import type { IdentityPlugin } from "./plugin.js";
/** One SSE frame. Every field is optional; `data` may be multi-line (emitted as multiple `data:` lines). */
export interface SSEMessage {
    readonly data?: string;
    readonly event?: string;
    readonly id?: string;
    /** Client reconnection delay hint, ms (coerced to an integer). */
    readonly retry?: number;
    /** A `: comment` line (e.g. a keep-alive ping). */
    readonly comment?: string;
}
/** The stream handed to the `run` callback. */
export interface SSEStream {
    /** Enqueue an event frame. No-op once the stream is closed. */
    send(message: SSEMessage): void;
    /** End the stream now. */
    close(): void;
    /** Aborts when the client disconnects - use it to tear down subscriptions/loops. */
    readonly signal: AbortSignal;
}
/** Minimal context shape `sse` needs - the live request, for its client-disconnect signal. */
export interface SSEContext {
    readonly req: Request;
}
export interface SSEInit {
    readonly status?: number;
    readonly headers?: ConstructorParameters<typeof Headers>[0];
    /** Send a `: ` comment ping every N ms so idle proxies don't drop the connection. */
    readonly keepAlive?: number;
}
/**
 * The stream handed to an `app.sse()` handler: `send` takes the route's TYPED event payload and
 * serializes it (JSON) into the SSE `data:` field - the compile-time half of the `sse` contract.
 */
export interface TypedSSEStream<Event> {
    /** Send one typed event. `init` sets the optional SSE frame fields (`event`, `id`, `retry`). */
    send(event: Event, init?: Pick<SSEMessage, "event" | "id" | "retry">): void;
    /** Send a `: comment` line (e.g. an explicit ping). */
    comment(text: string): void;
    /** End the stream now. */
    close(): void;
    /** Aborts when the client disconnects - use it to tear down subscriptions/loops. */
    readonly signal: AbortSignal;
}
/** Wrap a raw {@link SSEStream} in the typed, JSON-serializing surface `app.sse()` hands out. */
export declare function typedSSEStream<Event>(stream: SSEStream): TypedSSEStream<Event>;
export declare function sse(c: SSEContext, run: (stream: SSEStream) => void | Promise<void>, init?: SSEInit): Response;
/**
 * Enable `.sse()` streaming routes: `.use(streaming())` installs the SSE runtime. Without it, an
 * `.sse()` route is a registration error, so the ReadableStream framing stays out of non-SSE bundles.
 * The `sse()` / `typedSSEStream()` helpers ship from this same subpath for use inside handlers.
 */
export declare function streaming(): IdentityPlugin;
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