Implement caching

include/IAlbum.h

 #ifndef IALBUM_H
 #define IALBUM_H
 
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -16,7 +17,7 @@ class IAlbum
         virtual unsigned int releaseYear() = 0;
         virtual const std::string& shortSummary() = 0;
         virtual const std::string& artworkUrl() = 0;
-        virtual const std::vector<IAlbumTrack*>& tracks() = 0;
+        virtual const std::vector<std::shared_ptr<IAlbumTrack>>& tracks() = 0;
 };
 
 #endif // IALBUM_H

include/IAlbumTrack.h

 #ifndef IALBUMTRACK_H
 #define IALBUMTRACK_H
 
+#include <memory>
 #include <string>
 
 class IAlbum;
@@ -13,7 +14,7 @@ class IAlbumTrack
         virtual const std::string& genre() = 0;
         virtual const std::string& title() = 0;
         virtual unsigned int trackNumber() = 0;
-        virtual IAlbum* album() = 0;
+        virtual std::shared_ptr<IAlbum> album() = 0;
 };
 
 #endif // IALBUMTRACK_H

include/IFile.h

@@ -2,7 +2,7 @@
 #define IFILE_H
 
 #include <vector>
-
+#include <memory>
 #include "ITrackInformation.h"
 
 class IAlbumTrack;
@@ -16,15 +16,14 @@ class IFile
         virtual ~IFile() {}
 
         virtual unsigned int id() const = 0;
-        virtual IAlbumTrack* albumTrack() = 0;
+        virtual std::shared_ptr<IAlbumTrack> albumTrack() = 0;
         virtual unsigned int duration() = 0;
-        virtual IShowEpisode* showEpisode() = 0;
+        virtual std::shared_ptr<IShowEpisode> showEpisode() = 0;
         virtual int playCount() = 0;
         virtual const std::string& mrl() = 0;
-        virtual ILabel* addLabel( const std::string& label ) = 0;
-        virtual bool removeLabel( const ILabel* label ) = 0;
-        
-        virtual std::vector<ILabel*> labels() = 0;
+        virtual std::shared_ptr<ILabel> addLabel( const std::string& label ) = 0;
+        virtual bool removeLabel( const std::shared_ptr<ILabel>& label ) = 0;
+        virtual const std::vector<std::shared_ptr<ILabel>>& labels() = 0;
 };
 
 #endif // IFILE_H

include/ILabel.h

 #ifndef ILABEL_H
 #define ILABEL_H
 
+#include <memory>
 #include <vector>
 
 class IFile;
@@ -12,7 +13,7 @@ class ILabel
 
         virtual unsigned int id() const = 0;
         virtual const std::string& name() = 0;
-        virtual std::vector<IFile*> files() = 0;
+        virtual std::vector<std::shared_ptr<IFile>>& files() = 0;
         virtual bool link( IFile* file ) = 0;
         virtual bool unlink( IFile* file ) const = 0;
 };

include/IMediaLibrary.h

@@ -3,17 +3,20 @@
 
 #include <vector>
 #include <string>
+#include <memory>
 
-#include "IFile.h"
+class IFile;
+
+typedef std::shared_ptr<IFile> FilePtr;
 
 class IMediaLibrary
 {
     public:
         virtual ~IMediaLibrary() {}
         virtual bool initialize( const std::string& dbPath ) = 0;
-        virtual IFile* addFile( const std::string& path ) = 0;
-        virtual IFile* file( const std::string& path ) = 0;
-        virtual const std::vector<IFile*>& files() = 0;
+        virtual FilePtr addFile( const std::string& path ) = 0;
+        virtual FilePtr file( const std::string& path ) = 0;
+        virtual bool files( std::vector<FilePtr>& res ) = 0;
 };
 
 class MediaLibraryFactory

include/IShowEpisode.h

@@ -3,6 +3,7 @@
 
 class IShow;
 
+#include <memory>
 #include <string>
 
 class IShowEpisode
@@ -17,7 +18,7 @@ class IShowEpisode
         virtual unsigned int seasonNuber() = 0;
         virtual const std::string& shortSummary() = 0;
         virtual const std::string& tvdbId() = 0;
-        virtual IShow* show() = 0;
+        virtual std::shared_ptr<IShow> show() = 0;
 };
 
