nikoksr/notify

package mail

import (
    "context"
    "fmt"
    "net/smtp"
    "net/textproto"

    "github.com/jordan-wright/email"
)

// Mail struct holds necessary data to send emails.
type Mail struct {
    usePlainText      bool
    senderAddress     string
    smtpHostAddr      string
    smtpAuth          smtp.Auth
    receiverAddresses []string
}

// New returns a new instance of a Mail notification service.
func New(senderAddress, smtpHostAddress string) *Mail {
    return &Mail{
        usePlainText:      false,
        senderAddress:     senderAddress,
        smtpHostAddr:      smtpHostAddress,
        receiverAddresses: []string{},
    }
}

// BodyType is used to specify the format of the body.
type BodyType int

const (
    // PlainText is used to specify that the body is plain text.
    PlainText BodyType = iota
    // HTML is used to specify that the body is HTML.
    HTML
)

// AuthenticateSMTP authenticates you to send emails via smtp.
// Example values: "", "test@gmail.com", "password123", "smtp.gmail.com"
// For more information about smtp authentication, see here:
//
//    -> https://pkg.go.dev/net/smtp#PlainAuth
func (m *Mail) AuthenticateSMTP(identity, userName, password, host string) {
    m.smtpAuth = smtp.PlainAuth(identity, userName, password, host)
}

// AddReceivers takes email addresses and adds them to the internal address list. The Send method will send
// a given message to all those addresses.
func (m *Mail) AddReceivers(addresses ...string) {
    m.receiverAddresses = append(m.receiverAddresses, addresses...)
}

// BodyFormat can be used to specify the format of the body.
// Default BodyType is HTML.
func (m *Mail) BodyFormat(format BodyType) {
    switch format {
    case PlainText:
        m.usePlainText = true
    case HTML:
        m.usePlainText = false
    default:
        m.usePlainText = false
    }
}

func (m *Mail) newEmail(subject, message string) *email.Email {
    msg := &email.Email{
        To:      m.receiverAddresses,
        From:    m.senderAddress,
        Subject: subject,
        Headers: textproto.MIMEHeader{},
    }

    if m.usePlainText {
        msg.Text = []byte(message)
    } else {
        msg.HTML = []byte(message)
    }
    return msg
}

// Send takes a message subject and a message body and sends them to all previously set chats. Message body supports
// html as markup language.
func (m Mail) Send(ctx context.Context, subject, message string) error {
    msg := m.newEmail(subject, message)

    var err error
    select {
    case <-ctx.Done():
        err = ctx.Err()
    default:
        if err = msg.Send(m.smtpHostAddr, m.smtpAuth); err != nil {
            err = fmt.Errorf("send email: %w", err)
        }
    }

    return err
}