/*
 * Copyright (C) 2007-2023 Xagasoft, All rights reserved.
 *
 * This file is part of the libbu++ library and is released under the
 * terms of the license contained in the file LICENSE.
 */

#ifndef BU_MYRIAD_CACHE_H
#define BU_MYRIAD_CACHE_H

#include "bu/cachebase.h"
#include "bu/myriad.h"
#include "bu/myriadstream.h"
#include "bu/file.h"
#include "bu/streamstack.h"

namespace Bu
{
    template<typename keytype, typename obtype>
    class MyriadCache : public Bu::CacheBase<keytype, obtype>
    {
    public:
        MyriadCache( Bu::Stream &sStore, int iBlockSize=512, int iPreallocate=8 ) :
            sStore( sStore ),
            mStore( sStore, iBlockSize, iPreallocate ),
            bStructureChanged( false )
        {
            try
            {
                Bu::ReadWriteMutex::ReadLocker l( rwStore );
                Bu::MyriadStream ms = mStore.open(
                    1, Bu::Myriad::WriteNew|Bu::Myriad::Read
                    );
                Bu::Archive ar( ms, Bu::Archive::load );
                uint8_t uVer;
                ar >> uVer;
                switch( uVer )
                {
                    case 0:
                        ar >> hIndex;
                        break;
                }
            }
            catch(...)
            {
                try
                {
                    mStore.open( 1, Bu::Myriad::Create|Bu::Myriad::ReadWrite );
                    _sync();
                }
                catch(...)
                {
                    throw Bu::ExceptionBase("Error creating index stream.");
                }
            }
        }

        virtual ~MyriadCache()
        {
            Bu::CacheBase<keytype,obtype>::sync();
        }
       
        using typename Bu::CacheBase<keytype,obtype>::KeyList;
        using typename Bu::CacheBase<keytype,obtype>::ObjectType;
        
        virtual typename Bu::CacheBase<keytype,obtype>::KeyList getKeys() const
        {
            Bu::ReadWriteMutex::ReadLocker rl( rwStore );
            return hIndex.getKeys();
        }
        
        virtual int getSize() const
        {
            Bu::ReadWriteMutex::ReadLocker rl( rwStore );
            return hIndex.getSize();
        }

    protected:
        virtual bool _has( const keytype &key )
        {
            Bu::ReadWriteMutex::ReadLocker rl( rwStore );
            return hIndex.has( key );
        }

        virtual void _create( const obtype *o )
        {
            Bu::ReadWriteMutex::WriteLocker wl( rwStore );
            {
                Bu::Myriad::StreamId id = mStore.allocate();
                hIndex.insert( o->getKey(), id );
            }
            _save( o );

            bStructureChanged = true;
        }

        virtual void _erase( const keytype &k )
        {
            Bu::ReadWriteMutex::WriteLocker wl( rwStore );
            mStore.erase( hIndex.get( k ) );
            hIndex.erase( k );

            bStructureChanged = true;
        }

        virtual obtype *_load(
            typename Bu::CacheObject<keytype, obtype>::Initializer &initObj,
            const keytype &k
            )
        {
            Bu::MyriadStream ms = mStore.openStream( hIndex.get( k ) );
            return _cacheObjectLoad<keytype, obtype>( initObj, k, ms );
        }

        virtual void _save( const obtype *o )
        {
            Bu::MyriadStream ms = mStore.openStream( hIndex.get( o->getKey() ) );
            _cacheObjectSave( ms, o );
            ms.setSize( ms.tell() );
            
            mStore.sync();
        }

        virtual void _sync()
        {
            Bu::ReadWriteMutex::WriteLocker wl( rwStore );
            if( !bStructureChanged )
                return;

            Bu::MyriadStream ms = mStore.openStream( 1 );
            Bu::Archive ar( ms, Bu::Archive::save );
            ar << (uint8_t)0 << hIndex;
            ar.close();
            ms.setSize( ms.tell() );

            bStructureChanged = false;

            mStore.sync();
        }

    private:
        Bu::Stream &sStore;
        Bu::Myriad mStore;
        Bu::Hash<keytype, int> hIndex;
        mutable Bu::ReadWriteMutex rwStore;
        bool bStructureChanged;
    };
}

#endif