6 files changed, 60 insertions, 12 deletions

diff --git a/common/entitystore.cpp b/common/entitystore.cpp
index 5f44609..5296d53 100644
--- a/common/entitystore.cpp
+++ b/common/entitystore.cpp
@@ -28,17 +28,18 @@ EntityStore::EntityStore(const QByteArray &resourceType, const QByteArray &resou
 
 }
 
-QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> EntityStore::getLatest(const Sink::Storage::NamedDatabase &db, const QByteArray &uid, DomainTypeAdaptorFactoryInterface &adaptorFactory)
+QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> EntityStore::getLatest(const Sink::Storage::NamedDatabase &db, const QByteArray &uid, DomainTypeAdaptorFactoryInterface &adaptorFactory, qint64 &retrievedRevision)
 {
     QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> current;
     db.findLatest(uid,
-        [&current, &adaptorFactory](const QByteArray &key, const QByteArray &data) -> bool {
+        [&current, &adaptorFactory, &retrievedRevision](const QByteArray &key, const QByteArray &data) -> bool {
             Sink::EntityBuffer buffer(const_cast<const char *>(data.data()), data.size());
             if (!buffer.isValid()) {
                 Warning() << "Read invalid buffer from disk";
             } else {
                 Trace() << "Found value " << key;
                 current = adaptorFactory.createAdaptor(buffer.entity());
+                retrievedRevision = Sink::Storage::revisionFromKey(key);
             }
             return false;
         },
@@ -46,19 +47,36 @@ QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> EntityStore::getLatest(co
     return current;
 }
 
-QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> EntityStore::get(const Sink::Storage::NamedDatabase &db, const QByteArray &key, DomainTypeAdaptorFactoryInterface &adaptorFactory)
+QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> EntityStore::get(const Sink::Storage::NamedDatabase &db, const QByteArray &key, DomainTypeAdaptorFactoryInterface &adaptorFactory, qint64 &retrievedRevision)
 {
     QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> current;
     db.scan(key,
-        [&current, &adaptorFactory](const QByteArray &key, const QByteArray &data) -> bool {
+        [&current, &adaptorFactory, &retrievedRevision](const QByteArray &key, const QByteArray &data) -> bool {
             Sink::EntityBuffer buffer(const_cast<const char *>(data.data()), data.size());
             if (!buffer.isValid()) {
                 Warning() << "Read invalid buffer from disk";
             } else {
                 current = adaptorFactory.createAdaptor(buffer.entity());
+                retrievedRevision = Sink::Storage::revisionFromKey(key);
             }
             return false;
         },
         [](const Sink::Storage::Error &error) { Warning() << "Failed to read current value from storage: " << error.message; });
     return current;
 }
+
+QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> EntityStore::getPrevious(const Sink::Storage::NamedDatabase &db, const QByteArray &uid, qint64 revision, DomainTypeAdaptorFactoryInterface &adaptorFactory, qint64 &retrievedRevision)
+{
+    QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> current;
+    qint64 latestRevision = 0;
+    db.scan(uid,
+        [&current, &latestRevision, revision](const QByteArray &key, const QByteArray &) -> bool {
+            auto foundRevision = Sink::Storage::revisionFromKey(key);
+            if (foundRevision < revision && foundRevision > latestRevision) {
+                latestRevision = foundRevision;
+            }
+            return true;
+        },
+        [](const Sink::Storage::Error &error) { Warning() << "Failed to read current value from storage: " << error.message; }, true);
+    return get(db, Sink::Storage::assembleKey(uid, latestRevision), adaptorFactory, retrievedRevision);
+}
diff --git a/common/entitystore.h b/common/entitystore.h
index b6f8713..24f43b1 100644
--- a/common/entitystore.h
+++ b/common/entitystore.h
@@ -37,11 +37,12 @@ public:
     {
         auto typeName = ApplicationDomain::getTypeName<T>();
         auto mainDatabase = Storage::mainDatabase(mTransaction, typeName);
-        auto bufferAdaptor = getLatest(mainDatabase, identifier, *Sink::AdaptorFactoryRegistry::instance().getFactory<T>(mResourceType));
+        qint64 retrievedRevision = 0;
+        auto bufferAdaptor = getLatest(mainDatabase, identifier, *Sink::AdaptorFactoryRegistry::instance().getFactory<T>(mResourceType), retrievedRevision);
         if (!bufferAdaptor) {
             return T();
         }
-        return T(mResourceInstanceIdentifier, identifier, 0, bufferAdaptor);
+        return T(mResourceInstanceIdentifier, identifier, retrievedRevision, bufferAdaptor);
     }
 
     template<typename T>
@@ -49,17 +50,33 @@ public:
     {
         auto typeName = ApplicationDomain::getTypeName<T>();
         auto mainDatabase = Storage::mainDatabase(mTransaction, typeName);
-        auto bufferAdaptor = get(mainDatabase, key, *Sink::AdaptorFactoryRegistry::instance().getFactory<T>(mResourceType));
+        qint64 retrievedRevision = 0;
+        auto bufferAdaptor = get(mainDatabase, key, *Sink::AdaptorFactoryRegistry::instance().getFactory<T>(mResourceType), retrievedRevision);
         const auto identifier = Storage::uidFromKey(key);
         if (!bufferAdaptor) {
             return T();
         }
-        return T(mResourceInstanceIdentifier, identifier, 0, bufferAdaptor);
+        return T(mResourceInstanceIdentifier, identifier, retrievedRevision, bufferAdaptor);
     }
 
