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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 *    Copyright (c) [2017] Payara Foundation and/or its affiliates. All rights reserved.
 * 
 *     The contents of this file are subject to the terms of either the GNU
 *     General Public License Version 2 only ("GPL") or the Common Development
 *     and Distribution License("CDDL") (collectively, the "License").  You
 *     may not use this file except in compliance with the License.  You can
 *     obtain a copy of the License at
 *     https://github.com/payara/Payara/blob/master/LICENSE.txt
 *     See the License for the specific
 *     language governing permissions and limitations under the License.
 * 
 *     When distributing the software, include this License Header Notice in each
 *     file and include the License file at glassfish/legal/LICENSE.txt.
 * 
 *     GPL Classpath Exception:
 *     The Payara Foundation designates this particular file as subject to the "Classpath"
 *     exception as provided by the Payara Foundation in the GPL Version 2 section of the License
 *     file that accompanied this code.
 * 
 *     Modifications:
 *     If applicable, add the following below the License Header, with the fields
 *     enclosed by brackets [] replaced by your own identifying information:
 *     "Portions Copyright [year] [name of copyright owner]"
 * 
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 *     If you wish your version of this file to be governed by only the CDDL or
 *     only the GPL Version 2, indicate your decision by adding "[Contributor]
 *     elects to include this software in this distribution under the [CDDL or GPL
 *     Version 2] license."  If you don't indicate a single choice of license, a
 *     recipient has the option to distribute your version of this file under
 *     either the CDDL, the GPL Version 2 or to extend the choice of license to
 *     its licensees as provided above.  However, if you add GPL Version 2 code
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 */
package fish.payara.microprofile.faulttolerance.interceptors.fallback;

import fish.payara.microprofile.faulttolerance.FaultToleranceService;
import static fish.payara.microprofile.faulttolerance.FaultToleranceService.FALLBACK_HANDLER_METHOD_NAME;
import fish.payara.microprofile.faulttolerance.cdi.FaultToleranceCdiUtils;
import fish.payara.nucleus.requesttracing.domain.RequestEvent;
import java.lang.reflect.Method;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.interceptor.InvocationContext;
import org.eclipse.microprofile.config.Config;
import org.eclipse.microprofile.faulttolerance.ExecutionContext;
import org.eclipse.microprofile.faulttolerance.Fallback;
import org.eclipse.microprofile.faulttolerance.FallbackHandler;
import javax.enterprise.inject.spi.CDI;
import org.glassfish.api.invocation.InvocationManager;
import org.glassfish.internal.api.Globals;

/**
 * Class that executes the fallback policy defined by the @Fallback annotation.
 * @author Andrew Pielage
 */
public class FallbackPolicy {
    
    private static final Logger logger = Logger.getLogger(FallbackPolicy.class.getName());
    
    private final Class fallbackClass;
    private final String fallbackMethod;
    
    public FallbackPolicy(Fallback fallback, Config config, InvocationContext invocationContext) 
            throws ClassNotFoundException {     
        fallbackClass = (Class) Thread.currentThread().getContextClassLoader().loadClass(
                (String) FaultToleranceCdiUtils.getOverrideValue(config, Fallback.class, "value", 
                        invocationContext, String.class)
                .orElse(fallback.value().getName()));
        
        fallbackMethod = (String) FaultToleranceCdiUtils.getOverrideValue(config, Fallback.class, 
                "fallbackMethod", invocationContext, String.class)
                .orElse(fallback.fallbackMethod());
    }
    
    /**
     * Performs the fallback operation defined by the @Fallback annotation.
     * @param invocationContext The failing invocation context
     * @return The result of the executed fallback method
     * @throws Exception If the fallback method itself fails.
     */
    public Object fallback(InvocationContext invocationContext) throws Exception {
        Object fallbackInvocationContext = null;
        
        FaultToleranceService faultToleranceService = 
                Globals.getDefaultBaseServiceLocator().getService(FaultToleranceService.class);
        InvocationManager invocationManager = Globals.getDefaultBaseServiceLocator()
                .getService(InvocationManager.class);      
        RequestEvent requestEvent = new RequestEvent("FaultTolerance-Fallback");
        faultToleranceService.traceFaultToleranceEvent(requestEvent, invocationManager, invocationContext);    
        
        if (fallbackMethod != null && !fallbackMethod.isEmpty()) {
            logger.log(Level.FINE, "Using fallback method: {0}", fallbackMethod);
            
            fallbackInvocationContext = invocationContext.getMethod().getDeclaringClass()
                    .getDeclaredMethod(fallbackMethod, invocationContext.getMethod().getParameterTypes())
                    .invoke(invocationContext.getTarget(), invocationContext.getParameters());
        } else {
            logger.log(Level.FINE, "Using fallback class: {0}", fallbackClass.getName());
            
            ExecutionContext executionContext = new FaultToleranceExecutionContext(invocationContext.getMethod(), 
                    invocationContext.getParameters());
            
            fallbackInvocationContext = fallbackClass
                    .getDeclaredMethod(FALLBACK_HANDLER_METHOD_NAME, ExecutionContext.class)
                    .invoke(CDI.current().select(fallbackClass).get(), executionContext);
        }
        
        return fallbackInvocationContext;
    }
    
    /**
     * Default implementation class for the Fault Tolerance ExecutionContext interface
     */
    private class FaultToleranceExecutionContext implements ExecutionContext {

        private final Method method;
        private final Object[] parameters;
        
        public FaultToleranceExecutionContext(Method method, Object[] parameters) {
            this.method = method;
            this.parameters = parameters;
        }
        
        @Override
        public Method getMethod() {
            return method;
        }

        @Override
        public Object[] getParameters() {
            return parameters;
        }
    }
}