 #endif // ISHOWEPISODE_H

src/Album.cpp

@@ -3,6 +3,9 @@
 
 #include "SqliteTools.h"
 
+const std::string policy::AlbumTable::Name = "Album";
+const std::string policy::AlbumTable::CacheColumn = "id_album";
+
 Album::Album(sqlite3* dbConnection, sqlite3_stmt* stmt)
     : m_dbConnection( dbConnection )
 {
@@ -39,12 +42,13 @@ time_t Album::lastSyncDate()
     return m_lastSyncDate;
 }
 
-const std::vector<IAlbumTrack*>&Album::tracks()
+const std::vector<std::shared_ptr<IAlbumTrack>>& Album::tracks()
 {
     if ( m_tracks == NULL )
     {
+        m_tracks = new std::vector<std::shared_ptr<IAlbumTrack>>;
         const char* req = "SELECT * FROM AlbumTrack WHERE id_album = ?";
-        SqliteTools::fetchAll<AlbumTrack>( m_dbConnection, req, m_id, m_tracks );
+        SqliteTools::fetchAll<AlbumTrack>( m_dbConnection, req, m_id, *m_tracks );
     }
     return *m_tracks;
 }
@@ -61,9 +65,3 @@ bool Album::createTable( sqlite3* dbConnection )
             ")";
     return SqliteTools::createTable( dbConnection, req );
 }
-
-Album* Album::fetch(sqlite3* dbConnection, unsigned int albumTrackId)
-{
-    const char* req = "SELECT * FROM Album WHERE id_album = ?";
-    return SqliteTools::fetchOne<Album>( dbConnection, req, albumTrackId );
-}

src/Album.h

 #ifndef ALBUM_H
 #define ALBUM_H
 
+#include <memory>
 #include <sqlite3.h>
 
+#include "Cache.h"
 #include "IAlbum.h"
 
-class Album : public IAlbum
+namespace policy
+{
+struct AlbumTable
+{
+    static const std::string Name;
+    static const std::string CacheColumn;
+};
+}
+
+class Album : public IAlbum, public Cache<Album, IAlbum, policy::AlbumTable>
 {
     public:
         Album( sqlite3* dbConnection, sqlite3_stmt* stmt );
@@ -15,10 +26,9 @@ class Album : public IAlbum
         virtual const std::string& shortSummary();
         virtual const std::string& artworkUrl();
         virtual time_t lastSyncDate();
-        virtual const std::vector<IAlbumTrack*>& tracks();
+        virtual const std::vector<std::shared_ptr<IAlbumTrack>>& tracks();
 
         static bool createTable( sqlite3* dbConnection );
-        static Album* fetch( sqlite3* dbConnection, unsigned int albumTrackId );
 
     protected:
         sqlite3* m_dbConnection;
@@ -29,7 +39,9 @@ class Album : public IAlbum
         std::string m_artworkUrl;
         time_t m_lastSyncDate;
 
-        std::vector<IAlbumTrack*>* m_tracks;
+        std::vector<std::shared_ptr<IAlbumTrack>>* m_tracks;
+
+        friend class Cache<Album, IAlbum, policy::AlbumTable>;
 };
 
 #endif // ALBUM_H

src/AlbumTrack.cpp

@@ -2,6 +2,9 @@
 #include "Album.h"
 #include "SqliteTools.h"
 
+const std::string policy::AlbumTrackTable::Name = "AlbumTrack";
+const std::string policy::AlbumTrackTable::CacheColumn = "id_track";
+
 AlbumTrack::AlbumTrack( sqlite3* dbConnection, sqlite3_stmt* stmt )
     : m_dbConnection( dbConnection )
     , m_album( NULL )
@@ -41,12 +44,11 @@ unsigned int AlbumTrack::trackNumber()
     return m_trackNumber;
 }
 
