Some initial plumbing to test query serialization/deserialization so we

can make requests over websockets.

src/core/c_interface_wrappers.cpp

@@ -59,7 +59,7 @@
 #include <core/sdk/IStreamingEncoder.h>
 #include <core/sdk/IDevice.h>
 #include <core/sdk/IOutput.h>
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/library/ILibrary.h>
 #include <core/library/IIndexer.h>
 #include <core/library/track/TrackList.h>
@@ -1266,7 +1266,7 @@ mcsdk_export void mcsdk_svc_indexer_remove_callbacks(mcsdk_svc_indexer in, mcsdk
  * ILibrary
  */
 
-class mcsdk_db_wrapped_query: public LocalQueryBase {
+class mcsdk_db_wrapped_query: public QueryBase {
     public:
         mcsdk_db_wrapped_query(
             mcsdk_svc_library library,

src/core/core.vcxproj

@@ -500,6 +500,7 @@
     <ClCompile Include="library\LocalMetadataProxy.cpp" />
     <ClCompile Include="library\metadata\MetadataMap.cpp" />
     <ClCompile Include="library\metadata\MetadataMapList.cpp" />
+    <ClCompile Include="library\QueryRegistry.cpp" />
     <ClCompile Include="library\query\local\AlbumListQuery.cpp" />
     <ClCompile Include="library\query\local\AllCategoriesQuery.cpp" />
     <ClCompile Include="library\query\local\AppendPlaylistQuery.cpp" />
@@ -517,6 +518,7 @@
     <ClCompile Include="library\query\local\SetTrackRatingQuery.cpp" />
     <ClCompile Include="library\query\local\TrackMetadataQuery.cpp" />
     <ClCompile Include="library\query\local\util\CategoryQueryUtil.cpp" />
+    <ClCompile Include="library\RemoteLibrary.cpp" />
     <ClCompile Include="library\track\IndexerTrack.cpp" />
     <ClCompile Include="library\track\LibraryTrack.cpp" />
     <ClCompile Include="library\track\Track.cpp" />
@@ -577,8 +579,11 @@
     <ClInclude Include="library\LibraryFactory.h" />
     <ClInclude Include="library\LocalLibraryConstants.h" />
     <ClInclude Include="library\LocalMetadataProxy.h" />
+    <ClInclude Include="library\LocalQueryBase.h" />
     <ClInclude Include="library\metadata\MetadataMap.h" />
     <ClInclude Include="library\metadata\MetadataMapList.h" />
+    <ClInclude Include="library\QueryBase.h" />
+    <ClInclude Include="library\QueryRegistry.h" />
     <ClInclude Include="library\query\local\AlbumListQuery.h" />
     <ClInclude Include="library\query\local\AllCategoriesQuery.h" />
     <ClInclude Include="library\query\local\AppendPlaylistQuery.h" />
@@ -595,11 +600,11 @@
     <ClInclude Include="library\query\local\SearchTrackListQuery.h" />
     <ClInclude Include="library\query\local\SetTrackRatingQuery.h" />
     <ClInclude Include="library\query\local\TrackListQueryBase.h" />
-    <ClInclude Include="Library\query\local\LocalQueryBase.h" />
     <ClInclude Include="library\query\local\TrackMetadataQuery.h" />
     <ClInclude Include="library\query\local\util\CategoryQueryUtil.h" />
     <ClInclude Include="library\query\local\util\SdkWrappers.h" />
     <ClInclude Include="library\query\local\util\TrackSort.h" />
+    <ClInclude Include="library\RemoteLibrary.h" />
     <ClInclude Include="library\track\IndexerTrack.h" />
     <ClInclude Include="library\track\LibraryTrack.h" />
     <ClInclude Include="library\track\Track.h" />

