Backend extensions

backend/backend.go

@@ -11,10 +11,46 @@ import (
 // password is incorrect.
 var ErrInvalidCredentials = errors.New("Invalid credentials")
 
+type Extension string
+
+const (
+	ExtUIDPLUS Extension = "UIDPLUS"
+)
+
 // Backend is an IMAP server backend. A backend operation always deals with
 // users.
 type Backend interface {
 	// Login authenticates a user. If the username or the password is incorrect,
 	// it returns ErrInvalidCredentials.
 	Login(connInfo *imap.ConnInfo, username, password string) (User, error)
+
+	// SupportedExtensions returns the list of extension identifiers that
+	// are understood by the backend. Note that values are not capability names
+	// even though some may match corresponding names. In particular,
+	// parameters for capability names are not included.
+	//
+	// Result should contain an entry for each extension that is implemented
+	// by go-imap directly. There is no requirement to include extensions
+	// that are provided by separate libraries (e.g. go-imap-id), though
+	// it would not hurt - unknown values are silently ignored.
+	SupportedExtensions() []Extension
+}
+
+// ExtensionOption is an optional argument defined by IMAP extension
+// that may be passed to the backend.
+//
+// Backend implementation is supposed to use type assertions to determine
+// actual option data and the action needed.
+// Backend implementation SHOULD fail the command if it seen
+// an unknown ExtensionOption type passed to it.
+type ExtensionOption interface {
+	ExtOption()
+}
+
+// ExtensionResult is an optional value that may be returned by
+// backend.
+//
+// Unknown value types are ignored.
+type ExtensionResult interface {
+	ExtResult()
 }

backend/extensions.go

@@ -0,0 +1,38 @@
+package backend
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// ExpungeSeqSet may be passed to Mailbox.Expunge() to restrict message
+// deletion to the specified UIDs sequence set.
+//
+// See RFC 2359 for details.
+type ExpungeSeqSet struct {
+	*imap.SeqSet
+}
+
+func (ExpungeSeqSet) ExtOption() {}
+
+// CopyUIDs must be returned as a result for CopyMessages by backends that
+// implement UIDPLUS extension.
+//
+// See RFC 2359 for value details.
+type CopyUIDs struct {
+	Source      *imap.SeqSet
+	UIDValidity uint32
+	Dest        *imap.SeqSet
+}
+
+func (CopyUIDs) ExtResult() {}
+
+// AppendUID must be returned as a result for CreateMessage by backend that
+// implement UIDPLUS extension.
+//
+// See RFC 2359 for value details.
+type AppendUID struct {
+	UIDValidity uint32
+	UID         uint32
+}
+
+func (AppendUID) ExtResult() {}

backend/mailbox.go

@@ -1,8 +1,6 @@
 package backend
 
 import (
-	"time"
-
 	"github.com/emersion/go-imap"
 )
 
@@ -15,51 +13,30 @@ type Mailbox interface {
 	// Closes the mailbox.
 	Close() error
 
-	// Info returns this mailbox info.
-	Info() (*imap.MailboxInfo, error)
-
-	// Status returns this mailbox status. The fields Name, Flags, PermanentFlags
-	// and UnseenSeqNum in the returned MailboxStatus must be always populated.
-	// This function does not affect the state of any messages in the mailbox. See
-	// RFC 3501 section 6.3.10 for a list of items that can be requested.
-	Status(items []imap.StatusItem) (*imap.MailboxStatus, error)
-
-	// SetSubscribed adds or removes the mailbox to the server's set of "active"
-	// or "subscribed" mailboxes.
-	SetSubscribed(subscribed bool) error
-
-	// Check requests a checkpoint of the currently selected mailbox. A checkpoint
-	// refers to any implementation-dependent housekeeping associated with the
-	// mailbox (e.g., resolving the server's in-memory state of the mailbox with
-	// the state on its disk). A checkpoint MAY take a non-instantaneous amount of
-	// real time to complete. If a server implementation has no such housekeeping
-	// considerations, CHECK is equivalent to NOOP.
-	Check() error
+	// Poll requests any pending mailbox updates to be sent.
+	//
+	// Argument indicates whether EXPUNGE updates are permitted to be
+	// sent.
+	Poll(expunge bool) error
 
 	// ListMessages returns a list of messages. seqset must be interpreted as UIDs
 	// if uid is set to true and as message sequence numbers otherwise. See RFC
 	// 3501 section 6.4.5 for a list of items that can be requested.
 	//
 	// Messages must be sent to ch. When the function returns, ch must be closed.
-	ListMessages(uid bool, seqset *imap.SeqSet, items []imap.FetchItem, ch chan<- *imap.Message) error
+	ListMessages(uid bool, seqset *imap.SeqSet, items []imap.FetchItem,
+		ch chan<- *imap.Message, opts []ExtensionOption) ([]ExtensionResult, error)
 
