HTML encoding is not autodetected properly about colly HOT 6 OPEN

package colly

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"mime"
	"net/http"
	"strings"

	"github.com/PuerkitoBio/goquery"
	"github.com/saintfish/chardet"
	"golang.org/x/net/html/charset"
)

// Response is the representation of a HTTP response made by a Collector
type Response struct {
	// StatusCode is the status code of the Response
	StatusCode int
	// Body is the content of the Response
	Body []byte
	// Ctx is a context between a Request and a Response
	Ctx *Context
	// Request is the Request object of the response
	Request *Request
	// Headers contains the Response's HTTP headers
	Headers *http.Header
	// Trace contains the HTTPTrace for the request. Will only be set by the
	// collector if Collector.TraceHTTP is set to true.
	Trace *HTTPTrace
}

// Save writes response body to disk
func (r *Response) Save(fileName string) error {
	return ioutil.WriteFile(fileName, r.Body, 0644)
}

// FileName returns the sanitized file name parsed from "Content-Disposition"
// header or from URL
func (r *Response) FileName() string {
	_, params, err := mime.ParseMediaType(r.Headers.Get("Content-Disposition"))
	if fName, ok := params["filename"]; ok && err == nil {
		return SanitizeFileName(fName)
	}
	if r.Request.URL.RawQuery != "" {
		return SanitizeFileName(fmt.Sprintf("%s_%s", r.Request.URL.Path, r.Request.URL.RawQuery))
	}
	return SanitizeFileName(strings.TrimPrefix(r.Request.URL.Path, "/"))
}

func (r *Response) fixCharset(detectCharset bool, defaultEncoding string) error {
	if len(r.Body) == 0 {
		return nil
	}
	if defaultEncoding != "" {
		tmpBody, err := encodeBytes(r.Body, "text/plain; charset="+defaultEncoding)
		if err != nil {
			return err
		}
		r.Body = tmpBody
		return nil
	}
	contentType := strings.ToLower(r.Headers.Get("Content-Type"))

	if strings.Contains(contentType, "image/") ||
		strings.Contains(contentType, "video/") ||
		strings.Contains(contentType, "audio/") ||
		strings.Contains(contentType, "font/") {
		// These MIME types should not have textual data.

		return nil
	}

	if !strings.Contains(contentType, "charset") && strings.Contains(contentType, "text/html") {
		if !detectCharset {
			return nil
		}
		contentTypeBody := checkContentTypeInBody(string(r.Body))
		if contentTypeBody != "" {
			contentType = contentTypeBody
		}
	}

	if !strings.Contains(contentType, "charset") {
		if !detectCharset {
			return nil
		}
		d := chardet.NewTextDetector()
		r, err := d.DetectBest(r.Body)
		if err != nil {
			return err
		}
		contentType = "text/plain; charset=" + r.Charset
	}
	if strings.Contains(contentType, "utf-8") || strings.Contains(contentType, "utf8") {
		return nil
	}
	tmpBody, err := encodeBytes(r.Body, contentType)
	if err != nil {
		return err
	}
	r.Body = tmpBody
	return nil
}

func encodeBytes(b []byte, contentType string) ([]byte, error) {
	r, err := charset.NewReader(bytes.NewReader(b), contentType)
	if err != nil {
		return nil, err
	}
	return ioutil.ReadAll(r)
}

func checkContentTypeInBody(b string) string {
	reader := strings.NewReader(b)
	doc, err := goquery.NewDocumentFromReader(reader)
	if err != nil {
		fmt.Println(err)
	}
	metaContent, exists := doc.Find("meta[http-equiv='Content-Type']").Attr("content")
	if exists {
		return metaContent
	} else {
		return ""
	}
}