Previous selected tab as redux

src/background/reducers/index.js

@@ -1,15 +1,18 @@
 import settingReducer from './setting';
 import findReducer from './find';
+import tabReducer from './tab';
 
 // Make setting reducer instead of re-use
 const defaultState = {
   setting: settingReducer(undefined, {}),
   find: findReducer(undefined, {}),
+  tab: tabReducer(undefined, {}),
 };
 
 export default function reducer(state = defaultState, action = {}) {
   return Object.assign({}, state, {
     setting: settingReducer(state.setting, action),
     find: findReducer(state.find, action),
+    tab: tabReducer(state.tab, action),
   });
 }

src/background/reducers/tab.js

@@ -0,0 +1,19 @@
+import actions from 'background/actions';
+
+const defaultState = {
+  previousSelected: -1,
+  currentSelected: -1,
+};
+
+export default function reducer(state = defaultState, action = {}) {
+  switch (action.type) {
+  case actions.TAB_SELECTED:
+    return {
+      previousSelected: state.currentSelected,
+      currentSelected: action.tabId,
+    };
+  default:
+    return state;
+  }
+}
+