content: 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 { addColumn, removeColumn, moveColumn } from '../../actions/columns';
  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,
      shouldUpdateScroll: PropTypes.func,
      intl: PropTypes.object.isRequired,
      isLoading: PropTypes.bool,
      isUnread: PropTypes.bool,
      multiColumn: PropTypes.bool,
      hasMore: PropTypes.bool,
    };
  
    static defaultProps = {
      trackScroll: true,
    };
  
    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);
  
    handlePin = () => {
      const { columnId, dispatch } = this.props;
  
      if (columnId) {
        dispatch(removeColumn(columnId));
      } else {
        dispatch(addColumn('NOTIFICATIONS', {}));
      }
    }
  
    handleMove = (dir) => {
      const { columnId, dispatch } = this.props;
      dispatch(moveColumn(columnId, dir));
    }
  
    handleHeaderClick = () => {
      this.column.scrollTop();
    }
  
    setColumnRef = c => {
      this.column = c;
    }
  
    handleMoveUp = id => {
      const elementIndex = this.props.notifications.findIndex(item => item !== null && item.get('id') === id) - 1;
      this._selectChild(elementIndex);
    }
  
    handleMoveDown = id => {
      const elementIndex = this.props.notifications.findIndex(item => item !== null && item.get('id') === id) + 1;
      this._selectChild(elementIndex);
    }
  
    _selectChild (index) {
      const element = this.column.node.querySelector(`article:nth-of-type(${index + 1}) .focusable`);
  
      if (element) {
        element.focus();
      }
    }
  
    render () {
      const { intl, notifications, shouldUpdateScroll, isLoading, isUnread, columnId, multiColumn, hasMore, showFilterBar } = this.props;
      const pinned = !!columnId;
      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}`}
          trackScroll={!pinned}
          isLoading={isLoading}
          showLoading={isLoading && notifications.size === 0}
          hasMore={hasMore}
          emptyMessage={emptyMessage}
          onLoadMore={this.handleLoadOlder}
          onScrollToTop={this.handleScrollToTop}
          onScroll={this.handleScroll}
          shouldUpdateScroll={shouldUpdateScroll}
        >
          {scrollableContent}
        </ScrollableList>
      );
  
      return (
        <Column ref={this.setColumnRef} label={intl.formatMessage(messages.title)}>
          <ColumnHeader
            icon='bell'
            active={isUnread}
            title={intl.formatMessage(messages.title)}
            onPin={this.handlePin}
            onMove={this.handleMove}
            onClick={this.handleHeaderClick}
            pinned={pinned}
            multiColumn={multiColumn}
          >
            <ColumnSettingsContainer />
          </ColumnHeader>
          {filterBarContainer}
          {scrollContainer}
        </Column>
      );
    }
  
  }
  