Statuses: optimistic reply counter

app/soapbox/reducers/__tests__/statuses-test.js

@@ -1,8 +1,41 @@
 import reducer from '../statuses';
-import { Map as ImmutableMap } from 'immutable';
+import { Map as ImmutableMap, fromJS } from 'immutable';
+import {
+  STATUS_CREATE_REQUEST,
+  STATUS_CREATE_FAIL,
+} from 'soapbox/actions/statuses';
+
 
 describe('statuses reducer', () => {
   it('should return the initial state', () => {
     expect(reducer(undefined, {})).toEqual(ImmutableMap());
   });
+
+  describe('STATUS_CREATE_REQUEST', () => {
+    it('increments the replies_count of its parent', () => {
+      const state = fromJS({ '123': { replies_count: 4 } });
+
+      const action = {
+        type: STATUS_CREATE_REQUEST,
+        params: { in_reply_to_id: '123' },
+      };
+
+      const result = reducer(state, action).getIn(['123', 'replies_count']);
+      expect(result).toEqual(5);
+    });
+  });
+
+  describe('STATUS_CREATE_FAIL', () => {
+    it('decrements the replies_count of its parent', () => {
+      const state = fromJS({ '123': { replies_count: 5 } });
+
+      const action = {
+        type: STATUS_CREATE_FAIL,
+        params: { in_reply_to_id: '123' },
+      };
+
+      const result = reducer(state, action).getIn(['123', 'replies_count']);
+      expect(result).toEqual(4);
+    });
+  });
 });

app/soapbox/reducers/statuses.js

@@ -6,6 +6,8 @@ import {
   FAVOURITE_FAIL,
 } from '../actions/interactions';
 import {
+  STATUS_CREATE_REQUEST,
+  STATUS_CREATE_FAIL,
   STATUS_MUTE_SUCCESS,
   STATUS_UNMUTE_SUCCESS,
   STATUS_REVEAL,
@@ -33,6 +35,22 @@ const deleteStatus = (state, id, references) => {
   return state.delete(id);
 };
 
+const importPendingStatus = (state, { in_reply_to_id }) => {
+  if (in_reply_to_id) {
+    return state.updateIn([in_reply_to_id, 'replies_count'], 0, count => count + 1);
+  } else {
+    return state;
+  }
+};
+
+const deletePendingStatus = (state, { in_reply_to_id }) => {
+  if (in_reply_to_id) {
+    return state.updateIn([in_reply_to_id, 'replies_count'], 0, count => Math.max(0, count - 1));
+  } else {
+    return state;
+  }
+};
+
 const initialState = ImmutableMap();
 
 export default function statuses(state = initialState, action) {
@@ -41,6 +59,10 @@ export default function statuses(state = initialState, action) {
     return importStatus(state, action.status);
   case STATUSES_IMPORT:
     return importStatuses(state, action.statuses);
+  case STATUS_CREATE_REQUEST:
+    return importPendingStatus(state, action.params);
+  case STATUS_CREATE_FAIL:
+    return deletePendingStatus(state, action.params);
   case FAVOURITE_REQUEST:
     return state.update(action.status.get('id'), status =>
       status