/*
    *  Licensed to the Apache Software Foundation (ASF) under one
    *  or more contributor license agreements.  See the NOTICE file
    *  distributed with this work for additional information
    *  regarding copyright ownership.  The ASF licenses this file
    *  to you under the Apache License, Version 2.0 (the
    *  "License"); you may not use this file except in compliance
    *  with the License.  You may obtain a copy of the License at
    *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing,
   *  software distributed under the License is distributed on an
   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   *  KIND, either express or implied.  See the License for the
   *  specific language governing permissions and limitations
   *  under the License.
   *
   */
  package org.apache.mina.statemachine;
  
  import java.lang.reflect.InvocationHandler;
  import java.lang.reflect.Method;
  import java.lang.reflect.Proxy;
  
  import org.apache.mina.statemachine.context.SingletonStateContextLookup;
  import org.apache.mina.statemachine.context.StateContext;
  import org.apache.mina.statemachine.context.StateContextLookup;
  import org.apache.mina.statemachine.event.DefaultEventFactory;
  import org.apache.mina.statemachine.event.Event;
  import org.apache.mina.statemachine.event.EventArgumentsInterceptor;
  import org.apache.mina.statemachine.event.EventFactory;
  import org.apache.mina.statemachine.event.UnhandledEventException;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Used to create proxies which will forward all method calls on them to a
   * {@link StateMachine}.
   *
   * @author The Apache MINA Project (dev@mina.apache.org)
   */
  public class StateMachineProxyBuilder {
      private static final Logger log = LoggerFactory
              .getLogger(StateMachineProxyBuilder.class);
  
      private static final Object[] EMPTY_ARGUMENTS = new Object[0];
  
      private StateContextLookup contextLookup = new SingletonStateContextLookup();
  
      private EventFactory eventFactory = new DefaultEventFactory();
  
      private EventArgumentsInterceptor interceptor = null;
  
      private boolean ignoreUnhandledEvents = false;
  
      private boolean ignoreStateContextLookupFailure = false;
      
      private String name = null;
  
      /*
       * The classloader to use. Iif null we will use the current thread's 
       * context classloader.
       */
      private ClassLoader defaultCl = null; 
  
      public StateMachineProxyBuilder() {
      }
  
      /**
       * Sets the name of the proxy created by this builder. This will be used 
       * by the proxies <code>toString()</code> method. If not specified a default
       * auto generated name will be used.
       * 
       * @param name the name.
       * @return this {@link StateMachineProxyBuilder} for method chaining.
       */
      public StateMachineProxyBuilder setName(String name) {
          this.name = name;
          return this;
      }
      
      /**
       * Sets the {@link StateContextLookup} to be used. The default is to use
       * a {@link SingletonStateContextLookup}.
       * 
       * @param contextLookup the {@link StateContextLookup} to use.
       * @return this {@link StateMachineProxyBuilder} for method chaining. 
       */
      public StateMachineProxyBuilder setStateContextLookup(
              StateContextLookup contextLookup) {
          this.contextLookup = contextLookup;
          return this;
      }
  
      /**
       * Sets the {@link EventFactory} to be used. The default is to use a 
       * {@link DefaultEventFactory}.
       * 
      * @param eventFactory the {@link EventFactory} to use.
      * @return this {@link StateMachineProxyBuilder} for method chaining.
      */
     public StateMachineProxyBuilder setEventFactory(EventFactory eventFactory) {
         this.eventFactory = eventFactory;
         return this;
     }
 
     /**
      * Sets the {@link EventArgumentsInterceptor} to be used. By default no
      * {@link EventArgumentsInterceptor} will be used.
      * 
      * @param interceptor the {@link EventArgumentsInterceptor} to use.
      * @return this {@link StateMachineProxyBuilder} for method chaining.
      */
     public StateMachineProxyBuilder setEventArgumentsInterceptor(
             EventArgumentsInterceptor interceptor) {
         this.interceptor = interceptor;
         return this;
     }
 
     /**
      * Sets whether events which have no handler in the current state will raise 
      * an exception or be silently ignored. The default is to raise an 
      * exception. 
      * 
      * @param b <code>true</code> to ignore context lookup failures.
      * @return this {@link StateMachineProxyBuilder} for method chaining. 
      */
     public StateMachineProxyBuilder setIgnoreUnhandledEvents(boolean b) {
         this.ignoreUnhandledEvents = b;
         return this;
     }
 
