/* @flow */
/* eslint-disable no-param-reassign, arrow-body-style, dot-notation */

import { isFunction } from '../utils';
import type RelayResponse from '../RelayResponse';
import type { Middleware, RelayRequestAny } from '../definition';
import RRNLError from '../RRNLError';

export class RRNLAuthMiddlewareError extends RRNLError {
  constructor(msg: string) {
    super(msg);
    this.name = 'RRNLAuthMiddlewareError';
  }
}

export type AuthMiddlewareOpts = {|
  token?: string | Promise<string> | ((req: RelayRequestAny) => string | Promise<string>),
  tokenRefreshPromise?: (req: RelayRequestAny, res: RelayResponse) => string | Promise<string>,
  allowEmptyToken?: boolean,
  prefix?: string,
  header?: string,
|};

export default function authMiddleware(opts?: AuthMiddlewareOpts): Middleware {
  const {
    token: tokenOrThunk,
    tokenRefreshPromise,
    allowEmptyToken = false,
    prefix = 'Bearer ',
    header = 'Authorization',
  } = opts || {};

  let tokenRefreshInProgress = null;

  return (next) => async (req) => {
    try {
      // $FlowFixMe
      const token = await (isFunction(tokenOrThunk) ? tokenOrThunk(req) : tokenOrThunk);

      if (!token && tokenRefreshPromise && !allowEmptyToken) {
        throw new RRNLAuthMiddlewareError('Empty token');
      }

      if (token) {
        req.fetchOpts.headers[header] = `${prefix}${token}`;
      }
      const res = await next(req);
      return res;
    } catch (e) {
      if (e && tokenRefreshPromise) {
        if (e.message === 'Empty token' || (e.res && e.res.status === 401)) {
          if (tokenRefreshPromise) {
            if (!tokenRefreshInProgress) {
              tokenRefreshInProgress = Promise.resolve(tokenRefreshPromise(req, e.res))
                .then((newToken) => {
                  tokenRefreshInProgress = null;
                  return newToken;
                })
                .catch((err) => {
                  tokenRefreshInProgress = null;
                  throw err;
                });
            }

            return tokenRefreshInProgress.then((newToken) => {
              if (!newToken && !allowEmptyToken) {
                throw new RRNLAuthMiddlewareError('Empty token');
              }

              const newReq = req.clone();
              if (newToken) {
                newReq.fetchOpts.headers[header] = `${prefix}${newToken}`;
              } else {
                delete newReq.fetchOpts.headers[header];
              }

              return next(newReq); // re-run query with new token
            });
          }
        }
      }

      throw e;
    }
  };
}