Add x-goog-visitor-id (#360)

Co-authored-by: shoce <yogze@icloud.com>

Author: corny

client.go

@@ -605,6 +605,12 @@ func (c *Client) httpPost(ctx context.Context, url string, body interface{}) (*h
 	req.Header.Set("Content-Type", "application/json")
 	req.Header.Set("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8")
 
+	if xgoogvisitorid, err := getVisitorId(); err != nil {
+		return nil, err
+	} else {
+		req.Header.Set("x-goog-visitor-id", xgoogvisitorid)
+	}
+
 	resp, err := c.httpDo(req)
 	if err != nil {
 		return nil, err
@@ -618,6 +624,58 @@ func (c *Client) httpPost(ctx context.Context, url string, body interface{}) (*h
 	return resp, nil
 }
 
+var VisitorIdMaxAge = 10 * time.Hour
+var VisitorId struct {
+	Id    string
+	Ctime time.Time
+}
+
+func getVisitorId() (string, error) {
+	if VisitorId.Id != "" && time.Since(VisitorId.Ctime) < VisitorIdMaxAge {
+		return VisitorId.Id, nil
+	}
+
+	const sep = "\nytcfg.set("
+
+	var req http.Request
+	req.Header = http.Header{}
+	req.Header.Set("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.4 Safari/605.1.15")
+	req.URL = &url.URL{}
+	req.URL.Host = "www.youtube.com"
+	req.URL.Scheme = "https"
+	resp, err := http.DefaultClient.Do(&req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	data, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", err
+	}
+	_, data1, found := strings.Cut(string(data), sep)
+	if !found {
+		return "", err
+	}
+	var value struct {
+		InnertubeContext struct {
+			Client struct {
+				VisitorData string
+			}
+		} `json:"INNERTUBE_CONTEXT"`
+	}
+	if err := json.NewDecoder(strings.NewReader(data1)).Decode(&value); err != nil {
+		return "", err
+	}
+
+	if VisitorId.Id, err = url.PathUnescape(value.InnertubeContext.Client.VisitorData); err != nil {
+		return "", err
+	}
+
+	VisitorId.Ctime = time.Now()
+
+	return VisitorId.Id, nil
+}
+
 // httpPostBodyBytes reads the whole HTTP body and returns it
 func (c *Client) httpPostBodyBytes(ctx context.Context, url string, body interface{}) ([]byte, error) {
 	resp, err := c.httpPost(ctx, url, body)