/**
 * @file Dynamic trial-call timeout. Mirrors the Android
 * `TrialDeadlineEventListener` (plugin-android@video-balancer-24-2-on-main).
 *
 * When a candidate CDN is picked as a trial, a `TrialTag` is attached to the
 * segment so the XHR layer can recompute a tighter call deadline at
 * HEADERS_RECEIVED based on the announced Content-Length, the *current* good
 * CDN's bandwidth, and that CDN's idle ratio (L0). The new deadline replaces
 * the existing per-attempt total timer ONLY when it is stricter than the
 * baseline already armed by the network interceptor — the trial never gets
 * MORE time than the call would naturally have.
 */
/** Lower bound for the computed trial timeout, in milliseconds. */
export declare const MIN_TRIAL_TIMEOUT_MS = 500;
/**
 * Default safety factor on the "time given to the trial" side of the formula
 * (Android `TrialTag.safetyFactor = 0.75`). Values < 1 give the trial less
 * time than the current CDN would itself take to deliver the same chunk.
 */
export declare const DEFAULT_TRIAL_SAFETY_FACTOR = 0.75;
/**
 * Carrier attached to a VideoSegment that has been selected as a trial fetch
 * (a deliberate probe of an idle CDN). Provides everything the dynamic-deadline
 * recompute needs once response headers land.
 */
export interface TrialTag {
    /** Existing call-timeout when the trial was scheduled (ms). The deadline is
     *  shortened ONLY when the recompute is stricter than this value. */
    baselineCallTimeoutMs: number;
    /** Current (good) CDN's bandwidth in bits/sec, or null when the current CDN
     *  has no usable history yet — the recompute is skipped in that case. */
    currentCdnBandwidthBps: number | null;
    /** Current CDN's name (for diagnostics only). */
    currentCdnName: string | null;
    /** Per-trial safety factor; defaults to DEFAULT_TRIAL_SAFETY_FACTOR. */
    safetyFactor: number;
}
/**
 * Trial call-timeout in milliseconds.
 *
 *   tFallback = sizeBytes * 8 / bandwidthBps       (seconds on the current CDN)
 *   tTrial    = tFallback / (1 - l0) * l0 * sf     (slack offered by idle ratio)
 *   result    = max(min(tTrial, tFallback) * 1000, MIN_TRIAL_TIMEOUT_MS)
 *
 * Returns `-1` when the formula has no usable signal:
 *  - `sizeBytes <= 0` (no announced Content-Length, or zero-length response),
 *  - `bandwidthBps <= 0` (current CDN never produced a measurement), or
 *  - `l0 >= 1` (no concurrency samples yet — the EMA fold has nothing to compare).
 *
 * Android parity: TrialDeadlineEventListener.computeTrialTimeoutMs.
 */
export declare function computeTrialTimeoutMs(sizeBytes: number, bandwidthBps: number, l0: number, safetyFactor: number): number;
/**
 * Single-trial-slot guard. Mirrors Android's `TrialDeadlineRegistry.activeTrialCall`
 * — at most one trial in flight per balancer instance. Callers acquire the slot
 * before sending the trial XHR and release it on call end / abort.
 */
export declare class TrialSlot {
    private active;
    tryAcquire(xhr: XMLHttpRequest): boolean;
    release(xhr: XMLHttpRequest): void;
    isHeldBy(xhr: XMLHttpRequest): boolean;
    isActive(): boolean;
}