MM-28249 Auto follow threads (#15878)

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

store/sqlstore/thread_store.go

@@ -7,7 +7,9 @@ import (
 	"database/sql"
 	"github.com/mattermost/mattermost-server/v5/model"
 	"github.com/mattermost/mattermost-server/v5/store"
+	"github.com/mattermost/mattermost-server/v5/utils"
 	"github.com/pkg/errors"
+	"time"
 
 	sq "github.com/Masterminds/squirrel"
 )
@@ -25,9 +27,12 @@ func newSqlThreadStore(sqlStore SqlStore) store.ThreadStore {
 	}
 
 	for _, db := range sqlStore.GetAllConns() {
-		table := db.AddTableWithName(model.Thread{}, "Threads").SetKeys(false, "PostId")
-		table.ColMap("PostId").SetMaxSize(26)
-		table.ColMap("Participants").SetMaxSize(0)
+		tableThreads := db.AddTableWithName(model.Thread{}, "Threads").SetKeys(false, "PostId")
+		tableThreads.ColMap("PostId").SetMaxSize(26)
+		tableThreads.ColMap("Participants").SetMaxSize(0)
+		tableThreadMemberships := db.AddTableWithName(model.ThreadMembership{}, "ThreadMemberships").SetKeys(false, "PostId", "UserId")
+		tableThreadMemberships.ColMap("PostId").SetMaxSize(26)
+		tableThreadMemberships.ColMap("UserId").SetMaxSize(26)
 	}
 
 	return s
@@ -49,6 +54,11 @@ func threadToSlice(thread *model.Thread) []interface{} {
 func (s *SqlThreadStore) createIndexesIfNotExists() {
 	s.CreateIndexIfNotExists("idx_threads_last_reply_at", "Threads", "LastReplyAt")
 	s.CreateIndexIfNotExists("idx_threads_post_id", "Threads", "PostId")
+
+	s.CreateIndexIfNotExists("idx_thread_memberships_last_update_at", "ThreadMemberships", "LastUpdated")
+	s.CreateIndexIfNotExists("idx_thread_memberships_last_view_at", "ThreadMemberships", "LastViewed")
+	s.CreateIndexIfNotExists("idx_thread_memberships_post_id", "ThreadMemberships", "PostId")
+	s.CreateIndexIfNotExists("idx_thread_memberships_user_id", "ThreadMemberships", "UserId")
 }
 
 func (s *SqlThreadStore) SaveMultiple(threads []*model.Thread) ([]*model.Thread, int, error) {
@@ -106,3 +116,75 @@ func (s *SqlThreadStore) Delete(threadId string) error {
 
 	return nil
 }
+
+func (s *SqlThreadStore) SaveMembership(membership *model.ThreadMembership) (*model.ThreadMembership, error) {
+	if err := s.GetMaster().Insert(membership); err != nil {
+		return nil, errors.Wrapf(err, "failed to save thread membership with postid=%s userid=%s", membership.PostId, membership.UserId)
+	}
+
+	return membership, nil
+}
+
+func (s *SqlThreadStore) UpdateMembership(membership *model.ThreadMembership) (*model.ThreadMembership, error) {
+	if _, err := s.GetMaster().Update(membership); err != nil {
+		return nil, errors.Wrapf(err, "failed to update thread membership with postid=%s userid=%s", membership.PostId, membership.UserId)
+	}
+
+	return membership, nil
+}
+
+func (s *SqlThreadStore) GetMembershipsForUser(userId string) ([]*model.ThreadMembership, error) {
+	var memberships []*model.ThreadMembership
+	_, err := s.GetReplica().Select(&memberships, "SELECT * from ThreadMemberships WHERE UserId = :UserId", map[string]interface{}{"UserId": userId})
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to get thread membership with userid=%s", userId)
+	}
+	return memberships, nil
+}
+
+func (s *SqlThreadStore) GetMembershipForUser(userId, postId string) (*model.ThreadMembership, error) {
+	var membership model.ThreadMembership
+	err := s.GetReplica().SelectOne(&membership, "SELECT * from ThreadMemberships WHERE UserId = :UserId AND PostId = :PostId", map[string]interface{}{"UserId": userId, "PostId": postId})
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, store.NewErrNotFound("Thread", postId)
+		}
+		return nil, errors.Wrapf(err, "failed to get thread membership with userid=%s postid=%s", userId, postId)
+	}
+	return &membership, nil
+}
+
+func (s *SqlThreadStore) DeleteMembershipForUser(userId string, postId string) error {
+	if _, err := s.GetMaster().Exec("DELETE FROM ThreadMemberships Where PostId = :PostId AND UserId = :UserId", map[string]interface{}{"PostId": postId, "UserId": userId}); err != nil {
+		return errors.Wrap(err, "failed to update thread membership")
+	}
+
+	return nil
+}
+
+func (s *SqlThreadStore) CreateMembershipIfNeeded(userId, postId string) error {
+	membership, err := s.GetMembershipForUser(userId, postId)
+	now := utils.MillisFromTime(time.Now())
+	if err == nil {
+		if !membership.Following {
+			membership.Following = true
+			membership.LastUpdated = now
+			_, err = s.UpdateMembership(membership)
+		}
+		return err
+	}
+
+	var nfErr *store.ErrNotFound
+
+	if !errors.As(err, &nfErr) {
+		return errors.Wrap(err, "failed to get thread membership")
+	}
+	_, err = s.SaveMembership(&model.ThreadMembership{
+		PostId:      postId,
+		UserId:      userId,
+		Following:   true,
+		LastViewed:  0,
+		LastUpdated: now,
+	})
+	return err
+}