/*
 * 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.wicket.model;

import java.lang.reflect.Field;
import java.lang.reflect.Method;

import org.apache.wicket.Application;
import org.apache.wicket.Session;
import org.apache.wicket.WicketRuntimeException;
import org.apache.wicket.core.util.lang.PropertyResolver;
import org.apache.wicket.core.util.lang.PropertyResolverConverter;
import org.apache.wicket.util.string.Strings;

/**
 * Serves as a base class for different kinds of property models. By default, this class uses
 * {@link PropertyResolver} to resolve expressions on the target model object. Note that the
 * property resolver by default provides access to private members and methods. If guaranteeing
 * encapsulation of the target objects is a big concern, you should consider using an alternative
 * implementation.
 * 
 * @see PropertyResolver
 * @see org.apache.wicket.model.IDetachable
 * 
 * @author Chris Turner
 * @author Eelco Hillenius
 * @author Jonathan Locke
 * 
 * @param <T>
 *            The Model object type
 */
public abstract class AbstractPropertyModel<T> extends ChainingModel<T>
	implements
		IObjectClassAwareModel<T>,
		IPropertyReflectionAwareModel<T>
{
	private static final long serialVersionUID = 1L;

	/**
	 * Constructor
	 * 
	 * @param modelObject
	 *            The nested model object
	 */
	public AbstractPropertyModel(final Object modelObject)
	{
		super(modelObject);
	}

	@Override
	@SuppressWarnings("unchecked")
	public T getObject()
	{
		final String expression = propertyExpression();
		if (Strings.isEmpty(expression))
		{
			// Return a meaningful value for an empty property expression
			return (T) getInnermostModelOrObject();
		}
		else if (expression.startsWith("."))
		{
			throw new IllegalArgumentException(
				"Property expressions cannot start with a '.' character");
		}

		final Object target = getInnermostModelOrObject();
		if (target != null)
		{
			return (T)PropertyResolver.getValue(expression, target);
		}
		return null;
	}

	/**
	 * Gets the property expression for this model
	 * 
	 * @return The property expression
	 */
	public final String getPropertyExpression()
	{
		return propertyExpression();
	}

	/**
	 * Applies the property expression on the model object using the given object argument.
	 * 
	 * @param object
	 *            The object that will be used when setting a value on the model object
	 * @see IModel#setObject(Object)
	 */
	@Override
	@SuppressWarnings("unchecked")
	public void setObject(T object)
	{
		final String expression = propertyExpression();
		if (Strings.isEmpty(expression))
		{
			// TODO check, really do this?
			// why not just set the target to the object?
			Object target = getTarget();
			if (target instanceof IModel)
			{
				((IModel<T>)target).setObject(object);
			}
			else
			{
				setTarget(object);
			}
		}
		else
		{
			PropertyResolverConverter prc = new PropertyResolverConverter(
					Application.get().getConverterLocator(), Session.get().getLocale());
			PropertyResolver.setValue(expression, getInnermostModelOrObject(), object, prc);
		}
	}

	/**
	 * @return model object class
	 */
	@Override
	@SuppressWarnings("unchecked")
	public Class<T> getObjectClass()
	{
		final String expression = propertyExpression();
		final Object target = getInnermostModelOrObject();

		if (Strings.isEmpty(expression))
		{
			// Return a meaningful value for an empty property expression
			return (Class<T>)(target != null ? target.getClass() : null);
		}

		if (target != null)
		{
			try
			{
				return (Class<T>)PropertyResolver.getPropertyClass(expression, target);
			}
			catch (Exception e)
			{
				// ignore.
			}
		}
		else if (getTarget() instanceof IObjectClassAwareModel)
		{
			try
			{
				Class<?> targetClass = ((IObjectClassAwareModel<?>) getTarget()).getObjectClass();
				if (targetClass != null)
				{
					return PropertyResolver.getPropertyClass(expression, targetClass);
				}
			}
			catch (WicketRuntimeException e)
			{
				// it was just a try.
			}

		}
		return null;
	}

	@Override
	public Field getPropertyField()
	{
		String expression = propertyExpression();
		if (Strings.isEmpty(expression) == false)
		{
			Object target = getInnermostModelOrObject();
			if (target != null)
			{
				try
				{
					return PropertyResolver.getPropertyField(expression, target);
				}
				catch (Exception ignore)
				{
					// ignore.
				}
			}
		}
		return null;
	}

	@Override
	public Method getPropertyGetter()
	{
		String expression = propertyExpression();
		if (Strings.isEmpty(expression) == false)
		{
			Object target = getInnermostModelOrObject();
			if (target != null)
			{
				try
				{
					return PropertyResolver.getPropertyGetter(expression, target);
				}
				catch (Exception ignore)
				{
				}
			}
		}
		return null;
	}

	@Override
	public Method getPropertySetter()
	{
		String expression = propertyExpression();
		if (Strings.isEmpty(expression) == false)
		{
			Object target = getInnermostModelOrObject();
			if (target != null)
			{
				try
				{
					return PropertyResolver.getPropertySetter(expression, target);
				}
				catch (Exception ignore)
				{
				}
			}
		}
		return null;
	}

	/**
	 * @return The property expression for the component
	 */
	protected abstract String propertyExpression();

	/**
	 * @return The innermost model or the object if the target is not a model
	 */
	public final Object getInnermostModelOrObject()
	{
		Object object = getTarget();
		while (object instanceof IModel)
		{
			Object tmp = ((IModel<?>)object).getObject();
			if (tmp == object)
			{
				break;
			}
			object = tmp;
		}
		return object;
	}
}