-IAlbum* AlbumTrack::album()
+std::shared_ptr<IAlbum> AlbumTrack::album()
 {
-    if ( m_album == NULL && m_albumId != 0 )
+    if ( m_album == nullptr && m_albumId != 0 )
     {
-        const char* req = "SELECT * FROM Album WHERE id_album = ?";
-        m_album = SqliteTools::fetchOne<Album>( m_dbConnection, req, m_albumId );
+        m_album = Album::fetch( m_dbConnection, m_albumId );
     }
     return m_album;
 }

src/AlbumTrack.h

@@ -5,18 +5,28 @@
 #include <string>
 
 #include "IAlbumTrack.h"
+#include "Cache.h"
 
 class Album;
 
-class AlbumTrack : public IAlbumTrack
+namespace policy
+{
+struct AlbumTrackTable
+{
+    static const std::string Name;
+    static const std::string CacheColumn;
+};
+}
+
+class AlbumTrack : public IAlbumTrack, public Cache<AlbumTrack, IAlbumTrack, policy::AlbumTrackTable>
 {
     public:
         AlbumTrack( sqlite3* dbConnection, sqlite3_stmt* stmt );
 
-        virtual const std::string&genre();
-        virtual const std::string&title();
+        virtual const std::string& genre();
+        virtual const std::string& title();
         virtual unsigned int trackNumber();
-        virtual IAlbum*album();
+        virtual std::shared_ptr<IAlbum> album();
 
         static bool createTable( sqlite3* dbConnection );
 
@@ -28,7 +38,9 @@ class AlbumTrack : public IAlbumTrack
         unsigned int m_trackNumber;
         unsigned int m_albumId;
 
-        Album* m_album;
+        std::shared_ptr<Album> m_album;
+
+        friend class Cache<AlbumTrack, IAlbumTrack, policy::AlbumTrackTable>;
 };
 
