Make mention strings work.

src/components/post_status_form/post_status_form.js

 import statusPoster from '../../services/status_poster/status_poster.service.js'
+import { reject, map, uniqBy } from 'lodash';
+
+const buildMentionsString = ({user, attentions}, currentUser) => {
+
+  let allAttentions = [...attentions]
+
+  allAttentions.unshift(user)
+
+  allAttentions = uniqBy(allAttentions, 'id')
+  allAttentions = reject(allAttentions, {id: currentUser.id})
+
+  let mentions = map(allAttentions, (attention) => {
+    return `@${attention.screen_name}`
+  })
+
+  return mentions.join(' ') + ' '
+}
 
 const PostStatusForm = {
   props: [
-    'replyTo'
+    'replyTo',
+    'repliedUser',
+    'attentions'
   ],
   data () {
+    let statusText = ''
+
+    if (this.replyTo) {
+      const currentUser = this.$store.state.users.currentUser
+      statusText = buildMentionsString({ user: this.repliedUser, attentions: this.attentions }, currentUser)
+    }
+
     return {
-      newStatus: { }
+      newStatus: {
+        status: statusText
+      }
     }
   },
   methods: {

src/components/status/status.vue

@@ -45,7 +45,7 @@
             <favorite-button :status=status></favorite-button>
           </div>
 
-          <post-status-form v-if="replying" :reply-to="status.id"></post-status-form>
+          <post-status-form v-if="replying" :reply-to="status.id" :attentions="status.attentions" :repliedUser="status.user"></post-status-form>
         </div>
       </div>
     </div>