4 files changed, 141 insertions, 0 deletions
diff --git a/modules/container/filter.go b/modules/container/filter.go
new file mode 100644
index 0000000..37ec7c3
--- /dev/null
+++ b/modules/container/filter.go
@@ -0,0 +1,21 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package container
+
+import "slices"
+
+// FilterSlice ranges over the slice and calls include() for each element.
+// If the second returned value is true, the first returned value will be included in the resulting
+// slice (after deduplication).
+func FilterSlice[E any, T comparable](s []E, include func(E) (T, bool)) []T {
+	filtered := make([]T, 0, len(s)) // slice will be clipped before returning
+	seen := make(map[T]bool, len(s))
+	for i := range s {
+		if v, ok := include(s[i]); ok && !seen[v] {
+			filtered = append(filtered, v)
+			seen[v] = true
+		}
+	}
+	return slices.Clip(filtered)
+}
diff --git a/modules/container/filter_test.go b/modules/container/filter_test.go
new file mode 100644
index 0000000..ad304e5
--- /dev/null
+++ b/modules/container/filter_test.go
@@ -0,0 +1,28 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package container
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFilterMapUnique(t *testing.T) {
+	result := FilterSlice([]int{
+		0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
+	}, func(i int) (int, bool) {
+		switch i {
+		case 0:
+			return 0, true // included later
+		case 1:
+			return 0, true // duplicate of previous (should be ignored)
+		case 2:
+			return 2, false // not included
+		default:
+			return i, true
+		}
+	})
+	assert.Equal(t, []int{0, 3, 4, 5, 6, 7, 8, 9}, result)
+}
diff --git a/modules/container/set.go b/modules/container/set.go
new file mode 100644
index 0000000..1577998
--- /dev/null
+++ b/modules/container/set.go
@@ -0,0 +1,56 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package container
+
+type Set[T comparable] map[T]struct{}
+
+// SetOf creates a set and adds the specified elements to it.
+func SetOf[T comparable](values ...T) Set[T] {
+	s := make(Set[T], len(values))
+	s.AddMultiple(values...)
+	return s
+}
+
+// Add adds the specified element to a set.
+// Returns true if the element is added; false if the element is already present.
+func (s Set[T]) Add(value T) bool {
+	if _, has := s[value]; !has {
+		s[value] = struct{}{}
+		return true
+	}
+	return false
+}
+
+// AddMultiple adds the specified elements to a set.
+func (s Set[T]) AddMultiple(values ...T) {
+	for _, value := range values {
+		s.Add(value)
+	}
+}
+
+// Contains determines whether a set contains the specified element.
+// Returns true if the set contains the specified element; otherwise, false.
+func (s Set[T]) Contains(value T) bool {
+	_, has := s[value]
+	return has
+}
+
+// Remove removes the specified element.
+// Returns true if the element is successfully found and removed; otherwise, false.
+func (s Set[T]) Remove(value T) bool {
+	if _, has := s[value]; has {
+		delete(s, value)
+		return true
+	}
+	return false
+}
+
+// Values gets a list of all elements in the set.
+func (s Set[T]) Values() []T {
+	keys := make([]T, 0, len(s))
+	for k := range s {
+		keys = append(keys, k)
+	}
+	return keys
+}
diff --git a/modules/container/set_test.go b/modules/container/set_test.go
new file mode 100644
index 0000000..1502236
--- /dev/null
+++ b/modules/container/set_test.go
@@ -0,0 +1,36 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package container
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSet(t *testing.T) {
+	s := make(Set[string])
+
+	assert.True(t, s.Add("key1"))
+	assert.False(t, s.Add("key1"))
+	assert.True(t, s.Add("key2"))
+
+	assert.True(t, s.Contains("key1"))
+	assert.True(t, s.Contains("key2"))
+	assert.False(t, s.Contains("key3"))
+
+	assert.True(t, s.Remove("key2"))
+	assert.False(t, s.Contains("key2"))
+
+	assert.False(t, s.Remove("key3"))
+
+	s.AddMultiple("key4", "key5")
+	assert.True(t, s.Contains("key4"))
+	assert.True(t, s.Contains("key5"))
+
+	s = SetOf("key6", "key7")
+	assert.False(t, s.Contains("key1"))
+	assert.True(t, s.Contains("key6"))
+	assert.True(t, s.Contains("key7"))
+}