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/*
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.xwiki.properties.internal.converter;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import javax.inject.Singleton;

import org.apache.commons.beanutils.BeanUtilsBean;
import org.apache.commons.beanutils.ConversionException;
import org.apache.commons.beanutils.ConvertUtils;
import org.apache.commons.lang3.reflect.TypeUtils;
import org.xwiki.component.annotation.Component;
import org.xwiki.component.phase.Initializable;
import org.xwiki.properties.converter.Converter;

/**
 * {@link ConvertUtils}-based converter.
 * 
 * It's the default {@link Converter}, the one used when no other Converter could be found by
 * {@link org.xwiki.properties.ConverterManager}.
 *
 * @version $Id: af99f7ea18bcef1f09d99e442c0c80d3c19827e5 $
 * @since 2.0M2
 */
@Component
@Singleton
public class ConvertUtilsConverter implements Converter, Initializable
{
    /**
     * By default {@link ConvertUtils#convert(Object, Class)} does not throw any exceptions for failed conversions.
     * Instead it will return some default value corresponding to the target type. We must override this behavior in
     * order to get the desired functionality.
     */
    @Override
    public void initialize()
    {
        BeanUtilsBean.getInstance().getConvertUtils().register(true, false, 0);
    }

    /**
     * @param  the type in which the provided value has to be converted
     * @param targetType the type in which the provided value has to be converted
     * @param sourceValue the value to convert
     * @return the converted value
     */
    private  T convert(Class targetType, Object sourceValue)
    {
        T result;

        // We can't use Class#cast(Object) because ConvertUtils#convert always return Object form of the targetType even
        // if targetType is a primitive. When using casting syntax Object form is implicitly converter to proper
        // primitive type.
        try {
            result = (T) ConvertUtils.convert(sourceValue, targetType);
        } catch (ConversionException ex) {
            throw new org.xwiki.properties.converter.ConversionException("Error while performing type conversion", ex);
        }

        if (result == null) {
            return null;
        }

        // BeanUtils converters will return the passed value if no converter has been found. Thus we need to check
        // that the returned value is compatible with the expected type and raise a ConversionException if not.
        if (!TypeUtils.isAssignable(targetType, result.getClass())) {
            throw new org.xwiki.properties.converter.ConversionException(
                String.format("Failed to find a Converter to convert from [%s] to [%s]",
                    sourceValue.getClass().getName(), targetType.getName()));
        }

        return result;
    }

    @Override
    public Object convert(Type targetType, Object sourceValue)
    {
        Class clazz;
        if (targetType instanceof Class) {
            clazz = (Class) targetType;
        } else if (targetType instanceof ParameterizedType) {
            clazz = (Class) ((ParameterizedType) targetType).getRawType();
        } else {
            throw new org.xwiki.properties.converter.ConversionException("Unknown type [" + targetType + "]");
        }

        return convert(clazz, sourceValue);
    }
}