/**
 * autofallback.ts - AutoFallbackEmbeddingProvider.
 *
 * Composes a primary `EmbeddingProvider` (typically `OpenAIEmbeddingsProvider`)
 * and a fallback (typically `LocalLlamaCppProvider`). When the primary trips
 * its circuit breaker — or when persistent failures cross a threshold — calls
 * are routed to the fallback. After a recovery cooldown, the primary is
 * probed again; success closes the breaker and routing returns.
 *
 * Acceptance criterion 4 from i-qkarfffa: "Endpoint down → fallback local + WARN".
 *
 * Behavior summary:
 *   - Primary call succeeds → return; record success.
 *   - Primary throws CircuitOpenError → fall back, log WARN once per transition.
 *   - Primary throws any other error → fall back for THIS call only;
 *     count toward the failure-streak threshold.
 *   - When failure streak crosses threshold (default 3) → set our own
 *     "open until" timestamp; until expiry, route directly to fallback
 *     (skip primary entirely).
 *   - On expiry, retry primary opportunistically.
 *   - getModelId / getDimensions / dispose are delegated to whichever
 *     provider is currently active (or to the primary if both are usable).
 */
import type { EmbeddingProvider, ProviderEmbedOptions, ProviderEmbedding, ProviderHealth, ProviderKind } from "./provider.js";
export type AutoFallbackProviderConfig = {
    primary: EmbeddingProvider;
    fallback: EmbeddingProvider;
    /**
     * Number of consecutive non-CircuitOpenError failures before we suppress
     * primary calls and route directly to fallback. Default: 3.
     */
    failureStreakThreshold?: number;
    /**
     * Time in ms to keep routing through fallback after the breaker opens.
     * Default: 5 minutes (matches `OpenAIEmbeddingsProvider`'s circuit duration).
     */
    cooldownMs?: number;
    /**
     * Optional WARN sink. Defaults to writing to `process.stderr` once per
     * routing transition (closed→open and open→closed).
     */
    warn?: (msg: string) => void;
    /** Custom clock for tests */
    now?: () => number;
};
export type FallbackState = "primary" | "fallback";
export declare class AutoFallbackEmbeddingProvider implements EmbeddingProvider {
    readonly kind: ProviderKind;
    readonly primary: EmbeddingProvider;
    readonly fallback: EmbeddingProvider;
    private readonly failureStreakThreshold;
    private readonly cooldownMs;
    private readonly warn;
    private readonly now;
    private failureStreak;
    private fallbackUntil;
    private lastTransitionState;
    constructor(config: AutoFallbackProviderConfig);
    /**
     * Stable model id reported by the primary. The model-id guard runs against
     * the primary's id because that's what callers actually want when the
     * remote endpoint is online; on fallback-only operation, the local
     * provider should report a compatible id (in the default config, both
     * report "embeddinggemma" so this is moot).
     */
    getModelId(): string;
    getDimensions(): number | undefined;
    /**
     * Combined last-error from primary + fallback. Either, neither, or both legs
     * may have a tracked error after `embed()`/`embedBatch()` runs:
     *   - Both clean → undefined
     *   - Primary failed, fallback rescued → returns primary error (most useful)
     *   - Both failed → returns "primary: <msg> | fallback: <msg>"
     *   - Only primary skipped (cooldown), fallback also failed → returns fallback error
     */
    getLastError(): string | undefined;
    /** Current routing state (mostly for tests + observability) */
    getRoutingState(): FallbackState;
    /** Reset failure-streak + cooldown (mostly for tests / admin) */
    reset(): void;
    healthcheck(signal?: AbortSignal): Promise<ProviderHealth>;
    embed(text: string, options?: ProviderEmbedOptions): Promise<ProviderEmbedding | null>;
    embedBatch(texts: string[], options?: ProviderEmbedOptions): Promise<(ProviderEmbedding | null)[]>;
    dispose(): Promise<void>;
    /**
     * Generic dispatcher: try primary if not in cooldown, fall back on
     * `CircuitOpenError`, count other errors against the failure streak.
     * `op` is invoked with whichever provider is selected.
     */
    private run;
    private openCooldown;
    private transition;
}