package main

import (
	"fmt"
	"html/template"
	"io"
	"log"
	"net/http"
	"os"
	"path/filepath"
)

func handle(path string, handleFunc func(res http.ResponseWriter, req *http.Request) error) {
	http.HandleFunc("/", func(res http.ResponseWriter, req *http.Request) {
		err := handleFunc(res, req)
		if err != nil {
			log.Println(err)
			http.Error(res, err.Error(), 500)
		}
	})
}

func handleForm(res http.ResponseWriter, req *http.Request) error {
	tpl, err := template.ParseFiles("form.html")
	if err != nil {
		return err
	}
	var msg string
	if req.Method == http.MethodPost {
		file, header, err := req.FormFile("file")
		if err != nil {
			return err
		}

		tmpFile, err := os.Create(filepath.Join(os.TempDir(), header.Filename))
		if err != nil {
			return err
		}
		defer tmpFile.Close()

		sz, err := io.Copy(tmpFile, file)
		if err != nil {
			return err
		}
		msg = fmt.Sprintf("File uploaded (%d bytes)", sz)
	}
	tpl.Execute(res, msg)
	return nil
}

func main() {
	handle("/", handleForm)
	http.ListenAndServe(":9000", nil)
}