/**
 * AlertSink — Pluggable alert delivery for critical runtime events.
 *
 * Emits alerts for crash loops, restart limit exhaustion, heartbeat
 * timeouts, and other critical Supervisor events. Ships with a
 * webhook-based default implementation; custom sinks can be provided
 * via the `alerts.sink` config field.
 *
 * Configuration (forge.config):
 *
 *   alerts: {
 *     webhook: 'https://hooks.slack.com/...',
 *     // Optional overrides:
 *     headers: { Authorization: 'Bearer ...' },
 *     retries: 3,
 *     retryDelayMs: 1000,
 *     retryMaxDelayMs: 30000,
 *   }
 */
export type AlertSeverity = "critical" | "warning" | "info";
export interface Alert {
    /** Machine-readable event type */
    event: string;
    /** Human-readable summary */
    message: string;
    severity: AlertSeverity;
    /** ISO-8601 timestamp */
    timestamp: string;
    /** Additional structured data */
    details: Record<string, unknown>;
}
export interface AlertSinkConfig {
    /** Webhook URL for alert delivery */
    webhook?: string;
    /** Additional headers to include in webhook requests */
    headers?: Record<string, string>;
    /** Maximum number of retry attempts for failed deliveries (default: 3) */
    retries?: number;
    /** Base delay in ms for exponential backoff (default: 1000) */
    retryDelayMs?: number;
    /** Maximum delay in ms for exponential backoff (default: 30000) */
    retryMaxDelayMs?: number;
    /** Custom sink function — overrides webhook when provided */
    sink?: (alert: Alert) => Promise<void>;
}
/**
 * AlertSink delivers alerts to external systems with retry/backoff.
 *
 * Delivery is fire-and-forget from the caller's perspective — failed
 * alerts are logged but never block the Supervisor's main loop.
 */
export declare class AlertSink {
    private _config;
    private _retries;
    private _retryDelayMs;
    private _retryMaxDelayMs;
    private _deliveryQueue;
    private _stopped;
    constructor(config?: AlertSinkConfig);
    /** Whether this sink has a delivery target configured */
    get isConfigured(): boolean;
    /**
     * Emit an alert. Delivery is non-blocking — errors are caught and logged.
     * Alerts are serialized (one at a time) to avoid overwhelming the webhook.
     */
    emit(event: string, message: string, severity?: AlertSeverity, details?: Record<string, unknown>): void;
    /**
     * Wait for all pending alert deliveries to complete.
     * Useful for graceful shutdown.
     */
    flush(): Promise<void>;
    /** Stop accepting new alerts and drain pending deliveries */
    stop(): Promise<void>;
    /**
     * Deliver a single alert with retry/backoff.
     */
    private _deliver;
    /**
     * Send an alert via HTTP webhook POST.
     */
    private _deliverWebhook;
}
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