 	// SearchMessages searches messages. The returned list must contain UIDs if
 	// uid is set to true, or sequence numbers otherwise.
-	SearchMessages(uid bool, criteria *imap.SearchCriteria) ([]uint32, error)
-
-	// CreateMessage appends a new message to this mailbox. The \Recent flag will
-	// be added no matter flags is empty or not. If date is nil, the current time
-	// will be used.
-	//
-	// If the Backend implements Updater, it must notify the client immediately
-	// via a mailbox update.
-	CreateMessage(flags []string, date time.Time, body imap.Literal) error
+	SearchMessages(uid bool, criteria *imap.SearchCriteria, opts []ExtensionOption) ([]ExtensionResult, []uint32, error)
 
 	// UpdateMessagesFlags alters flags for the specified message(s).
 	//
 	// If the Backend implements Updater, it must notify the client immediately
 	// via a message update.
-	UpdateMessagesFlags(uid bool, seqset *imap.SeqSet, operation imap.FlagsOp, flags []string) error
+	UpdateMessagesFlags(uid bool, seqset *imap.SeqSet, operation imap.FlagsOp,
+		silent bool, flags []string, opts []ExtensionOption) ([]ExtensionResult, error)
 
 	// CopyMessages copies the specified message(s) to the end of the specified
 	// destination mailbox. The flags and internal date of the message(s) SHOULD
@@ -70,12 +47,12 @@ type Mailbox interface {
 	//
 	// If the Backend implements Updater, it must notify the client immediately
 	// via a mailbox update.
-	CopyMessages(uid bool, seqset *imap.SeqSet, dest string) error
+	CopyMessages(uid bool, seqset *imap.SeqSet, dest string, opts []ExtensionOption) ([]ExtensionResult, error)
 
 	// Expunge permanently removes all messages that have the \Deleted flag set
 	// from the currently selected mailbox.
 	//
 	// If the Backend implements Updater, it must notify the client immediately
 	// via an expunge update.
-	Expunge() error
+	Expunge(opts []ExtensionOption) ([]ExtensionResult, error)
 }

backend/memory/backend.go

@@ -22,6 +22,12 @@ func (be *Backend) Login(_ *imap.ConnInfo, username, password string) (backend.U
 	return nil, errors.New("Bad username or password")
 }
 
+func (be *Backend) SupportedExtensions() []backend.Extension {
+	return []backend.Extension{
+		backend.ExtUIDPLUS,
+	}
+}
+
 func New() *Backend {
 	user := &User{username: "username", password: "password"}
 

backend/memory/mailbox.go

@@ -1,9 +1,6 @@
 package memory
 
 import (
-	"io/ioutil"
-	"time"
-
 	"github.com/emersion/go-imap"
 	"github.com/emersion/go-imap/backend"
 	"github.com/emersion/go-imap/backend/backendutil"
@@ -19,11 +16,17 @@ type Mailbox struct {
 	user *User
 }
 
+type SelectedMailbox struct {
+	*Mailbox
+	conn     backend.Conn
+	readOnly bool
+}
+
 func (mbox *Mailbox) Name() string {
 	return mbox.name
 }
 
-func (mbox *Mailbox) Info() (*imap.MailboxInfo, error) {
+func (mbox *Mailbox) info() (*imap.MailboxInfo, error) {
 	info := &imap.MailboxInfo{
 		Delimiter: Delimiter,
 		Name:      mbox.name,
@@ -78,40 +81,11 @@ func (mbox *Mailbox) unseenSeqNum() uint32 {
 	return 0
 }
 
-func (mbox *Mailbox) Status(items []imap.StatusItem) (*imap.MailboxStatus, error) {
-	status := imap.NewMailboxStatus(mbox.name, items)
-	status.Flags = mbox.flags()
-	status.PermanentFlags = []string{"\\*"}
-	status.UnseenSeqNum = mbox.unseenSeqNum()
-
-	for _, name := range items {
-		switch name {
-		case imap.StatusMessages:
-			status.Messages = uint32(len(mbox.Messages))
-		case imap.StatusUidNext:
-			status.UidNext = mbox.uidNext()
-		case imap.StatusUidValidity:
-			status.UidValidity = 1
-		case imap.StatusRecent:
-			status.Recent = 0 // TODO
-		case imap.StatusUnseen:
-			status.Unseen = 0 // TODO
-		}
-	}
-
-	return status, nil
-}
-
-func (mbox *Mailbox) SetSubscribed(subscribed bool) error {
-	mbox.Subscribed = subscribed
+func (mbox *Mailbox) Poll(_ bool) error {
 	return nil
 }
 
-func (mbox *Mailbox) Check() error {
-	return nil
-}
-
-func (mbox *Mailbox) ListMessages(uid bool, seqSet *imap.SeqSet, items []imap.FetchItem, ch chan<- *imap.Message) error {
+func (mbox *Mailbox) ListMessages(uid bool, seqSet *imap.SeqSet, items []imap.FetchItem, ch chan<- *imap.Message, _ []backend.ExtensionOption) ([]backend.ExtensionResult, error) {
 	defer close(ch)
 
 	for i, msg := range mbox.Messages {
@@ -135,10 +109,10 @@ func (mbox *Mailbox) ListMessages(uid bool, seqSet *imap.SeqSet, items []imap.Fe
 		ch <- m
 	}
 
