fix #306

Fix spurious bidi rule violations in casefolding channel names
by stripping the # before starting the casefolding.

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 len(name) == 0 {
-
-	if err != nil {
-		return "", err
-	} else if len(lowered) == 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.

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})
 	}