Merge pull request #4 from xyproto/random

Add a function for selecting a random member of an enum

enum.go

@@ -2,7 +2,9 @@ package enum
 
 import (
 	"fmt"
+	"math/rand"
 	"strings"
+	"time"
 )
 
 // Member is an enum member, a specific value bound to a variable.
@@ -97,6 +99,24 @@ func (e Enum[M, V]) Members() []M {
 	return e.members
 }
 
+// Choice returns a randomly selected member of the enum.
+//
+// A random seed can be given (or be 0 to use time.Now().UnixNano() as the seed).
+// nil is returned only if the Enum contains no members.
+func (e Enum[M, V]) Choice(seed int64) *M {
+	lenMembers := len(e.members)
+	// Enum is empty
+	if lenMembers == 0 {
+		return nil
+	}
+	if seed == 0 {
+		seed = time.Now().UnixNano()
+	}
+	// nolint: gosec
+	r := rand.New(rand.NewSource(seed))
+	return &(e.members[r.Intn(lenMembers)])
+}
+
 // Values returns a slice of values of all members of the enum.
 func (e Enum[M, V]) Values() []V {
 	res := make([]V, 0, len(e.members))

enum_test.go

@@ -63,6 +63,29 @@ func TestEnum_Members(t *testing.T) {
 	is.Equal(Colors.Members(), exp)
 }
 
+func TestEnum_Choice(t *testing.T) {
+	is := is.New(t)
+	// Select a random color
+	m := Colors.Choice(0)
+	is.True(m != nil)
+	is.True(Colors.Contains(*m))
+	// Select a specific color using a specific random seed
+	m = Colors.Choice(254)
+	is.True(m != nil)
+	is.Equal(*m, Red)
+	// Select a specific color using a specific random seed
+	m = Colors.Choice(1337)
+	is.True(m != nil)
+	is.Equal(*m, Green)
+	// Select a specific color using a specific random seed
+	m = Colors.Choice(42)
+	is.True(m != nil)
+	is.Equal(*m, Blue)
+	// Check that selecting a random member from an empty Enum returns an error
+	emptyEnums := enum.New[string, Color]()
+	is.True(emptyEnums.Choice(0) == nil)
+}
+
 func TestEnum_Values(t *testing.T) {
 	is := is.New(t)
 	exp := []string{"red", "green", "blue"}