/**
 * Twig Payments — x402 Gate
 *
 * Payment flow:
 * 1. First run is free (stores baseline).
 * 2. Subsequent runs require $TWIG_MONITOR_PRICE USDC on Base.
 * 3. CLI prints wallet address + amount, user pastes tx hash.
 * 4. We verify on-chain via Base RPC (public Etherscan-compatible endpoint).
 * 5. Fail-open: if verification fails, log warning, mark unverified, but allow.
 * 6. Receipts stored in ~/.twig/receipts/<urlHash>.json (append-only).
 *
 * Wallet address MUST be provided via TWIG_PAYMENT_ADDRESS env var.
 */
import type { PaymentGateResult, PaymentReceipt, PaymentRequest } from './types.js';
export declare const PAYMENT_AMOUNT_DEFAULT = "0.50";
export declare const PAYMENT_CURRENCY = "USDC";
export declare const PAYMENT_CHAIN: "base";
export declare function getPaymentAddress(): string;
export declare function getPaymentAmount(): string;
export declare function getReceiptsDir(baseDir?: string): string;
export declare function loadReceipts(urlHash: string, baseDir?: string): PaymentReceipt[];
export declare function buildPaymentRequest(normalizedUrl: string): PaymentRequest;
/**
 * Verify a USDC transfer on Base by checking the tx receipt via JSON-RPC.
 *
 * TODO: Implement real on-chain verification:
 *   1. Call eth_getTransactionReceipt with txHash via BASE_RPC_URL
 *   2. Decode the ERC-20 Transfer log (topic0 = keccak256("Transfer(address,address,uint256)"))
 *   3. Verify log.topics[2] (to address) == recipientAddress (checksummed)
 *   4. Verify log.data (value) >= expectedAmount (in USDC base units, 6 decimals)
 *   5. Verify the log's contract address == USDC contract on Base
 *
 * Until implemented, returns false. The fail-open path in checkPaymentGate
 * handles false correctly by allowing with an [PAYMENT UNVERIFIED] marker.
 */
export declare function verifyOnChain(_txHash: string, _recipientAddress: string, _amount: string): Promise<boolean>;
/**
 * Main gate function.
 * - isFirstRun: if true, allow free (no payment check).
 * - txHash: user-provided transaction hash.
 * - normalizedUrl: used to check existing receipts.
 * - baseDir: override storage directory (for tests).
 */
export declare function checkPaymentGate(opts: {
    isFirstRun: boolean;
    txHash?: string;
    normalizedUrl: string;
    baseDir?: string;
}): Promise<PaymentGateResult>;