/**
 * Minimal PDF builder for retrieval receipts (no native deps).
 * @module lib/receiptPdf
 */

/**
 * @param {string} s
 * @returns {string}
 */
function pdfEscape(s) {
  return String(s).replace(/\\/g, '\\\\').replace(/\(/g, '\\(').replace(/\)/g, '\\)');
}

/**
 * @param {object} receipt
 * @returns {Buffer}
 */
export function buildReceiptPdf(receipt) {
  const lines = [
    'Verae Time — certified retrieval receipt',
    `Type: ${receipt.type}`,
    `Job ID: ${receipt.jobId}`,
    `SHA256: ${receipt.sha256 ?? ''}`,
    `Original timestamp: ${receipt.timestamp ?? ''}`,
    `Retrieved at: ${receipt.extraSeal?.retrievedAt ?? ''}`,
    `Tenant: ${receipt.extraSeal?.tenantId ?? ''}`,
    `Seal event: ${receipt.extraSeal?.event ?? ''}`,
    `Certificate: ${String(receipt.certificate ?? '').slice(0, 80)}`,
  ];

  const commands = lines
    .map((line, i) => {
      const y = 720 - i * 18;
      return `BT /F1 11 Tf 50 ${y} Td (${pdfEscape(line)}) Tj ET`;
    })
    .join('\n');

  const stream = `${commands}\n`;
  const objects = [
    '1 0 obj << /Type /Catalog /Pages 2 0 R >> endobj',
    '2 0 obj << /Type /Pages /Kids [3 0 R] /Count 1 >> endobj',
    '3 0 obj << /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] /Contents 4 0 R /Resources << /Font << /F1 5 0 R >> >> >> endobj',
    `4 0 obj << /Length ${Buffer.byteLength(stream)} >> stream\n${stream}endstream endobj`,
    '5 0 obj << /Type /Font /Subtype /Type1 /BaseFont /Helvetica >> endobj',
  ];

  let offset = '%PDF-1.4\n'.length;
  const xref = [0];
  let body = '%PDF-1.4\n';
  for (const obj of objects) {
    xref.push(offset);
    const chunk = `${obj}\n`;
    body += chunk;
    offset += Buffer.byteLength(chunk);
  }
  const xrefStart = offset;
  let xrefTable = `xref\n0 ${objects.length + 1}\n0000000000 65535 f \n`;
  for (let i = 1; i < xref.length; i += 1) {
    xrefTable += `${String(xref[i]).padStart(10, '0')} 00000 n \n`;
  }
  body += xrefTable;
  body += `trailer << /Size ${objects.length + 1} /Root 1 0 R >>\nstartxref\n${xrefStart}\n%%EOF\n`;
  return Buffer.from(body, 'utf8');
}