/**
 * @name payments/prepaid-credit-store
 * @description In-memory + file-persisted prepaid credit store for x402 sessions.
 *
 * Allows agents to prepay a USDC balance once (via standard x402 challenge →
 * sign → settle) and then make multiple tool calls without per-call 402
 * challenges. The server checks the prepaid balance in `onProtectedRequest`
 * and grants access by returning `{ grantAccess: true }` (standard x402
 * Lifecycle Hooks extension) when sufficient balance exists.
 *
 * The store is backed by a JSON file at ~/.config/mcp-sap/payments/prepaid.json
 * so credits survive server restarts. An in-memory Map provides fast lookups.
 *
 * @module payments/prepaid-credit-store
 */
/** Prepaid credit entry for a wallet. */
export interface PrepaidCredit {
    /** Unique session ID used as the X-SAP-Prepaid-Session header value. */
    sessionId: string;
    /** Wallet address that funded the session (payer). */
    wallet: string;
    /** Total USDC deposited when the session was created. */
    totalUsd: number;
    /** Remaining USDC balance. */
    remainingUsd: number;
    /** Per-call cost deducted on each granted request. */
    perCallCostUsd: number;
    /** ISO timestamp when the session was created. */
    createdAt: string;
    /** ISO timestamp when the session expires. */
    expiresAt: string;
    /** Number of calls made using this session. */
    callCount: number;
}
/** Result of checking prepaid credit. */
export interface PrepaidCheckResult {
    /** True if the session has enough balance for a call. */
    hasCredit: boolean;
    /** The session that was checked, if found. */
    sessionId?: string;
    /** Remaining balance after this call (if hasCredit). */
    remainingUsd?: number;
    /** Reason if no credit. */
    reason?: string;
}
/**
 * Prepaid credit store with file persistence.
 * Uses a Map for fast lookups and a JSON file for durability.
 */
export declare class PrepaidCreditStore {
    private readonly credits;
    private readonly filePath;
    private dirty;
    constructor(configDir?: string);
    /**
     * Create a new prepaid session. Called after a successful x402 settlement
     * for the `sap_payments_fund_prepaid` hosted tool.
     *
     * @param wallet — Payer wallet address.
     * @param amountUsd — Total USDC deposited.
     * @param perCallCostUsd — Cost per call that will be deducted.
     * @param ttlHours — Session TTL in hours (default 24).
     * @returns The created PrepaidCredit entry.
     */
    createSession(wallet: string, amountUsd: number, perCallCostUsd: number, ttlHours?: number): PrepaidCredit;
    /**
     * Check if a session has enough credit for a call and deduct it if so.
     * This is called by the monetization gate's `onProtectedRequest` hook.
     *
     * @param sessionId — Session ID from the X-SAP-Prepaid-Session header.
     * @param costUsd — Cost to deduct (defaults to session's perCallCostUsd).
     * @returns PrepaidCheckResult with hasCredit and remaining balance.
     */
    checkAndDeduct(sessionId: string, costUsd?: number): PrepaidCheckResult;
    /**
     * Get the remaining balance for a session without deducting.
     * @param sessionId — Session ID.
     * @returns PrepaidCredit or null if not found.
     */
    getBalance(sessionId: string): PrepaidCredit | null;
    /**
     * Get all active sessions for a wallet.
     * @param wallet — Wallet address.
     * @returns Array of PrepaidCredit entries.
     */
    getSessionsByWallet(wallet: string): PrepaidCredit[];
    /**
     * Manually close a session (refund unused balance is out of scope —
     * the balance simply becomes unavailable).
     * @param sessionId — Session ID to close.
     */
    closeSession(sessionId: string): boolean;
    /**
     * Prune expired sessions. Called periodically.
     */
    pruneExpired(): number;
    private load;
    private save;
    private startSyncTimer;
}
/**
 * Get the global PrepaidCreditStore singleton used by free payment tools.
 * Lazily creates the store on first access.
 */
export declare function getGlobalPrepaidStore(): PrepaidCreditStore;
/**
 * Set the global PrepaidCreditStore singleton. Called by the server when the
 * monetization gate is initialized so the tools share the same store instance.
 */
export declare function setGlobalPrepaidStore(store: PrepaidCreditStore): void;
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