/**
 * openai.ts - OpenAI-compatible HTTP embedding provider
 *
 * Talks to any endpoint that implements `POST /v1/embeddings` with the OpenAI
 * shape: request `{model, input: string|string[]}`, response
 * `{data: [{embedding: number[], index?: number}, ...]}`.
 * `index` is optional: Gemini's OpenAI-compat layer omits it and returns
 * embeddings in input order (session 7fcfc297). Missing index → array position.
 *
 * Used by qmd to delegate embeddings to an approved commercial HTTPS API.
 *
 * Features:
 *   - Batches input in groups of ≤64 (configurable via QMD_EMBED_BATCH_SIZE)
 *   - Retries 429 / 503 with exponential backoff (1s, 4s, 16s)
 *   - 429 gets its own, larger retry budget and honours `Retry-After`
 *     (header or `"Retry after 29s"` body text) — a shared gateway bucket
 *     refilling in 30s must not exhaust a 1s/4s/16s schedule (i-yghj098h)
 *   - Bulk lane (`embedBatch` with >1 input): a 429 pauses the WHOLE worker
 *     pool for the advertised cooldown and halves in-flight concurrency
 *     (AIMD), so reindex traffic yields the bucket to interactive callers
 *     instead of contending head-on with them
 *   - 4xx (non-429) → no retry, count as failure
 *   - Circuit breaker: >50% failures in a 60s window → OPEN for 5 min;
 *     callers receive failures and no model fallback is selected
 *   - Per-call timeout via AbortSignal (default QMD_EMBED_TIMEOUT_MS=30000)
 *   - Healthcheck via `GET /health` if available, else a probe embed call
 */
import type { EmbeddingProvider, ProviderEmbedOptions, ProviderEmbedding, ProviderHealth, ProviderKind } from "./provider.js";
/**
 * Default batch size — most OpenAI-compatible embedding endpoints accept up to
 * 2048 inputs per call but for memory and latency we cap at 64.
 */
export declare const DEFAULT_BATCH_SIZE = 64;
/**
 * Default in-flight concurrency cap for `embedBatch`. The qmd-embed-worker
 * exposes a 4-way semaphore (`MAX_CONCURRENT_REQUESTS=4`) and idles at
 * queue-depth 1.0 under sequential clients (i-fkpnar9i baseline). Defaulting
 * to 4 matches the worker's advertised concurrency without overshooting the
 * GPU. Override per-deploy via `QMD_EMBED_CONCURRENCY`. Setting to 1 reverts
 * to the legacy sequential dispatch.
 */
export declare const DEFAULT_CONCURRENCY = 4;
/**
 * Default per-request timeout (30 s). embeddinggemma-300M on RTX 4090 takes
 * <500ms per batch of 64 in practice; 30s is a safe upper bound.
 */
export declare const DEFAULT_TIMEOUT_MS = 30000;
/**
 * Retry backoff schedule (ms) for 429/503 responses. 3 attempts total
 * (initial + 2 retries) — aligns with issue spec "1s/4s/16s".
 */
export declare const RETRY_BACKOFFS_MS: readonly number[];
/**
 * Rate-limit (429) retry budget, separate from `RETRY_BACKOFFS_MS`.
 *
 * A 429 is backpressure, not a fault: the shared ai.mm.mk gateway answers
 * `{"detail":"Rate limit exceeded (tokens). Retry after 29s."}` with observed
 * retry-after values of 7s/29s/30s, while the generic schedule waits at most
 * 1+4+16 = 21s in total. Bulk reindex runs therefore burned all three attempts
 * inside one bucket refill and reported the chunk as failed (i-yghj098h).
 * 429s get their own attempt count and always wait at least as long as the
 * server asked for, capped by `RATE_LIMIT_MAX_BACKOFF_MS`.
 */
export declare const DEFAULT_RATE_LIMIT_RETRIES = 5;
/** Upper bound on a single rate-limit wait, so a bogus Retry-After can't hang a run. */
export declare const RATE_LIMIT_MAX_BACKOFF_MS = 60000;
/** Fallback wait when a 429 carries no parseable Retry-After (doubles per attempt). */
export declare const RATE_LIMIT_BASE_BACKOFF_MS = 5000;
/**
 * Consecutive successful bulk requests before the lane additively recovers one
 * unit of concurrency after a 429-triggered halving (AIMD).
 */
export declare const LANE_RECOVERY_STREAK = 8;
/**
 * Circuit breaker — flips OPEN when error rate exceeds threshold within
 * window. While OPEN, every call fails fast so the caller can fall back.
 */
export declare const CIRCUIT_WINDOW_MS = 60000;
export declare const CIRCUIT_OPEN_DURATION_MS: number;
export declare const CIRCUIT_FAILURE_RATE_THRESHOLD = 0.5;
export declare const CIRCUIT_MIN_SAMPLES = 4;
export type OpenAIProviderConfig = {
    /** Endpoint base URL — e.g. "https://ai.mm.mk" (no trailing slash) */
    endpoint: string;
    /** Optional bearer token sent as `Authorization: Bearer ...` */
    apiKey?: string;
    /**
     * Stable model identifier to report up via `getModelId()`.
