/*
    * 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.shiro.event.support;
  
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  
  /**
   * A event listener that invokes a target object's method that accepts a single event argument.
   *
   * @since 1.3
   */
  public class SingleArgumentMethodEventListener implements TypedEventListener {
  
      private final Object target;
      private final Method method;
  
      public SingleArgumentMethodEventListener(Object target, Method method) {
          this.target = target;
          this.method = method;
          //assert that the method is defined as expected:
          getMethodArgumentType(method);
  
          assertPublicMethod(method);
      }
  
      public Object getTarget() {
          return this.target;
      }
  
      public Method getMethod() {
          return this.method;
      }
  
      private void assertPublicMethod(Method method) {
          int modifiers = method.getModifiers();
          if (!Modifier.isPublic(modifiers)) {
              throw new IllegalArgumentException("Event handler method [" + method + "] must be public.");
          }
      }
  
      public boolean accepts(Object event) {
          return event != null && getEventType().isInstance(event);
      }
  
      public Class getEventType() {
          return getMethodArgumentType(getMethod());
      }
  
      public void onEvent(Object event) {
          Method method = getMethod();
          try {
              method.invoke(getTarget(), event);
          } catch (Exception e) {
              throw new IllegalStateException("Unable to invoke event handler method [" + method + "].", e);
          }
      }
  
      protected Class getMethodArgumentType(Method method) {
          Class[] paramTypes = method.getParameterTypes();
          if (paramTypes.length != 1) {
              //the default implementation expects a single typed argument and nothing more:
              String msg = "Event handler methods must accept a single argument.";
              throw new IllegalArgumentException(msg);
          }
          return paramTypes[0];
      }
  }