Add CIDR validation checker and tests to v2. (#132)

# Describe Request

Add CIDR validation checker and tests to v2.

# Change Type

New code.

v2/cidr.go

@@ -0,0 +1,42 @@
+// Copyright (c) 2023-2024 Onur Cinar.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+// https://github.com/cinar/checker
+
+package v2
+
+import (
+	"net"
+	"reflect"
+)
+
+const (
+	// nameCIDR is the name of the CIDR check.
+	nameCIDR = "cidr"
+)
+
+var (
+	// ErrNotCIDR indicates that the given value is not a valid CIDR.
+	ErrNotCIDR = NewCheckError("CIDR")
+)
+
+// IsCIDR checks if the value is a valid CIDR notation IP address and prefix length.
+func IsCIDR(value string) (string, error) {
+	_, _, err := net.ParseCIDR(value)
+	if err != nil {
+		return value, ErrNotCIDR
+	}
+
+	return value, nil
+}
+
+// checkCIDR checks if the value is a valid CIDR notation IP address and prefix length.
+func checkCIDR(value reflect.Value) (reflect.Value, error) {
+	_, err := IsCIDR(value.Interface().(string))
+	return value, err
+}
+
+// makeCIDR makes a checker function for the CIDR checker.
+func makeCIDR(_ string) CheckFunc[reflect.Value] {
+	return checkCIDR
+}

v2/cidr_test.go

@@ -0,0 +1,76 @@
+// Copyright (c) 2023-2024 Onur Cinar.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+// https://github.com/cinar/checker
+
+package v2_test
+
+import (
+	"fmt"
+	"testing"
+
+	v2 "github.com/cinar/checker/v2"
+)
+
+func ExampleIsCIDR() {
+	_, err := v2.IsCIDR("2001:db8::/32")
+	if err != nil {
+		fmt.Println(err)
+	}
+}
+
+func TestIsCIDRInvalid(t *testing.T) {
+	_, err := v2.IsCIDR("900.800.200.100//24")
+	if err == nil {
+		t.Fatal("expected error")
+	}
+}
+
+func TestIsCIDRValid(t *testing.T) {
+	_, err := v2.IsCIDR("2001:db8::/32")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestCheckCIDRNonString(t *testing.T) {
+	defer FailIfNoPanic(t, "expected panic")
+
+	type Network struct {
+		Subnet int `checkers:"cidr"`
+	}
+
+	network := &Network{}
+
+	v2.CheckStruct(network)
+}
+
+func TestCheckCIDRInvalid(t *testing.T) {
+	type Network struct {
+		Subnet string `checkers:"cidr"`
+	}
+
+	network := &Network{
+		Subnet: "900.800.200.100//24",
+	}
+
+	_, ok := v2.CheckStruct(network)
+	if ok {
+		t.Fatal("expected error")
+	}
+}
+
+func TestCheckCIDRValid(t *testing.T) {
+	type Network struct {
+		Subnet string `checkers:"cidr"`
+	}
+
+	network := &Network{
+		Subnet: "192.0.2.0/24",
+	}
+
+	_, ok := v2.CheckStruct(network)
+	if !ok {
+		t.Fatal("expected valid")
+	}
+}

v2/maker.go

@@ -18,6 +18,7 @@ type MakeCheckFunc func(params string) CheckFunc[reflect.Value]
 var makers = map[string]MakeCheckFunc{
 	nameAlphanumeric: makeAlphanumeric,
 	nameASCII:        makeASCII,
+	nameCIDR:         makeCIDR,
 	nameMaxLen:       makeMaxLen,
 	nameMinLen:       makeMinLen,
 	nameRequired:     makeRequired,