package mailer

import (
	"RenewCMS/internal/infrastructure/config"
	"errors"
	"net/smtp"
	"strings"
)

type loginAuth struct {
	username string
	password string
}

func (a *loginAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
	if !server.TLS && !isLoopback(server.Name) {
		return "", nil, errors.New("refusing to send credentials over an unencrypted connection")
	}
	return "LOGIN", nil, nil
}

func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
	if !more {
		return nil, nil
	}
	switch strings.ToLower(strings.TrimSpace(string(fromServer))) {
	case "username:":
		return []byte(a.username), nil
	case "password:":
		return []byte(a.password), nil
	}
	return nil, errors.New("unexpected server challenge")
}

func isLoopback(host string) bool {
	return host == "localhost" || host == "127.0.0.1" || host == "::1"
}

func selectAuth(mechanisms string, settings config.SmtpSettings) smtp.Auth {
	advertised := strings.Fields(strings.ToUpper(mechanisms))
	for _, mechanism := range advertised {
		if mechanism == "PLAIN" {
			return smtp.PlainAuth("", settings.Login, settings.Password, settings.Host)
		}
	}
	return &loginAuth{username: settings.Login, password: settings.Password}
}