-	return nil
+	return nil, nil
 }
 
-func (mbox *Mailbox) SearchMessages(uid bool, criteria *imap.SearchCriteria) ([]uint32, error) {
+func (mbox *Mailbox) SearchMessages(uid bool, criteria *imap.SearchCriteria, _ []backend.ExtensionOption) ([]backend.ExtensionResult, []uint32, error) {
 	var ids []uint32
 	for i, msg := range mbox.Messages {
 		seqNum := uint32(i + 1)
@@ -156,30 +130,11 @@ func (mbox *Mailbox) SearchMessages(uid bool, criteria *imap.SearchCriteria) ([]
 		}
 		ids = append(ids, id)
 	}
-	return ids, nil
-}
-
-func (mbox *Mailbox) CreateMessage(flags []string, date time.Time, body imap.Literal) error {
-	if date.IsZero() {
-		date = time.Now()
-	}
-
-	b, err := ioutil.ReadAll(body)
-	if err != nil {
-		return err
-	}
-
-	mbox.Messages = append(mbox.Messages, &Message{
-		Uid:   mbox.uidNext(),
-		Date:  date,
-		Size:  uint32(len(b)),
-		Flags: flags,
-		Body:  b,
-	})
-	return nil
+	return nil, ids, nil
 }
 
-func (mbox *Mailbox) UpdateMessagesFlags(uid bool, seqset *imap.SeqSet, op imap.FlagsOp, flags []string) error {
+func (mbox *SelectedMailbox) UpdateMessagesFlags(uid bool, seqset *imap.SeqSet, op imap.FlagsOp,
+	silent bool, flags []string, _ []backend.ExtensionOption) ([]backend.ExtensionResult, error) {
 	for i, msg := range mbox.Messages {
 		var id uint32
 		if uid {
@@ -192,17 +147,29 @@ func (mbox *Mailbox) UpdateMessagesFlags(uid bool, seqset *imap.SeqSet, op imap.
 		}
 
 		msg.Flags = backendutil.UpdateFlags(msg.Flags, op, flags)
+
+		if !silent {
+			updMsg := imap.NewMessage(uint32(i+1), []imap.FetchItem{imap.FetchFlags})
+			updMsg.Flags = msg.Flags
+			if uid {
+				updMsg.Items[imap.FetchUid] = nil
+				updMsg.Uid = msg.Uid
+			}
+			mbox.conn.SendUpdate(&backend.MessageUpdate{Message: updMsg})
+		}
 	}
 
-	return nil
+	return nil, nil
 }
 
-func (mbox *Mailbox) CopyMessages(uid bool, seqset *imap.SeqSet, destName string) error {
+func (mbox *Mailbox) CopyMessages(uid bool, seqset *imap.SeqSet, destName string, _ []backend.ExtensionOption) ([]backend.ExtensionResult, error) {
 	dest, ok := mbox.user.mailboxes[destName]
 	if !ok {
-		return backend.ErrNoSuchMailbox
+		return nil, backend.ErrNoSuchMailbox
 	}
 
+	var srcSet, destSet imap.SeqSet
+
 	for i, msg := range mbox.Messages {
 		var id uint32
 		if uid {
@@ -214,15 +181,32 @@ func (mbox *Mailbox) CopyMessages(uid bool, seqset *imap.SeqSet, destName string
 			continue
 		}
 
+		srcSet.AddNum(msg.Uid)
+
 		msgCopy := *msg
 		msgCopy.Uid = dest.uidNext()
 		dest.Messages = append(dest.Messages, &msgCopy)
+		destSet.AddNum(msgCopy.Uid)
 	}
 
-	return nil
+	return []backend.ExtensionResult{
+		backend.CopyUIDs{
+			Source:      &srcSet,
+			UIDValidity: 1,
+			Dest:        &destSet,
+		},
+	}, nil
 }
 
-func (mbox *Mailbox) Expunge() error {
+func (mbox *SelectedMailbox) Expunge(opts []backend.ExtensionOption) ([]backend.ExtensionResult, error) {
+	var allowedUIDs *imap.SeqSet
+	for _, opt := range opts {
+		switch opt := opt.(type) {
+		case backend.ExpungeSeqSet:
+			allowedUIDs = opt.SeqSet
+		}
+	}
+
 	for i := len(mbox.Messages) - 1; i >= 0; i-- {
 		msg := mbox.Messages[i]
 
@@ -234,12 +218,18 @@ func (mbox *Mailbox) Expunge() error {
 			}
 		}
 
+		if allowedUIDs != nil && !allowedUIDs.Contains(msg.Uid) {
+			continue
+		}
+
 		if deleted {
 			mbox.Messages = append(mbox.Messages[:i], mbox.Messages[i+1:]...)
+
+			mbox.conn.SendUpdate(&backend.ExpungeUpdate{SeqNum: uint32(i + 1)})
 		}
 	}
 
-	return nil
+	return nil, nil
 }
 
 func (mbox *Mailbox) Close() error {