From 3c086fb2e67b885d7c3a6bd417b0e2d6fc66074f Mon Sep 17 00:00:00 2001
From: Abiola Ibrahim <abiola89@gmail.com>
Date: Wed, 30 Dec 2015 21:47:37 +0100
Subject: [PATCH] Support for rewrite match group.

---
 middleware/rewrite/rewrite.go      | 15 ++++++++++++---
 middleware/rewrite/rewrite_test.go |  9 +++++++++
 middleware/rewrite/to.go           |  5 +++--
 middleware/rewrite/to_test.go      |  2 +-
 4 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/middleware/rewrite/rewrite.go b/middleware/rewrite/rewrite.go
index f173e754..60cc0b9d 100644
--- a/middleware/rewrite/rewrite.go
+++ b/middleware/rewrite/rewrite.go
@@ -54,7 +54,7 @@ func (s SimpleRule) Rewrite(fs http.FileSystem, r *http.Request) bool {
 		r.Header.Set(headerFieldName, r.URL.RequestURI())
 
 		// attempt rewrite
-		return To(fs, r, s.To)
+		return To(fs, r, s.To, newReplacer(r))
 	}
 	return false
 }
@@ -111,6 +111,7 @@ func NewComplexRule(base, pattern, to string, ext []string, ifs []If) (*ComplexR
 // Rewrite rewrites the internal location of the current request.
 func (r *ComplexRule) Rewrite(fs http.FileSystem, req *http.Request) bool {
 	rPath := req.URL.Path
+	replacer := newReplacer(req)
 
 	// validate base
 	if !middleware.Path(rPath).Matches(r.Base) {
@@ -130,8 +131,16 @@ func (r *ComplexRule) Rewrite(fs http.FileSystem, req *http.Request) bool {
 
 	// validate regexp if present
 	if r.Regexp != nil {
-		if !r.MatchString(rPath[start:]) {
+		matches := r.FindStringSubmatch(rPath[start:])
+		switch len(matches) {
+		case 0:
+			// no match
 			return false
+		default:
+			// set regexp match variables {1}, {2} ...
+			for i := 1; i < len(matches); i++ {
+				replacer.Set(fmt.Sprint(i), matches[i])
+			}
 		}
 	}
 
@@ -143,7 +152,7 @@ func (r *ComplexRule) Rewrite(fs http.FileSystem, req *http.Request) bool {
 	}
 
 	// attempt rewrite
-	return To(fs, req, r.To)
+	return To(fs, req, r.To, replacer)
 }
 
 // matchExt matches rPath against registered file extensions.
diff --git a/middleware/rewrite/rewrite_test.go b/middleware/rewrite/rewrite_test.go
index a538b79d..5b891606 100644
--- a/middleware/rewrite/rewrite_test.go
+++ b/middleware/rewrite/rewrite_test.go
@@ -31,6 +31,9 @@ func TestRewrite(t *testing.T) {
 		{"/abcd/", "ab", "/a/{dir}/{file}", ".html|"},
 		{"/abcde/", "ab", "/a#{fragment}", ".html|"},
 		{"/ab/", `.*\.jpg`, "/ajpg", ""},
+		{"/reggrp", `/ad/([0-9]+)([a-z]*)`, "/a{1}/{2}", ""},
+		{"/reg2grp", `(.*)`, "/{1}", ""},
+		{"/reg3grp", `(.*)/(.*)/(.*)`, "/{1}{2}{3}", ""},
 	}
 
 	for _, regexpRule := range regexps {
@@ -81,6 +84,12 @@ func TestRewrite(t *testing.T) {
 		{"/abcde/abcde.html", "/a"},
 		{"/abcde/abcde.html#1234", "/a#1234"},
 		{"/ab/ab.jpg", "/ajpg"},
+		{"/reggrp/ad/12", "/a12"},
+		{"/reggrp/ad/124a", "/a124/a"},
+		{"/reggrp/ad/124abc", "/a124/abc"},
+		{"/reg2grp/ad/124abc", "/ad/124abc"},
+		{"/reg3grp/ad/aa/66", "/adaa66"},
+		{"/reg3grp/ad612/n1n/ab", "/ad612n1nab"},
 	}
 
 	for i, test := range tests {
diff --git a/middleware/rewrite/to.go b/middleware/rewrite/to.go
index d6c7f521..8a577c5e 100644
--- a/middleware/rewrite/to.go
+++ b/middleware/rewrite/to.go
@@ -6,14 +6,15 @@ import (
 	"net/url"
 	"path"
 	"strings"
+
+	"github.com/mholt/caddy/middleware"
 )
 
 // To attempts rewrite. It attempts to rewrite to first valid path
 // or the last path if none of the paths are valid.
 // Returns true if rewrite is successful and false otherwise.
-func To(fs http.FileSystem, r *http.Request, to string) bool {
+func To(fs http.FileSystem, r *http.Request, to string, replacer middleware.Replacer) bool {
 	tos := strings.Fields(to)
-	replacer := newReplacer(r)
 
 	// try each rewrite paths
 	t := ""
diff --git a/middleware/rewrite/to_test.go b/middleware/rewrite/to_test.go
index 2d8b535a..6133c0b6 100644
--- a/middleware/rewrite/to_test.go
+++ b/middleware/rewrite/to_test.go
@@ -36,7 +36,7 @@ func TestTo(t *testing.T) {
 		if err != nil {
 			t.Error(err)
 		}
-		To(fs, r, test.to)
+		To(fs, r, test.to, newReplacer(r))
 		if uri(r.URL) != test.expected {
 			t.Errorf("Test %v: expected %v found %v", i, test.expected, uri(r.URL))
 		}