Modify LeftPanel to include a DragDropContext

that handles drag and drop for TagPanel and RoomList. This is to
allow the future feature of dragging between the two components.

src/components/structures/LeftPanel.js

@@ -17,22 +17,32 @@ limitations under the License.
 'use strict';
 
 import React from 'react';
+import PropTypes from 'prop-types';
 import classNames from 'classnames';
+import { DragDropContext } from 'react-beautiful-dnd';
+import { MatrixClient } from 'matrix-js-sdk';
 import { KeyCode } from 'matrix-react-sdk/lib/Keyboard';
 import sdk from 'matrix-react-sdk';
 import dis from 'matrix-react-sdk/lib/dispatcher';
 import MatrixClientPeg from 'matrix-react-sdk/lib/MatrixClientPeg';
-import CallHandler from 'matrix-react-sdk/lib/CallHandler';
-import AccessibleButton from 'matrix-react-sdk/lib/components/views/elements/AccessibleButton';
 import VectorConferenceHandler from '../../VectorConferenceHandler';
 
+import SettingsStore from "matrix-react-sdk/lib/settings/SettingsStore";
+import TagOrderActions from 'matrix-react-sdk/lib/actions/TagOrderActions';
+import RoomListActions from 'matrix-react-sdk/lib/actions/RoomListActions';
+
+
 var LeftPanel = React.createClass({
     displayName: 'LeftPanel',
 
     // NB. If you add props, don't forget to update
     // shouldComponentUpdate!
     propTypes: {
-        collapsed: React.PropTypes.bool.isRequired,
+        collapsed: PropTypes.bool.isRequired,
+    },
+
+    contextTypes: {
+        matrixClient: PropTypes.instanceOf(MatrixClient),
     },
 
     getInitialState: function() {
@@ -161,8 +171,54 @@ var LeftPanel = React.createClass({
         this.setState({ searchFilter: term });
     },
 
+    onDragEnd: function(result) {
+        // Dragged to an invalid destination, not onto a droppable
+        if (!result.destination) {
+            return;
+        }
+
+        const dest = result.destination.droppableId;
+
+        if (dest === 'tag-panel-droppable') {
+            // Dispatch synchronously so that the TagPanel receives an
+            // optimistic update from TagOrderStore before the previous
+            // state is shown.
+            dis.dispatch(TagOrderActions.moveTag(
+                this.context.matrixClient,
+                result.draggableId,
+                result.destination.index,
+            ), true);
+        } else {
+            this.onRoomTileEndDrag(result);
+        }
+    },
+
+    onRoomTileEndDrag: function(result) {
+        let newTag = result.destination.droppableId.split('_')[1];
+        let prevTag = result.source.droppableId.split('_')[1];
+        if (newTag === 'undefined') newTag = undefined;
+        if (prevTag === 'undefined') prevTag = undefined;
+
+        const roomId = result.draggableId.split('_')[1];
+
+        const oldIndex = result.source.index;
+        const newIndex = result.destination.index;
+
+        dis.dispatch(RoomListActions.tagRoom(
+            this.context.matrixClient,
+            MatrixClientPeg.get().getRoom(roomId),
+            prevTag, newTag,
+            oldIndex, newIndex,
+        ), true);
+    },
+
+    collectRoomList: function(ref) {
+        this._roomList = ref;
+    },
+
     render: function() {
         const RoomList = sdk.getComponent('rooms.RoomList');
+        const TagPanel = sdk.getComponent('structures.TagPanel');
         const BottomLeftMenu = sdk.getComponent('structures.BottomLeftMenu');
         const CallPreview = sdk.getComponent('voip.CallPreview');
 
@@ -184,15 +240,21 @@ var LeftPanel = React.createClass({
         );
 
         return (
+            <DragDropContext onDragEnd={this.onDragEnd}>
+                <div className="mx_LeftPanel_container">
+                    { SettingsStore.isFeatureEnabled("feature_tag_panel") ? <TagPanel /> : <div /> }
                     <aside className={classes} onKeyDown={ this._onKeyDown } onFocus={ this._onFocus } onBlur={ this._onBlur }>
                         { topBox }
                         <CallPreview ConferenceHandler={VectorConferenceHandler} />
                         <RoomList
+                            ref={this.collectRoomList}
                             collapsed={this.props.collapsed}
                             searchFilter={this.state.searchFilter}
                             ConferenceHandler={VectorConferenceHandler} />
                         <BottomLeftMenu collapsed={this.props.collapsed}/>
                     </aside>
+                </div>
+            </DragDropContext>
         );
     }
 });

src/skins/vector/css/vector-web/structures/_LeftPanel.scss

@@ -21,6 +21,10 @@ limitations under the License.
     flex-direction: column;
 }
 
+.mx_LeftPanel_container {
+    display: flex;
+}
+
 .mx_LeftPanel_hideButton {
     position: absolute;
     top: 10px;