[MM-55143] Disallow reacting with an emoji that does not exist, limit the total number of unique reactions per post (#25331)

* [MM-55143] Disallow reacting with an emoji that does not exist

* WIP for server limit on emoji reactions

* WIP

* Implement default limit of 25 unique emoji reactions

* Add modal for reaction limit

* Fix test

* PR feedback

* Fix i18n

* Update admin string

* Merge'd

* Fixing some issues, check limits correctly based on other users reactions

* Fix typos

* Fix lint/test

* Add tests, fix other tests

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/store/storetest/mocks/ReactionStore.go

@@ -94,6 +94,30 @@ func (_m *ReactionStore) DeleteOrphanedRowsByIds(r *model.RetentionIdsForDeletio
 	return r0
 }
 
+// ExistsOnPost provides a mock function with given fields: postId, emojiName
+func (_m *ReactionStore) ExistsOnPost(postId string, emojiName string) (bool, error) {
+	ret := _m.Called(postId, emojiName)
+
+	var r0 bool
+	var r1 error
+	if rf, ok := ret.Get(0).(func(string, string) (bool, error)); ok {
+		return rf(postId, emojiName)
+	}
+	if rf, ok := ret.Get(0).(func(string, string) bool); ok {
+		r0 = rf(postId, emojiName)
+	} else {
+		r0 = ret.Get(0).(bool)
+	}
+
+	if rf, ok := ret.Get(1).(func(string, string) error); ok {
+		r1 = rf(postId, emojiName)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // GetForPost provides a mock function with given fields: postID, allowFromCache
 func (_m *ReactionStore) GetForPost(postID string, allowFromCache bool) ([]*model.Reaction, error) {
 	ret := _m.Called(postID, allowFromCache)
@@ -146,6 +170,30 @@ func (_m *ReactionStore) GetForPostSince(postId string, since int64, excludeRemo
 	return r0, r1
 }
 
+// GetUniqueCountForPost provides a mock function with given fields: postId
+func (_m *ReactionStore) GetUniqueCountForPost(postId string) (int, error) {
+	ret := _m.Called(postId)
+
+	var r0 int
+	var r1 error
+	if rf, ok := ret.Get(0).(func(string) (int, error)); ok {
+		return rf(postId)
+	}
+	if rf, ok := ret.Get(0).(func(string) int); ok {
+		r0 = rf(postId)
+	} else {
+		r0 = ret.Get(0).(int)
+	}
+
+	if rf, ok := ret.Get(1).(func(string) error); ok {
+		r1 = rf(postId)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // PermanentDeleteBatch provides a mock function with given fields: endTime, limit
 func (_m *ReactionStore) PermanentDeleteBatch(endTime int64, limit int64) (int64, error) {
 	ret := _m.Called(endTime, limit)

server/channels/store/storetest/reaction_store.go

@@ -29,6 +29,8 @@ func TestReactionStore(t *testing.T, rctx request.CTX, ss store.Store, s SqlStor
 	t.Run("PermanentDeleteBatch", func(t *testing.T) { testReactionStorePermanentDeleteBatch(t, rctx, ss) })
 	t.Run("ReactionBulkGetForPosts", func(t *testing.T) { testReactionBulkGetForPosts(t, rctx, ss) })
 	t.Run("ReactionDeadlock", func(t *testing.T) { testReactionDeadlock(t, rctx, ss) })
+	t.Run("ExistsOnPost", func(t *testing.T) { testExistsOnPost(t, rctx, ss) })
+	t.Run("GetUniqueCountForPost", func(t *testing.T) { testGetUniqueCountForPost(t, rctx, ss) })
 }
 
 func testReactionSave(t *testing.T, rctx request.CTX, ss store.Store) {
@@ -873,3 +875,66 @@ func testReactionDeadlock(t *testing.T, rctx request.CTX, ss store.Store) {
 	}()
 	wg.Wait()
 }
+
+func testExistsOnPost(t *testing.T, rctx request.CTX, ss store.Store) {
+	post, _ := ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    model.NewId(),
+	})
+	emojiName := model.NewId()
+	reaction := &model.Reaction{
+		UserId:    model.NewId(),
+		PostId:    post.Id,
+		EmojiName: emojiName,
+	}
+	_, nErr := ss.Reaction().Save(reaction)
+	require.NoError(t, nErr)
+	exists, err := ss.Reaction().ExistsOnPost(post.Id, emojiName)
+	require.NoError(t, err)
+	require.True(t, exists)
+	exists, err = ss.Reaction().ExistsOnPost(post.Id, model.NewId())
+	require.NoError(t, err)
+	require.False(t, exists)
+}
+
+func testGetUniqueCountForPost(t *testing.T, rctx request.CTX, ss store.Store) {
+	post, _ := ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    model.NewId(),
+	})
+
+	userId := model.NewId()
+	emojiName := model.NewId()
+
+	reaction := &model.Reaction{
+		UserId:    userId,
+		PostId:    post.Id,
+		EmojiName: emojiName,
+	}
+	_, nErr := ss.Reaction().Save(reaction)
+	require.NoError(t, nErr)
+
+	sameReaction := &model.Reaction{
+		UserId:    model.NewId(),
+		PostId:    post.Id,
+		EmojiName: emojiName,
+	}
+	_, nErr = ss.Reaction().Save(sameReaction)
+	require.NoError(t, nErr)
+
+	newReaction := &model.Reaction{
+		UserId:    userId,
+		PostId:    post.Id,
+		EmojiName: model.NewId(),
+	}
+	_, nErr = ss.Reaction().Save(newReaction)
+	require.NoError(t, nErr)
+
+	totalReactions, err := ss.Reaction().GetForPost(post.Id, false)
+	require.NoError(t, err)
+	require.Equal(t, 3, len(totalReactions))
+
+	count, err := ss.Reaction().GetUniqueCountForPost(post.Id)
+	require.NoError(t, err)
+	require.Equal(t, 2, count)
+}