#!/usr/bin/env python3
"""x402 reference client — pay once, fetch premium data. Served by the gateway itself.

Any AI agent can copy-run this to consume the paid endpoint.
    pip install web3 eth-account requests
    PRIVATE_KEY=0x... python client.py
The wallet must hold >= the quoted USDC on Base + a little ETH for gas.
"""
import os, time, requests
from web3 import Web3
from eth_account import Account
from eth_account.messages import encode_defunct

BASE = "https://x402.obolpay.xyz"
ENDPOINT = BASE + "/api/v1/protected-data"
RPC = "https://mainnet.base.org"
UA = {"User-Agent": "x402-client/1.0"}   # NOTE: send a User-Agent (Cloudflare blocks empty/raw-urllib)


def main():
    pk = os.environ["PRIVATE_KEY"]
    acct = Account.from_key(pk)
    w3 = Web3(Web3.HTTPProvider(RPC))

    # 1) Read the free preview + payment challenge (no spend yet)
    r = requests.get(ENDPOINT, headers=UA, timeout=30)
    assert r.status_code == 402, r.status_code
    ch = r.json()["payment"]
    print("PREVIEW:", ch.get("preview"))          # <- evaluate before paying
    token = Web3.to_checksum_address(ch["token_contract"])
    to = Web3.to_checksum_address(ch["recipient"])
    amount = int(round(float(ch["amount"]) * 10 ** 6))   # USDC has 6 decimals
    domain, invoice = ch["signature_scheme"]["domain"], ch["invoice_id"]

    # 2) Pay: ERC-20 USDC transfer to the merchant
    erc20 = w3.eth.contract(address=token, abi=[{"name": "transfer", "type": "function",
        "stateMutability": "nonpayable", "inputs": [{"name": "to", "type": "address"},
        {"name": "value", "type": "uint256"}], "outputs": [{"type": "bool"}]}])
    tx = erc20.functions.transfer(to, amount).build_transaction({
        "from": acct.address, "nonce": w3.eth.get_transaction_count(acct.address),
        "chainId": ch["chain_id"], "gas": 120000,
        "maxFeePerGas": w3.eth.gas_price * 2, "maxPriorityFeePerGas": w3.to_wei(0.001, "gwei")})
    signed = acct.sign_transaction(tx)
    raw = getattr(signed, "raw_transaction", None) or signed.rawTransaction
    txh = w3.eth.send_raw_transaction(raw).hex()
    if not txh.startswith("0x"):
        txh = "0x" + txh
    print("TX:", txh)
    w3.eth.wait_for_transaction_receipt(txh)

    # 3) Sign the EIP-191 binding: x402:{domain}:{invoice_id}:{tx_hash}
    msg = "x402:" + domain + ":" + invoice + ":" + txh.lower()
    sig = Account.sign_message(encode_defunct(text=msg), pk).signature.hex()
    if not sig.startswith("0x"):
        sig = "0x" + sig

    # 4) Claim the data (poll while the chain confirms)
    headers = {**UA, "X-Payment-Invoice-ID": invoice, "X-Payment-Tx-Hash": txh, "X-Payment-Signature": sig}
    for _ in range(40):
        rr = requests.get(ENDPOINT, headers=headers, timeout=30)
        if rr.status_code == 200:
            print("DATA:", rr.json()["data"])
            return
        if rr.status_code == 402 and rr.json().get("retryable"):
            time.sleep(3)
            continue
        print("REJECTED:", rr.status_code, rr.text)
        return


if __name__ == "__main__":
    main()