main.go

package main

import (
	"errors"
	"html/template"
	"io/ioutil"
	"net/http"
	"regexp"
)

// Page is a data model used to hold metadata and contents
type Page struct {
	Title string
	Body  []byte
}

func (p *Page) save() error {
	filename := p.Title + ".txt"
	return ioutil.WriteFile(filename, p.Body, 0600)
}

func loadPage(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
}

var validPath = regexp.MustCompile("^/(edit|save|view)/([a-zA-Z0-9]+)$")

func getTitle(w http.ResponseWriter, r *http.Request) (string, error) {
	m := validPath.FindStringSubmatch(r.URL.Path)
	if m == nil {
		return "", errors.New("Invalid Page Title")
	}
	return m[2], nil
}

var templates = template.Must(template.ParseFiles("edit.html", "view.html"))

func renderTemplate(filename string, w http.ResponseWriter, d interface{}) {
	err := templates.ExecuteTemplate(w, filename, d)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

func viewHandler(w http.ResponseWriter, r *http.Request) {
	title, err := getTitle(w, r)
	if err != nil {
		return
	}
	page, err := loadPage(title)
	if err != nil {
		http.Redirect(w, r, "/edit/"+title, http.StatusFound)
		return
	}
	renderTemplate("view.html", w, page)
}

func editHandler(w http.ResponseWriter, r *http.Request) {
	title, err := getTitle(w, r)
	if err != nil {
		return
	}

	page, err := loadPage(title)
	if err != nil {
		page = &Page{Title: title}
	}

	renderTemplate("edit.html", w, page)
}

func saveHandler(w http.ResponseWriter, r *http.Request) {
	title, err := getTitle(w, r)
	if err != nil {
		return
	}
	body := r.FormValue("body")
	page := &Page{Title: title, Body: []byte(body)}
	err = page.save()
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	http.Redirect(w, r, "/view/"+title, http.StatusFound)
}

func main() {
	http.HandleFunc("/view/", viewHandler)
	http.HandleFunc("/edit/", editHandler)
	http.HandleFunc("/save/", saveHandler)
	http.ListenAndServe(":8888", nil)
}