Verify quote signatures

import { getAddress, hashTypedData, recoverAddress, type Address, type Hex } from 'viem';

type SignedQuote = {
  id: string;
  source: { chainId: number };
  intentHash: Hex | null;
  steps: { intents: { intentHash: Hex | null }[] }[];
  expiresAt: number;
  signature: Hex;
};

export async function verifyQuoteSignature(
  quote: SignedQuote,
  expectedSigner: Address,
): Promise<void> {
  if (quote.expiresAt <= Math.floor(Date.now() / 1000)) {
    throw new Error('Quote expired; request a fresh quote');
  }
  const hashes = [
    quote.intentHash,
    ...quote.steps.flatMap((step) => step.intents.map((intent) => intent.intentHash)),
  ].filter((hash): hash is Hex => hash !== null);
  const intentHashes = [...new Set(hashes.map((hash) => hash.toLowerCase() as Hex))].sort();
  if (intentHashes.length === 0) throw new Error('Quote has no signed intents');

  const digest = hashTypedData({
    domain: { name: 'EcoQuoteV1', version: '1', chainId: quote.source.chainId },
    types: { Quote: [
      { name: 'id', type: 'string' },
      { name: 'intentHashes', type: 'bytes32[]' },
      { name: 'expiresAt', type: 'uint64' },
    ] },
    primaryType: 'Quote',
    message: { id: quote.id, intentHashes, expiresAt: BigInt(quote.expiresAt) },
  });
  const signer = await recoverAddress({ hash: digest, signature: quote.signature });
  if (getAddress(signer) !== getAddress(expectedSigner)) {
    throw new Error('Quote signer does not match the source chain quoteSigner');
  }
}