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/*
 * Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
 *
 * Licensed 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. See accompanying
 * LICENSE file.
 */
package com.gemstone.gemfire.management.internal.web.shell.support;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import javax.management.ObjectName;

import com.gemstone.gemfire.management.internal.web.shell.HttpOperationInvoker;

/**
 * The HttpInvocationHandler class is an implementation of InvocationHandler serving as a proxy that uses HTTP remoting
 * for the actual method invocation on the target resource.
 * 
 * @author John Blum
 * @see java.lang.reflect.InvocationHandler
 * @see javax.management.ObjectName
 * @see com.gemstone.gemfire.management.internal.web.shell.HttpOperationInvoker
 * @since 7.5
 */
@SuppressWarnings("unused")
public class HttpInvocationHandler implements InvocationHandler {

  private final HttpOperationInvoker operationInvoker;

  private final ObjectName objectName;

  public HttpInvocationHandler(final HttpOperationInvoker operationInvoker, final ObjectName objectName) {
    assert operationInvoker != null : "The HTTP-based OperationInvoker cannot be null!";
    assert objectName != null : "The ObjectName of the resource on which the operation is invoked cannot be null!";
    this.operationInvoker = operationInvoker;
    this.objectName = objectName;
  }

  protected final ObjectName getObjectName() {
    return objectName;
  }

  protected final HttpOperationInvoker getOperationInvoker() {
    return operationInvoker;
  }

  protected boolean isAttributeAccessor(final Method method) {
    final String methodName = method.getName();
    return (methodName.startsWith("get") || methodName.startsWith("is"));
  }

  protected String getAttributeName(final Method method) {
    final String methodName = method.getName();
    // the attribute accessor method name either begins with 'get' or 'is' as defined by the JMX specification
    final int beginIndex = (methodName.startsWith("get") ? 3 : 2);
    return methodName.substring(beginIndex);
  }

  protected String getResourceName() {
    return getObjectName().getCanonicalName();
  }

  protected String[] getSignature(final Method method) {
    final List signature = new ArrayList();

    for (final Class parameterType : method.getParameterTypes()) {
      signature.add(parameterType.getName());
    }

    return signature.toArray(new String[signature.size()]);
  }

  @Override
  public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable {
    if (isAttributeAccessor(method)) {
      return getOperationInvoker().getAttribute(getResourceName(), getAttributeName(method));
    }
    else {
      return getOperationInvoker().invoke(getResourceName(), method.getName(), args, getSignature(method));
    }
  }

}