src/core/core.vcxproj.filters

@@ -241,6 +241,12 @@
     <ClCompile Include="c_interface_wrappers.cpp">
       <Filter>src</Filter>
     </ClCompile>
+    <ClCompile Include="library\RemoteLibrary.cpp">
+      <Filter>src\library</Filter>
+    </ClCompile>
+    <ClCompile Include="library\QueryRegistry.cpp">
+      <Filter>src\library</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="pch.hpp">
@@ -399,9 +405,6 @@
     <ClInclude Include="library\query\local\CategoryListQuery.h">
       <Filter>src\library\query\local</Filter>
     </ClInclude>
-    <ClInclude Include="Library\query\local\LocalQueryBase.h">
-      <Filter>src\library\query\local</Filter>
-    </ClInclude>
     <ClInclude Include="plugin\Plugins.h">
       <Filter>src\plugin</Filter>
     </ClInclude>
@@ -594,5 +597,17 @@
     <ClInclude Include="sdk\ReplayGain.h">
       <Filter>src\sdk\metadata</Filter>
     </ClInclude>
+    <ClInclude Include="library\RemoteLibrary.h">
+      <Filter>src\library</Filter>
+    </ClInclude>
+    <ClInclude Include="library\QueryRegistry.h">
+      <Filter>src\library</Filter>
+    </ClInclude>
+    <ClInclude Include="library\LocalQueryBase.h">
+      <Filter>src\library</Filter>
+    </ClInclude>
+    <ClInclude Include="library\QueryBase.h">
+      <Filter>src\library</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>

src/core/library/IQuery.h

@@ -54,11 +54,18 @@ namespace musik { namespace core { namespace db {
             } Status;
 
             virtual ~IQuery() { }
-
             virtual int GetStatus() = 0;
             virtual int GetId() = 0;
             virtual int GetOptions() = 0;
             virtual std::string Name() = 0;
     };
 
+    class ISerializableQuery: public IQuery {
+        public:
+            virtual ~ISerializableQuery() { }
+            virtual std::string SerializeQuery() = 0;
+            virtual std::string SerializeResult() = 0;
+            virtual void DeserializeResult(const std::string& data) = 0;
+    };
+
 } } }

src/core/library/LibraryFactory.cpp

@@ -35,6 +35,7 @@
 #include "pch.hpp"
 #include <core/library/LibraryFactory.h>
 #include <core/library/LocalLibrary.h>
+#include <core/library/RemoteLibrary.h>
 #include <core/db/Connection.h>
 #include <core/support/Common.h>
 #include <core/support/Preferences.h>
@@ -56,20 +57,21 @@ LibraryFactory::LibraryFactory() {
     for (size_t i = 0; i < libraries.size(); i++) {
         std::string name = libraries.at(i);
         int id = prefs->GetInt(name);
-        this->AddLibrary(id, LocalLibrary, name);
+        this->AddLibrary(id, LibraryType::Local, name);
     }
 
     if (this->libraries.empty()) {
-        this->CreateLibrary("Local Library", LocalLibrary);
+        this->CreateLibrary("Local Library", LibraryType::Local);
     }
 }
 
 LibraryFactory::~LibraryFactory() {
 }
 
-ILibraryPtr LibraryFactory::AddLibrary(int id, int type, const std::string& name)
+ILibraryPtr LibraryFactory::AddLibrary(int id, LibraryType type, const std::string& name) {
-{
+    ILibraryPtr library = (type == LibraryType::Local)
-    ILibraryPtr library = library::LocalLibrary::Create(name, id);
+        ? library::LocalLibrary::Create(name, id)
+        : library::RemoteLibrary::Create(name, id);
 
     if (library) {
         this->libraries.push_back(library);
@@ -88,7 +90,7 @@ void LibraryFactory::Shutdown() {
     Instance().libraries.clear();
 }
 
-ILibraryPtr LibraryFactory::CreateLibrary(const std::string& name, int type) {
+ILibraryPtr LibraryFactory::CreateLibrary(const std::string& name, LibraryType type) {
     auto prefs = Preferences::ForComponent(prefs::components::Libraries);
     std::vector<std::string> libraries;
     prefs->GetKeys(libraries);
@@ -113,7 +115,7 @@ ILibraryPtr LibraryFactory::CreateLibrary(const std::string& name, int type) {
     ++nextId; /* unique */
     prefs->SetInt(name, nextId);
 
-    return this->AddLibrary(nextId, LocalLibrary, name);
+    return this->AddLibrary(nextId, type, name);
 }
 
 LibraryFactory::LibraryVector& LibraryFactory::Libraries() {

src/core/library/LibraryFactory.h

@@ -48,8 +48,9 @@ namespace musik { namespace core {
             typedef std::map<int, ILibraryPtr> LibraryMap;
             typedef sigslot::signal0<> LibrariesUpdatedEvent;
 
-            enum LibraryType {
+            enum class LibraryType: int {
-                LocalLibrary = 1
+                Local = 1,
+                Remote = 2
             };
 
             ~LibraryFactory();
@@ -58,7 +59,7 @@ namespace musik { namespace core {
             static LibraryVector& Libraries();
             static ILibraryPtr Default();
 
