/*
 * Copyright 2004-2012 Sebastian Dietrich (Sebastian.Dietrich@e-movimento.com)
 *
 * 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 junit.extensions;

import java.util.Collection;

/**
 * This class is used to access a method or field of an object no matter what the access modifier of the method or field. The syntax
 * for accessing fields and methods is out of the ordinary because this class uses reflection to peel away protection.
 * <p>
 * a.k.a. The "ObjectMolester"
 * <p>
 * Here is an example of using this to access a private member: <br>
 * Given the following class <code>MyClass</code>: <br>
 * 
 * <pre>
 * public class MyClass {
 *    private String name; // private attribute
 * 
 *    // private constructor
 *    private MyClass() {
 *       super();
 *    }
 * 
 *    // private method
 *    private void setName(String newName) {
 *       this.name = newName;
 *    }
 * }
 * </pre>
 * 
 * We now want to access the class: <br>
 * 
 * <pre>
 * MyClass myObj = PA.instantiate(MyClass.class);
 * PA.invokeMethod(myObj, &quot;setName(java.lang.String)&quot;, &quot;myNewName&quot;);
 * String name = PA.getValue(myObj, &quot;name&quot;);
 * </pre>
 * 
 * This class extends {@link PrivilegedAccessor} by re-throwing checked {@link Exception}s as {@link RuntimeException}s.
 * 
 * 
 * @see PrivilegedAccessor
 * 
 * @author Sebastian Dietrich (sebastian.dietrich@e-movimento.com)
 * @author Lubos Bistak (lubos@bistak.sk)
 */
public class PA {
   private final Object instanceOrClass;

   /**
    * Private constructor to make it impossible to instantiate this class from outside of PA.
    * 
    * @param instanceOrClass
    */
   private PA(Object instanceOrClass) {
      this.instanceOrClass = instanceOrClass;
   }

   /**
    * Returns a string representation of the given object. The string has the following format: "<classname> {<attributes and values>}"
    * whereas <attributes and values> is a comma separated list with <attributeName>=<attributeValue> <atributes and values> includes
    * all attributes of the objects class followed by the attributes of its superclass (if any) and so on.
    * 
    * @param instanceOrClass the object or class to get a string representation of
    * @return a string representation of the given object
    * 
    * @see PrivilegedAccessor#toString(Object)
    */
   public static String toString(final Object instanceOrClass) {
      return PrivilegedAccessor.toString(instanceOrClass);
   }

   /**
    * Gets the name of all fields (public, private, protected, default) of the given instance or class. This includes as well all
    * fields (public, private, protected, default) of all its super classes.
    * 
    * @param instanceOrClass the instance or class to get the fields of
    * @return the collection of field names of the given instance or class
    * 
    * @see PrivilegedAccessor#getFieldNames(Object)
    */
   public static Collection<String> getFieldNames(final Object instanceOrClass) {
      return PrivilegedAccessor.getFieldNames(instanceOrClass);
   }

   /**
    * Gets the signatures of all methods (public, private, protected, default) of the given instance or class. This includes as well
    * all methods (public, private, protected, default) of all its super classes. This does not include constructors.
    * 
    * @param instanceOrClass the instance or class to get the method signatures of
    * @return the collection of method signatures of the given instance or class
    * 
    * @see PrivilegedAccessor#getMethodSignatures(Object)
    */
   public static Collection<String> getMethodSignatures(final Object instanceOrClass) {
      return PrivilegedAccessor.getMethodSignatures(instanceOrClass);
   }

   /**
    * Gets the value of the named field and returns it as an object. If instanceOrClass is a class then a static field is returned.
    * 
    * @param instanceOrClass the instance or class to get the field from
    * @param fieldName the name of the field
    * @return an object representing the value of the field
    * @throws IllegalArgumentException if the field does not exist
    * 
    * @see PrivilegedAccessor#getValue(Object,String)
    */
   public static Object getValue(final Object instanceOrClass, final String fieldName) {
      try {
         return PrivilegedAccessor.getValue(instanceOrClass, fieldName);
      } catch (Exception e) {
         throw new IllegalArgumentException("Can't get value of " + fieldName + " from " + instanceOrClass, e);
      }
   }

   /**
    * Gets the value of the named field and returns it as an object.
    * 
    * @param fieldName the name of the field
    * @return an object representing the value of the field
    * @throws IllegalArgumentException if the field does not exist
    * 
    * @see PA#getValue(Object,String)
    */
   public Object getValue(final String fieldName) {
      return PA.getValue(instanceOrClass, fieldName);
   }

