added real_ip and cloudflare_real_ip middlewares, fixed that some middlewares does not work properly

internal/net/http/middleware/custom_error_page.go

@@ -0,0 +1,75 @@
+package middleware
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/http"
+	"path/filepath"
+	"strings"
+
+	"github.com/sirupsen/logrus"
+	"github.com/yusing/go-proxy/internal/api/v1/error_page"
+	"github.com/yusing/go-proxy/internal/common"
+	gpHTTP "github.com/yusing/go-proxy/internal/net/http"
+)
+
+var CustomErrorPage = &Middleware{
+	before: func(next http.Handler, w ResponseWriter, r *Request) {
+		if !ServeStaticErrorPageFile(w, r) {
+			next.ServeHTTP(w, r)
+		}
+	},
+	modifyResponse: func(resp *Response) error {
+		// only handles non-success status code and html/plain content type
+		contentType := gpHTTP.GetContentType(resp.Header)
+		if !gpHTTP.IsSuccess(resp.StatusCode) && (contentType.IsHTML() || contentType.IsPlainText()) {
+			errorPage, ok := error_page.GetErrorPageByStatus(resp.StatusCode)
+			if ok {
+				errPageLogger.Debugf("error page for status %d loaded", resp.StatusCode)
+				io.Copy(io.Discard, resp.Body) // drain the original body
+				resp.Body.Close()
+				resp.Body = io.NopCloser(bytes.NewReader(errorPage))
+				resp.ContentLength = int64(len(errorPage))
+				resp.Header.Set("Content-Length", fmt.Sprint(len(errorPage)))
+				resp.Header.Set("Content-Type", "text/html; charset=utf-8")
+			} else {
+				errPageLogger.Errorf("unable to load error page for status %d", resp.StatusCode)
+			}
+			return nil
+		}
+		return nil
+	},
+}
+
+func ServeStaticErrorPageFile(w http.ResponseWriter, r *http.Request) bool {
+	path := r.URL.Path
+	if path != "" && path[0] != '/' {
+		path = "/" + path
+	}
+	if strings.HasPrefix(path, common.StaticFilePathPrefix) {
+		filename := path[len(common.StaticFilePathPrefix):]
+		file, ok := error_page.GetStaticFile(filename)
+		if !ok {
+			errPageLogger.Errorf("unable to load resource %s", filename)
+			return false
+		} else {
+			ext := filepath.Ext(filename)
+			switch ext {
+			case ".html":
+				w.Header().Set("Content-Type", "text/html; charset=utf-8")
+			case ".js":
+				w.Header().Set("Content-Type", "application/javascript; charset=utf-8")
+			case ".css":
+				w.Header().Set("Content-Type", "text/css; charset=utf-8")
+			default:
+				errPageLogger.Errorf("unexpected file type %q for %s", ext, filename)
+			}
+			w.Write(file)
+			return true
+		}
+	}
+	return false
+}
+
+var errPageLogger = logrus.WithField("middleware", "error_page")