-            ILibraryPtr CreateLibrary(const std::string& name, int type);
+            ILibraryPtr CreateLibrary(const std::string& name, LibraryType type);
             void Shutdown();
 
             ILibraryPtr GetLibrary(int identifier);
@@ -67,7 +68,7 @@ namespace musik { namespace core {
         private:
             LibraryFactory();
 
-            ILibraryPtr AddLibrary(int id, int type, const std::string& name);
+            ILibraryPtr AddLibrary(int id, LibraryType type, const std::string& name);
 
             LibraryVector libraries;
             LibraryMap libraryMap;

src/core/library/LocalLibrary.cpp

@@ -36,7 +36,7 @@
 
 #include <core/library/LocalLibrary.h>
 #include <core/config.h>
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/support/Common.h>
 #include <core/support/Preferences.h>
 #include <core/library/Indexer.h>

src/core/library/LocalLibrary.h

@@ -40,7 +40,7 @@
 #include <core/library/ILibrary.h>
 #include <core/library/IIndexer.h>
 #include <core/library/IQuery.h>
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 
 #include <thread>
 #include <mutex>
@@ -57,7 +57,7 @@ namespace musik { namespace core { namespace library {
         public std::enable_shared_from_this<LocalLibrary>
     {
         public:
-            using LocalQuery = musik::core::db::LocalQueryBase;
+            using LocalQuery = musik::core::db::QueryBase;
             using LocalQueryPtr = std::shared_ptr<LocalQuery>;
 
             static ILibraryPtr Create(std::string name, int id);

src/core/library/LocalMetadataProxy.cpp

@@ -173,7 +173,7 @@ class ExternalIdListToTrackListQuery : public TrackListQueryBase {
         std::shared_ptr<TrackList> result;
 };
 
-class RemoveFromPlaylistQuery : public LocalQueryBase {
+class RemoveFromPlaylistQuery : public QueryBase {
     public:
         RemoveFromPlaylistQuery(
             ILibraryPtr library,

src/core/library/QueryBase.h

@@ -45,16 +45,16 @@
 
 namespace musik { namespace core { namespace db {
 
-    class LocalQueryBase : public IQuery, public sigslot::has_slots<> {
+    class QueryBase: public ISerializableQuery, public sigslot::has_slots<> {
         public:
-            LocalQueryBase()
+            QueryBase()
             : status(0)
             , options(0)
             , queryId(nextId())
             , cancel(false) {
             }
 
-            virtual ~LocalQueryBase() {
+            virtual ~QueryBase() {
             }
 
             bool Run(musik::core::db::Connection &db) {
@@ -76,6 +76,8 @@ namespace musik { namespace core { namespace db {
                 return false;
             }
 
+            /* IQuery */
+
             virtual int GetStatus() {
                 std::unique_lock<std::mutex> lock(this->stateMutex);
                 return this->status;
@@ -100,6 +102,20 @@ namespace musik { namespace core { namespace db {
 
             virtual std::string Name() = 0;
 
+            /* ISerializableQuery */
+
+            virtual std::string SerializeQuery() {
+                throw std::runtime_error("not implemented");
+            }
+
+            virtual std::string SerializeResult() {
+                throw std::runtime_error("not implemented");
+            }
+
+            virtual void DeserializeResult(const std::string& data) {
+                throw std::runtime_error("not implemented");
+            }
+
         protected:
             void SetStatus(int status) {
                 std::unique_lock<std::mutex> lock(this->stateMutex);

src/core/library/QueryRegistry.cpp

@@ -0,0 +1,57 @@
+//////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2004-2019 musikcube team
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+//    * Redistributions of source code must retain the above copyright notice,
+//      this list of conditions and the following disclaimer.
+//
+//    * Redistributions in binary form must reproduce the above copyright
+//      notice, this list of conditions and the following disclaimer in the
+//      documentation and/or other materials provided with the distribution.
+//
+//    * Neither the name of the author nor the names of other contributors may
+//      be used to endorse or promote products derived from this software
+//      without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+//////////////////////////////////////////////////////////////////////////////
+
+#include "pch.hpp"
+
+#include "QueryRegistry.h"
+#include <core/library/query/local/LyricsQuery.h>
+
+using namespace musik::core::db;
+using namespace musik::core::db::local;
+
+namespace musik { namespace core { namespace library {
+
+    namespace QueryRegistry {
+        std::shared_ptr<ISerializableQuery> CreateLocalQueryFor(
+            const std::string& name, const std::string& data)
+        {
+            if (name == LyricsQuery::kQueryName) {
+                return LyricsQuery::DeserializeQuery(data);
+            }
+
+            return std::shared_ptr<ISerializableQuery>();
+        }
+    }
+
+} } }

