/**
 * Spent set storage interface and implementations
 * Prevents double-spending by tracking used block hashes
 */
/**
 * Interface for spent set storage implementations
 */
export interface SpentSetStorage {
    /**
     * Check if a block hash has been spent
     */
    has(blockHash: string): Promise<boolean>;
    /**
     * Mark a block hash as spent
     */
    add(blockHash: string): Promise<void>;
    /**
     * Atomically add a block hash only if it doesn't already exist.
     * Returns true if added successfully, false if already spent.
     * This is critical for preventing race conditions in settlement.
     */
    addIfNotExists(blockHash: string): Promise<boolean>;
}
/**
 * In-memory implementation of SpentSetStorage
 * Suitable for development and testing
 * For production, use a persistent storage implementation
 */
export declare class InMemorySpentSet implements SpentSetStorage {
    private spentHashes;
    private readonly ttlMs;
    /**
     * @param ttlMs Time-to-live in milliseconds (default: 30 days)
     */
    constructor(ttlMs?: number);
    has(blockHash: string): Promise<boolean>;
    add(blockHash: string): Promise<void>;
    addIfNotExists(blockHash: string): Promise<boolean>;
    /**
     * Get the number of spent hashes (for testing/debugging)
     */
    size(): number;
    /**
     * Clear all spent hashes (for testing)
     */
    clear(): void;
    /**
     * Manual prune of expired entries
     */
    prune(): void;
}
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