package app

import (
	"fmt"
	"image/png"
	"log"
	"net/url"
	"os"
	"path/filepath"
	"strings"
	"text/template"
	"time"
)

// Launcher is the source code template for a desktop launcher.
const Launcher = `[Desktop Entry]
Version=1.0
Name={{ .Name }}
GenericName={{ .Name }}
Comment=Progressive Web App
Exec={{ .Exec }}
Icon={{ .Icon }}
Terminal=false
Type=Application
StartupNotify=true
Categories=Network;
`

// Vars for the launcher template.
type Vars struct {
	Name string
	Exec string
	Icon string
}

// Install the launcher and icon.
func Install(p Parameters) {
	var (
		HOME     = os.Getenv("HOME")
		basename = UID(p)
	)

	if HOME == "" {
		panic("No $HOME variable found for current user!")
	}

	// Ensure directories exist.
	for _, path := range []string{
		filepath.Join(HOME, ".local", "share", "applications"),
		filepath.Join(HOME, ".config", "pwa-launcher"),
	} {
		err := os.MkdirAll(path, 0755)
		if err != nil {
			log.Fatalf("Failed to mkdir %s: %s", path, err)
		}
	}

	// Write the PNG image.
	var iconPath = filepath.Join(HOME, ".config", "pwa-launcher", basename+".png")
	log.Printf("Write icon to: %s", iconPath)
	icoFH, err := os.Create(iconPath)
	if err != nil {
		panic(err)
	}
	defer icoFH.Close()
	if err := png.Encode(icoFH, p.iconData); err != nil {
		panic(err)
	}

	// Write the desktop launcher.
	var launcherPath = filepath.Join(HOME, ".local", "share", "applications", basename+".desktop")
	log.Printf("Write launcher to: %s", launcherPath)

	fh, err := os.Create(launcherPath)
	if err != nil {
		panic(err)
	}
	defer fh.Close()
	t := template.Must(template.New("launcher").Parse(Launcher))
	err = t.Execute(fh, Vars{
		Name: p.Title,
		Exec: fmt.Sprintf(p.Exec, p.URL),
		Icon: iconPath,
	})
	if err != nil {
		panic(err)
	}
}

// UID generates a unique name for the launcher and icon files.
func UID(p Parameters) string {
	var name = "pwa-"

	uri, err := url.Parse(p.URL)
	if err == nil {
		name += strings.Replace(uri.Host, ":", "_", -1) + "-"
	}

	name += fmt.Sprintf("%d", time.Now().Unix())
	return name
}