Add pause feature

app/src/reducers/Tree.ts

@@ -7,6 +7,7 @@ export interface TreeState {
   tree?: q.Tree<TopicViewModel>
   selectedTopic?: q.TreeNode<TopicViewModel>
   filter?: string
+  paused: boolean
 }
 
 export type Action = ShowTree | SelectTopic
@@ -14,6 +15,8 @@ export type Action = ShowTree | SelectTopic
 export enum ActionTypes {
   TREE_SHOW_TREE = 'TREE_SHOW_TREE',
   TREE_SELECT_TOPIC = 'TREE_SELECT_TOPIC',
+  TREE_RESUME_UPDATES = 'TREE_RESUME_UPDATES',
+  TREE_PAUSE_UPDATES = 'TREE_PAUSE_UPDATES',
 }
 
 export interface ShowTree {
@@ -27,11 +30,26 @@ export interface SelectTopic {
   selectedTopic?: q.TreeNode<TopicViewModel>
 }
 
-const initialState: TreeState = { }
+export interface SetPause {
+  type: ActionTypes.TREE_PAUSE_UPDATES | ActionTypes.TREE_RESUME_UPDATES
+}
+
+const initialState: TreeState = {
+  paused: false,
+}
+
+const setPaused = (pause: boolean) => (state: TreeState, action: ShowTree) => {
+  return {
+    ...state,
+    paused: pause,
+  }
+}
 
 export const treeReducer = createReducer(initialState, {
   TREE_SHOW_TREE: showTree,
   TREE_SELECT_TOPIC: selectTopic,
+  TREE_PAUSE_UPDATES: setPaused(true),
+  TREE_RESUME_UPDATES: setPaused(false),
 })
 
 function showTree(state: TreeState, action: ShowTree) {