Implement resumable download queue (T-301)

core/downloader/application_observer.go

@@ -0,0 +1,79 @@
+package downloader
+
+import (
+	"context"
+
+	"softbox.local/core/application"
+)
+
+// ApplicationPublisher is implemented by application.Runtime.
+type ApplicationPublisher interface {
+	Publish(context.Context, application.Event) error
+}
+
+// ApplicationObserver maps downloader events to the documented application
+// event envelope and concrete payloads.
+type ApplicationObserver struct {
+	Publisher ApplicationPublisher
+}
+
+// PublishDownload implements Observer.
+func (observer ApplicationObserver) PublishDownload(
+	ctx context.Context,
+	event Event,
+) error {
+	if observer.Publisher == nil {
+		return nil
+	}
+	envelope := application.Event{
+		RequestID: event.RequestID,
+		AppID:     event.AppID,
+	}
+	switch event.Type {
+	case EventStarted:
+		envelope.Type = application.EventDownloadStarted
+		envelope.Payload = application.DownloadStartedPayload{
+			Attempt:    event.Attempt,
+			Done:       event.Done,
+			TotalKnown: event.TotalKnown,
+			Total:      event.Total,
+		}
+	case EventProgress:
+		envelope.Type = application.EventDownloadProgress
+		envelope.Payload = application.DownloadProgressPayload{
+			Attempt:       event.Attempt,
+			Done:          event.Done,
+			TotalKnown:    event.TotalKnown,
+			Total:         event.Total,
+			SpeedBytesSec: event.SpeedBytesSec,
+		}
+	case EventPaused:
+		envelope.Type = application.EventDownloadPaused
+		envelope.Payload = application.DownloadPausedPayload{
+			Attempt: event.Attempt,
+			Done:    event.Done,
+		}
+	case EventCompleted:
+		envelope.Type = application.EventDownloadCompleted
+		envelope.Payload = application.DownloadCompletedPayload{
+			Attempt: event.Attempt,
+			Done:    event.Done,
+			Path:    event.CompletedPath,
+		}
+	case EventFailed:
+		envelope.Type = application.EventDownloadFailed
+		envelope.Payload = application.DownloadFailedPayload{
+			Attempt:   event.Attempt,
+			Done:      event.Done,
+			ErrorCode: event.ErrorCode,
+		}
+	case EventCanceled:
+		envelope.Type = application.EventDownloadCanceled
+		envelope.Payload = application.DownloadCanceledPayload{
+			Attempt: event.Attempt,
+		}
+	default:
+		return nil
+	}
+	return observer.Publisher.Publish(ctx, envelope)
+}