/***
 * Copyright (c) 2009 Caelum - www.caelum.com.br/opensource
 * All rights reserved.
 *
 * 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 br.com.caelum.vraptor.converter;

import static com.google.common.base.Strings.isNullOrEmpty;

import javax.annotation.Priority;
import javax.enterprise.context.ApplicationScoped;
import javax.enterprise.inject.Alternative;
import javax.interceptor.Interceptor;

import br.com.caelum.vraptor.Convert;

/**
 * Accepts either the ordinal value or name. Null and empty strings are treated
 * as null.
 *
 * @author Guilherme Silveira
 */
@Convert(Enum.class)
@ApplicationScoped
@Alternative
@Priority(Interceptor.Priority.LIBRARY_BEFORE)
public class EnumConverter implements Converter {

	public static final String INVALID_MESSAGE_KEY = "is_not_a_valid_enum_value";

	/**
	 * Enums are always final, so I can suppress this warning safely
	 */
	@Override
	public Object convert(String value, Class type) {
		if (isNullOrEmpty(value)) {
			return null;
		}

		if (Character.isDigit(value.charAt(0))) {
			return resolveByOrdinal(value, type);
		} else {
			return resolveByName(value, type);
		}
	}

	private Object resolveByName(String value, Class enumType) {
		try {
			return Enum.valueOf(enumType, value);
		} catch (IllegalArgumentException e) {
			throw new ConversionException(new ConversionMessage(INVALID_MESSAGE_KEY, value));
		}
	}

	private Object resolveByOrdinal(String value, Class enumType) {
		try {
			int ordinal = Integer.parseInt(value);
			if (ordinal >= enumType.getEnumConstants().length) {
				throw new ConversionException(new ConversionMessage(INVALID_MESSAGE_KEY, value));
			}
			return enumType.getEnumConstants()[ordinal];
		} catch (NumberFormatException e) {
			throw new ConversionException(new ConversionMessage(INVALID_MESSAGE_KEY, value));
		}
	}

}