Refactor utf-8 conversion (irc) (#1767)

bridge/irc/charset.go

@@ -0,0 +1,32 @@
+package birc
+
+import (
+	"golang.org/x/text/encoding"
+	"golang.org/x/text/encoding/japanese"
+	"golang.org/x/text/encoding/korean"
+	"golang.org/x/text/encoding/simplifiedchinese"
+	"golang.org/x/text/encoding/traditionalchinese"
+	"golang.org/x/text/encoding/unicode"
+)
+
+var encoders = map[string]encoding.Encoding{
+	"utf-8":       unicode.UTF8,
+	"iso-2022-jp": japanese.ISO2022JP,
+	"big5":        traditionalchinese.Big5,
+	"gbk":         simplifiedchinese.GBK,
+	"euc-kr":      korean.EUCKR,
+	"gb2312":      simplifiedchinese.HZGB2312,
+	"shift-jis":   japanese.ShiftJIS,
+	"euc-jp":      japanese.EUCJP,
+	"gb18030":     simplifiedchinese.GB18030,
+}
+
+func toUTF8(from string, input string) string {
+	enc, ok := encoders[from]
+	if !ok {
+		return input
+	}
+
+	res, _ := enc.NewDecoder().String(input)
+	return res
+}