package dethnote

import (
	"bytes"
	"errors"
	"fmt"
	"net/mail"
	"net/smtp"
	"net/textproto"
	"regexp"
	"strconv"
)

var smtpURLRegexp = regexp.MustCompile(
	`^` + // bind to beginning
		`(?P<proto>(?:ssl|smtps)://)?` + // optional ssl:// protocol prefix
		`(?:(?P<user>[^:]+):` + // `username:password@` syntax either
		`(?P<pass>[^@]+)@)?` + // must exist or be entirely absent.
		`(?P<host>[^:]+):?` + // `host[:port]` standard case
		`(?P<port>[0-9]+)?` +
		`$`,
)

// MailConfig holds SMTP settings.
type MailConfig struct {
	Username string
	Password string
	Hostname string
	Port     int
	SSL      bool
}

func (m MailConfig) String() string {
	username := ""
	if m.Username != "" {
		username = fmt.Sprintf("'%s'@", m.Username)
	}
	return fmt.Sprintf("%s%s:%d", username, m.Hostname, m.Port)
}

// ParseSMTPUrl validates and parses out the SMTP URL.
func ParseSMTPUrl(url string) (MailConfig, error) {

	m := smtpURLRegexp.FindStringSubmatch(url)
	if len(m) == 0 {
		return MailConfig{}, errors.New("failed to match regexp")
	}

	ssl := m[1] != ""
	port, _ := strconv.Atoi(m[5])
	if port == 0 && ssl {
		port = 465
	} else if port == 0 {
		port = 25
	}

	return MailConfig{
		Username: m[2],
		Password: m[3],
		Hostname: m[4],
		Port:     port,
		SSL:      ssl,
	}, nil
}

// Mail is an email message to be delivered.
type Mail struct {
	From    string
	To      string
	Subject string
	HTML    string
}

// SetSMTP sets the SMTP config by URL.
func (s *Server) SetSMTP(url string) error {
	config, err := ParseSMTPUrl(url)
	if err != nil {
		return err
	}
	s.smtp = config
	Log.Info("Email server configuration: %s", config)
	return nil
}

// SendMail sends an email out.
func (s *Server) SendMail(m Mail) error {
	// Server config.
	cfg := s.smtp

	// validate from address
	from, err := mail.ParseAddress(m.From)
	if err != nil {
		return err
	}

	// validate to address
	to, err := mail.ParseAddress(m.To)
	if err != nil {
		return err
	}

	// set headers for html email
	header := textproto.MIMEHeader{}
	header.Set(textproto.CanonicalMIMEHeaderKey("from"), from.Address)
	header.Set(textproto.CanonicalMIMEHeaderKey("to"), to.Address)
	header.Set(textproto.CanonicalMIMEHeaderKey("content-type"), "text/html; charset=UTF-8")
	header.Set(textproto.CanonicalMIMEHeaderKey("mime-version"), "1.0")
	header.Set(textproto.CanonicalMIMEHeaderKey("subject"), m.Subject)

	// init empty message
	var buffer bytes.Buffer

	// write header
	for key, value := range header {
		buffer.WriteString(fmt.Sprintf("%s: %s\r\n", key, value[0]))
	}

	// write body
	buffer.WriteString(fmt.Sprintf("\r\n%s", m.HTML))

	// send email
	addr := fmt.Sprintf("%s:%d", cfg.Hostname, cfg.Port)
	auth := smtp.PlainAuth("", cfg.Username, cfg.Password, cfg.Hostname)
	return smtp.SendMail(addr, auth, from.Address, []string{to.Address}, buffer.Bytes())
}