src/core/library/QueryRegistry.h

@@ -0,0 +1,48 @@
+//////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2004-2019 musikcube team
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+//    * Redistributions of source code must retain the above copyright notice,
+//      this list of conditions and the following disclaimer.
+//
+//    * Redistributions in binary form must reproduce the above copyright
+//      notice, this list of conditions and the following disclaimer in the
+//      documentation and/or other materials provided with the distribution.
+//
+//    * Neither the name of the author nor the names of other contributors may
+//      be used to endorse or promote products derived from this software
+//      without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+//////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#include <core/library/IQuery.h>
+#include <string>
+#include <memory>
+
+namespace musik { namespace core { namespace library {
+
+    namespace QueryRegistry {
+        std::shared_ptr<musik::core::db::ISerializableQuery> CreateLocalQueryFor(
+            const std::string& name, const std::string& data);
+    }
+
+} } }

src/core/library/RemoteLibrary.cpp

@@ -0,0 +1,233 @@
+//////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2004-2019 musikcube team
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+//    * Redistributions of source code must retain the above copyright notice,
+//      this list of conditions and the following disclaimer.
+//
+//    * Redistributions in binary form must reproduce the above copyright
+//      notice, this list of conditions and the following disclaimer in the
+//      documentation and/or other materials provided with the distribution.
+//
+//    * Neither the name of the author nor the names of other contributors may
+//      be used to endorse or promote products derived from this software
+//      without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+//////////////////////////////////////////////////////////////////////////////
+
+#include "pch.hpp"
+
+#include <core/library/RemoteLibrary.h>
+#include <core/config.h>
+#include <core/support/Common.h>
+#include <core/support/Preferences.h>
+#include <core/library/Indexer.h>
+#include <core/library/IQuery.h>
+#include <core/library/QueryRegistry.h>
+#include <core/runtime/Message.h>
+#include <core/debug.h>
+
+#include <core/library/LibraryFactory.h> /* CAL TODO: remove this */
+
+static const std::string TAG = "RemoteLibrary";
+
+using namespace musik::core;
+using namespace musik::core::db;
+using namespace musik::core::library;
+using namespace musik::core::runtime;
+
+#define MESSAGE_QUERY_COMPLETED 5000
+
+class RemoteLibrary::QueryCompletedMessage: public Message {
+    public:
+        using QueryContextPtr = RemoteLibrary::QueryContextPtr;
+
+        QueryCompletedMessage(IMessageTarget* target, QueryContextPtr context)
+        : Message(target, MESSAGE_QUERY_COMPLETED, 0, 0) {
+            this->context = context;
+        }
+
+        virtual ~QueryCompletedMessage() {
+        }
+
+        QueryContextPtr GetContext() { return this->context; }
+
+    private:
+        QueryContextPtr context;
+};
+
+ILibraryPtr RemoteLibrary::Create(std::string name, int id) {
+    ILibraryPtr lib(new RemoteLibrary(name, id));
+    return lib;
+}
+
+RemoteLibrary::RemoteLibrary(std::string name,int id)
+: name(name)
+, id(id)
+, exit(false)
+, messageQueue(nullptr) {
+    this->identifier = std::to_string(id);
+    this->thread = new std::thread(std::bind(&RemoteLibrary::ThreadProc, this));
+}
+
+RemoteLibrary::~RemoteLibrary() {
+    this->Close();
+}
+
+int RemoteLibrary::Id() {
+    return this->id;
+}
+
+const std::string& RemoteLibrary::Name() {
+    return this->name;
+}
+
+void RemoteLibrary::Close() {
+    std::thread* thread = nullptr;
