import React, { useState, useEffect } from 'react';

import { Link } from 'react-router-dom';
import qs from 'qs';
import moment from 'moment';

import Message from './Message';
import Spinner from './Spinner';

import UserInfo from './UserInfo';

import { getMessages } from '../api';

/**
 * @typedef {Object} Query
 * @property {string} baseUrl
 * @property {Object=} search
 * @property {string} pageParam
 */

/**
 * @typedef {Object} PageProps
 * @property {import('history').History} history
 * @property {import('history').Location} location
 * @property {import('react-router').match} match
 * @property {string} search
 * @property {import('../api').SecureUser} visitor
 * @property {import('../api').Message[]} msgs
 */

/**
 * @param {PageProps} props
 */
export function Discover(props) {
  let search = qs.parse(props.location.search.substring(1));
  const query = {
    baseUrl: '/api/messages',
    search: search,
    pageParam: search.search ? 'page' : 'before_mid'
  };
  return (<Feed authRequired={false} query={query} {...props} />);
}

/**
 * @param {PageProps} props
 */
export function Discussions(props) {
  const query = {
    baseUrl: '/api/messages/discussions',
    pageParam: 'to'
  };
  return (<Feed authRequired={false} query={query} {...props} />);
}

/**
 * @param {PageProps} props
 */
export function Blog(props) {
  const { user } = props.match.params;
  let search = qs.parse(props.location.search.substring(1));
  search.uname = user;
  const query = {
    baseUrl: '/api/messages',
    search: search,
    pageParam: search.search ? 'page' : 'before_mid'
  };
  return (
    <>
      <div className="msg-cont">
        <UserInfo user={user} />
      </div>
      <Feed authRequired={false} query={query} {...props} />
    </>
  );
}

/**
 * @param {PageProps} props
 */
export function Tag(props) {
  const { tag } = props.match.params;
  const query = {
    baseUrl: '/api/messages',
    search: {
      tag: tag
    },
    pageParam: 'before_mid'
  };
  return (<Feed authRequired={false} query={query} {...props} />);
}

/**
 * @param {PageProps} props
 */
export function Home(props) {
  const query = {
    baseUrl: '/api/home',
    pageParam: 'before_mid'
  };
  return (<Feed authRequired={true} query={query} {...props} />);
}

/**
 * @param {{
  authRequired?: boolean,
  visitor: import('../api').SecureUser,
  history: import('history').History,
  location: import('history').Location,
  msgs: import('../api').Message[],
  query: Query
}} props
 */
function Feed(props) {
  const [msgs, setMsgs] = useState([]);
  const [loading, setLoading] = useState(true);
  const [nextpage, setNextpage] = useState(null);
  const [error, setError] = useState(false);

  useEffect(() => {
    let loadMessages = (hash = '', filter = '') => {
      document.body.scrollTop = 0;
      document.documentElement.scrollTop = 0;
      setMsgs([]);
      setLoading(true);
      const filterParams = qs.parse(filter);
      let params = Object.assign({}, filterParams || {}, props.query.search || {});
      let url = props.query.baseUrl;
      if (hash) {
        params.hash = hash;
      }
      if (!params.hash && props.authRequired) {
        props.history.push('/');
      }
      getMessages(url, params)
        .then(response => {
          const { data } = response;
          const { pageParam } = props.query;
          const lastMessage = data.slice(-1)[0] || {};
          const nextpage = getPageParam(pageParam, lastMessage, filterParams);
          setMsgs(data);
          setLoading(false);
          setNextpage(nextpage);
        }).catch(ex => {
          setError(true);
        });
    };
    loadMessages(props.visitor.hash, props.location.search.substring(1));
  }, [props]);

  let getPageParam = (pageParam, lastMessage, filterParams) => {
    const pageValue = pageParam === 'before_mid' ? lastMessage.mid : pageParam === 'page' ? (Number(filterParams.page) || 0) + 1 : moment.utc(lastMessage.updated).valueOf();
    let newFilter = { ...filterParams };
    newFilter[pageParam] = pageValue;
    return `?${qs.stringify(newFilter)}`;
  };
  const { tag } = qs.parse(location.search.substring(1)) || {};
  const nodes = (
    <>
      {
        tag && (
          <p className="page">
            <Link to={{ pathname: `/tag/${tag}` }}>
              <span>← All posts with tag&nbsp;</span><b>{tag}</b>
            </Link>
          </p>
        )
      }
      {
        msgs.map(msg =>
          <Message key={msg.mid} data={msg} visitor={props.visitor} />)
      }
      {
        msgs.length >= 20 && (
          <p className="page">
            <Link to={{ pathname: props.location.pathname, search: nextpage }} rel="prev">Next →</Link>
          </p>
        )
      }
    </>
  );
  return msgs.length > 0 ? (
    <div className="msgs">{nodes}</div>
  ) : error ? <div>error</div> : loading ? <div className="msgs"><Spinner /><Spinner /><Spinner /><Spinner /></div> : <div>No more messages</div>;
}