From 057f12e602cda3282bd3aa53590a4bd120789f3e Mon Sep 17 00:00:00 2001
From: Piotr Icikowski <piotrekicikowski@gmail.com>
Date: Tue, 28 May 2024 00:19:20 +0200
Subject: [PATCH] feat(pairs): add `Pairs`-related methods

---
 maps.go       |  9 -----
 pairs.go      | 28 ++++++++++++++++
 pairs_test.go | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 121 insertions(+), 9 deletions(-)
 create mode 100644 pairs.go
 create mode 100644 pairs_test.go

diff --git a/maps.go b/maps.go
index f4533c0..cddd4a4 100644
--- a/maps.go
+++ b/maps.go
@@ -1,14 +1,5 @@
 package generics
 
-// Pair represents key-value pair
-type Pair[K comparable, V any] struct {
-	Key   K
-	Value V
-}
-
-// Pairs represents collection of key-value pairs
-type Pairs[K comparable, V any] []Pair[K, V]
-
 // MapPairs returns list of map's key-value pairs
 func MapPairs[K comparable, V any](src map[K]V) Pairs[K, V] {
 	dst := make([]Pair[K, V], len(src))
diff --git a/pairs.go b/pairs.go
new file mode 100644
index 0000000..9f3b558
--- /dev/null
+++ b/pairs.go
@@ -0,0 +1,28 @@
+package generics
+
+// Pair represents key-value pair.
+type Pair[K comparable, V any] struct {
+	Key   K
+	Value V
+}
+
+// Pairs represents a collection of key-value pairs.
+type Pairs[K comparable, V any] []Pair[K, V]
+
+// Keys returns list of key-value pairs' keys.
+func (p Pairs[K, V]) Keys() []K {
+	dst := make([]K, len(p))
+	for i, pair := range p {
+		dst[i] = pair.Key
+	}
+	return dst
+}
+
+// Values returns list of key-value pairs' values.
+func (p Pairs[K, V]) Values() []V {
+	dst := make([]V, len(p))
+	for i, pair := range p {
+		dst[i] = pair.Value
+	}
+	return dst
+}
diff --git a/pairs_test.go b/pairs_test.go
new file mode 100644
index 0000000..1f914fc
--- /dev/null
+++ b/pairs_test.go
@@ -0,0 +1,93 @@
+package generics
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestPairsKeys(t *testing.T) {
+	tests := map[string]struct {
+		src Pairs[string, int]
+		dst []string
+	}{
+		"nil pairs": {
+			src: nil,
+			dst: []string{},
+		},
+		"empty pairs": {
+			src: Pairs[string, int]{},
+			dst: []string{},
+		},
+		"filled pairs": {
+			src: Pairs[string, int]{
+				{
+					Key:   "foo",
+					Value: 1,
+				},
+				{
+					Key:   "bar",
+					Value: 2,
+				},
+				{
+					Key:   "baz",
+					Value: 3,
+				},
+			},
+			dst: []string{
+				"foo",
+				"bar",
+				"baz",
+			},
+		},
+	}
+
+	for name, tc := range tests {
+		name, tc := name, tc
+		t.Run(name, func(t *testing.T) {
+			dst := tc.src.Keys()
+			require.ElementsMatch(t, tc.dst, dst)
+		})
+	}
+}
+
+func TestPairsValues(t *testing.T) {
+	tests := map[string]struct {
+		src Pairs[string, int]
+		dst []int
+	}{
+		"nil pairs": {
+			src: nil,
+			dst: []int{},
+		},
+		"empty pairs": {
+			src: Pairs[string, int]{},
+			dst: []int{},
+		},
+		"filled pairs": {
+			src: Pairs[string, int]{
+				{
+					Key:   "foo",
+					Value: 1,
+				},
+				{
+					Key:   "bar",
+					Value: 2,
+				},
+				{
+					Key:   "baz",
+					Value: 3,
+				},
+			},
+			dst: []int{1, 2, 3},
+		},
+	}
+
+	for name, tc := range tests {
+		name, tc := name, tc
+		t.Run(name, func(t *testing.T) {
+			dst := tc.src.Values()
+			require.ElementsMatch(t, tc.dst, dst)
+		})
+	}
+}