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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.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.util.Arrays;

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

/**
 * Bindings, usually created by a {@link org.activiti.engine.impl.juel.Tree}.
 * 
 * @author Christoph Beck
 */
public class Bindings implements TypeConverter {
  private static final long serialVersionUID = 1L;

  private static final Method[] NO_FUNCTIONS = new Method[0];
  private static final ValueExpression[] NO_VARIABLES = new ValueExpression[0];

  /**
   * Wrap a {@link Method} for serialization.
   */
  private static class MethodWrapper implements Serializable {
    private static final long serialVersionUID = 1L;

    private transient Method method;

    private MethodWrapper(Method method) {
      this.method = method;
    }

    private void writeObject(ObjectOutputStream out) throws IOException, ClassNotFoundException {
      out.defaultWriteObject();
      out.writeObject(method.getDeclaringClass());
      out.writeObject(method.getName());
      out.writeObject(method.getParameterTypes());
    }

    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
      in.defaultReadObject();
      Class type = (Class) in.readObject();
      String name = (String) in.readObject();
      Class[] args = (Class[]) in.readObject();
      try {
        method = type.getDeclaredMethod(name, args);
      } catch (NoSuchMethodException e) {
        throw new IOException(e.getMessage());
      }
    }
  }

  private transient Method[] functions;
  private final ValueExpression[] variables;
  private final TypeConverter converter;

  /**
   * Constructor.
   */
  public Bindings(Method[] functions, ValueExpression[] variables) {
    this(functions, variables, TypeConverter.DEFAULT);
  }

  /**
   * Constructor.
   */
  public Bindings(Method[] functions, ValueExpression[] variables, TypeConverter converter) {
    super();

    this.functions = functions == null || functions.length == 0 ? NO_FUNCTIONS : functions;
    this.variables = variables == null || variables.length == 0 ? NO_VARIABLES : variables;
    this.converter = converter == null ? TypeConverter.DEFAULT : converter;
  }

  /**
   * Get function by index.
   * 
   * @param index
   *          function index
   * @return method
   */
  public Method getFunction(int index) {
    return functions[index];
  }

  /**
   * Test if given index is bound to a function. This method performs an index check.
   * 
   * @param index
   *          identifier index
   * @return true if the given index is bound to a function
   */
  public boolean isFunctionBound(int index) {
    return index >= 0 && index < functions.length;
  }

  /**
   * Get variable by index.
   * 
   * @param index
   *          identifier index
   * @return value expression
   */
  public ValueExpression getVariable(int index) {
    return variables[index];
  }

  /**
   * Test if given index is bound to a variable. This method performs an index check.
   * 
   * @param index
   *          identifier index
   * @return true if the given index is bound to a variable
   */
  public boolean isVariableBound(int index) {
    return index >= 0 && index < variables.length && variables[index] != null;
  }

  /**
   * Apply type conversion.
   * 
   * @param value
   *          value to convert
   * @param type
   *          target type
   * @return converted value
   * @throws ELException
   */
  public  T convert(Object value, Class type) {
    return converter.convert(value, type);
  }

  @Override
  public boolean equals(Object obj) {
    if (obj instanceof Bindings) {
      Bindings other = (Bindings) obj;
      return Arrays.equals(functions, other.functions) && Arrays.equals(variables, other.variables) && converter.equals(other.converter);
    }
    return false;
  }

  @Override
  public int hashCode() {
    return Arrays.hashCode(functions) ^ Arrays.hashCode(variables) ^ converter.hashCode();
  }

  private void writeObject(ObjectOutputStream out) throws IOException, ClassNotFoundException {
    out.defaultWriteObject();
    MethodWrapper[] wrappers = new MethodWrapper[functions.length];
    for (int i = 0; i < wrappers.length; i++) {
      wrappers[i] = new MethodWrapper(functions[i]);
    }
    out.writeObject(wrappers);
  }

  private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
    in.defaultReadObject();
    MethodWrapper[] wrappers = (MethodWrapper[]) in.readObject();
    if (wrappers.length == 0) {
      functions = NO_FUNCTIONS;
    } else {
      functions = new Method[wrappers.length];
      for (int i = 0; i < functions.length; i++) {
        functions[i] = wrappers[i].method;
      }
    }
  }
}