     /**
      * Sets whether the failure to lookup a {@link StateContext} corresponding
      * to a method call on the proxy produced by this builder will raise an
      * exception or be silently ignored. The default is to raise an exception.
      * 
      * @param b <code>true</code> to ignore context lookup failures.
      * @return this {@link StateMachineProxyBuilder} for method chaining. 
      */
     public StateMachineProxyBuilder setIgnoreStateContextLookupFailure(boolean b) {
         this.ignoreStateContextLookupFailure = b;
         return this;
     }
 
     /**
      * Sets the class loader to use for instantiating proxies. The default is
      * to use the current threads context {@link ClassLoader} as returned by 
      * {@link Thread#getContextClassLoader()}.
      * 
      * @param cl the class loader
      * @return this {@link StateMachineProxyBuilder} for method chaining. 
      */
     public StateMachineProxyBuilder setClassLoader(ClassLoader cl) {
         this.defaultCl = cl;
         return this;
     }
 
     /**
      * Creates a proxy for the specified interface and which uses the specified 
      * {@link StateMachine}.
      * 
      * @param iface the interface the proxy will implement.
      * @param sm the {@link StateMachine} which will receive the events 
      *        generated by the method calls on the proxy.
      * @return the proxy object.
      */
     @SuppressWarnings("unchecked")
     public <T> T create(Class<T> iface, StateMachine sm) {
         return (T) create(new Class[] { iface }, sm);
     }
 
     /**
      * Creates a proxy for the specified interfaces and which uses the specified 
      * {@link StateMachine}.
      * 
      * @param ifaces the interfaces the proxy will implement.
      * @param sm the {@link StateMachine} which will receive the events 
      *        generated by the method calls on the proxy.
      * @return the proxy object.
      */
     public Object create(Class<?>[] ifaces, StateMachine sm) {
         ClassLoader cl = defaultCl;
         if (cl == null) {
            cl = Thread.currentThread().getContextClassLoader();
         }
 
         InvocationHandler handler = new MethodInvocationHandler(sm,
                 contextLookup, interceptor, eventFactory,
                 ignoreUnhandledEvents, ignoreStateContextLookupFailure, name);
 
         return Proxy.newProxyInstance(cl, ifaces, handler);
     }
     
     private static class MethodInvocationHandler implements InvocationHandler {
         private final StateMachine sm;
         private final StateContextLookup contextLookup;
         private final EventArgumentsInterceptor interceptor;
         private final EventFactory eventFactory;
         private final boolean ignoreUnhandledEvents;
         private final boolean ignoreStateContextLookupFailure;
         private final String name;
         
         public MethodInvocationHandler(StateMachine sm, StateContextLookup contextLookup,
                 EventArgumentsInterceptor interceptor, EventFactory eventFactory,
                 boolean ignoreUnhandledEvents, boolean ignoreStateContextLookupFailure, 
                 String name) {
             
             this.contextLookup = contextLookup;
             this.sm = sm;
             this.interceptor = interceptor;
             this.eventFactory = eventFactory;
             this.ignoreUnhandledEvents = ignoreUnhandledEvents;
             this.ignoreStateContextLookupFailure = ignoreStateContextLookupFailure;
             this.name = name;
         }
         
         public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
             if ("hashCode".equals(method.getName()) && args == null) {
                 return new Integer(System.identityHashCode(proxy));
             }
             if ("equals".equals(method.getName()) && args.length == 1) {
                 return Boolean.valueOf(proxy == args[0]);
             }
             if ("toString".equals(method.getName()) && args == null) {
                 return (name != null ? name : proxy.getClass().getName()) + "@" 
                         + Integer.toHexString(System.identityHashCode(proxy));
             }
 
             if (log.isDebugEnabled()) {
                 log.debug("Method invoked: " + method);
             }
 
             args = args == null ? EMPTY_ARGUMENTS : args;
             if (interceptor != null) {
                 args = interceptor.modify(args);
             }
 
             StateContext context = contextLookup.lookup(args);
 
             if (context == null) {
                 if (ignoreStateContextLookupFailure) {
                     return null;
                 }
                 throw new IllegalStateException("Cannot determine state "
                         + "context for method invocation: " + method);
             }
 
             Event event = eventFactory.create(context, method, args);
 
             try {
                 sm.handle(event);
             } catch (UnhandledEventException uee) {
                 if (!ignoreUnhandledEvents) {
                     throw uee;
                 }
             }
 
             return null;
         }
     }
 }