/*
 * Copyright 2005 the original author or authors.
 * 
 * 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.wamblee.security.authorization.hibernate;

import java.util.List;

import org.springframework.orm.hibernate3.HibernateTemplate;
import org.wamblee.persistence.AbstractPersistent;
import org.wamblee.persistence.hibernate.HibernateSupport;
import org.wamblee.security.authorization.AuthorizationRule;
import org.wamblee.security.authorization.AuthorizationService;
import org.wamblee.security.authorization.DefaultAuthorizationService;
import org.wamblee.security.authorization.Operation;
import org.wamblee.usermgt.UserAccessor;

/**
 * Authorization service with persistent storage.
 * This is a wrapper for {@link org.wamblee.security.authorization.DefaultAuthorizationService}
 * which refreshes the state of the service at certain time intervals. 
 *
 * @author Erik Brakkee
 */
public class PersistentAuthorizationService extends AbstractPersistent
        implements AuthorizationService {

    /**
     * Name of query to find the service by name.
     */
    private static final String FIND_QUERY = "findAuthorizationServiceByName";

    /**
     * Name of the query parameter for the service name.
     */
    private static final String NAME_PARAM = "name";

    /**
     * Authorization service to use.
     */
    private DefaultAuthorizationService service;

    /**
     * Hibernate template to use.
     */
    private HibernateTemplate template;

    /**
     * User accessor.
     */
    private UserAccessor userAccessor;
    
    /**
     * Name of the service. 
     */
    private String name; 

    /**
     * Refresh interval in milliseconds. 
     */
    private final long refreshInterval;
    
    /**
     * Last refresh time. 
     */
    private long lastRefreshTime; 

    /**
     * Constructs the persistent service.
     * 
     * @param aName
     *            Name of the service.
     * @param aTemplate
     *            Hibernate template for hibernate usage.
     * @param aAccessor
     *            User accessor.
     * @param aRefresh
     *            Whether or not to refresh the state of the service at the
     *            start of every operation.
     */
    public PersistentAuthorizationService(String aName,
            HibernateTemplate aTemplate, UserAccessor aAccessor,
            long aRefreshInterval) {
        template = aTemplate;
        refreshInterval = aRefreshInterval;
        lastRefreshTime = System.currentTimeMillis(); 
        userAccessor = aAccessor;
        name = aName; 
    }

    /**
     * Initialize service if needed. 
     */
    private void initialize() {
        if (service == null) {
            List<DefaultAuthorizationService> result = template
                    .findByNamedQueryAndNamedParam(FIND_QUERY, NAME_PARAM,
                            name);

            if (result.size() > 1) {
                throw new IllegalArgumentException(
                        "Returned more than one service for name '" + name
                                + "' (" + result.size() + ")");
            }

            if (result.size() == 0) {
                service = new DefaultAuthorizationService(userAccessor, name);
                template.persist(service);
            } else {
                service = result.get(0);
                service.setUserAccessor(userAccessor);
            }
        }
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.wamblee.security.authorization.AuthorizationService#isAllowed(java.lang.Object,
     *      org.wamblee.security.authorization.Operation)
     */
    public boolean isAllowed(Object aResource, Operation aOperation) {
        initialize();
        refresh();
        return service.isAllowed(aResource, aOperation);
    }
    
    /* (non-Javadoc)
     * @see org.wamblee.security.authorization.AuthorizationService#check(T, org.wamblee.security.authorization.Operation)
     */
    public <T> T check(T aResource, Operation aOperation) {
        initialize();
        refresh();
        return service.check(aResource, aOperation);
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.wamblee.security.authorization.AuthorizationService#getRules()
     */
    public AuthorizationRule[] getRules() {
        initialize();
        refresh();
        return service.getRules();
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.wamblee.security.authorization.AuthorizationService#appendRule(org.wamblee.security.authorization.AuthorizationRule)
     */
    public void appendRule(AuthorizationRule aRule) {
        initialize();
        refresh();
        service.appendRule(aRule);
        save();
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.wamblee.security.authorization.AuthorizationService#removeRule(int)
     */
    public void removeRule(int aIndex) {
        initialize();
        refresh();
        service.removeRule(aIndex);
        save();
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.wamblee.security.authorization.AuthorizationService#insertRuleAfter(int,
     *      org.wamblee.security.authorization.AuthorizationRule)
     */
    public void insertRuleAfter(int aIndex, AuthorizationRule aRule) {
        initialize();
        refresh();
        service.insertRuleAfter(aIndex, aRule);
        save();
    }

    /**
     * Refreshes the state of the service through hibernate.
     * 
     */
    private synchronized void refresh() {
        long time = System.currentTimeMillis(); 
        if ( time - lastRefreshTime > refreshInterval ) { 
            template.refresh(service);
            lastRefreshTime = time; 
        }
    }

    /**
     * Saves any changes to the service state if necessary.
     */
    private void save() {
        HibernateSupport.merge(template, service);
    }
}