Prepare next level of metadata synchronization

...by tracking synchronization (import/export) with an external source
with time stamps instead of only a boolean flag.

1 files changed, 11 insertions, 4 deletions

diff --git a/src/sources/metadatasource.h b/src/sources/metadatasource.h
index 56e9ade414..740f65e10b 100644
--- a/src/sources/metadatasource.h
+++ b/src/sources/metadatasource.h
@@ -1,7 +1,10 @@
 #pragma once
 
+#include <QDateTime>
 #include <QImage>
 
+#include <utility>
+
 #include "track/trackmetadata.h"
 #include "util/memory.h"
 
@@ -10,6 +13,10 @@ namespace mixxx {
 
 // API and abstract base class for parsing track metadata and
 // cover art.
+//
+// The time stamp returned from the source when importing/exporting
+// metadata reflects the current version of the metadata at the source
+// and can be used for synchronization purposes.
 class MetadataSource {
   public:
     virtual ~MetadataSource() {}
@@ -25,10 +32,10 @@ class MetadataSource {
     // and might be passed a nullptr if their result is not needed.
     // If no metadata is available for a track then the source should
     // return Unavailable as this default implementation does.
-    virtual ImportResult importTrackMetadataAndCoverImage(
+    virtual std::pair<ImportResult, QDateTime> importTrackMetadataAndCoverImage(
             TrackMetadata* /*pTrackMetadata*/,
             QImage* /*pCoverImage*/) const {
-        return ImportResult::Unavailable;
+        return std::make_pair(ImportResult::Unavailable, QDateTime());
     }
 
     enum class ExportResult {
@@ -40,9 +47,9 @@ class MetadataSource {
     // Update track metadata of the source.
     // Sources that are read-only and don't support updating of metadata
     // should return Unsupported as this default implementation does.
-    virtual ExportResult exportTrackMetadata(
+    virtual std::pair<ExportResult, QDateTime> exportTrackMetadata(
             const TrackMetadata& /*trackMetadata*/) const {
-        return ExportResult::Unsupported;
+        return std::make_pair(ExportResult::Unsupported, QDateTime());
     }
 };