package xmlUtil

import (
	"bytes"
	"encoding/xml"
	"fmt"
	"io"
	"strings"

	"golang.org/x/text/encoding/simplifiedchinese"
	"golang.org/x/text/transform"
)

func ChineseCharsetReader(charset string, input io.Reader) (io.Reader, error) {
	switch strings.ToUpper(charset) {
	case "GB18030":
		return transform.NewReader(input, simplifiedchinese.GB18030.NewDecoder()), nil
	case "GBK":
		return transform.NewReader(input, simplifiedchinese.GBK.NewDecoder()), nil
	case "GB2312", "HZ-GB2312":
		return transform.NewReader(input, simplifiedchinese.HZGB2312.NewDecoder()), nil
	default:
		return nil, fmt.Errorf("unsupported charset: %s", charset)
	}
}

func FormatXMLString(input string) (string, error) {
	var b bytes.Buffer
	decoder := xml.NewDecoder(strings.NewReader(input))
	decoder.CharsetReader = ChineseCharsetReader
	encoder := xml.NewEncoder(&b)
	encoder.Indent("", "	")

	for {
		token, err := decoder.Token()
		if err == io.EOF {
			break
		}
		if err != nil {
			return "", err
		}
		if err := encoder.EncodeToken(token); err != nil {
			return "", err
		}
	}

	encoder.Flush()
	return b.String(), nil
}