 #endif // ALBUMTRACK_H

src/Cache.h

+#ifndef CACHE_H
+#define CACHE_H
+
+#include <memory>
+#include <mutex>
+#include <unordered_map>
+
+#include "SqliteTools.h"
+
+template <typename TYPE>
+class PrimaryKeyCacheKeyPolicy
+{
+    public:
+        typedef unsigned int KeyType;
+        static unsigned int key( const std::shared_ptr<TYPE>& self )
+        {
+            return self->id();
+        }
+        static unsigned int key( sqlite3_stmt* stmt )
+        {
+            return Traits<unsigned int>::Load( stmt, 0 );
+        }
+};
+
+/**
+ * This utility class eases up the implementation of caching.
+ * It has a few assumptions about class that will use it:
+ * - The class is stored in database and has a dedicated type.
+ * - The class has a static std::string member named TableName, that can be used to generate
+ *   requests
+ * - The class has a static std::string member named CacheColumn, that holds the name of
+ *   the column that will act as a primary key in the cache.
+ * - The class has a public method of signature "unsigned int id()" that can be used to
+ *   fetch the primary key
+ * - The class has 2 contructors:
+ *      - One that takes a sqlite3* representing the active DB connection, and
+ *        a sqlite3_stmt* that holds the row currently being fetched. This CTOR is used by
+ *        the load method, when fetching an existing record which isn't cached yet.
+ *      - One that can be used to instantiate a new record, without parameter restriction
+ *
+ * Template parameter:
+ * - IMPL: The actual implementation. Typically the type that inherits this class
+ * - INTF: An interface that express the type. This is used when fetching containers, as they
+ *         are not polymorphic.
+ * - CACHECOLUMNTYPE: The type of the column representing a record in a unique way. Quite
+ *                    likely the primary key type
+ * - CACHECOLUMNINDEX: The index of the column used by the cache, to be able to fetch it
+ *                     from a sqlite3_stmt containing a row of the stored entity type.
+ *
+ * How to use it:
+ * - Inherit this class and specify the template parameter accordingly
+ * - Make this class a friend class of the class you inherit from
+ * - Implement the 2 static strings defined above.
+ */
+template <typename IMPL, typename INTF, typename TABLEPOLICY, typename CACHEPOLICY = PrimaryKeyCacheKeyPolicy<IMPL>>
+class Cache
+{
+    public:
+        static std::shared_ptr<IMPL> fetch( sqlite3* dbConnection, const typename CACHEPOLICY::KeyType& key )
+        {
+            std::lock_guard<std::mutex> lock( Mutex );
+            auto it = Store.find( key );
+            if ( it != Store.end() )
+                return it->second;
+            std::string req = "SELECT * FROM" + TABLEPOLICY::Name +
+                            " WHERE " + TABLEPOLICY::CacheColumn + " = ?";
+            auto res = SqliteTools::fetchOne<IMPL>( dbConnection, req.c_str(), key );
+            Store[key] = res;
+            return res;
+        }
+
+        /*
+         * Will fetch all elements from the database & cache them.
+         *
+         * @param res   A reference to the result vector. All existing elements will
+         *              be discarded.
+         */
+        static bool fetchAll( sqlite3* dbConnection, std::vector<std::shared_ptr<INTF>>& res )
+        {
+            std::string req = "SELECT * FROM " + TABLEPOLICY::Name;
+            return SqliteTools::fetchAll<IMPL, INTF>( dbConnection, req.c_str(), res );
+        }
+
+        static std::shared_ptr<IMPL> load( sqlite3* dbConnection, sqlite3_stmt* stmt )
+        {
+            auto cacheKey = CACHEPOLICY::key( stmt );
+
+            std::lock_guard<std::mutex> lock( Mutex );
+            auto it = Store.find( cacheKey );
+            if ( it != Store.end() )
+                return it->second;
+            auto inst = std::make_shared<IMPL>( dbConnection, stmt );
+            Store[cacheKey] = inst;
+            return inst;
+        }
+
+        /*
+         * Create a new instance of the cache class.
+         * This doesn't check for the existence of a similar entity already cached.
+         */
+        template <typename... Args>
+        static std::shared_ptr<IMPL> create( Args&&... args )
+        {
+            auto res = std::make_shared<IMPL>( std::forward<Args>( args )... );
+
+            typename CACHEPOLICY::KeyType cacheKey = CACHEPOLICY::key( res );
+
+            std::lock_guard<std::mutex> lock( Mutex );
+            Store[cacheKey] = res;
+            return res;
+        }
+
+    private:
+        static std::unordered_map<typename CACHEPOLICY::KeyType, std::shared_ptr<IMPL>> Store;
+        static std::mutex Mutex;
+};
+
+template <typename IMPL, typename INTF, typename TABLEPOLICY, typename CACHEPOLICY>
+std::unordered_map<typename CACHEPOLICY::KeyType, std::shared_ptr<IMPL>>
+Cache<IMPL, INTF, TABLEPOLICY, CACHEPOLICY>::Store;
+
+template <typename IMPL, typename INTF, typename TABLEPOLICY, typename CACHEPOLICY>
+std::mutex Cache<IMPL, INTF, TABLEPOLICY, CACHEPOLICY>::Mutex;
+
+#endif // CACHE_H

src/File.cpp

@@ -9,11 +9,12 @@
 #include "ShowEpisode.h"
 #include "SqliteTools.h"
 
+const std::string policy::FileTable::Name = "File";
+const std::string policy::FileTable::CacheColumn = "mrl";
+
 File::File( sqlite3* dbConnection, sqlite3_stmt* stmt )
     : m_dbConnection( dbConnection )
-    , m_albumTrack( NULL )
-    , m_showEpisode( NULL )
-    , m_labels( NULL )
+    , m_labels( nullptr )
 {
     m_id = sqlite3_column_int( stmt, 0 );
     m_type = (Type)sqlite3_column_int( stmt, 1 );
@@ -33,9 +34,7 @@ File::File( const std::string& mrl )
     , m_playCount( 0 )
     , m_showEpisodeId( 0 )
     , m_mrl( mrl )
-    , m_albumTrack( NULL )
-    , m_showEpisode( NULL )
-    , m_labels( NULL )
+    , m_labels( nullptr )
 {
 }
 
@@ -64,9 +63,9 @@ bool File::insert( sqlite3* dbConnection )
     return true;
 }
 
