package main

import (
	"context"
	"errors"
	"io"
	"log"
	"log/slog"
	"net/http"
	"time"

	"git.nakama.town/fmartingr/gotoolkit/model"
	"git.nakama.town/fmartingr/gotoolkit/service"
	"github.com/emersion/go-sasl"
	"github.com/emersion/go-smtp"
)

var _ model.Server = (*smtpServer)(nil)

type smtpServer struct {
	backend *smtp.Server
}

func (s *smtpServer) IsEnabled() bool {
	return true
}

func (s *smtpServer) Start(_ context.Context) error {
	slog.Info("Started SMTP server", slog.String("addr", s.backend.Addr))
	return s.backend.ListenAndServe()
}

func (s *smtpServer) Stop(ctx context.Context) error {
	slog.Info("Stopping SMTP server")
	return s.backend.Shutdown(ctx)
}

func NewSMTPServer(backend *smtp.Server) model.Server {
	return &smtpServer{
		backend: backend,
	}
}

// The Backend implements SMTP server methods.
type Backend struct{}

// NewSession is called after client greeting (EHLO, HELO).
func (bkd *Backend) NewSession(c *smtp.Conn) (smtp.Session, error) {
	return &Session{}, nil
}

// A Session is returned after successful login.
type Session struct{}

// AuthMechanisms returns a slice of available auth mechanisms; only PLAIN is
// supported in this example.
func (s *Session) AuthMechanisms() []string {
	return []string{sasl.Plain}
}

// Auth is the handler for supported authenticators.
func (s *Session) Auth(mech string) (sasl.Server, error) {
	return sasl.NewPlainServer(func(identity, username, password string) error {
		if username != "username" || password != "password" {
			return errors.New("Invalid username or password")
		}
		return nil
	}), nil
}

func (s *Session) Mail(from string, opts *smtp.MailOptions) error {
	log.Println("Mail from:", from, opts)
	return nil
}

func (s *Session) Rcpt(to string, opts *smtp.RcptOptions) error {
	log.Println("Rcpt to:", to)
	return nil
}

func (s *Session) Data(r io.Reader) error {
	_, err := http.Post("https://ntfy.sh/fmartingr-dev", "text/plain", r)
	if err != nil {
		slog.Error("Error sending message:", slog.String("err", err.Error()))
	}
	return nil
}

func (s *Session) Reset() {}

func (s *Session) Logout() error {
	return nil
}

// ExampleServer runs an example SMTP server.
//
// It can be tested manually with e.g. netcat:
//
//	> netcat -C localhost 1025
//	EHLO localhost
//	AUTH PLAIN
//	AHVzZXJuYW1lAHBhc3N3b3Jk
//	MAIL FROM:<root@nsa.gov>
//	RCPT TO:<root@gchq.gov.uk>
//	DATA
//	Hey <3
//	.
func main() {
	be := &Backend{}

	smtpBackend := smtp.NewServer(be)

	smtpBackend.Addr = "localhost:11025"
	smtpBackend.Domain = "localhost"
	smtpBackend.WriteTimeout = 10 * time.Second
	smtpBackend.ReadTimeout = 10 * time.Second
	smtpBackend.MaxMessageBytes = 1024 * 1024
	smtpBackend.MaxRecipients = 50
	smtpBackend.AllowInsecureAuth = true

	ctx := context.Background()
	smtpServer := NewSMTPServer(smtpBackend)

	svc, err := service.NewService([]model.Server{
		smtpServer,
	})
	if err != nil {
		slog.Error("Error creating service:", slog.String("err", err.Error()))
		return
	}

	if err := svc.Start(ctx); err != nil {
		slog.Error("Error starting service:", slog.String("err", err.Error()))
		return
	}

	if err := svc.WaitStop(ctx); err != nil {
		slog.Error("Error waiting for service interruption:", slog.String("err", err.Error()))
	}
}