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/*
 * Based on JUEL 2.2.1 code, 2006-2009 Odysseus Software GmbH
 *
 * 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.
 */
package org.activiti.engine.impl.juel;

import java.lang.reflect.Array;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import org.activiti.engine.impl.javax.el.ELContext;
import org.activiti.engine.impl.javax.el.ELException;

public class AstFunction extends AstRightValue implements FunctionNode {
  private final int index;
  private final String name;
  private final AstParameters params;
  private final boolean varargs;

  public AstFunction(String name, int index, AstParameters params) {
    this(name, index, params, false);
  }

  public AstFunction(String name, int index, AstParameters params, boolean varargs) {
    this.name = name;
    this.index = index;
    this.params = params;
    this.varargs = varargs;
  }

  /**
   * Invoke method.
   * 
   * @param bindings
   * @param context
   * @param base
   * @param method
   * @return method result
   * @throws InvocationTargetException
   * @throws IllegalAccessException
   */
  protected Object invoke(Bindings bindings, ELContext context, Object base, Method method) throws InvocationTargetException, IllegalAccessException {
    Class[] types = method.getParameterTypes();
    Object[] params = null;
    if (types.length > 0) {
      params = new Object[types.length];
      if (varargs && method.isVarArgs()) {
        for (int i = 0; i < params.length - 1; i++) {
          Object param = getParam(i).eval(bindings, context);
          if (param != null || types[i].isPrimitive()) {
            params[i] = bindings.convert(param, types[i]);
          }
        }
        int varargIndex = types.length - 1;
        Class varargType = types[varargIndex].getComponentType();
        int length = getParamCount() - varargIndex;
        Object array = null;
        if (length == 1) { // special: eventually use argument as is
          Object param = getParam(varargIndex).eval(bindings, context);
          if (param != null && param.getClass().isArray()) {
            if (types[varargIndex].isInstance(param)) {
              array = param;
            } else { // coerce array elements
              length = Array.getLength(param);
              array = Array.newInstance(varargType, length);
              for (int i = 0; i < length; i++) {
                Object elem = Array.get(param, i);
                if (elem != null || varargType.isPrimitive()) {
                  Array.set(array, i, bindings.convert(elem, varargType));
                }
              }
            }
          } else { // single element array
            array = Array.newInstance(varargType, 1);
            if (param != null || varargType.isPrimitive()) {
              Array.set(array, 0, bindings.convert(param, varargType));
            }
          }
        } else {
          array = Array.newInstance(varargType, length);
          for (int i = 0; i < length; i++) {
            Object param = getParam(varargIndex + i).eval(bindings, context);
            if (param != null || varargType.isPrimitive()) {
              Array.set(array, i, bindings.convert(param, varargType));
            }
          }
        }
        params[varargIndex] = array;
      } else {
        for (int i = 0; i < params.length; i++) {
          Object param = getParam(i).eval(bindings, context);
          if (param != null || types[i].isPrimitive()) {
            params[i] = bindings.convert(param, types[i]);
          }
        }
      }
    }
    return method.invoke(base, params);
  }

  @Override
  public Object eval(Bindings bindings, ELContext context) {
    Method method = bindings.getFunction(index);
    try {
      return invoke(bindings, context, null, method);
    } catch (IllegalAccessException e) {
      throw new ELException(LocalMessages.get("error.function.access", name), e);
    } catch (InvocationTargetException e) {
      throw new ELException(LocalMessages.get("error.function.invocation", name), e.getCause());
    }
  }

  @Override
  public String toString() {
    return name;
  }

  @Override
  public void appendStructure(StringBuilder b, Bindings bindings) {
    b.append(bindings != null && bindings.isFunctionBound(index) ? "" : name);
    params.appendStructure(b, bindings);
  }

  public int getIndex() {
    return index;
  }

  public String getName() {
    return name;
  }

  public boolean isVarArgs() {
    return varargs;
  }

  public int getParamCount() {
    return params.getCardinality();
  }

  protected AstNode getParam(int i) {
    return params.getChild(i);
  }

  public int getCardinality() {
    return 1;
  }

  public AstNode getChild(int i) {
    return i == 0 ? params : null;
  }
}