siliconflow-serverless-client/libs/client/src/middleware.ts


/**
 * A request configuration object.
 *
 * **Note:** This is a simplified version of the `RequestConfig` type from the
 * `fetch` API. It contains only the properties that are relevant for the
 * `fal-serverless` client. It also works around the fact that the `fetch` API
 * `Request` does not support mutability, its clone method has critical limitations
 * to our use case.
 */
export type RequestConfig = {
	url: string;
	headers?: Record<string, string | string[]>;
};

export type RequestMiddleware = (
	request: RequestConfig,
) => Promise<RequestConfig>;

/**
 * Setup a execution chain of middleware functions.
 *
 * @param middlewares one or more middleware functions.
 * @returns a middleware function that executes the given middlewares in order.
 */
export function withMiddleware(
	...middlewares: RequestMiddleware[]
): RequestMiddleware {
	return (config) =>
		middlewares.reduce(
			(configPromise, middleware) =>
				configPromise.then((req) => middleware(req)),
			Promise.resolve(config),
		);
}

export type RequestProxyConfig = {
	targetUrl: string;
};

export const TARGET_URL_HEADER = "x-siliconflow-target-url";

export function withProxy(config: RequestProxyConfig): RequestMiddleware {
	// when running on the server, we don't need to proxy the request
	if (typeof window === "undefined") {
		return (requestConfig) => Promise.resolve(requestConfig);
	}
	return (requestConfig) =>
		Promise.resolve({
			...requestConfig,
			url: config.targetUrl,
			headers: {
				...(requestConfig.headers || {}),
				[TARGET_URL_HEADER]: requestConfig.url,
			},
		});
}