/**
 * x402 + A2A in-band integration utilities (x402 v2 A2A transport).
 *
 * Port of the Python SDK's `payments_py/x402/a2a.py` `X402A2AUtils`. These
 * helpers bridge the x402 payment protocol with the A2A (Agent-to-Agent)
 * protocol, signalling payment state *in band* through A2A Task / Message
 * metadata instead of HTTP status codes and headers.
 *
 * The A2A transport equivalent of the MCP transport's `_meta["x402/payment"]`
 * keys is the A2A **task / message metadata** under the spec-defined
 * `x402.payment.*` keys (see {@link X402A2AMetadata}). The wire shapes are
 * defined by:
 *   - Coinbase x402 v2 A2A transport: specs/transports-v2/a2a.md
 *   - A2A x402 extension: https://github.com/google-agentic-commerce/a2a-x402
 *
 * These constants/keys are part of the specification and MUST NOT be changed.
 */
import type { Message, Task } from '@a2a-js/sdk';
import type { SettlePermissionsResult, X402PaymentRequired } from '../x402/facilitator-api.js';
/**
 * Protocol-defined payment states for the A2A x402 flow.
 *
 * Tracked in the `x402.payment.status` metadata field. Values are part of the
 * A2A x402 specification (Section 6: State Management) and must not be changed.
 */
export declare enum PaymentStatus {
    /** Payment requirements sent to client (task state `input-required`). */
    PAYMENT_REQUIRED = "payment-required",
    /** Payment payload received by server. */
    PAYMENT_SUBMITTED = "payment-submitted",
    /** Payment payload verified by the facilitator. */
    PAYMENT_VERIFIED = "payment-verified",
    /** Payment requirements rejected by the client. */
    PAYMENT_REJECTED = "payment-rejected",
    /** Payment settled on-chain successfully (task state `completed`). */
    PAYMENT_COMPLETED = "payment-completed",
    /** Payment verification or settlement failed (task state `failed`). */
    PAYMENT_FAILED = "payment-failed"
}
/**
 * Spec-defined A2A task / message metadata keys for the x402 protocol.
 *
 * As defined in the A2A x402 specification (Section 6: State Management). These
 * keys are part of the specification and must not be changed. Note these are
 * NOT the MCP `_meta["x402/payment"]` keys — A2A signals payment state through
 * Task / Message `metadata` instead.
 */
export declare const X402A2AMetadata: {
    /** Current payment flow stage. */
    readonly STATUS_KEY: "x402.payment.status";
    /** X402PaymentRequired object. */
    readonly REQUIRED_KEY: "x402.payment.required";
    /** PaymentPayload object (client → server). */
    readonly PAYLOAD_KEY: "x402.payment.payload";
    /** Array of SettleResponse receipts (server → client). */
    readonly RECEIPTS_KEY: "x402.payment.receipts";
    /** Error code on failure. */
    readonly ERROR_KEY: "x402.payment.error";
};
/**
 * Nevermined-specific (non-core-spec) marker set alongside `payment-verified`
 * when on-chain settlement is **deferred** to a batch process this handler does
 * not confirm. Lets a client distinguish "verified, will be charged out-of-band"
 * from a plain verify; spec-only clients ignore the unknown key. Value: `'deferred'`.
 */
export declare const X402_SETTLEMENT_DEFERRED_KEY = "x402.payment.settlement";
/**
 * Utilities for managing x402 payment state in A2A messages and tasks.
 *
 * Provides methods to extract payment status / requirements / payload from
 * incoming A2A messages and tasks, and to stamp payment-required, verified,
 * completed and failed state onto outgoing tasks — all via the spec-defined
 * `x402.payment.*` metadata keys.
 */
export declare class X402A2AUtils {
    static readonly STATUS_KEY: "x402.payment.status";
    static readonly REQUIRED_KEY: "x402.payment.required";
    static readonly PAYLOAD_KEY: "x402.payment.payload";
    static readonly RECEIPTS_KEY: "x402.payment.receipts";
    static readonly ERROR_KEY: "x402.payment.error";
    /** Extract the payment status from a Message's metadata, or `undefined`. */
    getPaymentStatusFromMessage(message?: Message | null): string | undefined;
    /** Extract the payment status from a Task's status message metadata, or `undefined`. */
    getPaymentStatus(task?: Task | null): string | undefined;
    /**
     * Extract the X402PaymentRequired object from a Message's metadata.
     *
     * Returns the raw object (already spec-shaped JSON). Returns `undefined` when
     * absent or not a plain object.
     */
    getPaymentRequirementsFromMessage(message?: Message | null): X402PaymentRequired | undefined;
    /** Extract the X402PaymentRequired object from a Task's status message metadata. */
    getPaymentRequirements(task?: Task | null): X402PaymentRequired | undefined;
    /**
     * Extract the in-band PaymentPayload object from a Message's metadata.
     *
     * The payload is untrusted client input that the server re-encodes into an
     * access token, so this rejects null, arrays and oversized payloads
     * (defense-in-depth, parity with the MCP `readPaymentPayload`).
     *
     * @returns The PaymentPayload object, or `undefined` when absent/invalid.
     */
    getPaymentPayloadFromMessage(message?: Message | null): Record<string, any> | undefined;
    /** Extract the in-band PaymentPayload object from a Task's status message metadata. */
    getPaymentPayload(task?: Task | null): Record<string, any> | undefined;
    /**
     * Set a Task to the payment-required state (`input-required`) with the
     * X402PaymentRequired object in `x402.payment.required` metadata.
     *
     * Mutates and returns `task` (in place), per the x402 v2 A2A transport.
     */
    createPaymentRequiredTask(task: Task, paymentRequired: X402PaymentRequired): Task;
    /**
     * Record payment verification on a Task: sets the `x402.payment.status`
     * metadata to `payment-verified`. Task state is left to the caller (the spec
     * keeps it `working`).
     */
    recordPaymentVerified(task: Task): Task;
    /**
     * Record a deferred (batch) settlement on a Task: the payload was verified but
     * on-chain settlement is deferred out-of-band (the handler never confirms it).
     * Sets `payment-verified` PLUS the Nevermined `x402.payment.settlement: 'deferred'`
     * marker, so a client can tell it will be charged out-of-band — distinct from a
     * plain verify where nothing is owed.
     */
    recordPaymentDeferred(task: Task): Task;
    /**
     * Record a successful settlement on a Task: sets the `x402.payment.status`
     * metadata to `payment-completed` and stores the SettleResponse receipt under
     * `x402.payment.receipts` (an array, per the spec).
     */
    recordPaymentSuccess(task: Task, settleResponse?: SettlePermissionsResult): Task;
    /**
     * Record a payment failure on a Task: `x402.payment.status = payment-failed`,
     * the error code under `x402.payment.error`, and (when available) the failed
     * SettleResponse under `x402.payment.receipts`.
     */
    recordPaymentFailure(task: Task, errorCode: string, errorResponse?: SettlePermissionsResult): Task;
}
/** Shared singleton, matching the Python `X402A2AUtils()` usage pattern. */
export declare const x402A2AUtils: X402A2AUtils;
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