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The LDAP Chai API, easy to use LDAP for Java developers.
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/*
 * LDAP Chai API
 * Copyright (c) 2006-2017 Novell, Inc.
 *
 * This library 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 library 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 library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package com.novell.ldapchai.provider;

import com.novell.ldapchai.util.internal.ChaiLogger;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

abstract class AbstractWrapper implements InvocationHandler
{


    private static final ChaiLogger LOGGER = ChaiLogger.getLogger( AbstractWrapper.class );
    protected ChaiProviderImplementor realProvider;

    /**
     * Wrap a pre-existing ChaiProvider with a WatchdogWrapper instance.
     *
     * @param chaiProvider a pre-existing {@code ChaiProvider}
     * @param enableSetting setting to mark if watchdog is enabled
     * @param wrapperClass chai provider wrapper
     * @return a wrapped {@code ChaiProvider} instance.
     * @throws Exception if there is any error instantiating the implementor instance.
     */
    protected static ChaiProviderImplementor factoryImpl(
            final Class wrapperClass,
            final ChaiSetting enableSetting,
            final ChaiProviderImplementor chaiProvider
    )
            throws Exception
    {
        //check to make sure watchdog ise enabled;
        final boolean isEnabled = Boolean.parseBoolean( chaiProvider.getChaiConfiguration().getSetting( enableSetting ) );
        if ( !isEnabled )
        {
            final String errorStr = "attempt to obtain " + wrapperClass.getName() + " wrapper when not enabled in chaiConfiguration";
            LOGGER.warn( () -> errorStr );
            throw new IllegalStateException( errorStr );
        }

        if ( Proxy.isProxyClass( chaiProvider.getClass() ) && wrapperClass.isInstance( chaiProvider ) )
        {
            LOGGER.warn( () -> "attempt to obtain " + wrapperClass.getName() + " wrapper for already wrapped ChaiProvider." );
            return chaiProvider;
        }

        try
        {
            final Constructor constructor = wrapperClass.getConstructor( ChaiProviderImplementor.class );
            final InvocationHandler wrapper = ( InvocationHandler ) constructor.newInstance( chaiProvider );
            final Object wrappedProvider = Proxy.newProxyInstance( chaiProvider.getClass().getClassLoader(), chaiProvider.getClass().getInterfaces(), wrapper );
            return ( ChaiProviderImplementor ) wrappedProvider;
        }
        catch ( Exception e )
        {
            final String errorMsg = "Chai internal error, unable to create wrapper for " + wrapperClass.getCanonicalName() + e.getMessage();
            LOGGER.error( () -> errorMsg, e );
            throw new Exception( errorMsg, e );
        }
    }

    static Object invoker( final ChaiProvider provider, final Method m, final Object[] args )
            throws Exception
    {
        try
        {
            // try to invoke the method.
            return m.invoke( provider, args );
        }
        catch ( IllegalAccessException e )
        {
            final String errorMsg = "unexpected api error: " + e.getMessage();
            LOGGER.warn( () -> errorMsg, e );
            throw new IllegalStateException( errorMsg );
        }
        catch ( InvocationTargetException e )
        {
            final Throwable realThrowable = e.getCause();
            if ( realThrowable instanceof Exception )
            {
                throw ( Exception ) realThrowable;
            }
            else
            {
                final String errorMsg = "unexpected api error: " + e.getMessage();
                LOGGER.warn( () -> errorMsg, e );
                throw new IllegalStateException( errorMsg );
            }
        }
    }
}