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
new file mode 100644
index 0000000000000000000000000000000000000000..7c2adf68b45e2113d7a5dc5ebe30a134135ae18f
--- /dev/null
+++ b/server/router/example_test.go
@@ -0,0 +1,123 @@
+// 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"
+	"log"
+	"math/rand"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"time"
+
+	"golang.org/x/net/context"
+
+	"github.com/luci/luci-go/server/router"
+)
+
+var (
+	durations  []time.Duration

[nodir, 2016/06/16 04:20:25]

consider removing, see below

[nishanths, 2016/06/16 22:11:26]

Done.

+	client     *http.Client

[nodir, 2016/06/16 04:20:25]

unsed

[nishanths, 2016/06/16 22:11:26]

Removed.

+	testServer *httptest.Server

[nodir, 2016/06/16 04:20:25]

unused

[nishanths, 2016/06/16 22:11:26]

Removed.

+)
+
+func Logger(c *router.Context, next router.Handler) {
+	log.Println(c.Request.URL.String())
+	next(c)
+}
+
+func Monitor(c *router.Context, next router.Handler) {
+	start := time.Now()
+	next(c)
+	durations = append(durations, time.Since(start))

[nodir, 2016/06/16 04:20:25]

maybe just print it to stdout? it will be more visible in output and will
simplify code

[nishanths, 2016/06/16 22:11:26]

Done.

+}
+
+func AuthCheck(c *router.Context, next router.Handler) {
+	var authenticated bool
+	if !authenticated {
+		c.WriteHeader(http.StatusUnauthorized)
+		return
+	}
+	next(c)
+}
+
+func GenerateRandom(c *router.Context, next router.Handler) {
+	secret := rand.Int()
+	c.Context = context.WithValue(c.Context, "secret", secret)
+	next(c)
+}
+
+func Root(c *router.Context) {
+	c.WriteHeader(http.StatusOK)
+}
+
+func Hello(c *router.Context) {
+	name := c.Params[0].Value
+	fmt.Fprintf(c, "Hello, %s", name)
+}
+
+func Random(c *router.Context) {
+	s := c.Value("secret").(int)
+	fmt.Fprintf(c, "secret: %d", s)
+}
+
+type Response struct {
+	status int
+	body   []byte
+}
+
+func (r Response) String() string {
+	if len(r.body) == 0 {
+		return strconv.Itoa(r.status)
+	}
+	return fmt.Sprintf("%d %s", r.status, r.body)
+}
+
+func makeRequest(client *http.Client, url string) Response {
+	res, err := client.Get(url + "/")
+	if err != nil {
+		panic(err)
+	}
+	defer res.Body.Close()
+	status := res.StatusCode
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		panic(err)
+	}
+	return Response{status, body}

[nodir, 2016/06/16 04:20:25]

to simplify, I'd return sprintf right here

[nishanths, 2016/06/16 22:11:26]

Done.

+}
+
+func makeRequests(server *httptest.Server) {

[nodir, 2016/06/16 04:20:25]

perhaps "url string" would be enough here

[nishanths, 2016/06/16 22:11:26]

Done.

+	c := &http.Client{}
+	c.Timeout = 10 * time.Second

[nodir, 2016/06/16 04:20:25]

why this is needed?

[nishanths, 2016/06/16 22:11:26]

If Timeout==0, the client waits infinitely for a response
(https://golang.org/src/net/http/client.go#L290). So, for instance, if the run
function had a bug, the tests would not finish running.

func run(...) {
       for {
              // infinite loop     
       }
}

But now that I think of it, the tests not finishing running holds true for any
such poorly written functions. 
Removed it. Also removed from router_test.go.

+	fmt.Println(makeRequest(c, server.URL+"/"))
+	fmt.Println(makeRequest(c, server.URL+"/hello/darknessmyoldfriend"))
+	fmt.Println(makeRequest(c, server.URL+"/authenticated/random"))
+}
+
+// Example_createServer demonstrates creating an HTTP server using the imported
+// router package.
+func Example_createServer() {
+	r := router.New()
+	r.Use(router.MiddlewareChain{Logger, Monitor})
+	r.GET("/", nil, Root)
+	r.GET("/hello/:name", nil, Hello)

[nodir, 2016/06/16 04:20:25]

consider inlining Root, Hello and Random to make example simpler

please remember that example has educational purpose and has higher requirements
for simplicity

[nishanths, 2016/06/16 22:11:26]

Done.

+
+	auth := r.Subrouter("authenticated")
+	auth.Use(router.MiddlewareChain{AuthCheck})
+	auth.GET("/random", router.MiddlewareChain{GenerateRandom}, Random)
+
+	server := httptest.NewServer(r)
+	defer server.Close()
+
+	makeRequests(server)
+
+	// Output:
+	// 200
+	// 200 Hello, darknessmyoldfriend
+	// 401
+}