import { HttpRequest } from './httpRequest';
import { HttpContext } from './httpContext';

/**
 * Interface for a method that executes an HTTP request and returns the HTTP context.
 *
 * The context contains the HTTP response and the HTTP request (which may or may not be the same
 * as the original HTTP request).
 */
export type HttpCallExecutor<T> = (
  request: HttpRequest,
  requestOptions: T
) => Promise<HttpContext>;

/**
 * Interface representing an HTTP interceptor method.
 *
 * HTTP interceptors are used to extend the HTTP call pipeline with new behavior or
 * features.
 *
 * An HTTP interceptor receives an HTTP request. It can modify the
 * HTTP request and then pass it along to the next HTTP interceptor in the chain which
 * then returns an HTTP response. It then returns this HTTP response, after optionally
 * modifying it.
 */
export type HttpInterceptorInterface<T> = (
  request: HttpRequest,
  requestOptions: T,
  next: HttpCallExecutor<T>
) => Promise<HttpContext>;

/** Pass-through HTTP interceptor. */
export function passThroughInterceptor<T>(
  request: HttpRequest,
  requestOptions: T,
  next: HttpCallExecutor<T>
): Promise<HttpContext> {
  return next(request, requestOptions);
}

/**
 * Combine multiple HTTP interceptors into one.
 */
export function combineHttpInterceptors<T>(
  interceptors: Array<HttpInterceptorInterface<T | undefined>>
): HttpInterceptorInterface<T | undefined> {
  return (firstRequest, firstOptions, next) => {
    for (let index = interceptors.length - 1; index >= 0; index--) {
      const current = interceptors[index];
      const last = next;
      next = (request, options) => current(request, options, last);
    }
    return next(firstRequest, firstOptions);
  };
}