Add unread indicator to conversations (#9009)

app/javascript/mastodon/reducers/conversations.js

@@ -6,6 +6,7 @@ import {
   CONVERSATIONS_FETCH_SUCCESS,
   CONVERSATIONS_FETCH_FAIL,
   CONVERSATIONS_UPDATE,
+  CONVERSATIONS_READ,
 } from '../actions/conversations';
 import compareId from '../compare_id';
 
@@ -18,6 +19,7 @@ const initialState = ImmutableMap({
 
 const conversationToMap = item => ImmutableMap({
   id: item.id,
+  unread: item.unread,
   accounts: ImmutableList(item.accounts.map(a => a.id)),
   last_status: item.last_status.id,
 });
@@ -80,6 +82,14 @@ export default function conversations(state = initialState, action) {
     return state.update('mounted', count => count + 1);
   case CONVERSATIONS_UNMOUNT:
     return state.update('mounted', count => count - 1);
+  case CONVERSATIONS_READ:
+    return state.update('items', list => list.map(item => {
+      if (item.get('id') === action.id) {
+        return item.set('unread', false);
+      }
+
+      return item;
+    }));
   default:
     return state;
   }