strings: disallow ':' in nicks

This matches the behavior of inspircd at the very least.

Previously, the comment above that section claimed ':' should be
disallowed, but the code didn't do so.

I also simplified the code a little bit and added tests.

irc/strings.go

@@ -44,8 +44,7 @@ func CasefoldChannel(name string) (string, error) {
 	// , is used as a separator
 	// * is used in mask matching
 	// ? is used in mask matching
-	if strings.Contains(lowered, " ") || strings.Contains(lowered, ",") ||
-		strings.Contains(lowered, "*") || strings.Contains(lowered, "?") {
+	if strings.ContainsAny(lowered, " ,*?") {
 		return "", errInvalidCharacter
 	}
 
@@ -73,11 +72,7 @@ func CasefoldName(name string) (string, error) {
 	// # is a channel prefix
 	// ~&@%+ are channel membership prefixes
 	// - I feel like disallowing
-	if strings.Contains(lowered, " ") || strings.Contains(lowered, ",") ||
-		strings.Contains(lowered, "*") || strings.Contains(lowered, "?") ||
-		strings.Contains(lowered, ".") || strings.Contains(lowered, "!") ||
-		strings.Contains(lowered, "@") ||
-		strings.Contains("#~&@%+-", string(lowered[0])) {
+	if strings.ContainsAny(lowered, " ,*?.!@:") || strings.ContainsAny(string(lowered[0]), "#~&@%+-") {
 		return "", errInvalidCharacter
 	}
 

irc/strings_test.go

@@ -0,0 +1,105 @@
+// Copyright (c) 2017 Euan Kemp
+// released under the MIT license
+
+package irc
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestCasefoldChannel(t *testing.T) {
+	type channelTest struct {
+		channel string
+		folded  string
+		err     bool
+	}
+	testCases := []channelTest{
+		{
+			channel: "#foo",
+			folded:  "#foo",
+		},
+		{
+			channel: "#rfc1459[noncompliant]",
+			folded:  "#rfc1459[noncompliant]",
+		},
+		{
+			channel: "#{[]}",
+			folded:  "#{[]}",
+		},
+		{
+			channel: "#FOO",
+			folded:  "#foo",
+		},
+		{
+			channel: "#bang!",
+			folded:  "#bang!",
+		},
+		{
+			channel: "#",
+			folded:  "#",
+		},
+	}
+
+	for _, errCase := range []string{
+		"", "#*starpower", "# NASA", "#interro?", "OOF#", "foo",
+	} {
+		testCases = append(testCases, channelTest{channel: errCase, err: true})
+	}
+
+	for i, tt := range testCases {
+		t.Run(fmt.Sprintf("case %d: %s", i, tt.channel), func(t *testing.T) {
+			res, err := CasefoldChannel(tt.channel)
+			if tt.err {
+				if err == nil {
+					t.Errorf("expected error")
+				}
+				return
+			}
+			if tt.folded != res {
+				t.Errorf("expected %v to be %v", tt.folded, res)
+			}
+		})
+	}
+}
+
+func TestCasefoldName(t *testing.T) {
+	type nameTest struct {
+		name   string
+		folded string
+		err    bool
+	}
+	testCases := []nameTest{
+		{
+			name:   "foo",
+			folded: "foo",
+		},
+		{
+			name:   "FOO",
+			folded: "foo",
+		},
+	}
+
+	for _, errCase := range []string{
+		"", "#", "foo,bar", "star*man*junior", "lo7t?",
+		"f.l", "excited!nick", "foo@bar", ":trail",
+		"~o", "&o", "@o", "%h", "+v", "-m",
+	} {
+		testCases = append(testCases, nameTest{name: errCase, err: true})
+	}
+
+	for i, tt := range testCases {
+		t.Run(fmt.Sprintf("case %d: %s", i, tt.name), func(t *testing.T) {
+			res, err := CasefoldName(tt.name)
+			if tt.err {
+				if err == nil {
+					t.Errorf("expected error")
+				}
+				return
+			}
+			if tt.folded != res {
+				t.Errorf("expected %v to be %v", tt.folded, res)
+			}
+		})
+	}
+}