/* 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.acls.afterinvocation;

import java.util.Collection;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.context.MessageSource;
import org.springframework.context.MessageSourceAware;
import org.springframework.context.support.MessageSourceAccessor;
import org.springframework.security.access.AccessDeniedException;
import org.springframework.security.access.ConfigAttribute;
import org.springframework.security.acls.model.AclService;
import org.springframework.security.acls.model.Permission;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.SpringSecurityMessageSource;


/**
 * Given a domain object instance returned from a secure object invocation, ensures the principal has
 * appropriate permission as defined by the {@link AclService}.
 * <p>
 * The <code>AclService</code> is used to retrieve the access control list (ACL) permissions associated with a
 * domain object instance for the current <code>Authentication</code> object.
 * <p>
 * This after invocation provider will fire if any  {@link ConfigAttribute#getAttribute()} matches the {@link
 * #processConfigAttribute}. The provider will then lookup the ACLs from the <tt>AclService</tt> and ensure the
 * principal is {@link org.springframework.security.acls.model.Acl#isGranted(List, List, boolean)
 * Acl.isGranted(List, List, boolean)} when presenting the {@link #requirePermission} array to that method.
 * <p>
 * Often users will set up an <code>AclEntryAfterInvocationProvider</code> with a {@link
 * #processConfigAttribute} of <code>AFTER_ACL_READ</code> and a {@link #requirePermission} of
 * <code>BasePermission.READ</code>. These are also the defaults.
 * <p>
 * If the principal does not have sufficient permissions, an <code>AccessDeniedException</code> will be thrown.
 * <p>
 * If the provided <tt>returnedObject</tt> is <code>null</code>, permission will always be granted and
 * <code>null</code> will be returned.
 * <p>
 * All comparisons and prefixes are case sensitive.
 */
public class AclEntryAfterInvocationProvider extends AbstractAclProvider implements MessageSourceAware {
    //~ Static fields/initializers =====================================================================================

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

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

    protected MessageSourceAccessor messages = SpringSecurityMessageSource.getAccessor();

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

    public AclEntryAfterInvocationProvider(AclService aclService, List<Permission> requirePermission) {
        this(aclService, "AFTER_ACL_READ", requirePermission);
    }

    public AclEntryAfterInvocationProvider(AclService aclService, String processConfigAttribute,
            List<Permission> requirePermission) {
        super(aclService, processConfigAttribute, requirePermission);
    }

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

    public Object decide(Authentication authentication, Object object, Collection<ConfigAttribute> config,
            Object returnedObject) throws AccessDeniedException {

        if (returnedObject == null) {
            // AclManager interface contract prohibits nulls
            // As they have permission to null/nothing, grant access
            logger.debug("Return object is null, skipping");

            return null;
        }

        if (!getProcessDomainObjectClass().isAssignableFrom(returnedObject.getClass())) {
            logger.debug("Return object is not applicable for this provider, skipping");

            return returnedObject;
        }

        for (ConfigAttribute attr : config) {
            if (!this.supports(attr)) {
                continue;
            }
            // Need to make an access decision on this invocation

            if (hasPermission(authentication, returnedObject)) {
                return returnedObject;
            }

            logger.debug("Denying access");

            throw new AccessDeniedException(messages.getMessage("AclEntryAfterInvocationProvider.noPermission",
                    new Object[] {authentication.getName(), returnedObject},
                    "Authentication {0} has NO permissions to the domain object {1}"));
        }

        return returnedObject;
    }

    public void setMessageSource(MessageSource messageSource) {
        this.messages = new MessageSourceAccessor(messageSource);
    }
}
