GODT-1657: Stable sync (still needs more tests)

internal/user/sync_flusher.go

@@ -0,0 +1,56 @@
+package user
+
+import (
+	"context"
+	"sync"
+
+	"github.com/ProtonMail/gluon/imap"
+	"github.com/ProtonMail/gluon/queue"
+)
+
+type flusher struct {
+	userID   string
+	updateCh *queue.QueuedChannel[imap.Update]
+
+	updates      []*imap.MessageCreated
+	maxChunkSize int
+	curChunkSize int
+
+	pushLock sync.Mutex
+}
+
+func newFlusher(userID string, updateCh *queue.QueuedChannel[imap.Update], maxChunkSize int) *flusher {
+	return &flusher{
+		userID:       userID,
+		updateCh:     updateCh,
+		maxChunkSize: maxChunkSize,
+	}
+}
+
+func (f *flusher) push(ctx context.Context, update *imap.MessageCreated) {
+	f.pushLock.Lock()
+	defer f.pushLock.Unlock()
+
+	f.updates = append(f.updates, update)
+
+	if f.curChunkSize += len(update.Literal); f.curChunkSize >= f.maxChunkSize {
+		f.flush(ctx, false)
+	}
+}
+
+func (f *flusher) flush(ctx context.Context, wait bool) {
+	if len(f.updates) == 0 {
+		return
+	}
+
+	f.updateCh.Enqueue(imap.NewMessagesCreated(f.updates...))
+	f.updates = nil
+	f.curChunkSize = 0
+
+	if wait {
+		update := imap.NewNoop()
+		defer update.WaitContext(ctx)
+
+		f.updateCh.Enqueue(update)
+	}
+}