just a tutorial followup

web.go

package main

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

const pagePath = "pages"
const viewPath = "/view/"
const viewLen = len(viewPath)
const editPath = "/edit/"
const editLen = len(editPath)
const savePath = "/save/"
const saveLen = len(savePath)

var templates = template.Must(template.ParseFiles("templates/edit.html", "templates/view.html"))
var nameValidator = regexp.MustCompile("^[-_a-zA-Z0-9]+$")

type Page struct {
  Title string
  Name string
  Body []byte
}

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

func loadPage(name string) (*Page, error) {
  filename := pagePath + "/" + name + ".txt"
  body, err := ioutil.ReadFile(filename)
  if err != nil {
    return nil, err
  }
  return &Page{Name: name, Body: body}, nil
}

func getName(w http.ResponseWriter, r *http.Request, lenPath int) (name string, err error) {
  name = r.URL.Path[lenPath:]
  if !nameValidator.MatchString(name) {
    http.NotFound(w, r)
    err = errors.New("Invalid Page Name")
  }
  return
}
func renderTemplate(w http.ResponseWriter, tmpl string, p *Page) {
  err := templates.ExecuteTemplate(w, tmpl + ".html", p)
  if err != nil {
    http.Error(w, err.Error(), http.StatusInternalServerError)
  }
  log.Printf("Page %s delivered.", p.Name)
}

func viewHandler(w http.ResponseWriter, r *http.Request) {
  name, err := getName(w, r, viewLen)
  if err != nil {
    return
  }
  p, err := loadPage(name)
  if err != nil {
    http.Redirect(w, r, "/edit/" + name, http.StatusFound)
    return
  }
  renderTemplate(w, "view", p)
}

func editHandler(w http.ResponseWriter, r *http.Request) {
  name, err := getName(w, r, editLen)
  if err != nil {
    return
  }
  p, err := loadPage(name)
  if err != nil {
    p = &Page{Name: name}
  }
  renderTemplate(w, "edit", p)
}

func saveHandler(w http.ResponseWriter, r *http.Request) {
  name, err := getName(w, r, saveLen)
  if err != nil {
    return
  }
  body := r.FormValue("body")
  p := &Page{Name: name, Body: []byte(body)}
  err = p.save()
  if err != nil {
    http.Error(w, err.Error(), http.StatusInternalServerError)
    return
  }
  http.Redirect(w, r, "/view/" + name, http.StatusFound)
}

func main() {
  http.HandleFunc(viewPath, viewHandler)
  http.HandleFunc(editPath, editHandler)
  http.HandleFunc(savePath, saveHandler)
  http.ListenAndServe(":8080", nil)
}