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() }