Make HTTP middleware easier to use

server/settings/admin/settings.go

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package admin
 
 import (
         "net/http"
 
         "github.com/julienschmidt/httprouter"
         "golang.org/x/net/context"
 
         "github.com/luci/luci-go/server/auth"
         "github.com/luci/luci-go/server/auth/xsrf"
+        "github.com/luci/luci-go/server/router"
         "github.com/luci/luci-go/server/settings"
         "github.com/luci/luci-go/server/templates"
 )
 
 type fieldWithValue struct {
         settings.UIField
         Value string
 }
 
 type validationError struct {
@@ skipping 12 matching lines @@
                 templates.MustRender(c, rw, "pages/error.html", templates.Args{
                         "Error": "No such settings",
                 })
                 return
         }
         if err := cb(id, page); err != nil {
                 replyError(c, rw, err)
         }
 }
 
-func settingsPageGET(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
+func settingsPageGET(ctx *router.Context) {
+        c, rw, p := ctx.Context, ctx.Writer, ctx.Params
+
         withPage(c, rw, p, func(id string, page settings.UIPage) error {
                 title, err := page.Title(c)
                 if err != nil {
                         return err
                 }
                 overview, err := page.Overview(c)
                 if err != nil {
                         return err
                 }
                 fields, err := page.Fields(c)
@@ skipping 17 matching lines @@
                         "ID":             id,
                         "Title":          title,
                         "Overview":       overview,
                         "Fields":         withValues,
                         "XsrfTokenField": xsrf.TokenField(c),
                 })
                 return nil
         })
 }
 
-func settingsPagePOST(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
+func settingsPagePOST(ctx *router.Context) {
+        c, rw, r, p := ctx.Context, ctx.Writer, ctx.Request, ctx.Params
+
         withPage(c, rw, p, func(id string, page settings.UIPage) error {
                 title, err := page.Title(c)
                 if err != nil {
                         return err
                 }
                 fields, err := page.Fields(c)
                 if err != nil {
                         return err
                 }
 
@@ skipping 31 matching lines @@
                 if err != nil {
                         return err
                 }
                 templates.MustRender(c, rw, "pages/done.html", templates.Args{
                         "ID":    id,
                         "Title": title,
                 })
                 return nil
         })
 }