export interface PlaceholderSessionOptions {
    prefix: string;
    ttlMs: number;
    maxMappings: number;
    secret: string;
}
export interface PlaceholderEntry {
    original: string;
    placeholder: string;
    category: string;
    createdAt: number;
}
export declare class PlaceholderSession {
    private readonly prefix;
    private readonly ttlMs;
    private readonly maxMappings;
    private readonly secret;
    private readonly forward;
    private readonly reverse;
    private readonly created;
    constructor(options: PlaceholderSessionOptions);
    private computeHash;
    getOrCreatePlaceholder(original: string, category: string): string;
    lookup(placeholder: string): string | undefined;
    cleanup(now: number): number;
    private evictIfNeeded;
    get size(): number;
}
export declare function getPlaceholderRegex(prefix: string): RegExp;
export declare function generateFallbackSecret(): string;