Prove. Commit. Verify.

import { sha256 } from '@noble/hashes/sha256';
import { verifyVRF, hexToBytes } from '@collectorcrypt/ecvrf';

// alpha = sha256(slotHash(32B) || utf8(lobbyId)) — the public VRF input.
export function vrfAlphaHex(slotHashHex: string, lobbyId: number): string {
  const slot = Buffer.from(slotHashHex.replace(/^0x/, ''), 'hex');
  const id = new TextEncoder().encode(String(lobbyId));
  const msg = new Uint8Array(slot.length + id.length);
  msg.set(slot, 0); msg.set(id, slot.length);
  return Buffer.from(sha256(msg)).toString('hex');
}

// The published roll IS the VRF output beta[0:32].
export function rollFromBeta(betaHex: string): string {
  return '0x' + betaHex.replace(/^0x/, '').slice(0, 64);
}

// USD-weighted winner pick — mirror of pickRoyaleWinnerFromRoll.
// Weight each depositor by round(valueUsd * 1e6) micro-USD, drop the
// service addresses (royale wallet + cold rake-burn), then walk the
// prefix-sum of weights with roll mod totalWeight.
export function weightedWinner(
  rollHex: string,
  cards: { depositor: string; valueUsd: number }[],
  exclude: string[],
): string {
  const ex = new Set(exclude);
  const w = new Map<string, bigint>();
  for (const c of cards) {
    if (ex.has(c.depositor)) continue;
    const micro = BigInt(Math.round(c.valueUsd * 1_000_000));
    w.set(c.depositor, (w.get(c.depositor) ?? 0n) + micro);
  }
  const rows = [...w.entries()].map(([address, balance]) => ({ address, balance }))
    .sort((a, b) => (a.address < b.address ? -1 : a.address > b.address ? 1 : 0));
  let total = 0n; const cum: bigint[] = [];
  for (const r of rows) { total += r.balance; cum.push(total); }
  const off = ((BigInt(rollHex) % total) + total) % total;
  let lo = 0, hi = cum.length;
  while (lo < hi) { const m = (lo + hi) >> 1; if (cum[m] <= off) lo = m + 1; else hi = m; }
  return rows[lo].address;
}

// Verify the ECVRF proof itself in-browser (no server, no CC dependency):
//   verifyVRF(hexToBytes(operatorKey), hexToBytes(alpha), hexToBytes(proof)) === true
// Cross-check operatorKey is the on-chain frozen one at
// https://vrf.collectorcrypt.com/#/verify.