Factored out set checks

util/set.go

@@ -0,0 +1,43 @@
+// This file is Free Software under the MIT License
+// without warranty, see README.md and LICENSES/MIT.txt for details.
+//
+// SPDX-License-Identifier: MIT
+//
+// SPDX-FileCopyrightText: 2023 German Federal Office for Information Security (BSI) <https://www.bsi.bund.de>
+// Software-Engineering: 2023 Intevation GmbH <https://intevation.de>
+
+package util
+
+// Set is a simple set type.
+type Set[K comparable] map[K]struct{}
+
+// Contains returns if the set contains a given key or not.
+func (s Set[K]) Contains(k K) bool {
+	_, found := s[k]
+	return found
+}
+
+// Add adds a key to the set.
+func (s Set[K]) Add(k K) {
+	s[k] = struct{}{}
+}
+
+// Keys returns the keys of the set.
+func (s Set[K]) Keys() []K {
+	keys := make([]K, 0, len(s))
+	for k := range s {
+		keys = append(keys, k)
+	}
+	return keys
+}
+
+// Difference returns the differnce of two sets.
+func (s Set[K]) Difference(t Set[K]) Set[K] {
+	d := Set[K]{}
+	for k := range s {
+		if !t.Contains(k) {
+			d.Add(k)
+		}
+	}
+	return d
+}