/**
 * @module
 * WeightedFallbackTransport — routes each send through a weighted-random
 * primary provider, then fails over through the remaining providers on error.
 * Works with email, SMS, WhatsApp, and push transports.
 *
 * @example
 * ```ts
 * import { WeightedFallbackTransport } from "sently/transports/weighted-fallback";
 * import { ResendTransport } from "sently/transports/resend";
 * import { SESTransport } from "sently/transports/ses";
 *
 * const transport = new WeightedFallbackTransport(
 *   [
 *     { transport: new ResendTransport({ apiKey }), weight: 80 },
 *     { transport: new SESTransport({ accessKeyId, secretAccessKey }), weight: 20 },
 *   ],
 *   { cooldownMs: 300_000 },
 * );
 * ```
 */
import type { DecoratedTransport, FallbackAugmentedResult } from "../core/decorated-transport.js";
import type { MailOptions, SendResult, VerifyResult } from "../core/types.js";
import { type FallbackOptions, FallbackTransport, type FallbackVerifyAllResult } from "./fallback.js";
/** A transport entry with a relative routing weight. */
export interface WeightedTransportEntry<TOptions = MailOptions, TResult = SendResult> {
    /** Transport instance. */
    transport: DecoratedTransport<TOptions, TResult>;
    /** Relative weight (e.g. 80 vs 20 → ~80% of sends try this provider first). */
    weight: number;
}
type MailerOnFallback = Parameters<FallbackTransport["setMailerOnFallback"]>[0];
/**
 * Weighted provider routing with failover on error.
 * Defaults preserve email {@link Transport} compatibility.
 */
export declare class WeightedFallbackTransport<TOptions = MailOptions, TResult = SendResult> implements DecoratedTransport<TOptions, FallbackAugmentedResult<TResult>> {
    readonly provider = "weighted-fallback";
    private readonly entries;
    private readonly fallbackOptions;
    private readonly random;
    private readonly inner;
    private mailerOnFallback;
    /**
     * Creates a weighted fallback transport.
     * @throws {Error} When entries is empty or total weight is zero.
     */
    constructor(entries: WeightedTransportEntry<TOptions, TResult>[], options?: FallbackOptions & {
        random?: () => number;
    });
    /**
     * Register a per-send onFallback callback from sender lifecycle hooks.
     * @internal Cleared after each send.
     */
    setMailerOnFallback(callback: MailerOnFallback | undefined): void;
    private buildOrder;
    private pickWeightedIndex;
    /** Sends via a weighted-random primary provider, failing over on error. */
    send(message: TOptions): Promise<FallbackAugmentedResult<TResult>>;
    /** Returns the first healthy provider in the chain. */
    verify(): Promise<VerifyResult>;
    /** Verifies every weighted provider in definition order. */
    verifyAll(): Promise<FallbackVerifyAllResult>;
    /** Closes every underlying transport. */
    close(): Promise<void>;
}
export {};