Using python to create item offer facing Invalid order signature

[zanight8]

Hi,

I am trying to use the https://testnets-api.opensea.io/api/v2/orders/sepolia/seaport/offers endpoint to create an offer.
However I get the error "errors":["['Invalid order signature']"]
I don't know how to make a correct signature with eip712.
My Python code to generate the signature:

import requests
import time
from web3 import Web3
from eth_account import Account
from eth_account.messages import encode_structured_data

ALCHEMY_URL = 'https://eth-sepolia.g.alchemy.com/v2/xxxxxxxxxxxxxxxxxxxxxxx'


WALLET_ADDRESS = '0xAAAAAAAAAAAAAAAAAAAAAAAAAAA'
PRIVATE_KEY = '0xXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'

OPENSEA_API_URL = 'https://testnets-api.opensea.io/api/v2/orders/sepolia/seaport/offers'

web3 = Web3(Web3.HTTPProvider(ALCHEMY_URL))


def to_checksum_address(address):
    return web3.to_checksum_address(address)


def create_offer():
    current_time = int(time.time())
    current_timestamp = current_time + 10

    payload = {
        "parameters": {
            "offerer": to_checksum_address(WALLET_ADDRESS),
            "offer": [
                {
                    "itemType": 1,
                    "token": "0x7b79995e5f793A07Bc00c21412e50Ecae098E7f9",
                    "identifierOrCriteria": 0,
                    "startAmount": 10000000000000000,
                    "endAmount": 10000000000000000
                }
            ],
            "consideration": [
                {
                    "itemType": 3,
                    "token": "0xXXXXXXXXXXXXXXXXXXXXXXXXXXX",
                    "identifierOrCriteria": 4,
                    "startAmount": 1,
                    "endAmount": 1,
                    "recipient": to_checksum_address(WALLET_ADDRESS)
                },
                {
                    "itemType": 1,
                    "token": "0x7b79995e5f793A07Bc00c21412e50Ecae098E7f9",
                    "identifierOrCriteria": 0,
                    "startAmount": 250000000000000,
                    "endAmount": 250000000000000,
                    "recipient": "0x0000a26b00c1F0DF003000390027140000fAa719"
                }
            ],
            "startTime": str(current_timestamp),
            "endTime": str(current_timestamp + 259200),
            "orderType": 3,
            "zone": "0x000056F7000000EcE9003ca63978907a00FFD100",
            "zoneHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
            "salt": web3.to_hex(web3.keccak(text=str(current_time))),
            "conduitKey": "0x0000007b02230091a7ed01230072f7006a004d60a8d4e71d599b8104250f0000",
            "totalOriginalConsiderationItems": 2,
            "counter": 0
        },
        "signature": "", 
        "protocol_address": "0x0000000000000068f116a894984e2db1123eb395"
    }

    eip712_domain = {
        "name": "Seaport",
        "version": "1.6",
        "chainId": 11155111,  
        "verifyingContract": "0x0000000000000068F116a894984e2DB1123eB395"
    }

    eip712_message = {
        "offerer": payload["parameters"]["offerer"],
        "offer": payload["parameters"]["offer"],
        "consideration": payload["parameters"]["consideration"],
        "startTime": int(payload["parameters"]["startTime"]),
        "endTime": int(payload["parameters"]["endTime"]),
        "orderType": payload["parameters"]["orderType"],
        "zone": payload["parameters"]["zone"],
        "zoneHash": web3.to_bytes(hexstr=payload["parameters"]["zoneHash"]),  
        "salt": int(payload["parameters"]["salt"], 16),
        "conduitKey": web3.to_bytes(hexstr=payload["parameters"]["conduitKey"]),
        "totalOriginalConsiderationItems": payload["parameters"]["totalOriginalConsiderationItems"],
        "counter": payload["parameters"]["counter"]
    }

    eip712_types = {
        "EIP712Domain": [
            {"name": "name", "type": "string"},
            {"name": "version", "type": "string"},
            {"name": "chainId", "type": "uint256"},
            {"name": "verifyingContract", "type": "address"}
        ],
        "OrderComponents": [
            {"name": "offerer", "type": "address"},
            {"name": "offer", "type": "OfferItem[]"},
            {"name": "consideration", "type": "ConsiderationItem[]"},
            {"name": "startTime", "type": "uint256"},
            {"name": "endTime", "type": "uint256"},
            {"name": "orderType", "type": "uint8"},
            {"name": "zone", "type": "address"},
            {"name": "zoneHash", "type": "bytes32"},
            {"name": "salt", "type": "uint256"},
            {"name": "conduitKey", "type": "bytes32"},
            {"name": "counter", "type": "uint256"}
        ],
        "OfferItem": [
            {"name": "itemType", "type": "uint8"},
            {"name": "token", "type": "address"},
            {"name": "identifierOrCriteria", "type": "uint256"},
            {"name": "startAmount", "type": "uint256"},
            {"name": "endAmount", "type": "uint256"}
        ],
        "ConsiderationItem": [
            {"name": "itemType", "type": "uint8"},
            {"name": "token", "type": "address"},
            {"name": "identifierOrCriteria", "type": "uint256"},
            {"name": "startAmount", "type": "uint256"},
            {"name": "endAmount", "type": "uint256"},
            {"name": "recipient", "type": "address"}
        ]
    }

    structured_data = {
        "types": eip712_types,
        "domain": eip712_domain,
        "primaryType": "OrderComponents",
        "message": eip712_message
    }

    signable_message = encode_structured_data(structured_data)
    signed_message = web3.eth.account.sign_message(signable_message, private_key=PRIVATE_KEY)
    payload['signature'] = signed_message.signature.hex()

    headers = {
        "accept": "application/json",
        "content-type": "application/json",
    }


    response = requests.post(OPENSEA_API_URL, json=payload, headers=headers)

    if response.status_code == 200:
        print('Offer created successfully:', response.json())
    else:
        print('Error creating offer:', response.status_code, response.text)

create_offer()