/**
 * Request Queue - Event Batching (PostHog-style)
 *
 * Batches multiple events together and sends them at configurable intervals.
 * This reduces the number of HTTP requests significantly for active users.
 *
 * Features:
 * - Configurable flush interval (default 3 seconds)
 * - Batches events by URL/batchKey
 * - Uses sendBeacon on page unload for reliable delivery
 * - Converts absolute timestamps to relative offsets before sending
 */
import type { TrackingEvent } from "./types";
export declare const DEFAULT_FLUSH_INTERVAL_MS = 3000;
export interface QueuedRequest {
    url: string;
    event: TrackingEvent;
    batchKey?: string;
    transport?: "xhr" | "sendBeacon";
}
export interface BatchedRequest {
    url: string;
    events: TrackingEvent[];
    batchKey?: string;
    transport?: "xhr" | "sendBeacon";
}
export interface RequestQueueConfig {
    flush_interval_ms?: number;
}
export declare class RequestQueue {
    private _isPaused;
    private _queue;
    private _flushTimeout?;
    private _flushTimeoutMs;
    private _sendRequest;
    constructor(sendRequest: (req: BatchedRequest) => void, config?: RequestQueueConfig);
    /**
     * Get the current queue length
     */
    get length(): number;
    /**
     * Enqueue an event for batched sending
     */
    enqueue(req: QueuedRequest): void;
    /**
     * Flush all queued events immediately using sendBeacon
     * Called on page unload to ensure events are delivered
     */
    unload(): void;
    /**
     * Enable the queue and start flushing
     */
    enable(): void;
    /**
     * Pause the queue (stops flushing but keeps events)
     */
    pause(): void;
    /**
     * Force an immediate flush
     */
    flush(): void;
    /**
     * Set up the flush timeout
     */
    private _setFlushTimeout;
    /**
     * Clear the flush timeout
     */
    private _clearFlushTimeout;
    /**
     * Flush all queued events now
     */
    private _flushNow;
    /**
     * Format the queue into batched requests by URL/batchKey
     */
    private _formatQueue;
}