(resolve => {
    const lines = text.replace(/\r\n/g, '\n').replace(/\r/g, '\n').split('\n').filter(l => l.trim());
    const total = lines.length - 1;

    function splitLine(l) {
      const r = []; let c = '', q = false;
      for (let i = 0; i < l.length; i++) {
        const ch = l[i];
        if (ch === '"') { q = !q; }
        else if (ch === ',' && !q) { r.push(c.trim()); c = ''; }
        else { c += ch; }
      }
      r.push(c.trim());
      return r;
    }

    if (total <= 500) {
      const result = parseCSV(text);
      onProgress && onProgress(100, result);
      resolve(result);
      return;
    }

    const headers = splitLine(lines[0]).map(h => h.replace(/^"|"$/g, '').trim());
    const rows = [];
    const CHUNK = 250;
    let i = 1;

    function step() {
      const end = Math.min(i + CHUNK, lines.length);
      for (; i < end; i++) {
        const vals = splitLine(lines[i]);
        const o = { __id: rows.length + 1 };
        headers.forEach((h, j) => { o[h] = (vals[j] || '').replace(/^"|"$/g, '').trim(); });
        rows.push(o);
      }
      const pct = Math.round((i - 1) / total * 100);
      onProgress && onProgress(pct, null);
      if (i < lines.length) {
        requestAnimationFrame(step);
      } else {
        const result = { headers, rows };
        onProgress && onProgress(100, result);
        resolve(result);
      }
    }
    requestAnimationFrame(step);
  });
}

export function fmtSize(bytes) {
  if (bytes < 1024) return bytes + ' B';
  if (bytes < 1048576) return (bytes / 1024).toFixed(1) + ' KB';
  return (bytes / 1048576).toFixed(2) + ' MB';
}

export function pKey(row) {
  return String(row.__id !== undefined ? row.__id : row.key);
}