+    template<typename T>
+    T readPrevious(const QByteArray &uid, qint64 revision) const
+    {
+        auto typeName = ApplicationDomain::getTypeName<T>();
+        auto mainDatabase = Storage::mainDatabase(mTransaction, typeName);
+        qint64 retrievedRevision = 0;
+        auto bufferAdaptor = getPrevious(mainDatabase, uid, revision, *Sink::AdaptorFactoryRegistry::instance().getFactory<T>(mResourceType), retrievedRevision);
+        if (!bufferAdaptor) {
+            return T();
+        }
+        return T(mResourceInstanceIdentifier, uid, retrievedRevision, bufferAdaptor);
+    }
+
+
 
-    static QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> getLatest(const Sink::Storage::NamedDatabase &db, const QByteArray &uid, DomainTypeAdaptorFactoryInterface &adaptorFactory);
-    static QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> get(const Sink::Storage::NamedDatabase &db, const QByteArray &key, DomainTypeAdaptorFactoryInterface &adaptorFactory);
+    static QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> getLatest(const Sink::Storage::NamedDatabase &db, const QByteArray &uid, DomainTypeAdaptorFactoryInterface &adaptorFactory, qint64 &retrievedRevision);
+    static QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> get(const Sink::Storage::NamedDatabase &db, const QByteArray &key, DomainTypeAdaptorFactoryInterface &adaptorFactory, qint64 &retrievedRevision);
+    static QSharedPointer<Sink::ApplicationDomain::BufferAdaptor> getPrevious(const Sink::Storage::NamedDatabase &db, const QByteArray &uid, qint64 revision, DomainTypeAdaptorFactoryInterface &adaptorFactory, qint64 &retrievedRevision);
 private:
     QByteArray mResourceType;
     QByteArray mResourceInstanceIdentifier;
diff --git a/common/sourcewriteback.h b/common/sourcewriteback.h
index 6c6eaab..9fe5c66 100644
--- a/common/sourcewriteback.h
+++ b/common/sourcewriteback.h
@@ -48,6 +48,12 @@ protected:
     //Read/Write access to sync storage
     RemoteIdMap &syncStore();
 
+    template <typename T>
+    T getPrevious(const T &entity)
+    {
+        return store().readPrevious<T>(entity.identifier(), entity.revision());
+    }
+
 private:
     //Read only access to main storage
     EntityStore &store();
diff --git a/common/storage.h b/common/storage.h
index 0527c4f..2661439 100644
--- a/common/storage.h
+++ b/common/storage.h
@@ -216,6 +216,7 @@ public:
 
     static QByteArray assembleKey(const QByteArray &key, qint64 revision);
     static QByteArray uidFromKey(const QByteArray &key);
+    static qint64 revisionFromKey(const QByteArray &key);
 
     static NamedDatabase mainDatabase(const Sink::Storage::Transaction &, const QByteArray &type);
 
diff --git a/common/storage_common.cpp b/common/storage_common.cpp
index 4ca484a..8227a98 100644
--- a/common/storage_common.cpp
+++ b/common/storage_common.cpp
@@ -163,6 +163,11 @@ QByteArray Storage::uidFromKey(const QByteArray &key)
     return key.mid(0, 38);
 }
 
+qint64 Storage::revisionFromKey(const QByteArray &key)
+{
+    return key.mid(39).toLongLong();
+}
+
 Storage::NamedDatabase Storage::mainDatabase(const Sink::Storage::Transaction &t, const QByteArray &type)
 {
     return t.openDatabase(type + ".main");
diff --git a/common/synchronizer.cpp b/common/synchronizer.cpp
index 4bd8a5b..1bac5d9 100644
--- a/common/synchronizer.cpp
+++ b/common/synchronizer.cpp
@@ -119,8 +119,8 @@ void Synchronizer::scanForRemovals(const QByteArray &bufferType, const std::func
 {
     entryGenerator([this, bufferType, &exists](const QByteArray &key) {
         auto sinkId = Sink::Storage::uidFromKey(key);
-        Trace() << "Checking for removal " << key;
         const auto remoteId = syncStore().resolveLocalId(bufferType, sinkId);
+        Trace() << "Checking for removal " << key << remoteId;
         // If we have no remoteId, the entity hasn't been replayed to the source yet
         if (!remoteId.isEmpty()) {
             if (!exists(remoteId)) {
@@ -144,7 +144,8 @@ void Synchronizer::createOrModify(const QByteArray &bufferType, const QByteArray
         createEntity(
             sinkId, bufferType, entity, *adaptorFactory, [this](const QByteArray &buffer) { enqueueCommand(Sink::Commands::CreateEntityCommand, buffer); });
     } else { // modification
-        if (auto current = store().getLatest(mainDatabase, sinkId, *adaptorFactory)) {
+        qint64 retrievedRevision = 0;
+        if (auto current = store().getLatest(mainDatabase, sinkId, *adaptorFactory, retrievedRevision)) {
             bool changed = false;
             for (const auto &property : entity.changedProperties()) {
                 if (entity.getProperty(property) != current->getProperty(property)) {