+
+    {
+        std::unique_lock<std::recursive_mutex> lock(this->mutex);
+        if (this->thread) {
+            thread = this->thread;
+            this->thread = nullptr;
+            this->queryQueue.clear();
+            this->exit = true;
+        }
+    }
+
+    if (thread) {
+        this->queueCondition.notify_all();
+        thread->join();
+        delete thread;
+    }
+}
+
+int RemoteLibrary::Enqueue(QueryPtr query, unsigned int options, Callback callback) {
+    auto serializableQuery = std::dynamic_pointer_cast<ISerializableQuery>(query);
+
+    if (serializableQuery) {
+        std::unique_lock<std::recursive_mutex> lock(this->mutex);
+
+        if (this->exit) { /* closed */
+            return -1;
+        }
+
+        auto context = std::make_shared<QueryContext>();
+        context->query = serializableQuery;
+        context->callback = callback;
+
+        if (options & ILibrary::QuerySynchronous) {
+            this->RunQuery(context, false); /* false = do not notify via QueryCompleted */
+        }
+        else {
+            queryQueue.push_back(context);
+            queueCondition.notify_all();
+        }
+
+        return query->GetId();
+    }
+
+    return -1;
+}
+
+RemoteLibrary::QueryContextPtr RemoteLibrary::GetNextQuery() {
+    std::unique_lock<std::recursive_mutex> lock(this->mutex);
+    while (!this->queryQueue.size() && !this->exit) {
+        this->queueCondition.wait(lock);
+    }
+    if (this->exit) {
+        return QueryContextPtr();
+    }
+    else {
+        auto front = queryQueue.front();
+        queryQueue.pop_front();
+        return front;
+    }
+}
+
+void RemoteLibrary::ThreadProc() {
+    while (!this->exit) {
+        auto query = GetNextQuery();
+        if (query) {
+            this->RunQuery(query);
+        }
+    }
+}
+
+void RemoteLibrary::RunQuery(QueryContextPtr context, bool notify) {
+    if (context) {
+        auto queryBytes = context->query->SerializeQuery();
+        auto localQuery = QueryRegistry::CreateLocalQueryFor(context->query->Name(), queryBytes);
+
+        auto onComplete = [this, notify, context, localQuery]() {
+            if (notify) {
+                if (this->messageQueue) {
+                    this->messageQueue->Post(std::make_shared<QueryCompletedMessage>(this, context));
+                }
+                else {
+                    this->QueryCompleted(localQuery.get());
+                }
+            }
+            else if (context->callback) {
+                context->callback(context->query);
+            }
+
+            context->query.reset();
+        };
+
+        if (!localQuery) {
+            onComplete();
+            return;
+        }
+
+        /* CAL TODO: eventually make the request over a websocket. right now we just
+        do everything via loopback to the local library for testing. */
+        LibraryFactory::Default()->Enqueue(
+            localQuery, 
+            0, 
+            [context, onComplete, localQuery](auto result) {
+                if (localQuery->GetStatus() == IQuery::Finished) {
+                    context->query->DeserializeResult(localQuery->SerializeResult());
+                }
+                onComplete();
+            });
+    }
+}
+
+void RemoteLibrary::SetMessageQueue(musik::core::runtime::IMessageQueue& queue) {
+    this->messageQueue = &queue;
+}
+
+void RemoteLibrary::ProcessMessage(musik::core::runtime::IMessage &message) {
+    if (message.Type() == MESSAGE_QUERY_COMPLETED) {
+        auto context = static_cast<QueryCompletedMessage*>(&message)->GetContext();
+        auto query = context->query;
+
+        this->QueryCompleted(context->query.get());
+
+        if (context->callback) {
+            context->callback(query);
+        }
+    }
+}
+
+musik::core::IIndexer* RemoteLibrary::Indexer() {
+    return nullptr;
+}

