Refactor: Rename NanoKVM to BatchuKVM and update server URL

server/utils/http.go

@@ -0,0 +1,56 @@
+package utils
+
+import (
+	"errors"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func Download(req *http.Request, target string) error {
+	log.Debugf("downloading %s to %s", req.URL.String(), target)
+	err := os.MkdirAll(filepath.Dir(target), 0o755)
+	if err != nil {
+		log.Errorf("create dir %s err: %s", filepath.Dir(target), err)
+		return err
+	}
+	out, err := os.OpenFile(target, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0o755)
+	if err != nil {
+		log.Errorf("cannot create file '%s', error: %s", target, err)
+		return err
+	}
+	defer func() {
+		_ = out.Close()
+	}()
+
+	resp, err := (&http.Client{}).Do(req)
+	if err != nil {
+		log.Errorf("request error: %s", err)
+		return err
+	}
+	defer func() {
+		_ = resp.Body.Close()
+	}()
+
+	if resp.StatusCode != http.StatusOK {
+		log.Errorf("request failed, status code: %d", resp.StatusCode)
+		return errors.New("update website is inaccessible right now")
+	}
+
+	contentType := resp.Header.Get("Content-Type")
+	if contentType != "application/octet-stream" && contentType != "application/zip" && contentType != "application/gzip" {
+		log.Debugf("unexpected content-type, it should be either octet-stream or (g)zip, but got: %s", contentType)
+		return errors.New("unsupported content type")
+	}
+
+	_, err = io.Copy(out, resp.Body)
+	if err != nil {
+		log.Errorf("download file to %s err: %s", target, err)
+		return err
+	}
+
+	return nil
+}