Indicator shows the add-on enabled

src/background/components/indicator.js

@@ -0,0 +1,38 @@
+import * as indicators from '../shared/indicators';
+import messages from 'shared/messages';
+
+export default class IndicatorComponent {
+  constructor(store) {
+    this.store = store;
+
+    messages.onMessage(this.onMessage.bind(this));
+
+    browser.tabs.onActivated.addListener((info) => {
+      return browser.tabs.query({ currentWindow: true }).then(() => {
+        return this.onTabActivated(info);
+      });
+    });
+  }
+
+  onTabActivated(info) {
+    return browser.tabs.sendMessage(info.tabId, {
+      type: messages.ADDON_ENABLED_QUERY,
+    }).then((resp) => {
+      return this.updateIndicator(resp.enabled);
+    });
+  }
+
+  onMessage(message) {
+    switch (message.type) {
+    case messages.ADDON_ENABLED_RESPONSE:
+      return this.updateIndicator(message.enabled);
+    }
+  }
+
+  updateIndicator(enabled) {
+    if (enabled) {
+      return indicators.enable();
+    }
+    return indicators.disable();
+  }
+}