src/core/library/RemoteLibrary.h

@@ -0,0 +1,110 @@
+//////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2004-2019 musikcube team
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+//    * Redistributions of source code must retain the above copyright notice,
+//      this list of conditions and the following disclaimer.
+//
+//    * Redistributions in binary form must reproduce the above copyright
+//      notice, this list of conditions and the following disclaimer in the
+//      documentation and/or other materials provided with the distribution.
+//
+//    * Neither the name of the author nor the names of other contributors may
+//      be used to endorse or promote products derived from this software
+//      without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+//////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#include <core/config.h>
+#include <core/db/Connection.h>
+
+#include <core/library/ILibrary.h>
+#include <core/library/IIndexer.h>
+#include <core/library/IQuery.h>
+
+#include <thread>
+#include <mutex>
+#include <condition_variable>
+
+#include <string>
+
+namespace musik { namespace core { namespace library {
+
+    class RemoteLibrary :
+        public ILibrary,
+        public musik::core::runtime::IMessageTarget,
+        public std::enable_shared_from_this<RemoteLibrary>
+    {
+        public:
+            static ILibraryPtr Create(std::string name, int id);
+
+            RemoteLibrary(const RemoteLibrary&) = delete;
+            virtual ~RemoteLibrary();
+
+            /* ILibrary */
+            virtual int Enqueue(
+                QueryPtr query,
+                unsigned int options = 0,
+                Callback = Callback()) override;
+
+            virtual musik::core::IIndexer *Indexer() override;
+            virtual int Id() override;
+            virtual const std::string& Name() override;
+            virtual void SetMessageQueue(musik::core::runtime::IMessageQueue& queue) override;
+            virtual musik::core::runtime::IMessageQueue& GetMessageQueue() override { return *messageQueue; }
+            virtual void Close() override;
+
+            /* IMessageTarget */
+            virtual void ProcessMessage(musik::core::runtime::IMessage &message) override;
+
+        private:
+            class QueryCompletedMessage;
+
+            struct QueryContext {
+                std::shared_ptr<musik::core::db::ISerializableQuery> query;
+                Callback callback;
+            };
+
+            using QueryContextPtr = std::shared_ptr<QueryContext>;
+            using QueryList = std::list<QueryContextPtr>;
+
+            RemoteLibrary(std::string name, int id); /* ctor */
+
+            void RunQuery(QueryContextPtr context, bool notify = true);
+            void ThreadProc();
+            QueryContextPtr GetNextQuery();
+
+            QueryList queryQueue;
+
+            musik::core::runtime::IMessageQueue* messageQueue;
+
+            std::string identifier;
+            int id;
+            std::string name;
+
+            std::thread* thread;
+            std::condition_variable_any queueCondition;
+            std::recursive_mutex mutex;
+            std::atomic<bool> exit;
+    };
+
+} } }

src/core/library/metadata/MetadataMap.cpp

@@ -35,7 +35,7 @@
 #include "pch.hpp"
 #include "MetadataMap.h"
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/library/LocalLibraryConstants.h>
 #include <core/db/Connection.h>
 #include <core/db/Statement.h>

src/core/library/query/local/AlbumListQuery.h

@@ -34,14 +34,14 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/library/query/local/util/CategoryQueryUtil.h>
 #include <core/library/metadata/MetadataMapList.h>
 #include <core/db/Connection.h>
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class AlbumListQuery : public musik::core::db::LocalQueryBase {
+    class AlbumListQuery : public musik::core::db::QueryBase {
         public:
             AlbumListQuery(
                 const std::string& filter = "");

src/core/library/query/local/AllCategoriesQuery.h

@@ -34,13 +34,13 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/library/query/local/util/SdkWrappers.h>
 #include <core/sdk/IValueList.h>
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class AllCategoriesQuery : public musik::core::db::LocalQueryBase {
+    class AllCategoriesQuery : public musik::core::db::QueryBase {
         public:
             using Result = SdkValueList::Shared;
 

src/core/library/query/local/AppendPlaylistQuery.h

@@ -34,14 +34,14 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/library/track/TrackList.h>
 #include <stdint.h>
 #include <vector>
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class AppendPlaylistQuery : public musik::core::db::LocalQueryBase {
+    class AppendPlaylistQuery : public musik::core::db::QueryBase {
         public:
             AppendPlaylistQuery(
                 musik::core::ILibraryPtr library,

src/core/library/query/local/CategoryListQuery.h

@@ -34,7 +34,7 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/library/query/local/util/CategoryQueryUtil.h>
 #include <core/library/query/local/util/SdkWrappers.h>
 #include <core/db/Statement.h>
@@ -45,7 +45,7 @@
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class CategoryListQuery : public musik::core::db::LocalQueryBase {
+    class CategoryListQuery : public musik::core::db::QueryBase {
         public:
             using Result = SdkValueList::Shared;
 

src/core/library/query/local/CategoryTrackListQuery.h

@@ -36,7 +36,7 @@
 
 #include <core/db/Connection.h>
 #include <core/library/track/Track.h>
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/library/query/local/util/CategoryQueryUtil.h>
 #include <core/library/query/local/util/TrackSort.h>
 #include <core/db/Statement.h>

src/core/library/query/local/DeletePlaylistQuery.h

@@ -35,12 +35,12 @@
 #pragma once
 
 #include <core/library/ILibrary.h>
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/db/Connection.h>
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class DeletePlaylistQuery : public musik::core::db::LocalQueryBase {
+    class DeletePlaylistQuery : public musik::core::db::QueryBase {
         public:
             DeletePlaylistQuery(
                 musik::core::ILibraryPtr library,

src/core/library/query/local/GetPlaylistQuery.h

@@ -36,7 +36,7 @@
 
 #include <core/db/Connection.h>
 #include <core/library/track/Track.h>
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 
 #include "TrackListQueryBase.h"
 

src/core/library/query/local/LyricsQuery.cpp

@@ -34,11 +34,16 @@
 
 #include "pch.hpp"
 #include "LyricsQuery.h"
+#include <json.hpp>
 
 using namespace musik::core::db;
 using namespace musik::core::db::local;
 using namespace musik::core::sdk;
 
