/** One provider's health, as tracked from real calls. */
export interface ProviderHealthSnapshot {
    /** The provider. */
    providerName: string;
    /** True when it is under the failure threshold and at or above the minimum score. */
    healthy: boolean;
    /** Successful calls recorded. */
    successes: number;
    /** Failed calls recorded. */
    failures: number;
    /** Failures in a row. */
    consecutiveFailures: number;
    /** Moving average of latency, in milliseconds. */
    avgLatencyMs: number;
    /** The most recent error, as text. */
    lastError?: string;
    /** ISO-8601 time of the last recorded call. */
    lastCheckedAt?: string;
    /**
     * From 0 to 100: 100, less 20 per consecutive failure up to 60, less 1 per second of average
     * latency up to 30.
     */
    score: number;
    /**
     * `unknown` with no recent calls to judge by, `unhealthy` past the failure threshold or under the
     * minimum score, `degraded` when calls are failing or slow but not enough to stop routing to it,
     * and `healthy` otherwise. Always set by `ProviderHealthMonitor`; optional so a hand-built snapshot
     * still type-checks.
     */
    status?: ProviderHealthStatus;
    /** True when the last call is older than `observationTtlMs`, so the figures above are old news. */
    stale?: boolean;
}
/** Where a provider stands, by what its recent calls say. */
export type ProviderHealthStatus = 'healthy' | 'degraded' | 'unhealthy' | 'unknown';
/** Health tracking for providers, used to route around unhealthy ones. */
export interface HealthConfig {
    /** Turns tracking on. Off by default, and then nothing is recorded. */
    enabled?: boolean;
    /** Consecutive failures that mark a provider unhealthy. Defaults to 3. */
    failureThreshold?: number;
    /** Score below which a provider is unhealthy. Defaults to 20. */
    minScore?: number;
    /**
     * How long a call's outcome counts, in milliseconds. A provider whose last call is older is
     * `unknown`, and is routed to as a provider never seen is, rather than kept down for a failure
     * hours ago or kept up for a success days ago. `checkProviders({ staleOnly: true })` refreshes it.
     * Defaults to never expiring, as before.
     */
    observationTtlMs?: number;
    /** Replaces the system clock, for tests. */
    now?: () => Date;
}
/** Tracks provider health from call outcomes and scores each provider for routing. */
export declare class ProviderHealthMonitor {
    private config;
    private states;
    constructor(config?: HealthConfig);
    private nowDate;
    /** Records a successful call and its latency. */
    recordSuccess(providerName: string, latencyMs: number): void;
    /** Records a failed call. */
    recordFailure(providerName: string, error: unknown): void;
    /** Every provider's health, or one provider's. */
    snapshot(providerName?: string): ProviderHealthSnapshot[];
    /** A provider's score, from 0 to 100. */
    score(providerName: string): number;
    /** Whether a provider is healthy. */
    isHealthy(providerName: string): boolean;
    /** Whether a provider's figures are too old to judge by, or there are none. */
    isUnknown(providerName: string): boolean;
    private isStale;
    private snapshotOne;
    private state;
}