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package mailinglist
import (
"context"
"errors"
"strings"
"github.com/emersion/go-sasl"
"github.com/emersion/go-smtp"
"github.com/mediocregopher/blog.mediocregopher.com/srv/cfg"
"github.com/mediocregopher/mediocre-go-lib/v2/mctx"
)
// Mailer is used to deliver emails to arbitrary recipients.
type Mailer interface {
Send(to, subject, body string) error
}
// NullMailer acts as a Mailer but actually just does nothing.
var NullMailer = nullMailer{}
type nullMailer struct{}
func (nullMailer) Send(to, subject, body string) error {
return nil
}
// MailerParams are used to initialize a new Mailer instance
type MailerParams struct {
SMTPAddr string
// Optional, if not given then no auth is attempted.
SMTPAuth sasl.Client
// The sending email address to use for all emails being sent.
SendAs string
}
// SetupCfg implement the cfg.Cfger interface.
func (m *MailerParams) SetupCfg(cfg *cfg.Cfg) {
cfg.StringVar(&m.SMTPAddr, "ml-smtp-addr", "", "Address of SMTP server to use for sending emails for the mailing list")
smtpAuthStr := cfg.String("ml-smtp-auth", "", "user:pass to use when authenticating with the mailing list SMTP server. The given user will also be used as the From address.")
cfg.OnInit(func(ctx context.Context) error {
if m.SMTPAddr == "" {
return nil
}
smtpAuthParts := strings.SplitN(*smtpAuthStr, ":", 2)
if len(smtpAuthParts) < 2 {
return errors.New("invalid -ml-smtp-auth")
}
m.SMTPAuth = sasl.NewPlainClient("", smtpAuthParts[0], smtpAuthParts[1])
m.SendAs = smtpAuthParts[0]
return nil
})
}
// Annotate implements mctx.Annotator interface.
func (m *MailerParams) Annotate(a mctx.Annotations) {
if m.SMTPAddr == "" {
return
}
a["smtpAddr"] = m.SMTPAddr
a["smtpSendAs"] = m.SendAs
}
type mailer struct {
params MailerParams
}
// NewMailer initializes and returns a Mailer which will use an external SMTP
// server to deliver email.
func NewMailer(params MailerParams) Mailer {
return &mailer{
params: params,
}
}
func (m *mailer) Send(to, subject, body string) error {
msg := []byte("From: " + m.params.SendAs + "\r\n" +
"To: " + to + "\r\n" +
"Subject: " + subject + "\r\n\r\n" +
body + "\r\n")
c, err := smtp.Dial(m.params.SMTPAddr)
if err != nil {
return err
}
defer c.Close()
if err = c.Auth(m.params.SMTPAuth); err != nil {
return err
}
if err = c.Mail(m.params.SendAs, nil); err != nil {
return err
}
if err = c.Rcpt(to); err != nil {
return err
}
w, err := c.Data()
if err != nil {
return err
}
if _, err = w.Write(msg); err != nil {
return err
}
if err = w.Close(); err != nil {
return err
}
return c.Quit()
}
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