+const std::string LyricsQuery::kQueryName = "LyricsQuery";
+
+/* IQuery */
+
 LyricsQuery::LyricsQuery(const std::string& trackExternalId) {
     this->trackExternalId = trackExternalId;
 }
@@ -70,4 +75,30 @@ bool LyricsQuery::OnRun(musik::core::db::Connection &db) {
     }
 
     return true;
+}
+
+/* ISerializableQuery */
+
+std::string LyricsQuery::SerializeQuery() {
+    nlohmann::json query;
+    query["name"] = this->Name();
+    query["options"] = {{ "trackExternalId", this->trackExternalId }};
+    return query.dump();
+}
+
+std::string LyricsQuery::SerializeResult() {
+    nlohmann::json query;
+    query["result"] = this->result;
+    return query.dump();
+}
+
+void LyricsQuery::DeserializeResult(const std::string& data) {
+    this->SetStatus(IQuery::Failed);
+    this->result = nlohmann::json::parse(data).value("result", "");
+    this->SetStatus(IQuery::Finished);
+}
+
+std::shared_ptr<LyricsQuery> LyricsQuery::DeserializeQuery(const std::string& data) {
+    nlohmann::json query = nlohmann::json::parse(data);
+    return std::make_shared<LyricsQuery>(query["options"].value("trackExternalId", ""));
 }

src/core/library/query/local/LyricsQuery.h

@@ -34,19 +34,27 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class LyricsQuery : public musik::core::db::LocalQueryBase {
+    class LyricsQuery: public musik::core::db::QueryBase {
         public:
+            static const std::string kQueryName;
+
             LyricsQuery(const std::string& trackExternalId);
             virtual ~LyricsQuery();
 
-            std::string Name() { return "LyricsQuery"; }
+            /* IQuery */
-
+            std::string Name() { return kQueryName; }
             virtual std::string GetResult();
 
+            /* ISerializableQuery */
+            virtual std::string SerializeQuery();
+            virtual std::string SerializeResult();
+            virtual void DeserializeResult(const std::string& data);
+            static std::shared_ptr<LyricsQuery> DeserializeQuery(const std::string& data);
+
         protected:
             virtual bool OnRun(musik::core::db::Connection &db);
 

src/core/library/query/local/MarkTrackPlayedQuery.h

@@ -34,11 +34,11 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class MarkTrackPlayedQuery: public musik::core::db::LocalQueryBase {
+    class MarkTrackPlayedQuery: public musik::core::db::QueryBase {
         public:
             MarkTrackPlayedQuery(const int64_t trackId);
             virtual ~MarkTrackPlayedQuery();

src/core/library/query/local/NowPlayingTrackListQuery.h

@@ -34,7 +34,7 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/audio/PlaybackService.h>
 
 #include "TrackListQueryBase.h"

src/core/library/query/local/PersistedPlayQueueQuery.h

@@ -34,12 +34,12 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/audio/PlaybackService.h>
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class PersistedPlayQueueQuery : public musik::core::db::LocalQueryBase {
+    class PersistedPlayQueueQuery : public musik::core::db::QueryBase {
         public:
             static PersistedPlayQueueQuery* Save(
                 musik::core::ILibraryPtr library,

src/core/library/query/local/SavePlaylistQuery.h

@@ -34,7 +34,7 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/library/track/TrackList.h>
 #include <core/db/Connection.h>
 #include <core/library/ILibrary.h>
@@ -42,7 +42,7 @@
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class SavePlaylistQuery : public musik::core::db::LocalQueryBase {
+    class SavePlaylistQuery : public musik::core::db::QueryBase {
         public:
             static std::shared_ptr<SavePlaylistQuery> Save(
                 musik::core::ILibraryPtr library,

