[MM-44488] Cloud limits: enforcing messages (#20362)

* Add new Job to keep updating the last_accessible_post time

* Filter out posts for funcs returning PostList model

* Separate methods to get and compute cache

* filter pinned posts

* For posts with sorted CreateAt order, support a faster form of filtering.

* Add inaccessible header for getPost and getPostsByIDs APIs

* replace manual binary search with the std. library

* in-place filter posts

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Nathaniel Allred <neallred@protonmail.com>

store/storetest/mocks/PostStore.go

@@ -287,6 +287,27 @@ func (_m *PostStore) GetMaxPostSize() int {
 	return r0
 }
 
+// GetNthRecentPostTime provides a mock function with given fields: n
+func (_m *PostStore) GetNthRecentPostTime(n int64) (int64, error) {
+	ret := _m.Called(n)
+
+	var r0 int64
+	if rf, ok := ret.Get(0).(func(int64) int64); ok {
+		r0 = rf(n)
+	} else {
+		r0 = ret.Get(0).(int64)
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func(int64) error); ok {
+		r1 = rf(n)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // GetOldest provides a mock function with given fields:
 func (_m *PostStore) GetOldest() (*model.Post, error) {
 	ret := _m.Called()

store/storetest/post_store.go

@@ -57,6 +57,7 @@ func TestPostStore(t *testing.T, ss store.Store, s SqlStore) {
 	t.Run("GetForThread", func(t *testing.T) { testPostStoreGetForThread(t, ss) })
 	t.Run("HasAutoResponsePostByUserSince", func(t *testing.T) { testHasAutoResponsePostByUserSince(t, ss) })
 	t.Run("GetPostsSinceForSync", func(t *testing.T) { testGetPostsSinceForSync(t, ss, s) })
+	t.Run("GetNthRecentPostTime", func(t *testing.T) { testGetNthRecentPostTime(t, ss) })
 }
 
 func testPostStoreSave(t *testing.T, ss store.Store) {
@@ -3765,3 +3766,98 @@ func getPostIds(posts []*model.Post, morePosts ...*model.Post) []string {
 	}
 	return ids
 }
+
+func testGetNthRecentPostTime(t *testing.T, ss store.Store) {
+	_, err := ss.Post().GetNthRecentPostTime(0)
+	assert.Error(t, err)
+	_, err = ss.Post().GetNthRecentPostTime(-1)
+	assert.Error(t, err)
+
+	diff := int64(10000)
+	now := utils.MillisFromTime(time.Now()) + diff
+
+	p1 := &model.Post{}
+	p1.ChannelId = model.NewId()
+	p1.UserId = model.NewId()
+	p1.Message = "test"
+	p1.CreateAt = now
+	p1, err = ss.Post().Save(p1)
+	require.NoError(t, err)
+
+	p2 := &model.Post{}
+	p2.ChannelId = p1.ChannelId
+	p2.UserId = p1.UserId
+	p2.Message = p1.Message
+	now = now + diff
+	p2.CreateAt = now
+	p2, err = ss.Post().Save(p2)
+	require.NoError(t, err)
+
+	bot1 := &model.Bot{
+		Username:    "username",
+		Description: "a bot",
+		OwnerId:     model.NewId(),
+		UserId:      model.NewId(),
+	}
+	_, err = ss.Bot().Save(bot1)
+	require.NoError(t, err)
+
+	b1 := &model.Post{}
+	b1.Message = "bot test"
+	b1.ChannelId = p1.ChannelId
+	b1.UserId = bot1.UserId
+	now = now + diff
+	b1.CreateAt = now
+	_, err = ss.Post().Save(b1)
+	require.NoError(t, err)
+
+	p3 := &model.Post{}
+	p3.ChannelId = p1.ChannelId
+	p3.UserId = p1.UserId
+	p3.Message = p1.Message
+	now = now + diff
+	p3.CreateAt = now
+	p3, err = ss.Post().Save(p3)
+	require.NoError(t, err)
+
+	s1 := &model.Post{}
+	s1.Type = model.PostTypeJoinChannel
+	s1.ChannelId = p1.ChannelId
+	s1.UserId = model.NewId()
+	s1.Message = "system_join_channel message"
+	now = now + diff
+	s1.CreateAt = now
+	_, err = ss.Post().Save(s1)
+	require.NoError(t, err)
+
+	p4 := &model.Post{}
+	p4.ChannelId = p1.ChannelId
+	p4.UserId = p1.UserId
+	p4.Message = p1.Message
+	now = now + diff
+	p4.CreateAt = now
+	p4, err = ss.Post().Save(p4)
+	require.NoError(t, err)
+
+	r, err := ss.Post().GetNthRecentPostTime(1)
+	assert.NoError(t, err)
+	assert.Equal(t, p4.CreateAt, r)
+
+	// Skip system post
+	r, err = ss.Post().GetNthRecentPostTime(2)
+	assert.NoError(t, err)
+	assert.Equal(t, p3.CreateAt, r)
+
+	// Skip system & bot post
+	r, err = ss.Post().GetNthRecentPostTime(3)
+	assert.NoError(t, err)
+	assert.Equal(t, p2.CreateAt, r)
+
+	r, err = ss.Post().GetNthRecentPostTime(4)
+	assert.NoError(t, err)
+	assert.Equal(t, p1.CreateAt, r)
+
+	_, err = ss.Post().GetNthRecentPostTime(10000)
+	assert.Error(t, err)
+	assert.IsType(t, &store.ErrNotFound{}, err)
+}