Add get_attachment command

Signed-off-by: Knut Ahlers <knut@ahlers.me>

commands.go

@@ -6,11 +6,13 @@ import (
 
 	"github.com/emersion/go-imap"
 	"github.com/emersion/go-imap/client"
+	"github.com/jhillyerd/enmime"
 	"github.com/pkg/errors"
+	log "github.com/sirupsen/logrus"
 )
 
 type command interface {
-	Execute(*client.Client, *imap.Message, io.Writer) error
+	Execute(*client.Client, *imap.Message, *enmime.Envelope, io.Writer) error
 }
 
 type commandTypeWrap struct {
@@ -31,6 +33,9 @@ func (c commandTypeWrap) rewrap(data []byte) (command, error) {
 	case "del_flags":
 		out = new(commandDelFlags)
 
+	case "get_attachment":
+		out = new(commandGetAttachment)
+
 	case "set_flags":
 		out = new(commandSetFlags)
 
@@ -46,7 +51,7 @@ type commandMove struct {
 	ToMailbox string `json:"to_mailbox"`
 }
 
-func (c commandMove) Execute(client *client.Client, msg *imap.Message, stdin io.Writer) error {
+func (c commandMove) Execute(client *client.Client, msg *imap.Message, mail *enmime.Envelope, stdin io.Writer) error {
 	s := &imap.SeqSet{}
 	s.AddNum(msg.Uid)
 
@@ -64,7 +69,7 @@ type commandAddFlags struct {
 	Flags []string `json:"flags"`
 }
 
-func (c commandAddFlags) Execute(client *client.Client, msg *imap.Message, stdin io.Writer) error {
+func (c commandAddFlags) Execute(client *client.Client, msg *imap.Message, mail *enmime.Envelope, stdin io.Writer) error {
 	var (
 		flags []interface{}
 		s     = &imap.SeqSet{}
@@ -85,7 +90,7 @@ type commandDelFlags struct {
 	Flags []string `json:"flags"`
 }
 
-func (c commandDelFlags) Execute(client *client.Client, msg *imap.Message, stdin io.Writer) error {
+func (c commandDelFlags) Execute(client *client.Client, msg *imap.Message, mail *enmime.Envelope, stdin io.Writer) error {
 	var (
 		flags []interface{}
 		s     = &imap.SeqSet{}
@@ -102,11 +107,28 @@ func (c commandDelFlags) Execute(client *client.Client, msg *imap.Message, stdin
 	)
 }
 
+type commandGetAttachment struct {
+	Filename string `json:"filename"`
+}
+
+func (c commandGetAttachment) Execute(client *client.Client, msg *imap.Message, mail *enmime.Envelope, stdin io.Writer) error {
+	a := attachmentFromMail(mail, c.Filename)
+	if a == nil {
+		log.WithFields(log.Fields{
+			"uid":      msg.Uid,
+			"filename": c.Filename,
+		}).Error("Requested attachment not found")
+		return errors.New("Attachment not found")
+	}
+
+	return errors.Wrap(json.NewEncoder(stdin).Encode(a), "Unable to encode attachment to JSON")
+}
+
 type commandSetFlags struct {
 	Flags []string `json:"flags"`
 }
 
-func (c commandSetFlags) Execute(client *client.Client, msg *imap.Message, stdin io.Writer) error {
+func (c commandSetFlags) Execute(client *client.Client, msg *imap.Message, mail *enmime.Envelope, stdin io.Writer) error {
 	var (
 		flags []interface{}
 		s     = &imap.SeqSet{}

handler.go

@@ -15,31 +15,6 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
-type mailTransport struct {
-	Attachments []string          `json:"attachments"`
-	Headers     map[string]string `json:"headers"`
-	HTML        string            `json:"html"`
-	Text        string            `json:"text"`
-}
-
-func mailToTransport(msg *enmime.Envelope) *mailTransport {
-	var out = &mailTransport{
-		Headers: map[string]string{},
-		HTML:    msg.HTML,
-		Text:    msg.Text,
-	}
-
-	for _, a := range msg.Attachments {
-		out.Attachments = append(out.Attachments, a.FileName)
-	}
-
-	for _, hn := range msg.GetHeaderKeys() {
-		out.Headers[hn] = msg.GetHeader(hn)
-	}
-
-	return out
-}
-
 type mailHandler struct {
 	Match   []matcher `yaml:"match"`
 	Command []string  `yaml:"command"`
@@ -89,7 +64,7 @@ func (m mailHandler) Process(imapClient *client.Client, msg *imap.Message, envel
 				continue
 			}
 
-			if err = c.Execute(imapClient, msg, stdin); err != nil {
+			if err = c.Execute(imapClient, msg, envelope, stdin); err != nil {
 				log.WithError(err).Error("Unable to execute command")
 				continue
 			}

transport.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"encoding/base64"
+
+	"github.com/jhillyerd/enmime"
+)
+
+type attachmentTransport struct {
+	FileName    string
+	Content     string
+	ContentType string
+}
+
+func attachmentFromMail(msg *enmime.Envelope, filename string) *attachmentTransport {
+	for _, a := range msg.Attachments {
+		if a.FileName == filename {
+			return &attachmentTransport{
+				Content:     base64.StdEncoding.EncodeToString(a.Content),
+				ContentType: a.ContentType,
+				FileName:    a.FileName,
+			}
+		}
+	}
+
+	return nil
+}
+
+type mailTransport struct {
+	Attachments []string          `json:"attachments"`
+	Headers     map[string]string `json:"headers"`
+	HTML        string            `json:"html"`
+	Text        string            `json:"text"`
+}
+
+func mailToTransport(msg *enmime.Envelope) *mailTransport {
+	var out = &mailTransport{
+		Headers: map[string]string{},
+		HTML:    msg.HTML,
+		Text:    msg.Text,
+	}
+
+	for _, a := range msg.Attachments {
+		out.Attachments = append(out.Attachments, a.FileName)
+	}
+
+	for _, hn := range msg.GetHeaderKeys() {
+		out.Headers[hn] = msg.GetHeader(hn)
+	}
+
+	return out
+}