   /**
    * Instantiates an object of the given class with the given arguments and the given argument types. If you want to instantiate a
    * member class, you must provide the object it is a member of as first argument.
    * 
    * @param fromClass the class to instantiate an object from
    * @param arguments the arguments to pass to the constructor
    * @param argumentTypes the fully qualified types of the arguments of the constructor
    * @return an object of the given type
    * @throws IllegalArgumentException if the class can't be instantiated. This could be the case if the number of actual and formal
    *            parameters differ; if an unwrapping conversion for primitive arguments fails; if, after possible unwrapping, a
    *            parameter value cannot be converted to the corresponding formal parameter type by a method invocation conversion; if
    *            this Constructor object enforces Java language access control and the underlying constructor is inaccessible; if the
    *            underlying constructor throws an exception; if the constructor could not be found; or if the class that declares the
    *            underlying constructor represents an abstract class.
    * 
    * @see PrivilegedAccessor#instantiate(Class,Class[],Object[])
    */
   public static <T> T instantiate(final Class<? extends T> fromClass, final Class<?>[] argumentTypes, final Object... arguments) {
      try {
         return PrivilegedAccessor.instantiate(fromClass, argumentTypes, correctVarargs(arguments));
      } catch (Exception e) {
         throw new IllegalArgumentException("Can't instantiate class " + fromClass + " with arguments " + arguments, e);
      }
   }

   /**
    * Instantiates an object of the given class with the given arguments. If you want to instantiate a member class, you must provide
    * the object it is a member of as first argument.
    * 
    * @param fromClass the class to instantiate an object from
    * @param arguments the arguments to pass to the constructor
    * @return an object of the given type
    * @throws IllegalArgumentException if the class can't be instantiated. This could be the case if the number of actual and formal
    *            parameters differ; if an unwrapping conversion for primitive arguments fails; or if, after possible unwrapping, a
    *            parameter value cannot be converted to the corresponding formal parameter type by a method invocation conversion; if
    *            this Constructor object enforces Java language access control and the underlying constructor is inaccessible; if the
    *            underlying constructor throws an exception; if the constructor could not be found; or if the class that declares the
    *            underlying constructor represents an abstract class.
    * 
    * @see PrivilegedAccessor#instantiate(Class,Object[])
    */
   public static <T> T instantiate(final Class<? extends T> fromClass, final Object... arguments) {
      try {
         return PrivilegedAccessor.instantiate(fromClass, correctVarargs(arguments));
      } catch (Exception e) {
         throw new IllegalArgumentException("Can't instantiate class " + fromClass + " with arguments " + arguments, e);
      }
   }

   /**
    * Calls a method on the given object instance with the given arguments. Arguments can be object types or representations for
    * primitives.
    * 
    * @param instanceOrClass the instance or class to invoke the method on
    * @param methodSignature the name of the method and the parameters <br>
    *           (e.g. "myMethod(java.lang.String, com.company.project.MyObject)")
    * @param arguments an array of objects to pass as arguments
    * @return the return value of this method or null if void
    * @throws IllegalArgumentException if the method could not be invoked. This could be the case if the method is inaccessible; if the
    *            underlying method throws an exception; if no method with the given <code>methodSignature</code> could be found; or if
    *            an argument couldn't be converted to match the expected type
    * 
    * @see PrivilegedAccessor#invokeMethod(Object,String,Object[])
    */
   public static Object invokeMethod(final Object instanceOrClass, final String methodSignature, final Object... arguments) {
      try {
         return PrivilegedAccessor.invokeMethod(instanceOrClass, methodSignature, correctVarargs(arguments));
      } catch (Exception e) {
         throw new IllegalArgumentException("Can't invoke method " + methodSignature + " on " + instanceOrClass + " with arguments "
            + arguments, e);
      }
   }

   /**
    * Calls a method with the given arguments. Arguments can be object types or representations for primitives.
    * 
    * @param methodSignature the name of the method and the parameters <br>
    *           (e.g. "myMethod(java.lang.String, com.company.project.MyObject)")
    * @param arguments an array of objects to pass as arguments
    * @return the return value of this method or null if void
    * @throws IllegalArgumentException if the method could not be invoked. This could be the case if the method is inaccessible; if the
    *            underlying method throws an exception; if no method with the given <code>methodSignature</code> could be found; or if
    *            an argument couldn't be converted to match the expected type
    * @see PA#invokeMethod(Object, String, Object...)
    */
   public Object invokeMethod(final String methodSignature, final Object... arguments) {
      return PA.invokeMethod(instanceOrClass, methodSignature, arguments);
   }