src/core/library/query/local/SetTrackRatingQuery.h

@@ -34,11 +34,11 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class SetTrackRatingQuery: public musik::core::db::LocalQueryBase {
+    class SetTrackRatingQuery: public musik::core::db::QueryBase {
         public:
             SetTrackRatingQuery(int64_t trackId, int rating);
             virtual ~SetTrackRatingQuery();

src/core/library/query/local/TrackListQueryBase.h

@@ -34,14 +34,14 @@
 
 #pragma once
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/db/Connection.h>
 #include <core/library/track/Track.h>
 #include <core/library/track/TrackList.h>
 
 namespace musik { namespace core { namespace db { namespace local {
 
-    class TrackListQueryBase : public musik::core::db::LocalQueryBase {
+    class TrackListQueryBase : public musik::core::db::QueryBase {
         public:
             typedef std::shared_ptr<musik::core::TrackList> Result;
             typedef std::shared_ptr<std::set<size_t> > Headers;

src/core/library/query/local/TrackMetadataQuery.h

@@ -32,13 +32,13 @@
 //
 //////////////////////////////////////////////////////////////////////////////
 
-#include "LocalQueryBase.h"
+#include <core/library/QueryBase.h>
 
 #include <core/library/track/Track.h>
 
 namespace musik { namespace core { namespace db { namespace local {
 
-class TrackMetadataQuery : public LocalQueryBase {
+class TrackMetadataQuery : public QueryBase {
     public:
         enum Type { Full, IdsOnly };
 

src/core/library/track/TrackList.cpp

@@ -35,7 +35,7 @@
 #include "pch.hpp"
 #include "TrackList.h"
 
-#include <core/library/query/local/LocalQueryBase.h>
+#include <core/library/QueryBase.h>
 #include <core/library/track/LibraryTrack.h>
 #include <core/library/LocalLibraryConstants.h>
 #include <core/library/track/Track.h>

src/musikcube/app/layout/LyricsLayout.cpp

@@ -38,6 +38,7 @@
 #include <core/support/Auddio.h>
 #include <core/support/Common.h>
 #include <core/library/query/local/LyricsQuery.h>
+#include <core/library/RemoteLibrary.h>
 #include <cursespp/App.h>
 #include <cursespp/Screen.h>
 #include <cursespp/ToastOverlay.h>
@@ -71,6 +72,9 @@ LyricsLayout::LyricsLayout(PlaybackService& playback, ILibraryPtr library)
     this->AddWindow(this->infoText);
 
     this->LoadLyricsForCurrentTrack();
+
+    this->remoteLibrary = musik::core::library::RemoteLibrary::Create("remote", 0xdeadbeef);
+    this->remoteLibrary->SetMessageQueue(Window::MessageQueue());
 }
 
 void LyricsLayout::OnLayout() {
@@ -137,7 +141,7 @@ void LyricsLayout::LoadLyricsForCurrentTrack() {
         this->SetState(State::Loading);
         auto trackExternalId = track->GetString("external_id");
         auto lyricsDbQuery = std::make_shared<LyricsQuery>(trackExternalId);
-        this->library->Enqueue(lyricsDbQuery, 0, [this, lyricsDbQuery, track](auto q) {
+        this->remoteLibrary->Enqueue(lyricsDbQuery, 0, [this, lyricsDbQuery, track](auto q) {
             auto localLyrics = lyricsDbQuery->GetResult();
             if (localLyrics.size()) {
                 this->OnLyricsLoaded(track, localLyrics);

src/musikcube/app/layout/LyricsLayout.h

@@ -28,9 +28,6 @@ namespace musik { namespace cube {
         private:
             enum class State: int { NotPlaying, Loading, Loaded, Failed };
 
-            void OnAdapterChanged(cursespp::SimpleScrollAdapter* adapter);
-            void OnSelectionChanged(cursespp::ListWindow* window, size_t index, size_t prev);
-            void OnPlaybackEvent(int playbackEvent);
             void OnTrackChanged(size_t index, musik::core::TrackPtr track);
             void OnLyricsLoaded(musik::core::TrackPtr track, const std::string& lyrics);
 
@@ -39,7 +36,7 @@ namespace musik { namespace cube {
             void UpdateAdapter(const std::string& lyrics);
 
             State state { State::NotPlaying };
-            musik::core::ILibraryPtr library;
+            musik::core::ILibraryPtr library, remoteLibrary;
             musik::core::audio::PlaybackService& playback;
             std::shared_ptr<cursespp::SimpleScrollAdapter> adapter;
             std::shared_ptr<cursespp::ListWindow> listView;