package org.litesoft.initfrom.server;

import org.litesoft.bo.views.*;
import org.litesoft.changemanagement.*;
import org.litesoft.commonfoundation.typeutils.*;
import org.litesoft.core.*;
import org.litesoft.initfrom.client.boviews.*;
import org.litesoft.initfrom.server.boviews.podataproviders.*;
import org.litesoft.initfrom.server.pos.*;

public class CurrentUserAccessor implements ServerStateChangedListener {
    public static synchronized CurrentUserAccessor get() {
        ServerStore zStore = ServerContext.get().getServerStore();
        CurrentUserAccessor zAccessor = zStore.get( CurrentUserAccessor.class );
        if ( zAccessor == null ) {
            zStore.set( CurrentUserAccessor.class, zAccessor = new CurrentUserAccessor() );
        }
        return zAccessor;
    }

    private boolean mViewStale;
    private ChangeListenerManager mRegisteredWithCLM;
    private User mPO;

    public User getRequiredUser() {
        User zUser = getOptionalUser( null );
        if ( zUser == null ) {
            throw new SessionExpiredException( "No Current User" );
        }
        return zUser;
    }

    public User getOptionalUser( String pDefaultUserLoginEmail ) {
        Pair zPair = getPair( pDefaultUserLoginEmail );
        if ( zPair.getVO() == null ) {
            return null;
        }
        if ( (zPair.getPO() == null) || !zPair.inSync() ) {
            zPair = refresh( zPair );
        }
        return zPair.getPO();
    }

    public UserView getUserView( String pDefaultUserLoginEmail ) {
        Pair zPair = getPair( pDefaultUserLoginEmail );
        if ( zPair.isStale() ) {
            zPair = refresh( zPair );
        }
        return zPair.getVO();
    }

    public void logout() {
        update( null, null );
    }

    public UserView updateUser( User pPO ) {
        UserView zView = getDataProvider().createView( pPO, false );
        update( zView, pPO );
        return zView;
    }

    private Pair refresh( Pair pPair ) {
        UserViewPoServerVoDataProvider zDP = getDataProvider();
        User zPO = (User) zDP.getPO( pPair.getVO().getID() );
        return update( zDP.createView( zPO, false ), zPO );
    }

    private Pair update( UserView pView, User pPO ) {
        Pair rv;
        User zOld, zNew;
        synchronized ( this ) {
            rv = new Pair( mViewStale = false, pView, pPO );
            ServerContext.get().getServerSession().setAttribute( UserView.class, pView );
            zOld = mPO;
            zNew = mPO = pPO;
        }
        if ( !Objects.areNonArraysEqual( zOld, zNew ) ) {
            if ( zOld != null ) {
                mRegisteredWithCLM.removeListener( this );
                mRegisteredWithCLM = null;
            }
            if ( zNew != null ) {
                (mRegisteredWithCLM = ChangeListenerManager.get()).addListener( this, User.class, zNew.getPersistentObjectUniqueKey() );
            }
        }
        return rv;
    }

    private Pair getPair( String pDefaultUserLoginEmail ) {
        synchronized ( this ) {
            UserView zView = ServerContext.get().getServerSession().getAttribute( UserView.class );
            if ( (zView != null) || (pDefaultUserLoginEmail == null) ) {
                return new Pair( mViewStale, zView, mPO );
            }
        }
        getDataProvider().loginDefaultUser( pDefaultUserLoginEmail );
        synchronized ( this ) {
            UserView zView = ServerContext.get().getServerSession().getAttribute( UserView.class );
            return new Pair( mViewStale, zView, mPO );
        }
    }

    @Override
    public synchronized void serverStateChanged( ServerStateChangeSet pServerStateChangeSet ) {
        mViewStale = true;
    }

    private UserViewPoServerVoDataProvider getDataProvider() {
        return (UserViewPoServerVoDataProvider) ServerContext.getMasterServerStore().get( ServerVoDataProviderMap.class ).get( UserView.class );
    }

    private static class Pair {
        private boolean mStale;
        private UserView mVO;
        private User mPO;

        private Pair( boolean pStale, UserView pVO, User pPO ) {
            mStale = (pVO != null) && pStale;
            mVO = pVO;
            mPO = pPO;
        }

        public boolean isStale() {
            return mStale;
        }

        public UserView getVO() {
            return mVO;
        }

        public User getPO() {
            return mPO;
        }

        public boolean inSync() // Only called when Both are !null
        {
            return !mStale && //
                   Objects.areNonArraysEqual( mPO.getID(), mVO.getID() ) && //
                   Objects.areNonArraysEqual( mPO.getRecordVersion(), mVO.getRecordVersion() );
        }
    }
}