/*
 * Copyright 2004-2012 the original author or authors.
 *
 * 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.springframework.binding.convert.service;

import org.springframework.binding.convert.ConversionExecutionException;
import org.springframework.binding.convert.ConversionExecutor;
import org.springframework.binding.convert.converters.TwoWayConverter;

/**
 * A special conversion executor used by {@link DefaultConversionService} that can dynamically resolve whether to do a
 * forward or "reverse" conversion using a {@link TwoWayConverter} based on the type of the object passed in.
 * 
 * Used in conjunction with custom converters to support dynamic conversion of collection elements.
 */
class TwoWayCapableConversionExecutor implements ConversionExecutor {

	private Class<?> sourceClass;

	private Class<?> targetClass;

	private TwoWayConverter converter;

	/**
	 * Creates a new two way conversion executor.
	 * @param sourceClass the source class to convert to (or from)
	 * @param targetClass the target class to convert from (or to)
	 * @param converter the two way converter
	 */
	public TwoWayCapableConversionExecutor(Class<?> sourceClass, Class<?> targetClass, TwoWayConverter converter) {
		this.sourceClass = sourceClass;
		this.targetClass = targetClass;
		this.converter = converter;
	}

	public Class<?> getSourceClass() {
		return sourceClass;
	}

	public Class<?> getTargetClass() {
		return targetClass;
	}

	public Object execute(Object source) throws ConversionExecutionException {
		if (source == null || converter.getSourceClass().isInstance(source)) {
			try {
				return converter.convertSourceToTargetClass(source, targetClass);
			} catch (Exception e) {
				throw new ConversionExecutionException(source, getSourceClass(), getTargetClass(), e);
			}
		} else if (converter.getTargetClass().isInstance(source)) {
			try {
				return converter.convertTargetToSourceClass(source, sourceClass);
			} catch (Exception e) {
				throw new ConversionExecutionException(source, converter.getTargetClass(), getSourceClass(), e);
			}
		} else {
			throw new ConversionExecutionException(source, getSourceClass(), getTargetClass(), "Source object "
					+ source + " to convert is expected to be an instance of [" + converter.getSourceClass().getName()
					+ "] or [" + converter.getTargetClass().getName() + "]");
		}
	}
}