From 79786009ced7c10d15ddc495f395965f1a4a7a94 Mon Sep 17 00:00:00 2001
From: Zeal Jagannatha <zealjagannatha@gmail.com>
Date: Mon, 23 Nov 2015 19:55:46 -0800
Subject: [PATCH] Added support for regexp flags

---
 flags_test.go | 11 +++++++++++
 parsers.go    | 13 +++++++++++++
 values.go     | 29 +++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

diff --git a/flags_test.go b/flags_test.go
index 64a3be5..9528e64 100644
--- a/flags_test.go
+++ b/flags_test.go
@@ -107,3 +107,14 @@ func TestRequiredWithEnvar(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, 123, *flag)
 }
+
+func TestRegexp(t *testing.T) {
+	app := New("test", "")
+	flag := app.Flag("reg", "").Regexp()
+	_, err := app.Parse([]string{"--reg", "^abc$"})
+	assert.NoError(t, err)
+	assert.NotNil(t, *flag)
+	assert.Equal(t, "^abc$", (*flag).String())
+	assert.Regexp(t, *flag, "abc")
+	assert.NotRegexp(t, *flag, "abcd")
+}
diff --git a/parsers.go b/parsers.go
index d9ad57e..3144fc1 100644
--- a/parsers.go
+++ b/parsers.go
@@ -4,6 +4,7 @@ import (
 	"net"
 	"net/url"
 	"os"
+	"regexp"
 	"time"
 
 	"github.com/alecthomas/units"
@@ -210,3 +211,15 @@ func (p *parserMixin) Counter() (target *int) {
 func (p *parserMixin) CounterVar(target *int) {
 	p.SetValue(newCounterValue(target))
 }
+
+// Regexp
+func (p *parserMixin) Regexp() (target **regexp.Regexp) {
+	target = new(*regexp.Regexp)
+	p.RegexpVar(target)
+	return
+}
+
+// Regexp
+func (p *parserMixin) RegexpVar(target **regexp.Regexp) {
+	p.SetValue(newRegexpValue(target))
+}
diff --git a/values.go b/values.go
index dbbb0e0..23ee87b 100644
--- a/values.go
+++ b/values.go
@@ -445,3 +445,32 @@ func (c *counterValue) Set(s string) error {
 func (c *counterValue) Get() interface{} { return (int)(*c) }
 func (c *counterValue) IsBoolFlag() bool { return true }
 func (c *counterValue) String() string   { return fmt.Sprintf("%d", *c) }
+
+// -- regexp.Regexp value
+type regexpValue struct {
+	r **regexp.Regexp
+}
+
+func newRegexpValue(r **regexp.Regexp) *regexpValue {
+	return &regexpValue{r}
+}
+
+func (r *regexpValue) Set(value string) error {
+	if re, err := regexp.Compile(value); err != nil {
+		return err
+	} else {
+		*r.r = re
+		return nil
+	}
+}
+
+func (r *regexpValue) Get() interface{} {
+	return (*regexp.Regexp)(*r.r)
+}
+
+func (r *regexpValue) String() string {
+	if *r.r == nil {
+		return "<nil>"
+	}
+	return (*r.r).String()
+}