lib: implement an eml message view

Implement a MessageView representation for eml data that are not stored
in a message store. With this, we can display any rfc822 message data in
the message viewer.

Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

2 files changed, 97 insertions, 3 deletions

diff --git a/lib/emlview.go b/lib/emlview.go
new file mode 100644
index 00000000..e0dcb436
--- /dev/null
+++ b/lib/emlview.go
@@ -0,0 +1,80 @@
+package lib
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/ProtonMail/go-crypto/openpgp"
+	_ "github.com/emersion/go-message/charset"
+
+	"git.sr.ht/~rjarry/aerc/lib/crypto"
+	"git.sr.ht/~rjarry/aerc/models"
+	"git.sr.ht/~rjarry/aerc/worker/lib"
+)
+
+// EmlMessage implements the RawMessage interface
+type EmlMessage []byte
+
+func (fm *EmlMessage) NewReader() (io.ReadCloser, error) {
+	return io.NopCloser(bytes.NewReader(*fm)), nil
+}
+
+func (fm *EmlMessage) UID() uint32 {
+	return 0xFFFFFFF
+}
+
+func (fm *EmlMessage) Labels() ([]string, error) {
+	return nil, nil
+}
+
+func (fm *EmlMessage) ModelFlags() ([]models.Flag, error) {
+	return []models.Flag{models.SeenFlag}, nil
+}
+
+// NewEmlMessageView provides a MessageView for a full message that is not
+// stored in a message store
+func NewEmlMessageView(full []byte, pgp crypto.Provider,
+	decryptKeys openpgp.PromptFunction, cb func(MessageView, error),
+) {
+	eml := EmlMessage(full)
+	messageInfo, err := lib.MessageInfo(&eml)
+	if err != nil {
+		cb(nil, err)
+		return
+	}
+	msv := &MessageStoreView{
+		messageInfo:   messageInfo,
+		messageStore:  nil,
+		message:       full,
+		details:       nil,
+		bodyStructure: nil,
+		setSeen:       false,
+	}
+
+	if usePGP(messageInfo.BodyStructure) {
+		reader := lib.NewCRLFReader(bytes.NewReader(full))
+		md, err := pgp.Decrypt(reader, decryptKeys)
+		if err != nil {
+			cb(nil, err)
+			return
+		}
+		msv.details = md
+		msv.message, err = io.ReadAll(md.Body)
+		if err != nil {
+			cb(nil, err)
+			return
+		}
+	}
+	entity, err := lib.ReadMessage(bytes.NewBuffer(msv.message))
+	if err != nil {
+		cb(nil, err)
+		return
+	}
+	bs, err := lib.ParseEntityStructure(entity)
+	if err != nil {
+		cb(nil, err)
+		return
+	}
+	msv.bodyStructure = bs
+	cb(msv, nil)
+}
diff --git a/lib/messageview.go b/lib/messageview.go
index 247cecbe..8507880b 100644
--- a/lib/messageview.go
+++ b/lib/messageview.go
@@ -28,6 +28,9 @@ type MessageView interface {
 	// Returns the message store that this message was originally sourced from
 	Store() *MessageStore
 
+	// Fetches the full message
+	FetchFull(cb func(io.Reader))
+
 	// Fetches a specific body part for this message
 	FetchBodyPart(part []int, cb func(io.Reader))
 
@@ -76,8 +79,8 @@ func NewMessageStoreView(messageInfo *models.MessageInfo, setSeen bool,
 	}
 
 	if usePGP(messageInfo.BodyStructure) {
-		store.FetchFull([]uint32{messageInfo.Uid}, func(fm *types.FullMessage) {
-			reader := lib.NewCRLFReader(fm.Content.Reader)
+		msv.FetchFull(func(fm io.Reader) {
+			reader := lib.NewCRLFReader(fm)
 			md, err := pgp.Decrypt(reader, decryptKeys)
 			if err != nil {
 				cb(nil, err)
@@ -130,8 +133,19 @@ func (msv *MessageStoreView) MessageDetails() *models.MessageDetails {
 	return msv.details
 }
 
+func (msv *MessageStoreView) FetchFull(cb func(io.Reader)) {
+	if msv.message == nil && msv.messageStore != nil {
+		msv.messageStore.FetchFull([]uint32{msv.messageInfo.Uid},
+			func(fm *types.FullMessage) {
+				cb(fm.Content.Reader)
+			})
+		return
+	}
+	cb(bytes.NewReader(msv.message))
+}
+
 func (msv *MessageStoreView) FetchBodyPart(part []int, cb func(io.Reader)) {
-	if msv.message == nil {
+	if msv.message == nil && msv.messageStore != nil {
 		msv.messageStore.FetchBodyPart(msv.messageInfo.Uid, part, cb)
 		return
 	}