     * Defaults to "embeddinggemma" to match qmd's existing DB rows.
     */
    modelId?: string;
    /**
     * Upstream model name sent in the HTTP request body. Often differs from
     * `modelId` (e.g. modelId="embeddinggemma" but upstream model="embeddinggemma:300m").
     */
    upstreamModel?: string;
    /** Batch size cap (default DEFAULT_BATCH_SIZE = 64) */
    batchSize?: number;
    /**
     * Max in-flight HTTP requests during a single `embedBatch` call. Default
     * `DEFAULT_CONCURRENCY=4` matches the worker semaphore. Set to 1 to force
     * legacy sequential dispatch (useful for benchmarks / regression bisect).
     */
    concurrency?: number;
    /** Per-request timeout in ms (default DEFAULT_TIMEOUT_MS = 30_000) */
    timeoutMs?: number;
    /** Custom fetch (for testing). Defaults to global `fetch`. */
    fetchImpl?: typeof fetch;
    /** Custom retry schedule (for testing). Defaults to RETRY_BACKOFFS_MS. */
    retryBackoffsMs?: readonly number[];
    /**
     * Extra retry attempts granted to 429 responses on top of the generic
     * schedule (default DEFAULT_RATE_LIMIT_RETRIES = 5, env
     * `QMD_EMBED_RATE_LIMIT_RETRIES`). Rate limits are backpressure, not faults.
     */
    rateLimitRetries?: number;
    /** Custom sleep impl (for testing). Defaults to setTimeout. */
    sleep?: (ms: number) => Promise<void>;
    /** Custom clock (for testing). Defaults to Date.now. */
    now?: () => number;
};
export type OpenAIEmbeddingsResponse = {
    object?: string;
    model?: string;
    data: Array<{
        object?: string;
        index?: number;
        embedding: number[];
    }>;
    usage?: {
        prompt_tokens?: number;
        total_tokens?: number;
    };
};
/** Map an OpenAI-compat embedding row onto the input slot. Missing `index` = row order. */
export declare function resolveOpenAIEmbeddingIndex(index: unknown, position: number, inputCount: number): number;
/**
 * Circuit breaker state — exported for tests
 */
export type CircuitState = "closed" | "open" | "half-open";
/**
 * Traffic lane for a single `embedBatch` call. `bulk` = reindex traffic
 * (multi-input batch), which self-throttles via `BulkLaneGate` and is
 * attributed separately in `X-AI-Caller`. `interactive` = query-time embeds,
 * which are never made to wait behind a bulk cooldown.
 */
export type EmbedLane = "interactive" | "bulk";
/**
 * Determine whether an HTTP status is retryable. 429 (Too Many Requests)
 * and 503 (Service Unavailable) are retried; 4xx (other than 429) are not.
 */
export declare function isRetryableStatus(status: number): boolean;
/**
 * Extract the server-advertised cooldown from a rate-limited response.
 *
 * Two sources, in priority order:
 *   1. the standard `Retry-After` header — delta-seconds or an HTTP-date;
 *   2. the ai.mm.mk body text, which states the cooldown in prose only:
 *      `{"detail":"Rate limit exceeded (tokens). Retry after 29s.", ...}`.
 *
 * Returns `undefined` when neither source yields a sane positive duration, so
 * the caller falls back to its own schedule. Values are clamped to
 * `RATE_LIMIT_MAX_BACKOFF_MS`.
 */
export declare function parseRetryAfterMs(headerValue: string | null | undefined, bodyPreview?: string, now?: () => number): number | undefined;
/**
 * Chunk an array into pieces of ≤ size each. `size` MUST be ≥ 1.
 */
export declare function chunkArray<T>(items: T[], size: number): T[][];
/**
 * Sliding-window circuit breaker. Tracks the last N samples (min 4) over a
 * 60-second window; flips OPEN when failure rate exceeds 50%, then auto-
 * resets to HALF-OPEN after 5 minutes — at which point the next probe
 * decides whether to close (success) or re-open (failure).
 */
export declare class CircuitBreaker {
    private samples;
    private state;
    private openedAt;
    private readonly windowMs;
    private readonly openDurationMs;
    private readonly threshold;
    private readonly minSamples;
    private readonly now;
    constructor(opts?: {
        windowMs?: number;
        openDurationMs?: number;
        threshold?: number;
        minSamples?: number;
        now?: () => number;
    });
    getState(): CircuitState;
    /**
     * Returns true when calls should be short-circuited (skip HTTP, fall back).
     * Side-effects: may transition OPEN → HALF-OPEN if the open window expired.
     */
    shouldFailFast(): boolean;
    /** Record a successful call. */
    recordSuccess(): void;
    /** Record a failed call. May trigger OPEN. */
    recordFailure(): void;
    /** Force-reset the breaker (used by tests / admin) */
    reset(): void;
    private pushSample;
    private evaluate;
    private tickAutoReset;
}
/**
 * Raised when the circuit breaker is OPEN and a call is short-circuited.
