/*
    * 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.commons.jxpath.functions;
  
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  
  import org.apache.commons.jxpath.ExpressionContext;
  import org.apache.commons.jxpath.Function;
  import org.apache.commons.jxpath.JXPathInvalidAccessException;
  import org.apache.commons.jxpath.util.TypeUtils;
  import org.apache.commons.jxpath.util.ValueUtils;
  
  /**
   * An XPath extension function implemented as an individual Java method.
   */
  public class MethodFunction implements Function {
  
      private static final Object[] EMPTY_ARRAY = {};
      private final Method method;
  
      /**
       * Constructs a new MethodFunction.
       *
       * @param method implementing Method
       */
      public MethodFunction(final Method method) {
          this.method = ValueUtils.getAccessibleMethod(method);
      }
  
      @Override
      public Object invoke(final ExpressionContext context, Object[] parameters) {
          try {
              Object target;
              Object[] args;
              if (Modifier.isStatic(method.getModifiers())) {
                  target = null;
                  if (parameters == null) {
                      parameters = EMPTY_ARRAY;
                  }
                  int pi = 0;
                  final Class[] types = method.getParameterTypes();
                  if (types.length >= 1 && ExpressionContext.class.isAssignableFrom(types[0])) {
                      pi = 1;
                  }
                  args = new Object[parameters.length + pi];
                  if (pi == 1) {
                      args[0] = context;
                  }
                  for (int i = 0; i < parameters.length; i++) {
                      args[i + pi] = TypeUtils.convert(parameters[i], types[i + pi]);
                  }
              } else {
                  int pi = 0;
                  final Class[] types = method.getParameterTypes();
                  if (types.length >= 1 && ExpressionContext.class.isAssignableFrom(types[0])) {
                      pi = 1;
                  }
                  target = TypeUtils.convert(parameters[0], method.getDeclaringClass());
                  args = new Object[parameters.length - 1 + pi];
                  if (pi == 1) {
                      args[0] = context;
                  }
                  for (int i = 1; i < parameters.length; i++) {
                      args[pi + i - 1] = TypeUtils.convert(parameters[i], types[i + pi - 1]);
                  }
              }
              return method.invoke(target, args);
          } catch (Throwable ex) {
              if (ex instanceof InvocationTargetException) {
                  ex = ((InvocationTargetException) ex).getTargetException();
              }
              throw new JXPathInvalidAccessException("Cannot invoke " + method, ex);
          }
      }
  
      @Override
      public String toString() {
          return method.toString();
      }
  }