-IAlbumTrack* File::albumTrack()
+std::shared_ptr<IAlbumTrack> File::albumTrack()
 {
-    if ( m_albumTrack == NULL && m_albumTrackId != 0 )
+    if ( m_albumTrack == nullptr && m_albumTrackId != 0 )
     {
         const char* req = "SELECT * FROM AlbumTrack WHERE id_track = ?";
         m_albumTrack = SqliteTools::fetchOne<AlbumTrack>( m_dbConnection, req, m_albumTrackId );
@@ -79,24 +78,24 @@ unsigned int File::duration()
     return m_duration;
 }
 
-IShowEpisode*File::showEpisode()
+std::shared_ptr<IShowEpisode> File::showEpisode()
 {
-    if ( m_showEpisode == NULL && m_showEpisodeId != 0 )
+    if ( m_showEpisode == nullptr && m_showEpisodeId != 0 )
     {
-        const char* req = "SELECT * FROM ShowEpisode WHERE id_episode = ?";
-        m_showEpisode = SqliteTools::fetchOne<ShowEpisode>( m_dbConnection, req, m_showEpisodeId );
+        m_showEpisode = ShowEpisode::fetch( m_dbConnection, m_showEpisodeId );
     }
     return m_showEpisode;
 }
 
-std::vector<ILabel*> File::labels()
+const std::vector<std::shared_ptr<ILabel>>& File::labels()
 {
-    if ( m_labels == NULL )
+    if ( m_labels == nullptr )
     {
+        m_labels = new std::vector<std::shared_ptr<ILabel>>;
         const char* req = "SELECT l.* FROM Label l "
                 "LEFT JOIN LabelFileRelation lfr ON lfr.id_label = l.id_label "
                 "WHERE lfr.id_file = ?";
-        SqliteTools::fetchAll<Label>( m_dbConnection, req, m_id, m_labels );
+        SqliteTools::fetchAll<Label>( m_dbConnection, req, m_id, *m_labels );
     }
     return *m_labels;
 }
@@ -111,24 +110,23 @@ const std::string& File::mrl()
     return m_mrl;
 }
 
-ILabel* File::addLabel(const std::string& label)
+std::shared_ptr<ILabel> File::addLabel(const std::string& label)
 {
-    Label* l = new Label( label );
+    auto l = Label::create( label );
     if ( l->insert( m_dbConnection ) == false )
     {
-        delete l;
-        return NULL;
+        return nullptr;
     }
     l->link( this );
     return l;
 }
 
-bool File::removeLabel( const ILabel* label )
+bool File::removeLabel( const std::shared_ptr<ILabel>& label )
 {
-    if ( m_labels != NULL )
+    if ( m_labels != false )
     {
-        std::vector<ILabel*>::iterator it = m_labels->begin();
-        std::vector<ILabel*>::iterator ite = m_labels->end();
+        auto it = m_labels->begin();
+        auto ite = m_labels->end();
         while ( it != ite )
         {
             if ( (*it)->id() == label->id() )
@@ -149,6 +147,7 @@ unsigned int File::id() const
 
 bool File::createTable(sqlite3* connection)
 {
+    //FIXME: File is hardcoded
     const char* req = "CREATE TABLE IF NOT EXISTS File("
             "id_file INTEGER PRIMARY KEY AUTOINCREMENT,"
             "type INTEGER,"
@@ -160,3 +159,14 @@ bool File::createTable(sqlite3* connection)
             ")";
     return SqliteTools::createTable( connection, req );
 }
+
+
+const std::string& policy::FileCache::key(const std::shared_ptr<File> self )
+{
+    return self->mrl();
+}
+
+std::string policy::FileCache::key(sqlite3_stmt* stmt)
+{
+    return Traits<std::string>::Load( stmt, 6 );
+}

src/File.h

 #ifndef FILE_H
 #define FILE_H
 
+
 #include <sqlite3.h>
 
 #include "IFile.h"
+#include "Cache.h"
 
 class Album;
 class ShowEpisode;
 class AlbumTrack;
 
