// Guestbook -- main (starter). This file is finished. Finish
// guestbook/guestbook.go and templates/home.html.
//
// Run from this folder, because the template and the data file are relative to
// it:
//   cd projects/06-guestbook/starter
//   go run .

package main

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

	"guestbookapp/guestbook"
)

const templateFile = "templates/home.html"
const dataFile = "messages.json"

// homeData is everything the template needs.
type homeData struct {
	Error    string
	Name     string
	Text     string
	Messages []guestbook.Message
}

var homeTemplate *template.Template
var book *guestbook.Book

// showHome builds the page in memory, and sends it only if that worked.
func showHome(w http.ResponseWriter, status int, data homeData) {
	data.Messages = book.Messages()

	var page bytes.Buffer
	err := homeTemplate.Execute(&page, data)
	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")
	w.WriteHeader(status)
	page.WriteTo(w)
}

func handleHome(w http.ResponseWriter, r *http.Request) {
	showHome(w, http.StatusOK, homeData{})
}

func handleAdd(w http.ResponseWriter, r *http.Request) {
	name := r.FormValue("name")
	text := r.FormValue("text")

	message, err := guestbook.NewMessage(name, text)
	if err != nil {
		// Show the form again, with what the visitor typed.
		data := homeData{Error: err.Error(), Name: name, Text: text}
		showHome(w, http.StatusBadRequest, data)
		return
	}

	err = book.Add(message)
	if err != nil {
		fmt.Println("Save error:", err)
		http.Error(w, "The message could not be saved.", http.StatusInternalServerError)
		return
	}

	http.Redirect(w, r, "/", http.StatusSeeOther)
}

func main() {
	parsed, err := template.ParseFiles(templateFile)
	if err != nil {
		fmt.Println("Could not read the template:", err)
		fmt.Println("Run this program from its own folder, and check the template.")
		return
	}
	homeTemplate = parsed

	opened, err := guestbook.Open(dataFile)
	if err != nil {
		fmt.Println("Could not load the messages:", err)
		fmt.Println("Fix or remove the file, then start the server again.")
		return
	}
	book = opened

	http.HandleFunc("GET /{$}", handleHome)
	http.HandleFunc("POST /messages", handleAdd)

	fmt.Println("Guestbook 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)
	}
}