import { Envelope, HostEnvelope, HostOp, PluginEnvelope, PluginOp } from '../protocol/envelope.js';
export type EnvelopeHandler<E extends Envelope = Envelope> = (env: E) => void;
/** Subset of the DOM `Window` we depend on. Tests pass a stub. */
export interface MessageWindow {
    addEventListener(type: 'message', listener: (event: MessageEvent) => void, options?: {
        signal?: AbortSignal;
    }): void;
    removeEventListener(type: 'message', listener: (event: MessageEvent) => void): void;
}
export interface MessageTarget {
    postMessage(message: unknown, targetOrigin: string): void;
}
export interface BusOptions {
    /** Identity check on every receive. Tightens the trust boundary. */
    allowedOrigins: string[];
    /** Optional handle to a specific `MessageEventSource` we expect. */
    expectedSource?: MessageEventSource | null;
    /** Stub-friendly window. Defaults to the platform `window` at runtime. */
    window?: MessageWindow;
}
declare abstract class BaseMessageBus<TSend extends Envelope, TRecv extends Envelope> {
    protected readonly options: BusOptions;
    protected handlers: Set<EnvelopeHandler<TRecv>>;
    protected disposed: boolean;
    private readonly listener;
    private readonly hostWindow;
    constructor(options: BusOptions);
    on(handler: EnvelopeHandler<TRecv>): () => void;
    dispose(): void;
    protected abstract get target(): MessageTarget;
    protected abstract get targetOrigin(): string;
    protected abstract isExpectedDirection(env: Envelope): env is TRecv;
    send(envelope: TSend): void;
    private handleMessage;
}
export interface IframeBusOptions extends BusOptions {
    /** The parent we postMessage UP to. Defaults to `window.parent`. */
    parent?: MessageTarget;
}
/**
 * The bus a plugin instance uses to talk to its host shell. Send a
 * `PluginEnvelope` UP, receive `HostEnvelope`s DOWN.
 */
export declare class IframeMessageBus extends BaseMessageBus<PluginEnvelope, HostEnvelope> {
    private readonly parentTarget;
    private readonly origin;
    constructor(opts: IframeBusOptions);
    protected get target(): MessageTarget;
    protected get targetOrigin(): string;
    protected isExpectedDirection(env: Envelope): env is HostEnvelope;
}
export interface ParentBusOptions extends BusOptions {
    /** The iframe element we postMessage DOWN to. */
    iframe: HTMLIFrameElement;
}
/**
 * The bus a host page uses to talk to one iframe-mounted plugin instance.
 * Send a `HostEnvelope` DOWN, receive `PluginEnvelope`s UP.
 */
export declare class ParentMessageBus extends BaseMessageBus<HostEnvelope, PluginEnvelope> {
    private readonly iframe;
    private readonly origin;
    constructor(opts: ParentBusOptions);
    protected get target(): MessageTarget;
    protected get targetOrigin(): string;
    protected isExpectedDirection(env: Envelope): env is PluginEnvelope;
}
export declare function buildHostEnvelope<P = unknown>(kind: HostOp, payload: P, requestId?: string): HostEnvelope<P>;
export declare function buildPluginEnvelope<P = unknown>(kind: PluginOp, payload: P, requestId?: string): PluginEnvelope<P>;
export {};
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