-class File : public IFile
+class File;
+
+namespace policy
+{
+struct FileTable
+{
+    static const std::string Name;
+    static const std::string CacheColumn;
+};
+struct FileCache
+{
+    typedef std::string KeyType;
+    static const std::string& key(const std::shared_ptr<File> self);
+    static std::string key( sqlite3_stmt* stmt );
+};
+}
+
+class File : public IFile, public Cache<File, IFile, policy::FileTable, policy::FileCache>
 {
     public:
+
+
         enum Type
         {
             VideoType, // Any video file, not being a tv show episode
@@ -21,26 +42,29 @@ class File : public IFile
             UnknownType,
         };
 
+        // Those should be private, however the standard states that the expression
+        // ::new (pv) T(std::forward(args)...)
+        // shall be well-formed, and private constructor would prevent that.
+        // There might be a way with a user-defined allocator, but we'll see that later...
         File(sqlite3* dbConnection , sqlite3_stmt* stmt);
         File( const std::string& mrl );
 
         bool insert(sqlite3* dbConnection);
+        static bool createTable(sqlite3* connection);
 
         virtual unsigned int id() const;
-        virtual IAlbumTrack* albumTrack();
+        virtual std::shared_ptr<IAlbumTrack> albumTrack();
         virtual unsigned int duration();
-        virtual IShowEpisode* showEpisode();
-        virtual std::vector<ILabel*> labels();
+        virtual std::shared_ptr<IShowEpisode> showEpisode();
+        virtual const std::vector<std::shared_ptr<ILabel>>& labels();
         virtual int playCount();
         virtual const std::string& mrl();
-        virtual ILabel* addLabel( const std::string &label );
-        virtual bool removeLabel( const ILabel* label );
-
-        static bool createTable( sqlite3* connection );
+        virtual std::shared_ptr<ILabel> addLabel( const std::string &label );
+        virtual bool removeLabel(const std::shared_ptr<ILabel>& label );
 
     private:
         sqlite3* m_dbConnection;
-    
+
         // DB fields:
         unsigned int m_id;
         Type m_type;
@@ -52,9 +76,11 @@ class File : public IFile
 
         // Auto fetched related properties
         Album* m_album;
-        AlbumTrack* m_albumTrack;
-        ShowEpisode* m_showEpisode;
-        std::vector<ILabel*>* m_labels;
+        std::shared_ptr<AlbumTrack> m_albumTrack;
+        std::shared_ptr<ShowEpisode> m_showEpisode;
+        std::vector<std::shared_ptr<ILabel>>* m_labels;
+
+        friend class Cache<File, IFile, policy::FileTable, policy::FileCache>;
 };
 
 #endif // FILE_H

src/Label.cpp

@@ -6,6 +6,9 @@
 #include "File.h"
 #include "SqliteTools.h"
 
+const std::string policy::LabelTable::Name = "Label";
+const std::string policy::LabelTable::CacheColumn = "id_label";
+
 Label::Label( sqlite3* dbConnection, sqlite3_stmt* stmt )
     : m_dbConnection( dbConnection )
     , m_files( NULL )
@@ -33,21 +36,22 @@ const std::string& Label::name()
     return m_name;
 }
 
-std::vector<IFile*> Label::files()
+std::vector<std::shared_ptr<IFile>>& Label::files()
 {
-    if ( m_files == NULL )
+    if ( m_files == nullptr )
     {
+        m_files = new std::vector<std::shared_ptr<IFile>>;
         const char* req = "SELECT f.* FROM Files f "
                 "LEFT JOIN LabelFileRelation lfr ON lfr.id_file = f.id_file "
                 "WHERE lfr.id_label = ?";
-        SqliteTools::fetchAll<File>( m_dbConnection, req, m_id, m_files );
+        SqliteTools::fetchAll<File>( m_dbConnection, req, m_id, *m_files );
     }
     return *m_files;
 }
 
 bool Label::insert( sqlite3* dbConnection )
 {
-    assert( m_dbConnection == NULL );
+    assert( m_dbConnection == nullptr );
     assert( m_id == 0 );
     sqlite3_stmt* stmt;