Make HTTP middleware easier to use

server/router/example_test.go

Index: server/router/example_test.go
diff --git a/server/router/example_test.go b/server/router/example_test.go
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+// 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 router_test
+
+import (
+	"fmt"
+	"io/ioutil"
+	"math/rand"
+	"net/http"
+	"net/http/httptest"
+
+	"golang.org/x/net/context"
+
+	"github.com/luci/luci-go/server/router"
+)
+
+func Logger(c *router.Context, next router.Handler) {
+	fmt.Println(c.Request.URL)
+	next(c)
+}
+
+func AuthCheck(c *router.Context, next router.Handler) {
+	var authenticated bool
+	if !authenticated {
+		c.Writer.WriteHeader(http.StatusUnauthorized)
+		c.Writer.Write([]byte("Authentication failed"))
+		return
+	}
+	next(c)
+}
+
+func GenerateSecret(c *router.Context, next router.Handler) {
+	c.Context = context.WithValue(c.Context, "secret", rand.Int())
+	next(c)
+}
+
+func makeRequest(client *http.Client, url string) string {
+	res, err := client.Get(url + "/")
+	if err != nil {
+		panic(err)
+	}
+	defer res.Body.Close()
+	p, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		panic(err)
+	}
+	if len(p) == 0 {
+		return fmt.Sprintf("%d", res.StatusCode)
+	}
+	return fmt.Sprintf("%d %s", res.StatusCode, p)
+}
+
+func makeRequests(url string) {
+	c := &http.Client{}
+	fmt.Println(makeRequest(c, url+"/hello"))
+	fmt.Println(makeRequest(c, url+"/hello/darknessmyoldfriend"))
+	fmt.Println(makeRequest(c, url+"/authenticated/secret"))
+}
+
+// Example_createServer demonstrates creating an HTTP server using the router
+// package.
+func Example_createServer() {
+	r := router.New()
+	r.Use(router.MiddlewareChain{Logger})
+	r.GET("/hello", nil, func(c *router.Context) {
+		fmt.Fprintf(c.Writer, "Hello")
+	})
+	r.GET("/hello/:name", nil, func(c *router.Context) {
+		fmt.Fprintf(c.Writer, "Hello %s", c.Params.ByName("name"))
+	})
+
+	auth := r.Subrouter("authenticated")
+	auth.Use(router.MiddlewareChain{AuthCheck})
+	auth.GET("/secret", router.MiddlewareChain{GenerateSecret}, func(c *router.Context) {
+		fmt.Fprintf(c.Writer, "secret: %d", c.Context.Value("secret"))
+	})
+
+	server := httptest.NewServer(r)
+	defer server.Close()
+
+	makeRequests(server.URL)
+
+	// Output:
+	// /hello
+	// 200 Hello
+	// /hello/darknessmyoldfriend
+	// 200 Hello darknessmyoldfriend
+	// /authenticated/secret
+	// 401 Authentication failed
+}