add chapter 15.6 (#682)

eBook/examples/chapter_15/wiki/wiki.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"net/http"
+	"io/ioutil"
+	"log"
+	"regexp"
+	"text/template"
+)
+
+const lenPath = len("/view/")
+
+var titleValidator = regexp.MustCompile("^[a-zA-Z0-9]+$")
+var templates = make(map[string]*template.Template)
+var err error
+
+type Page struct {
+	Title string
+	Body  []byte
+}
+
+func init() {
+	for _, tmpl := range []string{"edit", "view"} {
+		templates[tmpl] = template.Must(template.ParseFiles(tmpl + ".html"))
+	}
+}
+
+func main() {
+	http.HandleFunc("/view/", makeHandler(viewHandler))
+	http.HandleFunc("/edit/", makeHandler(editHandler))
+	http.HandleFunc("/save/", makeHandler(saveHandler))
+	err := http.ListenAndServe("localhost:8080", nil)
+	if err != nil {
+		log.Fatal("ListenAndServe: ", err.Error())
+	}
+}
+
+func makeHandler(fn func(http.ResponseWriter, *http.Request, string)) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		title := r.URL.Path[lenPath:]
+		if !titleValidator.MatchString(title) {
+			http.NotFound(w, r)
+			return
+		}
+		fn(w, r, title)
+	}
+}
+
+func viewHandler(w http.ResponseWriter, r *http.Request, title string) {
+	p, err := load(title)
+	if err != nil { // page not found
+		http.Redirect(w, r, "/edit/"+title, http.StatusFound)
+		return
+	}
+	renderTemplate(w, "view", p)
+}
+
+func editHandler(w http.ResponseWriter, r *http.Request, title string) {
+	p, err := load(title)
+	if err != nil {
+		p = &Page{Title: title}
+	}
+	renderTemplate(w, "edit", p)
+}
+
+func saveHandler(w http.ResponseWriter, r *http.Request, title string) {
+	body := r.FormValue("body")
+	p := &Page{Title: title, Body: []byte(body)}
+	err := p.save()
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	http.Redirect(w, r, "/view/"+title, http.StatusFound)
+}
+
+func renderTemplate(w http.ResponseWriter, tmpl string, p *Page) {
+	err := templates[tmpl].Execute(w, p)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+	}
+}
+
+func (p *Page) save() error {
+	filename := p.Title + ".txt"
+	// file created with read-write permissions for the current user only
+	return ioutil.WriteFile(filename, p.Body, 0600)
+}
+
+func load(title string) (*Page, error) {
+	filename := title + ".txt"
+	body, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	return &Page{Title: title, Body: body}, nil
+}