/*
 * 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.access.intercept;

import java.util.Collection;

import org.aopalliance.intercept.MethodInvocation;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.security.access.AccessDeniedException;
import org.springframework.security.access.ConfigAttribute;
import org.springframework.security.core.Authentication;
import org.springframework.util.Assert;

/**
 * Allows users to determine whether they have "before invocation" privileges for a given
 * method invocation.
 * <p>
 * Of course, if an
 * {@link org.springframework.security.access.intercept.AfterInvocationManager} is used to
 * authorize the <em>result</em> of a method invocation, this class cannot assist
 * determine whether or not the <code>AfterInvocationManager</code> will enable access.
 * Instead this class aims to allow applications to determine whether or not the current
 * principal would be allowed to at least attempt to invoke the method, irrespective of
 * the "after" invocation handling.
 * </p>
 *
 * @author Ben Alex
 */
public class MethodInvocationPrivilegeEvaluator implements InitializingBean {
	// ~ Static fields/initializers
	// =====================================================================================

	protected static final Log logger = LogFactory
			.getLog(MethodInvocationPrivilegeEvaluator.class);

	// ~ Instance fields
	// ================================================================================================

	private AbstractSecurityInterceptor securityInterceptor;

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

	public void afterPropertiesSet() throws Exception {
		Assert.notNull(securityInterceptor, "SecurityInterceptor required");
	}

	public boolean isAllowed(MethodInvocation mi, Authentication authentication) {
		Assert.notNull(mi, "MethodInvocation required");
		Assert.notNull(mi.getMethod(),
				"MethodInvocation must provide a non-null getMethod()");

		Collection<ConfigAttribute> attrs = securityInterceptor
				.obtainSecurityMetadataSource().getAttributes(mi);

		if (attrs == null) {
			if (securityInterceptor.isRejectPublicInvocations()) {
				return false;
			}

			return true;
		}

		if (authentication == null || authentication.getAuthorities().isEmpty()) {
			return false;
		}

		try {
			securityInterceptor.getAccessDecisionManager().decide(authentication, mi,
					attrs);
		}
		catch (AccessDeniedException unauthorized) {
			if (logger.isDebugEnabled()) {
				logger.debug(mi.toString() + " denied for " + authentication.toString(),
						unauthorized);
			}

			return false;
		}

		return true;
	}

	public void setSecurityInterceptor(AbstractSecurityInterceptor securityInterceptor) {
		Assert.notNull(securityInterceptor, "AbstractSecurityInterceptor cannot be null");
		Assert.isTrue(
				MethodInvocation.class.equals(securityInterceptor.getSecureObjectClass()),
				"AbstractSecurityInterceptor does not support MethodInvocations");
		Assert.notNull(securityInterceptor.getAccessDecisionManager(),
				"AbstractSecurityInterceptor must provide a non-null AccessDecisionManager");
		this.securityInterceptor = securityInterceptor;
	}
}
