/**
 * Convert a value to a CSV cell-friendly format.
 * Primitives pass through; objects/arrays are stringified; dates are formatted.
 */
function toCsvValue(val) {
  if (val === null || val === undefined) return '';
  if (val instanceof Date) return val.toISOString();
  if (typeof val === 'number' || typeof val === 'boolean') return String(val);
  if (typeof val === 'string') return val;
  if (typeof val === 'object') {
    if (Array.isArray(val)) return val.map(toCsvValue).join(', ');
    return JSON.stringify(val);
  }
  return String(val);
}

/**
 * Escape a CSV field per RFC 4180: wrap in double quotes, escape internal quotes by doubling.
 */
function escapeCsvField(str) {
  if (str == null) return '""';
  const s = String(str);
  if (s.includes('"') || s.includes(',') || s.includes('\n') || s.includes('\r')) {
    return '"' + s.replace(/"/g, '""') + '"';
  }
  return s;
}

/**
 * Generate a CSV buffer from tabular data.
 * @param {Array<Object>} data - Array of row objects (keys = column headers)
 * @param {Object} options - Options
 * @param {string[]} [options.columnOrder] - Optional column order (uses Object.keys of first row if not provided)
 * @returns {Buffer} CSV file as buffer
 */
export function generateCsvTable(data, options = {}) {
  const { columnOrder } = options;

  if (!data || data.length === 0) {
    return Buffer.from('', 'utf8');
  }

  const keys = columnOrder || Object.keys(data[0]).filter((k) => !k.startsWith('@'));
  const headerRow = keys.map((k) => escapeCsvField(k)).join(',');
  const lines = [headerRow];

  for (const row of data) {
    const values = keys.map((key) => escapeCsvField(toCsvValue(row[key])));
    lines.push(values.join(','));
  }

  const csv = lines.join('\n');
  return Buffer.from(csv, 'utf8');
}