/*
 * Copyright 2020 Spotify AB
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import React from 'react';
import { List, ListSubheader } from '@material-ui/core';
import { EscalationUsersEmptyState } from './EscalationUsersEmptyState';
import { EscalationUser } from './EscalationUser';
import { useAsync } from 'react-use';
import { pagerDutyApiRef } from '../../api';
import { useApi, Progress } from '@backstage/core';
import { Alert } from '@material-ui/lab';

type Props = {
  policyId: string;
};

export const EscalationPolicy = ({ policyId }: Props) => {
  const api = useApi(pagerDutyApiRef);

  const { value: users, loading, error } = useAsync(async () => {
    const oncalls = await api.getOnCallByPolicyId(policyId);
    const usersItem = oncalls
      .sort((a, b) => a.escalation_level - b.escalation_level)
      .map(oncall => oncall.user);

    return usersItem;
  });

  if (error) {
    return (
      <Alert severity="error">
        Error encountered while fetching information. {error.message}
      </Alert>
    );
  }

  if (loading) {
    return <Progress />;
  }

  if (!users?.length) {
    return <EscalationUsersEmptyState />;
  }

  return (
    <List dense subheader={<ListSubheader>ON CALL</ListSubheader>}>
      {users!.map((user, index) => (
        <EscalationUser key={index} user={user} />
      ))}
    </List>
  );
};
