feat: add diff util

pkg/diff/diff.go

@@ -0,0 +1,66 @@
+package diff
+
+import "github.com/samber/lo"
+
+type Diff[T comparable, S ~[]T] struct {
+	additionsMap map[T]struct{}
+	additions    S
+
+	removalsMap map[T]struct{}
+	removals    S
+}
+
+func (d Diff[T, S]) Has(item T) bool {
+	return d.InAdditions(item) || d.InRemovals(item)
+}
+
+func (d Diff[T, S]) InAdditions(item T) bool {
+	if _, ok := d.additionsMap[item]; ok {
+		return true
+	}
+
+	return false
+}
+
+func (d Diff[T, S]) InRemovals(item T) bool {
+	if _, ok := d.removalsMap[item]; ok {
+		return true
+	}
+
+	return false
+}
+
+func (d Diff[T, S]) Additions() S {
+	return d.additions
+}
+
+func (d Diff[T, S]) Removals() S {
+	return d.removals
+}
+
+func (d Diff[T, S]) HasChanged() bool {
+	return len(d.additions) > 0 || len(d.removals) > 0
+}
+
+func (d Diff[T, S]) Changed() S {
+	return append(d.additions, d.removals...)
+}
+
+func New[T comparable, S ~[]T](base, new S) *Diff[T, S] {
+	additions, removals := lo.Difference(base, new)
+
+	additionsMap := lo.SliceToMap(additions, func(item T) (T, struct{}) {
+		return item, struct{}{}
+	})
+
+	removalsMap := lo.SliceToMap(removals, func(item T) (T, struct{}) {
+		return item, struct{}{}
+	})
+
+	return &Diff[T, S]{
+		additionsMap: additionsMap,
+		additions:    additions,
+		removalsMap:  removalsMap,
+		removals:     removals,
+	}
+}

pkg/diff/diff_test.go

@@ -0,0 +1,85 @@
+package diff
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDiff(t *testing.T) {
+	tests := []struct {
+		Name string
+
+		Base []string
+		New  []string
+
+		ExpectedAdditions []string
+		ExpectedRemovals  []string
+	}{
+		{
+			Name: "No change",
+			Base: []string{
+				"diff-1",
+				"diff-2",
+			},
+			New: []string{
+				"diff-2",
+				"diff-1",
+			},
+		},
+		{
+			Name: "Add new item",
+			Base: []string{
+				"diff-1",
+				"diff-2",
+				"diff-3",
+			},
+			New: []string{
+				"diff-2",
+				"diff-1",
+			},
+			ExpectedAdditions: []string{
+				"diff-3",
+			},
+		},
+		{
+			Name: "Remove old item",
+			Base: []string{
+				"diff-2",
+			},
+			New: []string{
+				"diff-2",
+				"diff-1",
+			},
+			ExpectedRemovals: []string{
+				"diff-1",
+			},
+		},
+		{
+			Name: "Add and remove items",
+			Base: []string{
+				"diff-1",
+				"diff-3",
+			},
+			New: []string{
+				"diff-2",
+				"diff-1",
+			},
+			ExpectedAdditions: []string{
+				"diff-3",
+			},
+			ExpectedRemovals: []string{
+				"diff-2",
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.Name, func(t *testing.T) {
+			diff := New(test.Base, test.New)
+
+			assert.ElementsMatch(t, test.ExpectedAdditions, diff.Additions())
+			assert.ElementsMatch(t, test.ExpectedRemovals, diff.Removals())
+		})
+	}
+}