package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"strings"

	webpush "github.com/SherClockHolmes/webpush-go"
	"github.com/joho/godotenv"
)

func main() {
	writeEnv := flag.Bool("write-env", false, "VAPID-Schlüssel direkt in eine .env-Datei schreiben")
	envPath := flag.String("env", ".env", "Pfad der zu aktualisierenden .env-Datei")
	flag.Parse()

	_ = godotenv.Load()

	privateKey, publicKey, err := webpush.GenerateVAPIDKeys()
	if err != nil {
		log.Fatal(err)
	}

	email := strings.TrimSpace(os.Getenv("ADMIN_EMAIL"))
	if email == "" {
		email = "admin@example.com"
	}

	values := map[string]string{
		"VAPID_PUBLIC_KEY":  publicKey,
		"VAPID_PRIVATE_KEY": privateKey,
		"VAPID_SUBSCRIBER":  "mailto:" + email,
	}

	if *writeEnv {
		if err := writeVAPIDEnv(*envPath, values); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("VAPID-Konfiguration wurde in %s geschrieben.\n", *envPath)
		return
	}

	fmt.Printf("VAPID_PUBLIC_KEY=%s\n", values["VAPID_PUBLIC_KEY"])
	fmt.Printf("VAPID_PRIVATE_KEY=%s\n", values["VAPID_PRIVATE_KEY"])
	fmt.Printf("VAPID_SUBSCRIBER=%s\n", values["VAPID_SUBSCRIBER"])
}

func writeVAPIDEnv(path string, values map[string]string) error {
	content, err := os.ReadFile(path)
	if err != nil && !os.IsNotExist(err) {
		return err
	}

	lines := []string{}
	if len(content) > 0 {
		lines = strings.Split(strings.ReplaceAll(string(content), "\r\n", "\n"), "\n")
	}

	for _, line := range lines {
		key, value, found := strings.Cut(line, "=")
		if !found {
			continue
		}
		if (key == "VAPID_PUBLIC_KEY" || key == "VAPID_PRIVATE_KEY") &&
			strings.TrimSpace(value) != "" {
			return fmt.Errorf("in %s sind bereits VAPID-Schlüssel vorhanden", path)
		}
	}

	updated := map[string]bool{}
	for index, line := range lines {
		key, _, found := strings.Cut(line, "=")
		if !found {
			continue
		}
		if value, ok := values[key]; ok {
			lines[index] = key + "=" + value
			updated[key] = true
		}
	}

	for _, key := range []string{
		"VAPID_PUBLIC_KEY",
		"VAPID_PRIVATE_KEY",
		"VAPID_SUBSCRIBER",
	} {
		if !updated[key] {
			lines = append(lines, key+"="+values[key])
		}
	}

	output := strings.TrimRight(strings.Join(lines, "\n"), "\n") + "\n"
	return os.WriteFile(path, []byte(output), 0o600)
}