1 files changed, 69 insertions, 2 deletions
diff --git a/scalar.go b/scalar.go
index 67b4540..e79b002 100644
--- a/scalar.go
+++ b/scalar.go
@@ -3,11 +3,57 @@ package arg
 import (
 	"encoding"
 	"fmt"
+	"net"
+	"net/mail"
 	"reflect"
 	"strconv"
 	"time"
 )
 
+// The reflected form of some special types
+var (
+	textUnmarshalerType = reflect.TypeOf([]encoding.TextUnmarshaler{}).Elem()
+	durationType        = reflect.TypeOf(time.Duration(0))
+	mailAddressType     = reflect.TypeOf(mail.Address{})
+	ipType              = reflect.TypeOf(net.IP{})
+	macType             = reflect.TypeOf(net.HardwareAddr{})
+)
+
+// isScalar returns true if the type can be parsed from a single string
+func isScalar(t reflect.Type) (scalar, boolean bool) {
+	// If it implements encoding.TextUnmarshaler then use that
+	if t.Implements(textUnmarshalerType) {
+		// scalar=YES, boolean=NO
+		return true, false
+	}
+
+	// If we have a pointer then dereference it
+	if t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+
+	// Check for other special types
+	switch t {
+	case durationType, mailAddressType, ipType, macType:
+		// scalar=YES, boolean=NO
+		return true, false
+	}
+
+	// Fall back to checking the kind
+	switch t.Kind() {
+	case reflect.Bool:
+		// scalar=YES, boolean=YES
+		return true, true
+	case reflect.String, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
+		reflect.Float32, reflect.Float64:
+		// scalar=YES, boolean=NO
+		return true, false
+	}
+	// scalar=NO, boolean=NO
+	return false, false
+}
+
 // set a value from a string
 func setScalar(v reflect.Value, s string) error {
 	if !v.CanSet() {
@@ -35,11 +81,32 @@ func setScalar(v reflect.Value, s string) error {
 	// Switch on concrete type
 	switch scalar.(type) {
 	case time.Duration:
-		x, err := time.ParseDuration(s)
+		duration, err := time.ParseDuration(s)
+		if err != nil {
+			return err
+		}
+		v.Set(reflect.ValueOf(duration))
+		return nil
+	case mail.Address:
+		addr, err := mail.ParseAddress(s)
+		if err != nil {
+			return err
+		}
+		v.Set(reflect.ValueOf(*addr))
+		return nil
+	case net.IP:
+		ip := net.ParseIP(s)
+		if ip == nil {
+			return fmt.Errorf(`invalid IP address: "%s"`, s)
+		}
+		v.Set(reflect.ValueOf(ip))
+		return nil
+	case net.HardwareAddr:
+		ip, err := net.ParseMAC(s)
 		if err != nil {
 			return err
 		}
-		v.Set(reflect.ValueOf(x))
+		v.Set(reflect.ValueOf(ip))
 		return nil
 	}