/*
 * 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.web.access;

import java.util.Collection;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.security.access.AccessDeniedException;
import org.springframework.security.access.ConfigAttribute;
import org.springframework.security.access.intercept.AbstractSecurityInterceptor;
import org.springframework.security.core.Authentication;
import org.springframework.security.web.FilterInvocation;
import org.springframework.util.Assert;

/**
 * Allows users to determine whether they have privileges for a given web URI.
 *
 * @author Ben Alex
 * @author Luke Taylor
 * @since 3.0
 */
public class DefaultWebInvocationPrivilegeEvaluator implements
		WebInvocationPrivilegeEvaluator {
	// ~ Static fields/initializers
	// =====================================================================================

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

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

	private final AbstractSecurityInterceptor securityInterceptor;

	// ~ Constructors
	// ===================================================================================================

	public DefaultWebInvocationPrivilegeEvaluator(
			AbstractSecurityInterceptor securityInterceptor) {
		Assert.notNull(securityInterceptor, "SecurityInterceptor cannot be null");
		Assert.isTrue(
				FilterInvocation.class.equals(securityInterceptor.getSecureObjectClass()),
				"AbstractSecurityInterceptor does not support FilterInvocations");
		Assert.notNull(securityInterceptor.getAccessDecisionManager(),
				"AbstractSecurityInterceptor must provide a non-null AccessDecisionManager");

		this.securityInterceptor = securityInterceptor;
	}

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

	/**
	 * Determines whether the user represented by the supplied <tt>Authentication</tt>
	 * object is allowed to invoke the supplied URI.
	 *
	 * @param uri the URI excluding the context path (a default context path setting will
	 * be used)
	 */
	public boolean isAllowed(String uri, Authentication authentication) {
		return isAllowed(null, uri, null, authentication);
	}

	/**
	 * Determines whether the user represented by the supplied <tt>Authentication</tt>
	 * object is allowed to invoke the supplied URI, with the given .
	 * <p>
	 * Note the default implementation of <tt>FilterInvocationSecurityMetadataSource</tt>
	 * disregards the <code>contextPath</code> when evaluating which secure object
	 * metadata applies to a given request URI, so generally the <code>contextPath</code>
	 * is unimportant unless you are using a custom
	 * <code>FilterInvocationSecurityMetadataSource</code>.
	 *
	 * @param uri the URI excluding the context path
	 * @param contextPath the context path (may be null, in which case a default value
	 * will be used).
	 * @param method the HTTP method (or null, for any method)
	 * @param authentication the <tt>Authentication</tt> instance whose authorities should
	 * be used in evaluation whether access should be granted.
	 * @return true if access is allowed, false if denied
	 */
	public boolean isAllowed(String contextPath, String uri, String method,
			Authentication authentication) {
		Assert.notNull(uri, "uri parameter is required");

		FilterInvocation fi = new FilterInvocation(contextPath, uri, method);
		Collection<ConfigAttribute> attrs = securityInterceptor
				.obtainSecurityMetadataSource().getAttributes(fi);

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

			return true;
		}

		if (authentication == null) {
			return false;
		}

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

			return false;
		}

		return true;
	}
}
