#!/usr/bin/env node
/* Stamp each given HTML page with today's date + its own MD5 and SHA-256.
 *
 * A file can't contain its own hash directly (writing the hash changes the
 * hash). So the hashes are computed over the page with the two hash fields
 * ZEROED, then the real values are written back (same length, so the file the
 * verifier hashes-after-zeroing is exactly what we hashed). Self-consistent and
 * idempotent.
 *
 * Verify a served page:  sed the md5 field to 32 zeros and the sha256 field to
 * 64 zeros, then `md5sum` / `sha256sum` — must match the printed values.
 *
 *   node web/stamp.js web/chat.html web/zebra-audio.html web/how-it-works.html
 */
const { readFileSync, writeFileSync } = require('fs');
const { createHash } = require('crypto');

const date = process.env.STAMP_DATE || new Date().toISOString().slice(0, 10);
const Z32 = '0'.repeat(32), Z64 = '0'.repeat(64);
let bad = 0;

for (const f of process.argv.slice(2)) {
  let s = readFileSync(f, 'utf8');
  if (!/class="stamp-md5"/.test(s)) { console.error(`! ${f}: no integrity footer, skipped`); bad++; continue; }
  s = s.replace(/(<span class="stamp-date">)[^<]*(<\/span>)/, `$1${date}$2`);
  s = s.replace(/(<span class="stamp-md5">)[0-9a-fA-F]*(<\/span>)/, `$1${Z32}$2`)
       .replace(/(<span class="stamp-sha">)[0-9a-fA-F]*(<\/span>)/, `$1${Z64}$2`);
  const md5 = createHash('md5').update(s).digest('hex');
  const sha = createHash('sha256').update(s).digest('hex');
  s = s.replace(`<span class="stamp-md5">${Z32}</span>`, `<span class="stamp-md5">${md5}</span>`)
       .replace(`<span class="stamp-sha">${Z64}</span>`, `<span class="stamp-sha">${sha}</span>`);
  writeFileSync(f, s);
  console.log(`${f}\n  date   ${date}\n  md5    ${md5}\n  sha256 ${sha}`);
}
process.exit(bad ? 1 : 0);