blgo/handler/handler.go

package handler

import (
	"fmt"
	"net/http"
	"os"
)

var fs = http.FileServer(http.Dir("static/"))

// Index is the handler that displays the index page.
func Index(w http.ResponseWriter, r *http.Request) {
	CurrentTheme.ExecuteTemplate(w, "index.tmpl", nil)
}

// Handler is the mux-ing handler.
func Handler(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path == "/" {
		Index(w, r)
		return
	}
	if r.URL.Path == "/style.css" {
		TemplateStyle(w, r)
		return
	}
	if Static(w, r) {
		return
	}
	Post(w, r)
}

// TemplateStyle is a handler that servers the style of the current template.
func TemplateStyle(w http.ResponseWriter, r *http.Request) {
	if themeCSS == nil {
		// 404 if the theme CSS doesn't exist as it's optional.
		CurrentTheme.ExecuteTemplate(w, "404.tmpl", nil)
		return
	}
	w.Header().Add("Content-Type", "text/css")
	_, _ = w.Write(themeCSS)
}

// Static is a handler that serves static content if available.
// If it has served something (the static file or an error), it returns true.
func Static(w http.ResponseWriter, r *http.Request) bool {
	fileName := "static" + r.URL.Path

	// Check if the file exists and is not a directory.
	info, err := os.Stat(fileName)
	if os.IsNotExist(err) || (info != nil && info.IsDir()) {
		return false
	}
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		CurrentTheme.ExecuteTemplate(w, "500.tmpl", fmt.Errorf("error reading static folder: %w", err))
		return true
	}

	// The file probably exist now. Even if there's a mismatch, the malicious attacker can only get a
	// 404 or a directory listing.
	fs.ServeHTTP(w, r)
	return true
}