// This Source Code is in the Public Domain per: http://litesoft.org/License.txt
package org.litesoft.orsup.lazyload;

import org.litesoft.orsup.base.*;
import org.litesoft.orsup.nonpublic.*;

public abstract class AbstractLazyLoadToOne<Owner extends PersistentObjectImpl, Them extends PersistentObjectImpl> extends AbstractLazyLoadTo<Owner, Them>
{
    protected Them mValue = null;
    protected Object mDBValue = null;

    protected AbstractLazyLoadToOne( Owner pOwner, AbstractAttributeAccessorSCDtoOne<Owner, Them> pSCDtoOne )
    {
        super( pOwner, pSCDtoOne );
    }

    public abstract AbstractAttributeAccessorSCDtoOne<Owner, Them> getSCDtoOne();

    @Override
    public final String getAttributeName()
    {
        return getSCDtoOne().getName();
    }

    @Override
    protected final boolean isThemDependantOnUs()
    {
        return getSCDtoOne().isThemDependantOnUs();
    }

    /**
     * @param pDBValue !null
     */
    abstract protected PersistentObject<?> LL_loadValueWithNonNull( Object pDBValue );

    public final Them LL_getValue()
    {
        if ( !mLoaded )
        {
            if ( mDBValue != null )
            {
                //noinspection unchecked
                mValue = (Them) LL_loadValueWithNonNull( mDBValue );
            }
            mLoaded = true;
        }
        return mValue;
    }

    public final void LL_setValue( Them pNewThem, String pBackRefAttributeNameOnNewThem )
    {
        backbackdoorSetValue( pNewThem, pBackRefAttributeNameOnNewThem );
        if ( (mValue != null) && (pBackRefAttributeNameOnNewThem != null) )
        {
            getToManyLazyLoader( pNewThem, pBackRefAttributeNameOnNewThem ).backdoorAddValue( mOwner );
        }
    }

    public Object db_getValue()
    {
        return mDBValue;
    }

    public void db_setValue( Object pPOKey )
    {
        mDBValue = pPOKey;
    }

    @Override
    protected final void releaseLoadeds()
    {
        mValue = null;
    }

    /**
     * Note Only called when the New Them is NOT the same as the Old Them
     *
     * @param pNewThem                       Nullable
     * @param pBackRefAttributeNameOnNewThem
     */
    final void backdoorSetValue( Them pNewThem, String pBackRefAttributeNameOnNewThem )
    {
        Them zCurThem = LL_getValue();
        Object newDBValue = extract_db_value( pNewThem, pBackRefAttributeNameOnNewThem );
        PersistentObjectImpl.BackDoor.verifyMutabilityOnChangeToOneOn( mOwner, //
                                                                       getSCDtoOne(), //
                                                                       zCurThem, mDBValue, //
                                                                       pNewThem, newDBValue //
        );
        backbackdoorSetValue( pNewThem, pBackRefAttributeNameOnNewThem );
    }

    final void backbackdoorSetValue( Them pNewThem, String pBackRefAttributeNameOnNewThem )
    {
        Them zCurThem = LL_getValue();
        if ( zCurThem != null )
        {
            String zBackRefAttributeNameOnNewThem = getBackRefOnUnWire( pBackRefAttributeNameOnNewThem );
            if ( zBackRefAttributeNameOnNewThem != null )
            {
                getToManyLazyLoader( zCurThem, zBackRefAttributeNameOnNewThem ).backdoorRemoveValue( mOwner );
            }
            if ( isThemDependantOnUs() )
            {
                zCurThem.requestDelete();
            }
        }
        mDBValue = extract_db_value( pNewThem, pBackRefAttributeNameOnNewThem );
        mValue = pNewThem;
    }

    public final Object extract_db_value( PersistentObjectImpl pNewThem, String pBackRefAttributeNameOnNewThem )
    {
        return (pNewThem == null) ? null : LL_extract_db_value( pNewThem, pBackRefAttributeNameOnNewThem );
    }

    private AbstractLazyLoadToMany<Them, Owner> getToManyLazyLoader( Them pThem, String pBackRefAttributeNameOnNewThem )
    {
        checkTransactions( pThem );
        MetaDataForPO zMDForPO = pThem.getMetaDataForPO();
        AttributeAccessorSCD scd = zMDForPO.getAccessorSCDrequired( pBackRefAttributeNameOnNewThem );
        //noinspection unchecked
        return ((AbstractAttributeAccessorSCDtoMany) scd).getValueHolder( pThem );
    }

    abstract protected String getBackRefOnUnWire( String pBackRefAttributeNameOnNewThem );

    /**
     * @param pNewThem !null
     */
    abstract protected Object LL_extract_db_value( PersistentObjectImpl pNewThem, String pBackRefAttributeNameOnNewThem );
}