package main

import (
	"bufio"
	"context"
	"fmt"
	"os"
	"strconv"
	"strings"

	"github.com/gotd/td/session"
	"github.com/gotd/td/telegram"
	"github.com/gotd/td/telegram/auth"
	"github.com/gotd/td/tg"
)

func main() {
	apiID := mustEnvInt("TELEGRAM__API_ID")
	apiHash := mustEnv("TELEGRAM__API_HASH")
	sessionFile := mustEnv("TELEGRAM__SESSION_FILE")

	phone := strings.TrimSpace(os.Getenv("TELEGRAM__PHONE"))
	if phone == "" {
		phone = prompt("Phone (e.g. +79991234567): ")
	}

	password := strings.TrimSpace(os.Getenv("TELEGRAM__PASSWORD"))
	if password == "" {
		password = prompt("2FA password (empty if not set): ")
	}

	ctx := context.Background()

	client := telegram.NewClient(apiID, apiHash, telegram.Options{
		SessionStorage: &session.FileStorage{Path: sessionFile},
	})

	err := client.Run(ctx, func(ctx context.Context) error {
		return client.Auth().IfNecessary(ctx, auth.NewFlow(
			auth.Constant(phone, password, auth.CodeAuthenticatorFunc(
				func(ctx context.Context, sentCode *tg.AuthSentCode) (string, error) {
					return prompt("Enter code: "), nil
				},
			)),
			auth.SendCodeOptions{},
		))
	})
	if err != nil {
		fmt.Fprintf(os.Stderr, "auth failed: %v\n", err)
		os.Exit(1)
	}

	fmt.Println("✓ Authorized")
}

func mustEnv(key string) string {
	value := strings.TrimSpace(os.Getenv(key))
	if value == "" {
		fmt.Fprintf(os.Stderr, "missing required env: %s\n", key)
		os.Exit(1)
	}
	return value
}

func mustEnvInt(key string) int {
	raw := mustEnv(key)
	v, err := strconv.Atoi(raw)
	if err != nil {
		fmt.Fprintf(os.Stderr, "invalid int in %s: %v\n", key, err)
		os.Exit(1)
	}
	return v
}

func prompt(label string) string {
	fmt.Print(label)
	reader := bufio.NewReader(os.Stdin)
	value, _ := reader.ReadString('\n')
	return strings.TrimSpace(value)
}