import React from 'react';
import { connect } from 'react-redux';
import PropTypes from 'prop-types';
import ImmutablePropTypes from 'react-immutable-proptypes';
import Column from '../../components/column';
import ColumnHeader from '../../components/column_header';
import { expandNotifications, scrollTopNotifications } from '../../actions/notifications';
import NotificationContainer from './containers/notification_container';
import { defineMessages, injectIntl, FormattedMessage } from 'react-intl';
import ColumnSettingsContainer from './containers/column_settings_container';
import FilterBarContainer from './containers/filter_bar_container';
import { createSelector } from 'reselect';
import { List as ImmutableList } from 'immutable';
import { debounce } from 'lodash';
import ScrollableList from '../../components/scrollable_list';
import LoadGap from '../../components/load_gap';

const messages = defineMessages({
  title: { id: 'column.notifications', defaultMessage: 'Notifications' },
});

const getNotifications = createSelector([
  state => state.getIn(['settings', 'notifications', 'quickFilter', 'show']),
  state => state.getIn(['settings', 'notifications', 'quickFilter', 'active']),
  state => ImmutableList(state.getIn(['settings', 'notifications', 'shows']).filter(item => !item).keys()),
  state => state.getIn(['notifications', 'items']),
], (showFilterBar, allowedType, excludedTypes, notifications) => {
  if (!showFilterBar || allowedType === 'all') {
    // used if user changed the notification settings after loading the notifications from the server
    // otherwise a list of notifications will come pre-filtered from the backend
    // we need to turn it off for FilterBar in order not to block ourselves from seeing a specific category
    return notifications.filterNot(item => item !== null && excludedTypes.includes(item.get('type')));
  }
  return notifications.filter(item => item !== null && allowedType === item.get('type'));
});

const mapStateToProps = state => ({
  showFilterBar: state.getIn(['settings', 'notifications', 'quickFilter', 'show']),
  notifications: getNotifications(state),
  isLoading: state.getIn(['notifications', 'isLoading'], true),
  isUnread: state.getIn(['notifications', 'unread']) > 0,
  hasMore: state.getIn(['notifications', 'hasMore']),
});

export default @connect(mapStateToProps)
@injectIntl
class Notifications extends React.PureComponent {

  static propTypes = {
    columnId: PropTypes.string,
    notifications: ImmutablePropTypes.list.isRequired,
    showFilterBar: PropTypes.bool.isRequired,
    dispatch: PropTypes.func.isRequired,
    intl: PropTypes.object.isRequired,
    isLoading: PropTypes.bool,
    isUnread: PropTypes.bool,
    hasMore: PropTypes.bool,
  };

  componentWillUnmount () {
    this.handleLoadOlder.cancel();
    this.handleScrollToTop.cancel();
    this.handleScroll.cancel();
    this.props.dispatch(scrollTopNotifications(false));
  }

  handleLoadGap = (maxId) => {
    this.props.dispatch(expandNotifications({ maxId }));
  };

  handleLoadOlder = debounce(() => {
    const last = this.props.notifications.last();
    this.props.dispatch(expandNotifications({ maxId: last && last.get('id') }));
  }, 300, { leading: true });

  handleScrollToTop = debounce(() => {
    this.props.dispatch(scrollTopNotifications(true));
  }, 100);

  handleScroll = debounce(() => {
    this.props.dispatch(scrollTopNotifications(false));
  }, 100);

  setColumnRef = c => {
    this.column = c;
  }

  handleMoveUp = id => {
    const elementIndex = this.props.notifications.findIndex(item => item !== null && item.get('id') === id) - 1;
    this._selectChild(elementIndex, true);
  }

  handleMoveDown = id => {
    const elementIndex = this.props.notifications.findIndex(item => item !== null && item.get('id') === id) + 1;
    this._selectChild(elementIndex, false);
  }

  _selectChild (index, align_top) {
    const container = this.column.node;
    const element = container.querySelector(`article:nth-of-type(${index + 1}) .focusable`);

    if (element) {
      if (align_top && container.scrollTop > element.offsetTop) {
        element.scrollIntoView(true);
      } else if (!align_top && container.scrollTop + container.clientHeight < element.offsetTop + element.offsetHeight) {
        element.scrollIntoView(false);
      }
      element.focus();
    }
  }

  render () {
    const { intl, notifications, isLoading, isUnread, columnId, hasMore, showFilterBar } = this.props;
    const emptyMessage = <FormattedMessage id='empty_column.notifications' defaultMessage="You don't have any notifications yet. Interact with others to start the conversation." />;

    let scrollableContent = null;

    const filterBarContainer = showFilterBar
      ? (<FilterBarContainer />)
      : null;

    if (isLoading && this.scrollableContent) {
      scrollableContent = this.scrollableContent;
    } else if (notifications.size > 0 || hasMore) {
      scrollableContent = notifications.map((item, index) => item === null ? (
        <LoadGap
          key={'gap:' + notifications.getIn([index + 1, 'id'])}
          disabled={isLoading}
          maxId={index > 0 ? notifications.getIn([index - 1, 'id']) : null}
          onClick={this.handleLoadGap}
        />
      ) : (
        <NotificationContainer
          key={item.get('id')}
          notification={item}
          accountId={item.get('account')}
          onMoveUp={this.handleMoveUp}
          onMoveDown={this.handleMoveDown}
        />
      ));
    } else {
      scrollableContent = null;
    }

    this.scrollableContent = scrollableContent;

    const scrollContainer = (
      <ScrollableList
        scrollKey={`notifications-${columnId}`}
        isLoading={isLoading}
        showLoading={isLoading && notifications.size === 0}
        hasMore={hasMore}
        emptyMessage={emptyMessage}
        onLoadMore={this.handleLoadOlder}
        onScrollToTop={this.handleScrollToTop}
        onScroll={this.handleScroll}
      >
        {scrollableContent}
      </ScrollableList>
    );

    return (
      <Column ref={this.setColumnRef} label={intl.formatMessage(messages.title)}>
        <ColumnHeader icon='bell' active={isUnread} title={intl.formatMessage(messages.title)}>
          <ColumnSettingsContainer />
        </ColumnHeader>
        {filterBarContainer}
        {scrollContainer}
      </Column>
    );
  }

}