From ecf59d4a55448e1cfbc558e09a83a422e0167228 Mon Sep 17 00:00:00 2001
From: gihnius <gihnius@gmail.com>
Date: Fri, 21 Mar 2014 10:52:46 +0800
Subject: [PATCH 1/3] add target blank attr

---
 html.go        | 35 +++++++++++++++++++++++++++++++++++
 inline_test.go | 16 ++++++++++++++--
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/html.go b/html.go
index 38aceed..b033489 100644
--- a/html.go
+++ b/html.go
@@ -31,6 +31,7 @@ const (
 	HTML_SKIP_SCRIPT                          // skip embedded <script> elements
 	HTML_SAFELINK                             // only link to trusted protocols
 	HTML_NOFOLLOW_LINKS                       // only link with rel="nofollow"
+	HTML_HREF_TARGET_BLANK                    // add a blank target
 	HTML_TOC                                  // generate a table of contents
 	HTML_OMIT_CONTENTS                        // skip the main contents (for a standalone table of contents)
 	HTML_COMPLETE_PAGE                        // generate a complete HTML page
@@ -413,6 +414,15 @@ func (options *Html) AutoLink(out *bytes.Buffer, link []byte, kind int) {
 		out.WriteString("mailto:")
 	}
 	attrEscape(out, link)
+
+	if options.flags&HTML_NOFOLLOW_LINKS != 0 {
+		out.WriteString("\" rel=\"nofollow")
+	}
+	// blank target only add to external link
+	if options.flags&HTML_HREF_TARGET_BLANK != 0 && !isRelativeLink(link) {
+		out.WriteString("\" target=\"_blank")
+	}
+
 	out.WriteString("\">")
 
 	// Pretty print: if we get an email address as
@@ -503,6 +513,11 @@ func (options *Html) Link(out *bytes.Buffer, link []byte, title []byte, content
 	if options.flags&HTML_NOFOLLOW_LINKS != 0 {
 		out.WriteString("\" rel=\"nofollow")
 	}
+	// blank target only add to external link
+	if options.flags&HTML_HREF_TARGET_BLANK != 0 && !isRelativeLink(link) {
+		out.WriteString("\" target=\"_blank")
+	}
+
 	out.WriteString("\">")
 	out.Write(content)
 	out.WriteString("</a>")
@@ -788,3 +803,23 @@ func doubleSpace(out *bytes.Buffer) {
 		out.WriteByte('\n')
 	}
 }
+
+func isRelativeLink(link []byte) (yes bool) {
+	yes = false
+
+	// a tag begin with '#'
+	if link[0] == '#' {
+		yes = true
+	}
+
+	// link begin with '/' but not '//', the second maybe a protocol relative link
+	if len(link) >= 2 && link[0] == '/' && link[1] != '/' {
+		yes = true
+	}
+
+	// only the root '/'
+	if len(link) == 1 && link[0] == '/' {
+		yes = true
+	}
+	return
+}
diff --git a/inline_test.go b/inline_test.go
index 405e121..6369d7a 100644
--- a/inline_test.go
+++ b/inline_test.go
@@ -429,6 +429,18 @@ func TestNofollowLink(t *testing.T) {
 	doTestsInlineParam(t, tests, 0, HTML_SAFELINK|HTML_NOFOLLOW_LINKS)
 }
 
+func TestHrefTargetBlank(t *testing.T) {
+	var tests = []string{
+        // internal link
+		"[foo](/bar/)\n",
+		"<p><a href=\"/bar/\">foo</a></p>\n",
+
+		"[foo](http://example.com)\n",
+		"<p><a href=\"http://example.com\" target=\"_blank\">foo</a></p>\n",
+	}
+	doTestsInlineParam(t, tests, 0, HTML_SAFELINK|HTML_HREF_TARGET_BLANK)
+}
+
 func TestSafeInlineLink(t *testing.T) {
 	var tests = []string{
 		"[foo](/bar/)\n",
@@ -605,9 +617,9 @@ func TestFootnotes(t *testing.T) {
 [^b]: Paragraph 1
 
 	Paragraph 2
-	
+
 	` + "```\n\tsome code\n\t```" + `
-	
+
 	Paragraph 3
 
 No longer in the footnote

From 93484b1424ae21ae8bef25778033d4a89bd4dba9 Mon Sep 17 00:00:00 2001
From: gihnius <gihnius@gmail.com>
Date: Fri, 21 Mar 2014 11:14:58 +0800
Subject: [PATCH 2/3] add nofollow ref for non internal links only

---
 html.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/html.go b/html.go
index b033489..7d7a0eb 100644
--- a/html.go
+++ b/html.go
@@ -415,7 +415,7 @@ func (options *Html) AutoLink(out *bytes.Buffer, link []byte, kind int) {
 	}
 	attrEscape(out, link)
 
-	if options.flags&HTML_NOFOLLOW_LINKS != 0 {
+	if options.flags&HTML_NOFOLLOW_LINKS != 0 && !isRelativeLink(link) {
 		out.WriteString("\" rel=\"nofollow")
 	}
 	// blank target only add to external link
@@ -510,7 +510,7 @@ func (options *Html) Link(out *bytes.Buffer, link []byte, title []byte, content
 		out.WriteString("\" title=\"")
 		attrEscape(out, title)
 	}
-	if options.flags&HTML_NOFOLLOW_LINKS != 0 {
+	if options.flags&HTML_NOFOLLOW_LINKS != 0 && !isRelativeLink(link) {
 		out.WriteString("\" rel=\"nofollow")
 	}
 	// blank target only add to external link

From c9977f0c0bc6d08e7537bffcf0d2dbd622fba98d Mon Sep 17 00:00:00 2001
From: gihnius <gihnius@gmail.com>
Date: Fri, 21 Mar 2014 11:17:31 +0800
Subject: [PATCH 3/3] test: add nofollow ref for non internal links only

---
 inline_test.go | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/inline_test.go b/inline_test.go
index 6369d7a..cafd242 100644
--- a/inline_test.go
+++ b/inline_test.go
@@ -424,7 +424,10 @@ func TestInlineLink(t *testing.T) {
 func TestNofollowLink(t *testing.T) {
 	var tests = []string{
 		"[foo](/bar/)\n",
-		"<p><a href=\"/bar/\" rel=\"nofollow\">foo</a></p>\n",
+		"<p><a href=\"/bar/\">foo</a></p>\n",
+
+		"[foo](http://bar.com/foo/)\n",
+		"<p><a href=\"http://bar.com/foo/\" rel=\"nofollow\">foo</a></p>\n",
 	}
 	doTestsInlineParam(t, tests, 0, HTML_SAFELINK|HTML_NOFOLLOW_LINKS)
 }