Every Daily Deed draw is provably fair.

// Paste this into your browser console
const seed = 'PASTE_REVEALED_SEED_HERE';
const data = new TextEncoder().encode(seed);
const hashBuffer = await crypto.subtle.digest('SHA-256', data);
const hash = Array.from(new Uint8Array(hashBuffer))
  .map(b => b.toString(16).padStart(2, '0'))
  .join('');
console.log('Computed hash:', hash);
// Compare to the commitment hash on the campaign page. They must match.

// Deterministic winner verification. Matches services/api/src/lib/drawCommitment.ts
async function deterministicUniformInt(seed, n, counter = 0) {
  if (n === 1) return 0;
  const bitLength  = Math.ceil(Math.log2(n)) + 1;
  const byteLength = Math.min(Math.ceil(bitLength / 8), 6); // cap at 48 bits
  const domain     = Math.pow(2, byteLength * 8);
  const limit      = Math.floor(domain / n) * n;
  for (let i = 0; i < 1024; i++) {
    const buf = new TextEncoder().encode(`${seed}:${counter}`);
    const out = new Uint8Array(await crypto.subtle.digest('SHA-256', buf));
    let raw = 0;
    for (let b = 0; b < byteLength; b++) raw = raw * 256 + out[b];
    if (raw < limit) return raw % n;
    counter++;
  }
  throw new Error('rejection sampling did not converge');
}

async function selectWinnerEntryNumber(seed, totalEntries) {
  return 1 + await deterministicUniformInt(seed, totalEntries);
}

// Usage
const winner = await selectWinnerEntryNumber('PASTE_SEED_HERE', TOTAL_ENTRIES);
console.log('Winning entry position:', winner);
// Should match the winning position published on the campaign page.