/***
 * 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 java.text.MessageFormat;
import java.util.ResourceBundle;

import br.com.caelum.vraptor.Convert;
import br.com.caelum.vraptor.Converter;
import br.com.caelum.vraptor.ioc.ApplicationScoped;
import br.com.caelum.vraptor.ioc.PrototypeScoped;

/**
 * Accepts either the ordinal value or name. Null and empty strings are treated
 * as null.
 *
 * @author Guilherme Silveira
 */
@Convert(Enum.class)
@PrototypeScoped
public class EnumConverter<T extends Enum<T>> implements Converter<T> {
	private static final String IS_NOT_A_VALID_ENUM_VALUE = "is_not_a_valid_enum_value";

	/**
	 * Enums are always final, so I can suppress this warning safely
	 */
	@SuppressWarnings("unchecked")
	public T convert(String value, Class<? extends T> type, ResourceBundle bundle) {
		if (isNullOrEmpty(value)) {
			return null;
		}
			
		if (Character.isDigit(value.charAt(0))) {
			return resolveByOrdinal(value, (Class<T>) type, bundle);
		} else {
			return resolveByName(value, (Class<T>) type, bundle);
		}
	}

	private T resolveByName(String value, Class<T> enumType, ResourceBundle bundle) {
		try {
			return Enum.valueOf(enumType, value);
		} catch (IllegalArgumentException e) {
				throw new ConversionError(MessageFormat.format(bundle.getString(IS_NOT_A_VALID_ENUM_VALUE), value));
		}
	}

	private T resolveByOrdinal(String value, Class<T> enumType, ResourceBundle bundle) {
		try {
			int ordinal = Integer.parseInt(value);
			if (ordinal >= enumType.getEnumConstants().length) {
					throw new ConversionError(MessageFormat.format(bundle.getString(IS_NOT_A_VALID_ENUM_VALUE), value));
			}
			return enumType.getEnumConstants()[ordinal];
		} catch (NumberFormatException e) {
				throw new ConversionError(MessageFormat.format(bundle.getString(IS_NOT_A_VALID_ENUM_VALUE), value));
		}
	}

}