/* 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.acegisecurity.vote;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Iterator;

import org.acegisecurity.Authentication;
import org.acegisecurity.AuthorizationServiceException;
import org.acegisecurity.ConfigAttribute;
import org.acegisecurity.ConfigAttributeDefinition;
import org.acegisecurity.acls.Acl;
import org.acegisecurity.acls.AclService;
import org.acegisecurity.acls.NotFoundException;
import org.acegisecurity.acls.Permission;
import org.acegisecurity.acls.objectidentity.ObjectIdentity;
import org.acegisecurity.acls.objectidentity.ObjectIdentityRetrievalStrategy;
import org.acegisecurity.acls.objectidentity.ObjectIdentityRetrievalStrategyImpl;
import org.acegisecurity.acls.sid.Sid;
import org.acegisecurity.acls.sid.SidRetrievalStrategy;
import org.acegisecurity.acls.sid.SidRetrievalStrategyImpl;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.Assert;


/**
 * <p>Given a domain object instance passed as a method argument, ensures the principal has appropriate permission
 * as indicated by the {@link AclService}.</p>
 *  <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>
 *  <p>The voter will vote if any  {@link ConfigAttribute#getAttribute()} matches the {@link
 * #processConfigAttribute}. The provider will then locate the first method argument of type {@link
 * #processDomainObjectClass}. Assuming that method argument is non-null, the provider will then lookup the ACLs from
 * the <code>AclManager</code> and ensure the principal is  {@link Acl#isGranted(org.acegisecurity.acls.Permission[],
 * org.acegisecurity.acls.sid.Sid[], boolean)}  when presenting the {@link #requirePermission} array to that method.</p>
 *  <p>If the method argument is <code>null</code>, the voter will abstain from voting. If the method argument
 * could not be found, an {@link org.acegisecurity.AuthorizationServiceException} will be thrown.</p>
 *  <p>In practical terms users will typically setup a number of <code>AclEntryVoter</code>s. Each will have a
 * different {@link #processDomainObjectClass}, {@link #processConfigAttribute} and {@link #requirePermission}
 * combination. For example, a small application might employ the following instances of <code>AclEntryVoter</code>:
 *  <ul>
 *      <li>Process domain object class <code>BankAccount</code>, configuration attribute
 *      <code>VOTE_ACL_BANK_ACCONT_READ</code>, require permission <code>BasePermission.READ</code></li>
 *      <li>Process domain object class <code>BankAccount</code>, configuration attribute
 *      <code>VOTE_ACL_BANK_ACCOUNT_WRITE</code>, require permission list <code>BasePermission.WRITE</code> and
 *      <code>BasePermission.CREATE</code> (allowing the principal to have <b>either</b> of these two permissions</li>
 *      <li>Process domain object class <code>Customer</code>, configuration attribute
 *      <code>VOTE_ACL_CUSTOMER_READ</code>, require permission <code>BasePermission.READ</code></li>
 *      <li>Process domain object class <code>Customer</code>, configuration attribute
 *      <code>VOTE_ACL_CUSTOMER_WRITE</code>, require permission list <code>BasePermission.WRITE</code> and
 *      <code>BasePermission.CREATE</code></li>
 *  </ul>
 *  Alternatively, you could have used a common superclass or interface for the {@link #processDomainObjectClass}
 * if both <code>BankAccount</code> and <code>Customer</code> had common parents.</p>
 *  <p>If the principal does not have sufficient permissions, the voter will vote to deny access.</p>
 *  <p>All comparisons and prefixes are case sensitive.</p>
 *
 * @author Ben Alex
 * @version $Id: AclEntryVoter.java 1784 2007-02-24 21:00:24Z luke_t $
 */
public class AclEntryVoter extends AbstractAclVoter {
    //~ Static fields/initializers =====================================================================================

    private static final Log logger = LogFactory.getLog(AclEntryVoter.class);

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

    private AclService aclService;
    private ObjectIdentityRetrievalStrategy objectIdentityRetrievalStrategy = new ObjectIdentityRetrievalStrategyImpl();
    private SidRetrievalStrategy sidRetrievalStrategy = new SidRetrievalStrategyImpl();
    private String internalMethod;
    private String processConfigAttribute;
    private Permission[] requirePermission;

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

    public AclEntryVoter(AclService aclService, String processConfigAttribute, Permission[] requirePermission) {
        Assert.notNull(processConfigAttribute, "A processConfigAttribute is mandatory");
        Assert.notNull(aclService, "An AclService is mandatory");

        if ((requirePermission == null) || (requirePermission.length == 0)) {
            throw new IllegalArgumentException("One or more requirePermission entries is mandatory");
        }

        this.aclService = aclService;
        this.processConfigAttribute = processConfigAttribute;
        this.requirePermission = requirePermission;
    }

