import 'isomorphic-fetch';

type HttpMethod = 'GET' | 'PUT' | 'POST' | 'PATCH' | 'DELETE';
export interface IResponse<T> {
  ok: boolean;
  status: number;
  statusText?: string;
  type: string;
  url: string;
  data?: T;
}

export interface IHttpHeaders {
  [id: string]: string;
}

async function request<T>(
  method: HttpMethod,
  requestUrl: string,
  data?: object,
  headers?: IHttpHeaders,
): Promise<IResponse<T>> {
  const payload = {
    method,
    body: data ? JSON.stringify(data) : undefined,
    headers: {},
  };
  if (data) {
    Object.assign(payload.headers, {
      Accept: 'application/json',
      'Content-Type': 'application/json',
    });
  }
  if (headers) {
    Object.assign(payload.headers, headers);
  }

  const response = await fetch(requestUrl, payload);
  const { ok, status, statusText, type, url } = response;
  const result = { ok, status, statusText, type, url, data: undefined };
  if (ok) {
    // Attempt to parse the response as JSON.
    const contentType = (response.headers as any)._headers['content-type'];
    if (contentType[0].startsWith('application/json')) {
      result.data = await response.json();
    }
  }
  return result;
}

function get<T>(url: string, headers?: IHttpHeaders): Promise<IResponse<T>> {
  return request<T>('GET', url, undefined, headers);
}

function put<T>(
  url: string,
  data?: object,
  headers?: IHttpHeaders,
): Promise<IResponse<T>> {
  return request<T>('PUT', url, data, headers);
}

function post<T>(
  url: string,
  data?: object,
  headers?: IHttpHeaders,
): Promise<IResponse<T>> {
  return request<T>('POST', url, data, headers);
}

function patch<T>(
  url: string,
  data?: object,
  headers?: IHttpHeaders,
): Promise<IResponse<T>> {
  return request<T>('PATCH', url, data, headers);
}

function del<T>(url: string, headers?: IHttpHeaders): Promise<IResponse<T>> {
  return request<T>('DELETE', url, undefined, headers);
}

function headers(httpHeaders: IHttpHeaders) {
  return {
    get: <T>(url: string): Promise<IResponse<T>> => get<T>(url, httpHeaders),
    put: <T>(url: string, data?: object): Promise<IResponse<T>> =>
      put<T>(url, data, httpHeaders),
    post: <T>(url: string, data?: object): Promise<IResponse<T>> =>
      post<T>(url, data, httpHeaders),
    patch: <T>(url: string, data?: object): Promise<IResponse<T>> =>
      patch<T>(url, data, httpHeaders),
    delete: <T>(url: string): Promise<IResponse<T>> => del<T>(url, httpHeaders),
    headers: (append: IHttpHeaders) => headers({ ...httpHeaders, ...append }),
  };
}

export { get, put, post, patch, del as delete, headers };
export default { get, put, post, patch, delete: del, headers };