Forbid removing the last admin user (#28337)

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

2 files changed, 40 insertions, 4 deletions

diff --git a/models/error.go b/models/error.go
index b7bb967b73..83dfe29805 100644
--- a/models/error.go
+++ b/models/error.go
@@ -57,6 +57,21 @@ func (err ErrUserOwnPackages) Error() string {
 	return fmt.Sprintf("user still has ownership of packages [uid: %d]", err.UID)
 }
 
+// ErrDeleteLastAdminUser represents a "DeleteLastAdminUser" kind of error.
+type ErrDeleteLastAdminUser struct {
+	UID int64
+}
+
+// IsErrDeleteLastAdminUser checks if an error is a ErrDeleteLastAdminUser.
+func IsErrDeleteLastAdminUser(err error) bool {
+	_, ok := err.(ErrDeleteLastAdminUser)
+	return ok
+}
+
+func (err ErrDeleteLastAdminUser) Error() string {
+	return fmt.Sprintf("can not delete the last admin user [uid: %d]", err.UID)
+}
+
 // ErrNoPendingRepoTransfer is an error type for repositories without a pending
 // transfer request
 type ErrNoPendingRepoTransfer struct {
diff --git a/models/user/user.go b/models/user/user.go
index 204c8f41b6..6d1b1aef18 100644
--- a/models/user/user.go
+++ b/models/user/user.go
@@ -730,9 +730,18 @@ func CreateUser(ctx context.Context, u *User, overwriteDefault ...*CreateUserOve
 	return committer.Commit()
 }
 
+// IsLastAdminUser check whether user is the last admin
+func IsLastAdminUser(ctx context.Context, user *User) bool {
+	if user.IsAdmin && CountUsers(ctx, &CountUserFilter{IsAdmin: util.OptionalBoolTrue}) <= 1 {
+		return true
+	}
+	return false
+}
+
 // CountUserFilter represent optional filters for CountUsers
 type CountUserFilter struct {
 	LastLoginSince *int64
+	IsAdmin        util.OptionalBool
 }
 
 // CountUsers returns number of users.
@@ -741,13 +750,25 @@ func CountUsers(ctx context.Context, opts *CountUserFilter) int64 {
 }
 
 func countUsers(ctx context.Context, opts *CountUserFilter) int64 {
-	sess := db.GetEngine(ctx).Where(builder.Eq{"type": "0"})
+	sess := db.GetEngine(ctx)
+	cond := builder.NewCond()
+	cond = cond.And(builder.Eq{"type": UserTypeIndividual})
 
-	if opts != nil && opts.LastLoginSince != nil {
-		sess = sess.Where(builder.Gte{"last_login_unix": *opts.LastLoginSince})
+	if opts != nil {
+		if opts.LastLoginSince != nil {
+			cond = cond.And(builder.Gte{"last_login_unix": *opts.LastLoginSince})
+		}
+
+		if !opts.IsAdmin.IsNone() {
+			cond = cond.And(builder.Eq{"is_admin": opts.IsAdmin.IsTrue()})
+		}
+	}
+
+	count, err := sess.Where(cond).Count(new(User))
+	if err != nil {
+		log.Error("user.countUsers: %v", err)
 	}
 
-	count, _ := sess.Count(new(User))
 	return count
 }