/*
 * Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * 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.security.authentication.dao;

import org.springframework.security.authentication.AuthenticationServiceException;
import org.springframework.security.core.userdetails.UserDetails;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.BeanUtils;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.Assert;

import java.lang.reflect.Method;
import java.beans.PropertyDescriptor;

/**
 * Obtains a salt from a specified property of the
 * {@link org.springframework.security.core.userdetails.User} object.
 * <p>
 * This allows you to subclass <code>User</code> and provide an additional bean getter for
 * a salt. You should use a synthetic value that does not change, such as a database
 * primary key. Do not use <code>username</code> if it is likely to change.
 *
 * @author Ben Alex
 */
public class ReflectionSaltSource implements SaltSource, InitializingBean {
	// ~ Instance fields
	// ================================================================================================

	private String userPropertyToUse;

	// ~ Methods
	// ========================================================================================================

	public void afterPropertiesSet() throws Exception {
		Assert.hasText(userPropertyToUse, "A userPropertyToUse must be set");
	}

	/**
	 * Performs reflection on the passed <code>User</code> to obtain the salt.
	 * <p>
	 * The property identified by <code>userPropertyToUse</code> must be available from
	 * the passed <code>User</code> object. If it is not available, an
	 * {@link AuthenticationServiceException} will be thrown.
	 *
	 * @param user which contains the method identified by <code>userPropertyToUse</code>
	 *
	 * @return the result of invoking <tt>user.userPropertyToUse()</tt>, or if the method
	 * doesn't exist, <tt>user.getUserPropertyToUse()</tt>.
	 *
	 * @throws AuthenticationServiceException if reflection fails
	 */
	public Object getSalt(UserDetails user) {
		Method saltMethod = findSaltMethod(user);

		try {
			return saltMethod.invoke(user);
		}
		catch (Exception exception) {
			throw new AuthenticationServiceException(exception.getMessage(), exception);
		}
	}

	private Method findSaltMethod(UserDetails user) {
		Method saltMethod = ReflectionUtils.findMethod(user.getClass(),
				userPropertyToUse, new Class[0]);

		if (saltMethod == null) {
			PropertyDescriptor pd = BeanUtils.getPropertyDescriptor(user.getClass(),
					userPropertyToUse);

			if (pd != null) {
				saltMethod = pd.getReadMethod();
			}

			if (saltMethod == null) {
				throw new AuthenticationServiceException(
						"Unable to find salt method on user Object. Does the class '"
								+ user.getClass().getName()
								+ "' have a method or getter named '" + userPropertyToUse
								+ "' ?");
			}
		}

		return saltMethod;
	}

	protected String getUserPropertyToUse() {
		return userPropertyToUse;
	}

	/**
	 * The method name to call to obtain the salt. Can be either a method name or a bean
	 * property name. If your <code>UserDetails</code> contains a
	 * <code>UserDetails.getSalt()</code> method, you should set this property to
	 * "getSalt" or "salt".
	 *
	 * @param userPropertyToUse the name of the <b>getter</b> to call to obtain the salt
	 * from the <code>UserDetails</code>
	 */
	public void setUserPropertyToUse(String userPropertyToUse) {
		this.userPropertyToUse = userPropertyToUse;
	}

	public String toString() {
		return "ReflectionSaltSource[ userPropertyToUse='" + userPropertyToUse + "'; ]";
	}
}
