storage: update benchmarking emulator with real URLs

- Allow URLs for Go, Node, Java.
- Add 1mb and 100mb files.
- Add --port flag.
- Add README.md.

Change-Id: If650bf88e705de002cac31a82393c7da104b355e
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/44013
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: kokoro <noreply+kokoro@google.com>
diff --git a/storage/internal/benchserver/README.md b/storage/internal/benchserver/README.md
new file mode 100644
index 0000000..53f2175
--- /dev/null
+++ b/storage/internal/benchserver/README.md
@@ -0,0 +1,10 @@
+# benchserver
+
+A simple Storage emulator for benchmarking purposes.
+
+## Running
+
+```
+cd benchserver
+go run *.go --port 8080
+```
diff --git a/storage/internal/benchserver/main.go b/storage/internal/benchserver/main.go
index e24a9e2..204dbda 100644
--- a/storage/internal/benchserver/main.go
+++ b/storage/internal/benchserver/main.go
@@ -16,22 +16,91 @@
 package main
 
 import (
+	"crypto/rand"
 	"encoding/json"
+	"flag"
+	"fmt"
+	"io"
+	"io/ioutil"
 	"log"
 	"net/http"
+	"os"
 
 	"google.golang.org/api/googleapi"
-	"google.golang.org/api/storage/v1"
+	raw "google.golang.org/api/storage/v1"
 )
 
+var (
+	port  = flag.String("port", "", "specify a port to run on")
+	files = map[string][]byte{} // objectName -> contents
+)
+
+func init() {
+	oneMB, err := ioutil.ReadAll(io.LimitReader(rand.Reader, 1000000))
+	if err != nil {
+		log.Fatal(err)
+	}
+	files["oneMB"] = oneMB
+
+	oneHundredMB, err := ioutil.ReadAll(io.LimitReader(rand.Reader, 100000000))
+	if err != nil {
+		log.Fatal(err)
+	}
+	files["oneHundredMB"] = oneHundredMB
+}
+
 func main() {
-	// Serves the read from an object.
-	http.HandleFunc("/some-bucket-name/some-object-name", func(resp http.ResponseWriter, req *http.Request) {
-	})
-	// Serves the write to an object.
-	http.HandleFunc("/b/some-bucket-name/o/", func(resp http.ResponseWriter, req *http.Request) {
+	flag.Parse()
+	if *port == "" {
+		log.Fatalf("usage: %s --port=8080", os.Args[0])
+	}
+
+	// Read.
+	for objectName, contents := range files {
+		contents := contents
+
+		// Go: Download object.
+		http.HandleFunc("/some-bucket-name/"+objectName, func(resp http.ResponseWriter, req *http.Request) {
+			if _, err := resp.Write(contents); err != nil {
+				log.Fatal(err)
+			}
+		})
+
+		// Node: Download object.
+		http.HandleFunc("/b/some-bucket-name/o/"+objectName, func(resp http.ResponseWriter, req *http.Request) {
+			fmt.Println("emulator read <<NODE>> called")
+			if _, err := resp.Write(contents); err != nil {
+				log.Fatal(err)
+			}
+		})
+
+		// Java: Download metadata (pointing to download link for object).
+		http.HandleFunc("/storage/v1/b/some-bucket-name/o/"+objectName, func(resp http.ResponseWriter, req *http.Request) {
+			fmt.Println("emulator metadata read <<JAVA>> called")
+			resp.Header().Set("Content-Type", "application/json")
+			if _, err := fmt.Fprintf(resp, `{
+	"name": "%s-download",
+	"bucket": "some-bucket-name-download",
+	"generation": "1"
+}`, objectName); err != nil {
+				log.Fatal(err)
+			}
+		})
+
+		// Java: Download object.
+		http.HandleFunc(fmt.Sprintf("/download/storage/v1/b/some-bucket-name-download/o/%s-download", objectName), func(resp http.ResponseWriter, req *http.Request) {
+			fmt.Println("emulator read <<JAVA>> called")
+			if _, err := resp.Write(contents); err != nil {
+				log.Fatal(err)
+			}
+		})
+	}
+
+	// Write.
+	http.HandleFunc("/b/some-bucket-name/o", func(resp http.ResponseWriter, req *http.Request) {
+		fmt.Println("emulator write called")
 		resp.Header().Set("Content-Type", "application/json")
-		ret := &storage.Object{
+		ret := &raw.Object{
 			ServerResponse: googleapi.ServerResponse{
 				Header:         resp.Header(),
 				HTTPStatusCode: http.StatusCreated,
@@ -41,6 +110,6 @@
 			log.Fatal(err)
 		}
 	})
-	log.Println("listening on localhost:8080")
-	log.Fatal(http.ListenAndServe(":8080", nil))
+	log.Printf("listening on localhost:%s\n", *port)
+	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", *port), nil))
 }