threading: add backend capabilities to workers

This patch provides a method to report backend capabilities to the UI.
The intial capabilities included in the report are Sort and Thread.
Having these available to the UI enables the client to better handle
server side threading.

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

models/models.go

@@ -51,6 +51,15 @@ type DirectoryInfo struct {
 
 	// set to true if the value counts are accurate
 	AccurateCounts bool
+
+	// Caps contains the backend capabilities
+	Caps *Capabilities
+}
+
+// Capabilities provides the backend capabilities
+type Capabilities struct {
+	Sort   bool
+	Thread bool
 }
 
 // A MessageInfo holds information about the structure of a message

worker/imap/checkmail.go

@@ -31,6 +31,7 @@ func (w *IMAPWorker) handleCheckMailMessage(msg *types.CheckMail) {
 					Exists: int(status.Messages),
 					Recent: int(status.Recent),
 					Unseen: int(status.Unseen),
+					Caps:   w.caps,
 				},
 				SkipSort: true,
 			}, nil)

worker/imap/worker.go

@@ -66,6 +66,8 @@ type IMAPWorker struct {
 	idler    *idler
 	observer *observer
 	cache    *leveldb.DB
+
+	caps *models.Capabilities
 }
 
 func NewIMAPWorker(worker *types.Worker) (types.Backend, error) {
@@ -75,6 +77,7 @@ func NewIMAPWorker(worker *types.Worker) (types.Backend, error) {
 		selected: &imap.MailboxStatus{},
 		idler:    newIdler(imapConfig{}, worker),
 		observer: newObserver(imapConfig{}, worker),
+		caps:     &models.Capabilities{},
 	}, nil
 }
 
@@ -83,6 +86,16 @@ func (w *IMAPWorker) newClient(c *client.Client) {
 	w.client = &imapClient{c, sortthread.NewThreadClient(c), sortthread.NewSortClient(c)}
 	w.idler.SetClient(w.client)
 	w.observer.SetClient(w.client)
+	sort, err := w.client.sort.SupportSort()
+	if err == nil && sort {
+		w.caps.Sort = true
+		w.worker.Logger.Println("Server Capability found: Sort")
+	}
+	thread, err := w.client.thread.SupportThread()
+	if err == nil && thread {
+		w.caps.Thread = true
+		w.worker.Logger.Println("Server Capability found: Thread")
+	}
 }
 
 func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
@@ -226,6 +239,7 @@ func (w *IMAPWorker) handleImapUpdate(update client.Update) {
 				Exists: int(status.Messages),
 				Recent: int(status.Recent),
 				Unseen: int(status.Unseen),
+				Caps:   w.caps,
 			},
 		}, nil)
 	case *client.MessageUpdate:

worker/maildir/worker.go

@@ -186,6 +186,11 @@ func (w *Worker) getDirectoryInfo(name string) *models.DirectoryInfo {
 		Unseen: 0,
 
 		AccurateCounts: false,
+
+		Caps: &models.Capabilities{
+			Sort:   true,
+			Thread: false,
+		},
 	}
 
 	dir := w.c.Dir(name)

worker/notmuch/worker.go

@@ -228,6 +228,11 @@ func (w *worker) gatherDirectoryInfo(name string, query string) (
 			// total unread
 			Unseen:         count.Unread,
 			AccurateCounts: true,
+
+			Caps: &models.Capabilities{
+				Sort:   true,
+				Thread: true,
+			},
 		},
 	}
 	return info, nil