Add basic SMTP support

1 files changed, 112 insertions, 0 deletions

diff --git a/smtp.go b/smtp.go
new file mode 100644
index 0000000..d4b8ea2
--- /dev/null
+++ b/smtp.go
@@ -0,0 +1,112 @@
+package koushin
+
+import (
+	"fmt"
+	"time"
+	"io"
+
+	"github.com/emersion/go-message/mail"
+	"github.com/emersion/go-smtp"
+)
+
+func (s *Server) connectSMTP() (*smtp.Client, error) {
+	var c *smtp.Client
+	var err error
+	if s.smtp.tls {
+		c, err = smtp.DialTLS(s.smtp.host, nil)
+		if err != nil {
+			return nil, fmt.Errorf("failed to connect to SMTPS server: %v", err)
+		}
+	} else {
+		c, err = smtp.Dial(s.smtp.host)
+		if err != nil {
+			return nil, fmt.Errorf("failed to connect to SMTP server: %v", err)
+		}
+		if !s.smtp.insecure {
+			if err := c.StartTLS(nil); err != nil {
+				c.Close()
+				return nil, fmt.Errorf("STARTTLS failed: %v", err)
+			}
+		}
+	}
+
+	return c, err
+}
+
+type OutgoingMessage struct {
+	from string
+	to []string
+	subject string
+	text string
+}
+
+func (msg *OutgoingMessage) WriteTo(w io.Writer) error {
+	from := []*mail.Address{{"", msg.from}}
+
+	to := make([]*mail.Address, len(msg.to))
+	for i, addr := range msg.to {
+		to[i] = &mail.Address{"", addr}
+	}
+
+	var h mail.Header
+	h.SetDate(time.Now())
+	h.SetAddressList("From", from)
+	h.SetAddressList("To", to)
+	h.SetText("Subject", msg.subject)
+
+	mw, err := mail.CreateWriter(w, h)
+	if err != nil {
+		return fmt.Errorf("failed to create mail writer: %v", err)
+	}
+
+	var th mail.InlineHeader
+	th.Set("Content-Type", "text/plain; charset=utf-8")
+
+	tw, err := mw.CreateSingleInline(th)
+	if err != nil {
+		return fmt.Errorf("failed to create text part: %v", err)
+	}
+	defer tw.Close()
+
+	if _, err := io.WriteString(tw, msg.text); err != nil {
+		return fmt.Errorf("failed to write text part: %v", err)
+	}
+
+	if err := tw.Close(); err != nil {
+		return fmt.Errorf("failed to close text part: %v", err)
+	}
+
+	if err := mw.Close(); err != nil {
+		return fmt.Errorf("failed to close mail writer: %v", err)
+	}
+
+	return nil
+}
+
+func sendMessage(c *smtp.Client, msg *OutgoingMessage) error {
+	if err := c.Mail(msg.from, nil); err != nil {
+		return fmt.Errorf("MAIL FROM failed: %v", err)
+	}
+
+	for _, to := range msg.to {
+		if err := c.Rcpt(to); err != nil {
+			return fmt.Errorf("RCPT TO failed: %v", err)
+		}
+	}
+
+	w, err := c.Data()
+	if err != nil {
+		return fmt.Errorf("DATA failed: %v", err)
+	}
+	defer w.Close()
+
+	if err := msg.WriteTo(w); err != nil {
+		return fmt.Errorf("failed to write outgoing message: %v", err)
+	}
+
+	if err := w.Close(); err != nil {
+		return fmt.Errorf("failed to close SMTP data writer: %v", err)
+	}
+
+	return nil
+}