/**
 * Context is the metadata associated with a freighter transport request.
 * @property target - The target the request is being issued to.
 * @property protocol - The protocol used to issue the request.
 * @property params - Arbitrary string parameters that can be set by client side
 * middleware and read by server side middleware.
 */
export interface Context {
    target: string;
    role: Role;
    protocol: string;
    params: Record<string, string>;
}
export declare const ROLES: readonly ["client", "server"];
export type Role = (typeof ROLES)[number];
/**
 * Next executes the next middleware in the chain, returning the resulting context. It
 * throws if any downstream middleware or the finalizer throws.
 */
export type Next = (ctx: Context) => Promise<Context>;
/**
 * Middleware represents a general middleware function that can be used to parse/attach
 * metadata to a request or alter its behavior. It should call next to continue the
 * chain and may throw to abort the request.
 */
export type Middleware = (ctx: Context, next: Next) => Promise<Context>;
/**
 * Finalizer is a middleware that is executed as the last step in the chain. Finalizer
 * middleware should be used to execute the request. It throws if the request fails.
 */
type Finalizer = (ctx: Context) => Promise<Context>;
/**
 * MiddlewareCollector is a class that can be used to collect and execute middleware in
 * order to implement the Transport interface.
 */
export declare class MiddlewareCollector {
    middleware: Middleware[];
    /** Implements the Transport interface */
    use(...mw: Middleware[]): void;
    /**
     * Executes middleware in order, passing the the metadata to each middleware until the
     * end of the chain is reached. It then calls the finalizer with the metadata.
     * @param ctx - The context to pass to the middleware.
     * @returns The context produced by the chain. Throws if any middleware or the
     * finalizer throws.
     */
    executeMiddleware(ctx: Context, finalizer: Finalizer): Promise<Context>;
}
export {};
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