1 files changed, 143 insertions, 0 deletions
diff --git a/src/mailinglist/mailer.go b/src/mailinglist/mailer.go
new file mode 100644
index 0000000..07d6c3a
--- /dev/null
+++ b/src/mailinglist/mailer.go
@@ -0,0 +1,143 @@
+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"
+	"github.com/mediocregopher/mediocre-go-lib/v2/mlog"
+)
+
+// Mailer is used to deliver emails to arbitrary recipients.
+type Mailer interface {
+	Send(to, subject, body string) error
+}
+
+type logMailer struct {
+	logger *mlog.Logger
+}
+
+// NewLogMailer returns a Mailer instance which will not actually send any
+// emails, it will only log to the given Logger when Send is called.
+func NewLogMailer(logger *mlog.Logger) Mailer {
+	return &logMailer{logger: logger}
+}
+
+func (l *logMailer) Send(to, subject, body string) error {
+	ctx := mctx.Annotate(context.Background(),
+		"to", to,
+		"subject", subject,
+	)
+	l.logger.Info(ctx, "would have sent email")
+	return nil
+}
+
+// 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()
+}