import uuid, time
from eth_account import Account
from eth_account.messages import encode_typed_data
from web3 import Web3

class EIP712Signer:
    def __init__(self, private_key: str, contract_address: str, chain_id: int):
        self.account = Account.from_key(private_key)
        self.contract_address = Web3.to_checksum_address(contract_address)
        self.chain_id = chain_id

    def build_typed_data(self, gateway_uuid_bytes: bytes, merkle_root_bytes: bytes, object_count: int, nonce: int, timestamp: int) -> dict:
        return {
            "types": {
                "EIP712Domain": [
                    {"name": "name", "type": "string"},
                    {"name": "version", "type": "string"},
                    {"name": "chainId", "type": "uint256"},
                    {"name": "verifyingContract", "type": "address"}
                ],
                "AuditReceipt": [
                    {"name": "gatewayUuid", "type": "bytes16"},
                    {"name": "merkleRoot", "type": "bytes32"},
                    {"name": "objectCount", "type": "uint256"},
                    {"name": "timestamp", "type": "uint256"},
                    {"name": "nonce", "type": "uint256"}
                ]
            },
            "primaryType": "AuditReceipt",
            "domain": {"name": "AuditReceiptLedger", "version": "1", "chainId": self.chain_id, "verifyingContract": self.contract_address},
            "message": {"gatewayUuid": gateway_uuid_bytes, "merkleRoot": merkle_root_bytes, "objectCount": object_count, "timestamp": timestamp, "nonce": nonce}
        }

    def sign_audit_receipt(self, gateway_uuid_str: str, merkle_root_hex: str, object_count: int, nonce: int) -> dict:
        g_bytes = uuid.UUID(gateway_uuid_str).bytes
        m_bytes = bytes.fromhex(merkle_root_hex.replace("0x", ""))
        ts = int(time.time())

        typed_data = self.build_typed_data(g_bytes, m_bytes, object_count, nonce, ts)
        sig = self.account.sign_message(encode_typed_data(full_message=typed_data)).signature.hex()

        return {
            "receipt": {"gatewayUuid": "0x" + g_bytes.hex(), "merkleRoot": "0x" + m_bytes.hex(), "objectCount": object_count, "timestamp": ts, "nonce": nonce},
            "signature": sig,
            "signer": self.account.address
        }