function getHeaders() {
  const headers = new Headers();
  headers.append("Accept", "application/json");
  headers.append("Content-Type", "application/json");
  return headers;
}

function internalFetch(url, options) {
  return fetch(url, options).then((res) =>
    res.text().then((text) => {
      let t = text ? JSON.parse(text) : res.statusText;
      if (!res.ok) {
        if (res.status === 404) throw new Error(t || "Not found");

        if (res.status >= 400 && res.status < 600 && t) throw t;

        throw new Error(t || "Unknown error");
      }
      return t;
    })
  );
}

export function post(url, body) {
  const options = {
    method: "POST",
    body: JSON.stringify(body),
    headers: getHeaders()
  };
  return internalFetch(url, options);
}

export function put(url, body) {
  const options = {
    method: "PUT",
    body: JSON.stringify(body),
    headers: getHeaders()
  };
  return internalFetch(url, options);
}

export function get(url) {
  const options = {
    method: "GET",
    headers: getHeaders()
  };
  return internalFetch(url, options);
}

export function del(url) {
  const options = {
    method: "DELETE",
    headers: getHeaders()
  };
  return internalFetch(url, options);
}