[MM-17069] Api endpoint to unread a channel (#11794)

* [MM-17069] endpoint to unread a channel from post

* [MM-17069] update mock

* [MM-17069] first passing test

* [MM-17069] fix SQL typo

* [MM-17069] fix msgCount

* add tests

* [MM-17069] Fix tests

* [MM-16069] Remove trash, add comments

* [MM-16069] Add message to errors

* [MM-17069] fix go fmt

* [MM-17069] return an UnreadChannel response

* [MM-17069] added unauthorized test

* [MM-17069] fix operator

* [MM-17069] refactor tests

* [MM-16069] back to green tests

* [MM-17069] change url to include user

* [MM-17069] Fixing code review comments

* [MM-17069] One shouldn't fix manually what a machine can fix better

* [MM-17069] change response type, update tests

* [MM-17069] fix permission error

* [MM-17069] Add tests for edit_other_users permission

* [MM-17069] no magic numbers

app/channel.go

@@ -1754,6 +1754,18 @@ func (a *App) UpdateChannelLastViewedAt(channelIds []string, userId string) *mod
 	return nil
 }
 
+// MarkChanelAsUnreadFromPost will take a post and set the channel as unread from that one.
+func (a *App) MarkChannelAsUnreadFromPost(postID string, userID string) (*model.ChannelUnreadAt, *model.AppError) {
+
+	post, err := a.GetSinglePost(postID)
+	if err != nil {
+		return nil, err
+	}
+
+	unreadMentions := 0 // TODO: calculate this value, setting it to zero for now.
+	return a.Srv.Store.Channel().UpdateLastViewedAtPost(post, userID, unreadMentions)
+}
+
 func (a *App) esAutocompleteChannels(teamId, term string, includeDeleted bool) (*model.ChannelList, *model.AppError) {
 	channelIds, err := a.Elasticsearch.SearchChannels(teamId, term)
 	if err != nil {

app/channel_test.go

@@ -1041,3 +1041,103 @@ func TestSearchChannelsForUser(t *testing.T) {
 		searchAndCheck(t, "dev", []string{"test-dev-1", "test-dev-2", "dev-3"})
 	})
 }
+
+func TestMarkChannelAsUnreadFromPost(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+
+	u1 := th.BasicUser
+	u2 := th.BasicUser2
+	c1 := th.BasicChannel
+	pc1 := th.CreatePrivateChannel(th.BasicTeam)
+	th.AddUserToChannel(u2, c1)
+	th.AddUserToChannel(u1, pc1)
+	th.AddUserToChannel(u2, pc1)
+
+	p1 := th.CreatePost(c1)
+	p2 := th.CreatePost(c1)
+	p3 := th.CreatePost(c1)
+
+	pp1 := th.CreatePost(pc1)
+	require.NotNil(t, pp1)
+	pp2 := th.CreatePost(pc1)
+
+	unread, err := th.App.GetChannelUnread(c1.Id, u1.Id)
+	require.Nil(t, err)
+	require.Equal(t, int64(4), unread.MsgCount)
+	unread, err = th.App.GetChannelUnread(c1.Id, u2.Id)
+	require.Nil(t, err)
+	require.Equal(t, int64(4), unread.MsgCount)
+	err = th.App.UpdateChannelLastViewedAt([]string{c1.Id, pc1.Id}, u1.Id)
+	require.Nil(t, err)
+	err = th.App.UpdateChannelLastViewedAt([]string{c1.Id, pc1.Id}, u2.Id)
+	require.Nil(t, err)
+	unread, err = th.App.GetChannelUnread(c1.Id, u2.Id)
+	require.Nil(t, err)
+	require.Equal(t, int64(0), unread.MsgCount)
+
+	t.Run("Unread but last one", func(t *testing.T) {
+		response, err := th.App.MarkChannelAsUnreadFromPost(p2.Id, u1.Id)
+		require.Nil(t, err)
+		require.NotNil(t, response)
+		assert.Equal(t, int64(3), response.MsgCount)
+		unread, err := th.App.GetChannelUnread(c1.Id, u1.Id)
+		require.Nil(t, err)
+		assert.Equal(t, int64(1), unread.MsgCount)
+		assert.Equal(t, p2.CreateAt, response.LastViewedAt)
+	})
+
+	t.Run("Unread last one", func(t *testing.T) {
+		response, err := th.App.MarkChannelAsUnreadFromPost(p3.Id, u1.Id)
+		require.Nil(t, err)
+		require.NotNil(t, response)
+		assert.Equal(t, int64(4), response.MsgCount)
+		unread, err := th.App.GetChannelUnread(c1.Id, u1.Id)
+		require.Nil(t, err)
+		assert.Equal(t, int64(0), unread.MsgCount)
+		assert.Equal(t, p3.CreateAt, response.LastViewedAt)
+	})
+
+	t.Run("Unread first one", func(t *testing.T) {
+		response, err := th.App.MarkChannelAsUnreadFromPost(p1.Id, u1.Id)
+		require.Nil(t, err)
+		require.NotNil(t, response)
+		assert.Equal(t, int64(2), response.MsgCount)
+		unread, err := th.App.GetChannelUnread(c1.Id, u1.Id)
+		require.Nil(t, err)
+		assert.Equal(t, int64(2), unread.MsgCount)
+		assert.Equal(t, p1.CreateAt, response.LastViewedAt)
+	})
+
+	t.Run("Other users are unaffected", func(t *testing.T) {
+		unread, err := th.App.GetChannelUnread(c1.Id, u2.Id)
+		require.Nil(t, err)
+		assert.Equal(t, int64(0), unread.MsgCount)
+
+	})
+
+	t.Run("Unread on a private channel", func(t *testing.T) {
+		response, err := th.App.MarkChannelAsUnreadFromPost(pp1.Id, u1.Id)
+		require.Nil(t, err)
+		require.NotNil(t, response)
+		assert.Equal(t, int64(1), response.MsgCount)
+		unread, err := th.App.GetChannelUnread(pc1.Id, u1.Id)
+		require.Nil(t, err)
+		assert.Equal(t, int64(1), unread.MsgCount)
+		assert.Equal(t, pp1.CreateAt, response.LastViewedAt)
+
+		response, err = th.App.MarkChannelAsUnreadFromPost(pp2.Id, u1.Id)
+		assert.Nil(t, err)
+		assert.Equal(t, int64(2), response.MsgCount)
+		unread, err = th.App.GetChannelUnread(pc1.Id, u1.Id)
+		require.Nil(t, err)
+		assert.Equal(t, int64(0), unread.MsgCount)
+		assert.Equal(t, pp2.CreateAt, response.LastViewedAt)
+	})
+
+	t.Run("Can't unread an imaginary post", func(t *testing.T) {
+		response, err := th.App.MarkChannelAsUnreadFromPost("invalid4ofngungryquinj976y", u1.Id)
+		assert.NotNil(t, err)
+		assert.Nil(t, response)
+	})
+}