update book code

eBook/examples/chapter_19/goto_v4/main.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"net/http"
+)
+
+var (
+	listenAddr = flag.String("http", ":8080", "http listen address")
+	dataFile   = flag.String("file", "store.json", "data store file name")
+	hostname   = flag.String("host", "localhost:8080", "http host name")
+)
+
+var store *URLStore
+
+func main() {
+	flag.Parse()
+	store = NewURLStore(*dataFile)
+	http.HandleFunc("/", Redirect)
+	http.HandleFunc("/add", Add)
+	http.ListenAndServe(*listenAddr, nil)
+}
+
+func Redirect(w http.ResponseWriter, r *http.Request) {
+	key := r.URL.Path[1:]
+	url := store.Get(key)
+	if url == "" {
+		http.NotFound(w, r)
+		return
+	}
+	http.Redirect(w, r, url, http.StatusFound)
+}
+
+func Add(w http.ResponseWriter, r *http.Request) {
+	url := r.FormValue("url")
+	if url == "" {
+		fmt.Fprint(w, AddForm)
+		return
+	}
+	key := store.Put(url)
+	fmt.Fprintf(w, "http://%s/%s", *hostname, key)
+}
+
+const AddForm = `
+<form method="POST" action="/add">
+URL: <input type="text" name="url">
+<input type="submit" value="Add">
+</form>
+`