import assert from "assert";
const API = process.env.NEXT_PUBLIC_API || "/api";

export enum ApiMethods {
  GET = "GET",
  POST = "POST",
  PUT = "PUT",
}

export enum ApiResulState {
  SUCCESS,
  ERROR,
}

type SuccessApiResult = {
  state: ApiResulState.SUCCESS;
  message: string;
  user: User;
};

type FailureApiResult = { state: ApiResulState.ERROR; error: string };

export type FetchApiResult = SuccessApiResult | FailureApiResult;

type FetchApi = <T>(
  path: string,
  method: ApiMethods,
  body: T
) => Promise<FetchApiResult>;

const fetchApi: FetchApi = async (path, method, body) => {
  const response = await fetch(`${API}${path}`, {
    method: method,
    body: JSON.stringify(body),
  });

  const { message, ...result } = await response.json();

  if (response.ok) {
    return { state: ApiResulState.SUCCESS, message, user: result };
  } else {
    return {
      state: ApiResulState.ERROR,
      error: message.replace("Incorect", "Incorrect"),
    };
  }
};

export interface FetchApiInterface<T> {
  (body: T): Promise<FetchApiResult>;
}

export const login: FetchApiInterface<
  Pick<User, "email" | "password">
> = async (body) => {
  const response = await fetchApi("/login", ApiMethods.POST, body);
  switch (response.state) {
    case ApiResulState.SUCCESS: {
      const user = await fetchUserData(body.email);
      return {
        ...response,
        user,
      };
    }
    default:
      return response;
  }
};

export const register: FetchApiInterface<
  Pick<User, "email" | "password">
> = async (body) => {
  return fetchApi("/register", ApiMethods.POST, body);
};

export const updateUser: FetchApiInterface<
  Partial<User> & Pick<User, "id">
> = async ({ id, ...body }) => {
  const response = await fetchApi(`/user/${id}`, ApiMethods.PUT, body);
  switch (response.state) {
    case ApiResulState.SUCCESS: {
      return {
        ...response,
        user: {
          ...response.user,
          id: id,
        },
      };
    }
    default:
      return response;
  }
};

const fetchUsers = async (): Promise<Array<User>> => {
  const response = await fetch("/api/users");
  if (response.ok) {
    return response.json();
  } else {
    return Promise.resolve([]);
  }
};

const fetchUserData = async (email: string): Promise<User> => {
  const users = await fetchUsers();
  const user = users.find((user) => user.email === email);
  assert(user);
  return user;
};

const apiPaths = {
  login,
  register,
  updateUser,
};

export default apiPaths;