   /**
    * Corrects varargs to their initial form. If you call a method with an object-array as last argument the Java varargs mechanism
    * converts this array in single arguments. This method returns an object array if the arguments are all of the same type.
    * 
    * @param arguments the possibly converted arguments of a vararg method
    * @return arguments possibly converted
    */
   private static Object[] correctVarargs(final Object... arguments) {
      if ((arguments == null) || changedByVararg(arguments)) return new Object[] {arguments};
      return arguments;
   }

   /**
    * Tests if the arguments were changed by vararg. Arguments are changed by vararg if they are of a non primitive array type. E.g.
    * arguments[] = Object[String[]] is converted to String[] while e.g. arguments[] = Object[int[]] is not converted and stays
    * Object[int[]]
    * 
    * Unfortunately we can't detect the difference for arg = Object[primitive] since arguments[] = Object[Object[primitive]] which is
    * converted to Object[primitive] and arguments[] = Object[primitive] which stays Object[primitive]
    * 
    * and we can't detect the difference for arg = Object[non primitive] since arguments[] = Object[Object[non primitive]] is converted
    * to Object[non primitive] and arguments[] = Object[non primitive] stays Object[non primitive]
    * 
    * @param parameters the parameters
    * @return true if parameters were changes by varargs, false otherwise
    */
   private static boolean changedByVararg(final Object[] parameters) {
      if ((parameters.length == 0) || (parameters[0] == null)) return false;

      if (parameters.getClass() == Object[].class) return false;

      return true;
   }

   /**
    * Sets the value of the named field. If fieldName denotes a static field, provide a class, otherwise provide an instance. If the
    * fieldName denotes a final field, this method could fail with an IllegalAccessException, since setting the value of final fields
    * at other times than instantiation can have unpredictable effects.<br/>
    * <br/>
    * Example:<br/>
    * <br/>
    * <code>
    * String myString = "Test"; <br/>
    * <br/>
    * //setting the private field value<br/>
    * PrivilegedAccessor.setValue(myString, "value", new char[] {'T', 'e', 's', 't'});<br/>
    * <br/>
    * //setting the static final field serialVersionUID - MIGHT FAIL<br/>
    * PrivilegedAccessor.setValue(myString.getClass(), "serialVersionUID", 1);<br/>
    * <br/>
    * </code>
    * 
    * @param instanceOrClass the instance or class to set the field
    * @param fieldName the name of the field
    * @param value the new value of the field
    * @throws IllegalArgumentException if the value could not be set. This could be the case if no field with the given
    *            <code>fieldName</code> can be found; or if the field was final
    * 
    * @see PrivilegedAccessor.setValue(Object,String,Object)
    */
   public static PA setValue(final Object instanceOrClass, final String fieldName, final Object value) {
      try {
         PrivilegedAccessor.setValue(instanceOrClass, fieldName, value);
      } catch (Exception e) {
         throw new IllegalArgumentException("Can't set value " + value + " at " + fieldName + " in " + instanceOrClass, e);
      }
      return new PA(instanceOrClass);
   }

   /**
    * Sets the value of the named field. If fieldName denotes a static field, provide a class, otherwise provide an instance. If the
    * fieldName denotes a final field, this method could fail with an IllegalAccessException, since setting the value of final fields
    * at other times than instantiation can have unpredictable effects.<br/>
    * <br/>
    * Example:<br/>
    * <br/>
    * <code>
    * String myString = "Test"; <br/>
    * <br/>
    * //setting the private field value<br/>
    * PrivilegedAccessor.setValue(myString, "value", new char[] {'T', 'e', 's', 't'});<br/>
    * <br/>
    * //setting the static final field serialVersionUID - MIGHT FAIL<br/>
    * PrivilegedAccessor.setValue(myString.getClass(), "serialVersionUID", 1);<br/>
    * <br/>
    * </code>
    * 
    * @param fieldName the name of the field
    * @param value the new value of the field
    * @throws IllegalArgumentException if the value could not be set. This could be the case if no field with the given
    *            <code>fieldName</code> can be found; or if the field was final
    * 
    * @see PA.setValue(Object,String,Object)
    */
   public PA setValue(final String fieldName, final Object value) {
      PA.setValue(instanceOrClass, fieldName, value);
      return this;
   }
}