move find x not in y for int64 slices to utils

pkg/utils/slice_difference.go

@@ -0,0 +1,37 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-2021 Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public Licensee as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public Licensee for more details.
+//
+// You should have received a copy of the GNU Affero General Public Licensee
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package utils
+
+// find the elements which appear in slice1,but not in slice2
+func NotIn(slice1 []int64, slice2 []int64) []int64 {
+	var diff []int64
+
+	for _, s1 := range slice1 {
+		found := false
+		for _, s2 := range slice2 {
+			if s1 == s2 {
+				found = true
+				break
+			}
+		}
+		// int64 not found. We add it to return slice
+		if !found {
+			diff = append(diff, s1)
+		}
+	}
+	return diff
+}