feat: add gzip support for static filter (#1875)

* feat: add gzip support for static filter

* Update static_filter.go

---------

Co-authored-by: hsluoyz <hsluoyz@qq.com>

routers/static_filter.go

@@ -15,6 +15,8 @@
 package routers
 
 import (
+	"compress/gzip"
+	"io"
 	"net/http"
 	"os"
 	"strings"
@@ -28,6 +30,7 @@ import (
 var (
 	oldStaticBaseUrl = "https://cdn.casbin.org"
 	newStaticBaseUrl = conf.GetConfigString("staticBaseUrl")
+	enableGzip, _    = conf.GetConfigBool("enableGzip")
 )
 
 func StaticFilter(ctx *context.Context) {
@@ -53,7 +56,7 @@ func StaticFilter(ctx *context.Context) {
 
 	path2 := strings.TrimLeft(path, "web/build/images/")
 	if util.FileExist(path2) {
-		http.ServeFile(ctx.ResponseWriter, ctx.Request, path2)
+		makeGzipResponse(ctx.ResponseWriter, ctx.Request, path2)
 		return
 	}
 
@@ -62,7 +65,7 @@ func StaticFilter(ctx *context.Context) {
 	}
 
 	if oldStaticBaseUrl == newStaticBaseUrl {
-		http.ServeFile(ctx.ResponseWriter, ctx.Request, path)
+		makeGzipResponse(ctx.ResponseWriter, ctx.Request, path)
 	} else {
 		serveFileWithReplace(ctx.ResponseWriter, ctx.Request, path, oldStaticBaseUrl, newStaticBaseUrl)
 	}
@@ -89,3 +92,24 @@ func serveFileWithReplace(w http.ResponseWriter, r *http.Request, name string, o
 		panic(err)
 	}
 }
+
+type gzipResponseWriter struct {
+	io.Writer
+	http.ResponseWriter
+}
+
+func (w gzipResponseWriter) Write(b []byte) (int, error) {
+	return w.Writer.Write(b)
+}
+
+func makeGzipResponse(w http.ResponseWriter, r *http.Request, path string) {
+	if !enableGzip || !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
+		http.ServeFile(w, r, path)
+		return
+	}
+	w.Header().Set("Content-Encoding", "gzip")
+	gz := gzip.NewWriter(w)
+	defer gz.Close()
+	gzw := gzipResponseWriter{Writer: gz, ResponseWriter: w}
+	http.ServeFile(gzw, r, path)
+}