enum SigningScheme {
  EIP712 = 0,   // Structured data signing (recommended)
  ETHSIGN = 1,  // Legacy eth_sign RPC
  EIP1271 = 2,  // Smart contract signatures
  PRESIGN = 3,  // On-chain pre-approval
}

const signature = await signOrder(
  settlementDomain,
  order,
  wallet,
  SigningScheme.EIP712
);

const signature = await signOrder(
  settlementDomain,
  order,
  wallet,
  SigningScheme.ETHSIGN
);

const eip1271Sig: Eip1271Signature = {
  scheme: SigningScheme.EIP1271,
  verifier: safeAddress,
  data: signatureBytes,
};

const encoded = encodeEip1271SignatureData(eip1271Sig);

const preSignSig: PreSignSignature = {
  scheme: SigningScheme.PRESIGN,
  signer: ownerAddress,
};

interface EcdsaSignature {
  scheme: SigningScheme.EIP712 | SigningScheme.ETHSIGN;
  data: string; // r, s, v values
}

interface Eip1271Signature {
  scheme: SigningScheme.EIP1271;
  verifier: string;
  data: string;
}

interface PreSignSignature {
  scheme: SigningScheme.PRESIGN;
  signer: string;
}

async function signOrder(
  domain: TypedDataDomain,
  order: Order,
  signer: Signer,
  scheme: SigningScheme.EIP712 | SigningScheme.ETHSIGN
): Promise<EcdsaSignature>;

function encodeEip1271SignatureData(signature: {
  verifier: string;
  data: string;
}): string;

function decodeEip1271SignatureData(encoded: string): {
  verifier: string;
  data: string;
};