sqlite: Add support for pagination

Makefile.am

@@ -124,6 +124,7 @@ noinst_HEADERS = \
 	src/database/DatabaseHelpers.h \
 	src/database/SqliteConnection.h \
 	src/database/SqliteErrors.h \
+	src/database/SqliteQuery.h \
 	src/database/SqliteTools.h \
 	src/database/SqliteTraits.h \
 	src/database/SqliteTransaction.h \

src/database/SqliteQuery.h

+/*****************************************************************************
+ * Media Library
+ *****************************************************************************
+ * Copyright (C) 2015 Hugo Beauzée-Luyssen, Videolabs
+ *
+ * Authors: Hugo Beauzée-Luyssen<hugo@beauzee.fr>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#pragma once
+
+#include "medialibrary/IQuery.h"
+#include "SqliteConnection.h"
+#include "SqliteTools.h"
+
+#include <vector>
+#include <functional>
+#include <string>
+
+namespace medialibrary
+{
+
+template <typename Impl, typename Intf, typename... RequestParams>
+class SqliteQuery : public IQuery<Intf>
+{
+public:
+    using Result = typename IQuery<Intf>::Result;
+
+    template <typename... Params>
+    SqliteQuery( MediaLibraryPtr ml, std::string field, std::string base,
+                     Params&&... params )
+        : m_ml( ml )
+        , m_field( field )
+        , m_base( base )
+        , m_params( std::forward<Params>( params )... )
+        , m_count( 0 )
+        , m_hasCount( false )
+    {
+    }
+
+    virtual size_t count() override
+    {
+        if ( m_hasCount == true )
+            return m_count;
+
+        std::string req = "SELECT COUNT() " + m_base;
+        auto dbConn = m_ml->getConn();
+        auto ctx = dbConn->acquireReadContext();
+        sqlite::Statement stmt( dbConn->handle(), req );
+        stmt.execute( m_params );
+        auto row = stmt.row();
+        row >> m_count;
+        assert(stmt.row() == nullptr );
+        m_hasCount = true;
+        return m_count;
+    }
+
+    virtual Result items( uint32_t nbItems, uint32_t offset ) override
+    {
+        const std::string req = "SELECT " + m_field + " " + m_base + " LIMIT ? OFFSET ?";
+        return Impl::template fetchAll<Intf>( m_ml, req, m_params, nbItems, offset );
+    }
+
+    virtual Result all() override
+    {
+        const std::string req = "SELECT " + m_field + " " + m_base;
+        return Impl::template fetchAll<Intf>( m_ml, req, m_params );
+    }
+
+private:
+    MediaLibraryPtr m_ml;
+    std::string m_field;
+    std::string m_base;
+    std::tuple<typename std::decay<RequestParams>::type...> m_params;
+
+    size_t m_count;
+    bool m_hasCount;
+};
+
+template <typename Impl, typename Intf = Impl, typename... Args>
+Query<Intf> make_query( MediaLibraryPtr ml, std::string field, std::string base,
+                            Args&&... args )
+{
+    return std::unique_ptr<IQuery<Intf>>(
+        new SqliteQuery<Impl, Intf, Args...>( ml, std::move( field ),
+                                            std::move( base ),
+                                            std::forward<Args>( args )... )
+    );
+}
+
+}