package main

import (
	"fmt"
	"net/http"
)

const pageFormat = `<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>%s</title>
</head>
<body>
<h1>%s</h1>
<p>%s</p>
<p><a href="/">Home</a> | <a href="/about">About</a> | <a href="/games">Games</a></p>
</body>
</html>
`

// writePage sends a whole page. The title and the body must be text from this
// program, never text from a visitor, because they go into the HTML as they are.
func writePage(w http.ResponseWriter, status int, title string, body string) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.WriteHeader(status)
	fmt.Fprintf(w, pageFormat, title, title, body)
}

func handleHome(w http.ResponseWriter, r *http.Request) {
	writePage(w, http.StatusOK, "Home", "Welcome to a small site.")
}

func handleAbout(w http.ResponseWriter, r *http.Request) {
	writePage(w, http.StatusOK, "About", "This site is one Go file.")
}

func handleGames(w http.ResponseWriter, r *http.Request) {
	writePage(w, http.StatusOK, "Games", "Number Guess and Monster Battle.")
}

func handleNotFound(w http.ResponseWriter, r *http.Request) {
	writePage(w, http.StatusNotFound, "Not found", "There is no page at this address.")
}

func main() {
	http.HandleFunc("GET /{$}", handleHome)
	http.HandleFunc("GET /about", handleAbout)
	http.HandleFunc("GET /games", handleGames)
	http.HandleFunc("GET /", handleNotFound)

	fmt.Println("Server running at http://localhost:8080")
	fmt.Println("Press Ctrl+C to stop it.")

	err := http.ListenAndServe("localhost:8080", nil)
	if err != nil {
		fmt.Println("Server stopped:", err)
	}
}