Fetch Public and TWKN timelines when viewed.

src/modules/api.js

@@ -2,11 +2,32 @@ import backendInteractorService from '../services/backend_interactor_service/bac
 
 const api = {
   state: {
-    backendInteractor: backendInteractorService()
+    backendInteractor: backendInteractorService(),
+    fetchers: {}
   },
   mutations: {
     setBackendInteractor (state, backendInteractor) {
       state.backendInteractor = backendInteractor
+    },
+    addFetcher (state, {timeline, fetcher}) {
+      state.fetchers[timeline] = fetcher
+    },
+    removeFetcher (state, {timeline}) {
+      delete state.fetchers[timeline]
+    }
+  },
+  actions: {
+    startFetching (store, timeline) {
+      // Don't start fetching if we already are.
+      if (!store.state.fetchers[timeline]) {
+        const fetcher = store.state.backendInteractor.startFetching({timeline, store})
+        store.commit('addFetcher', {timeline, fetcher})
+      }
+    },
+    stopFetching (store, timeline) {
+      const fetcher = store.state.fetchers[timeline]
+      window.clearInterval(fetcher)
+      store.commit('removeFetcher', {timeline})
     }
   }
 }