From 40e63dbbe8a3076cbbf7808d2f633a368f28d8a6 Mon Sep 17 00:00:00 2001
From: Shivaram Lingamneni <slingamn@cs.stanford.edu>
Date: Wed, 5 Dec 2018 22:35:36 -0500
Subject: [PATCH 1/2] fix #306

Fix spurious bidi rule violations in casefolding channel names
by stripping the # before starting the casefolding.
---
 irc/strings.go      | 21 ++++++++++++++-------
 irc/strings_test.go | 11 +++++++++++
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/irc/strings.go b/irc/strings.go
index 2ccea99c..c5385853 100644
--- a/irc/strings.go
+++ b/irc/strings.go
@@ -39,18 +39,25 @@ func Casefold(str string) (string, error) {
 
 // CasefoldChannel returns a casefolded version of a channel name.
 func CasefoldChannel(name string) (string, error) {
-	lowered, err := Casefold(name)
-
-	if err != nil {
-		return "", err
-	} else if len(lowered) == 0 {
+	if len(name) == 0 {
 		return "", errStringIsEmpty
 	}
 
-	if lowered[0] != '#' {
+	// don't casefold the preceding #'s
+	var start int
+	for start = 0; start < len(name) && name[start] == '#'; start += 1 {
+	}
+
+	if start == 0 {
+		// no preceding #'s
 		return "", errInvalidCharacter
 	}
 
+	lowered, err := Casefold(name[start:])
+	if err != nil {
+		return "", err
+	}
+
 	// space can't be used
 	// , is used as a separator
 	// * is used in mask matching
@@ -59,7 +66,7 @@ func CasefoldChannel(name string) (string, error) {
 		return "", errInvalidCharacter
 	}
 
-	return lowered, err
+	return name[:start] + lowered, err
 }
 
 // CasefoldName returns a casefolded version of a nick/user name.
diff --git a/irc/strings_test.go b/irc/strings_test.go
index 7f23af83..513a4f8f 100644
--- a/irc/strings_test.go
+++ b/irc/strings_test.go
@@ -40,10 +40,21 @@ func TestCasefoldChannel(t *testing.T) {
 			channel: "#",
 			folded:  "#",
 		},
+		{
+			channel: "#中文频道",
+			folded:  "#中文频道",
+		},
+		{
+			// Hebrew; it's up to the client to display this right-to-left, including the #
+			channel: "#שלום",
+			folded:  "#שלום",
+		},
 	}
 
 	for _, errCase := range []string{
 		"", "#*starpower", "# NASA", "#interro?", "OOF#", "foo",
+		// bidi violation mixing latin and hebrew characters:
+		"#shalomעליכם",
 	} {
 		testCases = append(testCases, channelTest{channel: errCase, err: true})
 	}

From 92eca4d795ef60e6364278949738f6445088cfea Mon Sep 17 00:00:00 2001
From: Shivaram Lingamneni <slingamn@cs.stanford.edu>
Date: Thu, 6 Dec 2018 06:46:11 -0500
Subject: [PATCH 2/2] add more test cases

---
 irc/strings_test.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/irc/strings_test.go b/irc/strings_test.go
index 513a4f8f..48a7d538 100644
--- a/irc/strings_test.go
+++ b/irc/strings_test.go
@@ -40,6 +40,14 @@ func TestCasefoldChannel(t *testing.T) {
 			channel: "#",
 			folded:  "#",
 		},
+		{
+			channel: "##",
+			folded:  "##",
+		},
+		{
+			channel: "##Ubuntu",
+			folded:  "##ubuntu",
+		},
 		{
 			channel: "#中文频道",
 			folded:  "#中文频道",