/* 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.security.access.AccessDeniedException;
import org.springframework.security.access.AuthorizationServiceException;
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;


/**
 * <p>
 * Given a <code>Collection</code> of domain object instances returned from a secure object invocation, remove
 * any <code>Collection</code> elements the principal does not have appropriate permission to access as defined by the
 * {@link AclService}.
 * <p>
 * The <code>AclService</code> is used to retrieve the access control list (ACL) permissions associated with
 * each <code>Collection</code> domain object instance element 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 <code>AclService</code> and ensure the
 * principal is {@link org.springframework.security.acls.model.Acl#isGranted(List, List, boolean) Acl.isGranted()}
 * when presenting the {@link #requirePermission} array to that method.
 * <p>
 * If the principal does not have permission, that element will not be included in the returned
 * <code>Collection</code>.
 * <p>
 * Often users will setup a <code>BasicAclEntryAfterInvocationProvider</code> with a {@link
 * #processConfigAttribute} of <code>AFTER_ACL_COLLECTION_READ</code> and a {@link #requirePermission} of
 * <code>BasePermission.READ</code>. These are also the defaults.
 * <p>
 * If the provided <code>returnObject</code> is <code>null</code>, a <code>null</code><code>Collection</code>
 * will be returned. If the provided <code>returnObject</code> is not a <code>Collection</code>, an {@link
 * AuthorizationServiceException} will be thrown.
 * <p>
 * All comparisons and prefixes are case sensitive.
 *
 * @author Ben Alex
 * @author Paulo Neves
 */
public class AclEntryAfterInvocationCollectionFilteringProvider extends AbstractAclProvider {
    //~ Static fields/initializers =====================================================================================

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

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

    public AclEntryAfterInvocationCollectionFilteringProvider(AclService aclService, List<Permission> requirePermission) {
        super(aclService, "AFTER_ACL_COLLECTION_READ", requirePermission);
    }

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

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

        if (returnedObject == null) {
            logger.debug("Return object is null, skipping");

            return null;
        }

        for (ConfigAttribute attr : config) {
            if (!this.supports(attr)) {
                continue;
            }

            // Need to process the Collection for this invocation
            Filterer filterer;

            if (returnedObject instanceof Collection) {
                filterer = new CollectionFilterer((Collection) returnedObject);
            } else if (returnedObject.getClass().isArray()) {
                filterer = new ArrayFilterer((Object[]) returnedObject);
            } else {
                throw new AuthorizationServiceException("A Collection or an array (or null) was required as the "
                        + "returnedObject, but the returnedObject was: " + returnedObject);
            }

            // Locate unauthorised Collection elements
            for (Object domainObject : filterer) {
                // Ignore nulls or entries which aren't instances of the configured domain object class
                if (domainObject == null || !getProcessDomainObjectClass().isAssignableFrom(domainObject.getClass())) {
                    continue;
                }

                if(!hasPermission(authentication, domainObject)) {
                    filterer.remove(domainObject);

                    if (logger.isDebugEnabled()) {
                        logger.debug("Principal is NOT authorised for element: " + domainObject);
                    }
                }
            }

            return filterer.getFilteredObject();
        }

        return returnedObject;
    }
}
