package main

import (
	"bytes"
	"fmt"
	"html/template"
	"net/http"
)

type greetPage struct {
	Name string
}

const greetText = `<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Hello</title>
</head>
<body>
<p>Hello, {{.Name}}!</p>
</body>
</html>
`

var greetTemplate = template.Must(template.New("greet").Parse(greetText))

func handleGreet(w http.ResponseWriter, r *http.Request) {
	name := r.URL.Query().Get("name")
	if name == "" {
		http.Error(w, "Please give a name.", http.StatusBadRequest)
		return
	}

	var page bytes.Buffer
	err := greetTemplate.Execute(&page, greetPage{Name: name})
	if err != nil {
		fmt.Println("Template error:", err)
		http.Error(w, "The page could not be built.", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	page.WriteTo(w)
}

func main() {
	http.HandleFunc("GET /greet", handleGreet)

	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)
	}
}