Deselect message history message when topic selection changes

Fixes #93

app/src/reducers/Sidebar.ts

@@ -0,0 +1,44 @@
+import * as q from '../../../backend/src/Model'
+import { Action } from 'redux'
+import { createReducer } from './lib'
+import { Record } from 'immutable'
+
+interface SidebarModel {
+  compareMessage?: q.Message
+}
+
+const initialStateFactory = Record<SidebarModel>({
+  compareMessage: undefined,
+})
+
+export type Action = SetCompareMessage
+export enum ActionTypes {
+  SIDEBAR_SET_COMPARE_MESSAGE = 'SIDEBAR_SET_COMPARE_MESSAGE',
+  SIDEBAR_RESET_STORE = 'SIDEBAR_RESET_STORE',
+}
+
+export type SidebarState = Record<SidebarModel>
+
+const actions: {[s: string]: (state: SidebarState, action: Action) => SidebarState} = {
+  SIDEBAR_SET_COMPARE_MESSAGE: setCompareMessage,
+  SIDEBAR_RESET_STORE: resetStore,
+}
+
+export const sidebarReducer = createReducer(initialStateFactory(), actions)
+
+export interface SetCompareMessage {
+  type: ActionTypes.SIDEBAR_SET_COMPARE_MESSAGE
+  message?: q.Message
+}
+
+function setCompareMessage(state: SidebarState, action: SetCompareMessage): SidebarState {
+  return state.set('compareMessage', action.message)
+}
+
+export interface ResetStore {
+  type: ActionTypes.SIDEBAR_RESET_STORE
+}
+
+function resetStore(): SidebarState {
+  return initialStateFactory()
+}

app/src/reducers/index.ts

@@ -5,6 +5,7 @@ import { GlobalState, globalState } from './Global'
 import { publishReducer, PublishState } from './Publish'
 import { Record } from 'immutable'
 import { settingsReducer, SettingsState } from './Settings'
+import { sidebarReducer, SidebarState } from './Sidebar'
 import { treeReducer, TreeState } from './Tree'
 
 export interface AppState {
@@ -12,6 +13,7 @@ export interface AppState {
   tree: TreeState
   settings: Record<SettingsState>,
   publish: PublishState
+  sidebar: SidebarState,
   connection: ConnectionState
   connectionManager: ConnectionManagerState
 }
@@ -19,6 +21,7 @@ export interface AppState {
 export default combineReducers({
   globalState,
   publish: publishReducer,
+  sidebar: sidebarReducer,
   connection: connectionReducer,
   settings: settingsReducer,
   tree: treeReducer,