 */
export declare class CircuitOpenError extends Error {
    constructor(message?: string);
}
/**
 * Persistent (non-retryable) HTTP error from upstream. Includes status code.
 */
export declare class HttpError extends Error {
    readonly status: number;
    readonly bodyPreview: string;
    /** Server-advertised cooldown for 429s, when the response stated one. */
    readonly retryAfterMs?: number;
    constructor(status: number, bodyPreview: string, retryAfterMs?: number);
}
/**
 * Client-side bulk lane for reindex traffic (i-yghj098h).
 *
 * qmd's bulk embedding shares the interactive ai.mm.mk token bucket. Without a
 * server-side per-caller budget, the only way bulk traffic can stop contending
 * head-on with interactive callers is to police itself:
 *
 *   - a 429 on ANY worker pauses the ENTIRE pool for the advertised cooldown
 *     (one shared promise — concurrent 429s coalesce instead of stacking N
 *     cooldowns), so the bucket refills for interactive callers rather than
 *     being re-drained by the remaining workers;
 *   - the in-flight cap halves on each cooldown (floor 1) and recovers one unit
 *     per `LANE_RECOVERY_STREAK` successes — classic AIMD, so a run settles at
 *     whatever share the bucket actually has spare.
 *
 * Deliberately clock-free: cooldowns are modelled as a promise produced by the
 * injected `sleep`, so tests drive them with a fake sleep and no fake clock.
 */
export declare class BulkLaneGate {
    private readonly maxPermits;
    private readonly sleep;
    private permits;
    private inFlight;
    private okStreak;
    private cooldown;
    private waiters;
    constructor(maxPermits: number, sleep: (ms: number) => Promise<void>);
    /** Current in-flight cap — exported state for tests/diagnostics. */
    get permitCount(): number;
    /** True while the lane is serving a rate-limit cooldown. */
    get isCoolingDown(): boolean;
    /** Take a slot, waiting out any cooldown and respecting the current cap. */
    acquire(): Promise<void>;
    /** Return a slot. Always call from a `finally`. */
    release(): void;
    /**
     * Enter (or join) a cooldown of `waitMs` and halve the in-flight cap.
     * Returns the shared cooldown promise — the caller awaits it INSTEAD of
     * sleeping itself, so a burst of 429s costs one cooldown, not one each.
     */
    penalize(waitMs: number): Promise<void>;
    /** Record a successful bulk request; recovers one permit per success streak. */
    noteSuccess(): void;
    private wakeOne;
    private wakeAll;
}
export declare class OpenAIEmbeddingsProvider implements EmbeddingProvider {
    readonly kind: ProviderKind;
    private readonly endpoint;
    private readonly apiKey?;
    private readonly modelId;
    private readonly upstreamModel;
    private readonly batchSize;
    private readonly concurrency;
    private readonly timeoutMs;
    private readonly fetchImpl;
    private readonly retryBackoffsMs;
    private readonly rateLimitRetries;
    private readonly sleep;
    private readonly now;
    private dimensions;
    private lastError;
    readonly breaker: CircuitBreaker;
    /** Shared bulk-traffic lane — see `BulkLaneGate`. */
    readonly lane: BulkLaneGate;
    constructor(config: OpenAIProviderConfig);
    getModelId(): string;
    getDimensions(): number | undefined;
    /**
     * Most recent per-chunk failure message (HTTP status + body preview, malformed
     * JSON, timeout, abort reason). Returns `undefined` after a successful call
     * or before the first call. See `EmbeddingProvider.getLastError`.
     */
    getLastError(): string | undefined;
    /** Endpoint URL configured at construction time — used by callers when
     *  building error messages for failed first-chunk probes. */
    getEndpoint(): string;
    healthcheck(signal?: AbortSignal): Promise<ProviderHealth>;
    embed(text: string, options?: ProviderEmbedOptions): Promise<ProviderEmbedding | null>;
    embedBatch(texts: string[], options?: ProviderEmbedOptions): Promise<(ProviderEmbedding | null)[]>;
    dispose(): Promise<void>;
    /**
     * Format a request-failure context string for `lastError`. Includes endpoint
     * + HTTP status + body preview when the error was an `HttpError`, otherwise
     * falls back to the message of the underlying error (or the value itself
     * when not an Error). Kept short — body preview is already capped at 1024
     * chars by `HttpError`, but we trim further here for the dimension-probe
     * thrown error which surfaces directly to users.
     */
    private formatErrorContext;
    private buildHeaders;
    /**
     * Single HTTP request with retry on 429/503. Returns embeddings indexed
     * the same as `texts`. Throws on non-retryable failure or all attempts
     * exhausted.
     */
    private requestWithRetry;
    /**
     * How long to wait after a 429. The server's own `Retry-After` wins when it
     * gave one; otherwise fall back to the configured schedule (so injected test
     * schedules stay authoritative) and then to an exponential 5s/10s/20s… ramp.
     * Always clamped to `RATE_LIMIT_MAX_BACKOFF_MS`.
     */
    private rateLimitWaitMs;
    /**
     * Issue one HTTP attempt to `POST /v1/embeddings`. Does NOT retry.
     */
    private requestOnce;
}