package main

import (
	"errors"
	"fmt"
	"log/slog"
	"net/smtp"
	"os"

	"git.nakama.town/fmartingr/smtp2shoutrrr"
)

// The PLAIN mechanism name.
const Plain = "PLAIN"

type plainClient struct {
	Identity string
	Username string
	Password string
}

func (a *plainClient) Start(si *smtp.ServerInfo) (mech string, ir []byte, err error) {
	mech = Plain
	ir = []byte(a.Identity + "\x00" + a.Username + "\x00" + a.Password)
	return
}

func (a *plainClient) Next(challenge []byte, b bool) (response []byte, err error) {
	slog.Debug("SASL challenge received", slog.String("challenge", string(challenge)))
	return nil, nil
}

// NewPlainClient is a client implementation of the PLAIN authentication
// mechanism, as described in RFC 4616. Unlike smtp.PlainAuth it does not
// require a TLS connection, which the development server does not offer.
// Authorization identity may be left blank to indicate that it is the same as
// the username.
func NewPlainClient(identity, username, password string) smtp.Auth {
	return &plainClient{identity, username, password}
}

const configPath = "config.toml"

func main() {
	if err := run(); err != nil {
		slog.Error("sendmail failed", slog.String("err", err.Error()))
		os.Exit(1)
	}
}

func run() error {
	config, err := smtp2shoutrrr.LoadConfig(configPath)
	if err != nil {
		return fmt.Errorf("loading configuration: %w", err)
	}

	// The development server listens on localhost without TLS.
	hostname := "localhost"
	auth := NewPlainClient("", config.Username, config.Password)

	slog.Info("Using first recipient configuration to send a test email")

	if len(config.Recipients) == 0 {
		return errors.New("no recipients found in configuration")
	}

	if len(config.Recipients[0].Addresses) == 0 {
		return errors.New("no email addresses found in first recipient configuration")
	}

	recipients := []string{config.Recipients[0].Addresses[0]}
	msg := []byte("Subject: Test notification\r\n\r\nThis is a test notification")
	from := "hello@localhost"

	return smtp.SendMail(fmt.Sprintf("%s:%d", hostname, config.Port), auth, from, recipients, msg)
}