Refactor routers directory (#15800)

* refactor routers directory

* move func used for web and api to common

* make corsHandler a function to prohibit side efects

* rm unused func

Co-authored-by: 6543 <6543@obermui.de>

routers/common/middleware.go

@@ -0,0 +1,76 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package common
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"code.gitea.io/gitea/modules/context"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/chi-middleware/proxy"
+	"github.com/go-chi/chi/middleware"
+)
+
+// Middlewares returns common middlewares
+func Middlewares() []func(http.Handler) http.Handler {
+	var handlers = []func(http.Handler) http.Handler{
+		func(next http.Handler) http.Handler {
+			return http.HandlerFunc(func(resp http.ResponseWriter, req *http.Request) {
+				next.ServeHTTP(context.NewResponse(resp), req)
+			})
+		},
+	}
+
+	if setting.ReverseProxyLimit > 0 {
+		opt := proxy.NewForwardedHeadersOptions().
+			WithForwardLimit(setting.ReverseProxyLimit).
+			ClearTrustedProxies()
+		for _, n := range setting.ReverseProxyTrustedProxies {
+			if !strings.Contains(n, "/") {
+				opt.AddTrustedProxy(n)
+			} else {
+				opt.AddTrustedNetwork(n)
+			}
+		}
+		handlers = append(handlers, proxy.ForwardedHeaders(opt))
+	}
+
+	handlers = append(handlers, middleware.StripSlashes)
+
+	if !setting.DisableRouterLog && setting.RouterLogLevel != log.NONE {
+		if log.GetLogger("router").GetLevel() <= setting.RouterLogLevel {
+			handlers = append(handlers, LoggerHandler(setting.RouterLogLevel))
+		}
+	}
+	if setting.EnableAccessLog {
+		handlers = append(handlers, context.AccessLogger())
+	}
+
+	handlers = append(handlers, func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(resp http.ResponseWriter, req *http.Request) {
+			// Why we need this? The Recovery() will try to render a beautiful
+			// error page for user, but the process can still panic again, and other
+			// middleware like session also may panic then we have to recover twice
+			// and send a simple error page that should not panic any more.
+			defer func() {
+				if err := recover(); err != nil {
+					combinedErr := fmt.Sprintf("PANIC: %v\n%s", err, string(log.Stack(2)))
+					log.Error("%v", combinedErr)
+					if setting.IsProd() {
+						http.Error(resp, http.StatusText(500), 500)
+					} else {
+						http.Error(resp, combinedErr, 500)
+					}
+				}
+			}()
+			next.ServeHTTP(resp, req)
+		})
+	})
+	return handlers
+}