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

    /**
     * Optionally specifies a method of the domain object that will be used to obtain a contained domain
     * object. That contained domain object will be used for the ACL evaluation. This is useful if a domain object
     * contains a parent that an ACL evaluation should be targeted for, instead of the child domain object (which
     * perhaps is being created and as such does not yet have any ACL permissions)
     *
     * @return <code>null</code> to use the domain object, or the name of a method (that requires no arguments) that
     *         should be invoked to obtain an <code>Object</code> which will be the domain object used for ACL
     *         evaluation
     */
    public String getInternalMethod() {
        return internalMethod;
    }

    public String getProcessConfigAttribute() {
        return processConfigAttribute;
    }

    public void setInternalMethod(String internalMethod) {
        this.internalMethod = internalMethod;
    }

    public void setObjectIdentityRetrievalStrategy(ObjectIdentityRetrievalStrategy objectIdentityRetrievalStrategy) {
        Assert.notNull(objectIdentityRetrievalStrategy, "ObjectIdentityRetrievalStrategy required");
        this.objectIdentityRetrievalStrategy = objectIdentityRetrievalStrategy;
    }

    public void setSidRetrievalStrategy(SidRetrievalStrategy sidRetrievalStrategy) {
        Assert.notNull(sidRetrievalStrategy, "SidRetrievalStrategy required");
        this.sidRetrievalStrategy = sidRetrievalStrategy;
    }

    public boolean supports(ConfigAttribute attribute) {
        if ((attribute.getAttribute() != null) && attribute.getAttribute().equals(getProcessConfigAttribute())) {
            return true;
        } else {
            return false;
        }
    }

    public int vote(Authentication authentication, Object object, ConfigAttributeDefinition config) {
        Iterator iter = config.getConfigAttributes();

        while (iter.hasNext()) {
            ConfigAttribute attr = (ConfigAttribute) iter.next();

            if (this.supports(attr)) {
                // Need to make an access decision on this invocation
                // Attempt to locate the domain object instance to process
                Object domainObject = getDomainObjectInstance(object);

                // Evaluate if we are required to use an inner domain object
                if (domainObject != null && internalMethod != null && (!"".equals(internalMethod))) {
                    try {
                        Class clazz = domainObject.getClass();
                        Method method = clazz.getMethod(internalMethod, new Class[] {});
                        domainObject = method.invoke(domainObject, new Object[] {});
                    } catch (NoSuchMethodException nsme) {
                        throw new AuthorizationServiceException("Object of class '" + domainObject.getClass()
                            + "' does not provide the requested internalMethod: " + internalMethod);
                    } catch (IllegalAccessException iae) {
                        if (logger.isDebugEnabled()) {
                            logger.debug("IllegalAccessException", iae);

                            if (iae.getCause() != null) {
                                logger.debug("Cause: " + iae.getCause().getMessage(), iae.getCause());
                            }
                        }

                        throw new AuthorizationServiceException("Problem invoking internalMethod: " + internalMethod
                            + " for object: " + domainObject);
                    } catch (InvocationTargetException ite) {
                        if (logger.isDebugEnabled()) {
                            logger.debug("InvocationTargetException", ite);

                            if (ite.getCause() != null) {
                                logger.debug("Cause: " + ite.getCause().getMessage(), ite.getCause());
                            }
                        }

                        throw new AuthorizationServiceException("Problem invoking internalMethod: " + internalMethod
                            + " for object: " + domainObject);
                    }
                }

                // If domain object is null, vote to abstain
                if (domainObject == null) {
                    if (logger.isDebugEnabled()) {
                        logger.debug("Voting to abstain - domainObject is null");
                    }

                    return AccessDecisionVoter.ACCESS_ABSTAIN;
                }

                // Obtain the OID applicable to the domain object
                ObjectIdentity objectIdentity = objectIdentityRetrievalStrategy.getObjectIdentity(domainObject);

                // Obtain the SIDs applicable to the principal
                Sid[] sids = sidRetrievalStrategy.getSids(authentication);

                Acl acl;

                try {
                    // Lookup only ACLs for SIDs we're interested in
                    acl = aclService.readAclById(objectIdentity, sids);
                } catch (NotFoundException nfe) {
                    if (logger.isDebugEnabled()) {
                        logger.debug("Voting to deny access - no ACLs apply for this principal");
                    }

                    return AccessDecisionVoter.ACCESS_DENIED;
                }

                try {
                    if (acl.isGranted(requirePermission, sids, false)) {
                        if (logger.isDebugEnabled()) {
                            logger.debug("Voting to grant access");
                        }

                        return AccessDecisionVoter.ACCESS_GRANTED;
                    } else {
                        if (logger.isDebugEnabled()) {
                            logger.debug(
                                "Voting to deny access - ACLs returned, but insufficient permissions for this principal");
                        }

                        return AccessDecisionVoter.ACCESS_DENIED;
                    }
                } catch (NotFoundException nfe) {
                    if (logger.isDebugEnabled()) {
                        logger.debug("Voting to deny access - no ACLs apply for this principal");
                    }

                    return AccessDecisionVoter.ACCESS_DENIED;
                }
            }
        }

        // No configuration attribute matched, so abstain
        return AccessDecisionVoter.ACCESS_ABSTAIN;
    }
}
