/*
 * 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;

import org.wamblee.persistence.AbstractPersistent;

import org.wamblee.usermgt.User;
import org.wamblee.usermgt.UserAccessor;

import java.util.ArrayList;
import java.util.List;


/**
 * Default implementation of an authorization service.  To determine
 * whether access to a resource is allowed, the service consults a number of
 * authorization rules in a fixed order. The first rule that gives a result
 * GRANTED or  DENIED determines the result of the evaluation. Rules that
 * return any other result are  ignoed. If none of the rules match, than
 * access is denied.
 *
 * @author Erik Brakkee
 */
public class DefaultAuthorizationService extends AbstractPersistent
    implements AuthorizationService {
    /**
     * List of ordered authorization rules.
     */
    private List<AuthorizationRule> rules;

    /**
     * User accessor used to obtain the current user.
     */
    private UserAccessor userAccessor;

    /**
     * Name for this instance of the authorization service.
     */
    private String name;

/**
     * Constructs the service. 
     * @param aAccessor User accessor. 
     * @param aName Name of this instance of the service. 
     */
    public DefaultAuthorizationService(UserAccessor aAccessor, String aName) {
        rules            = new ArrayList<AuthorizationRule>();
        userAccessor     = aAccessor;
        name             = aName;
    }

/**
     * Constructs the authorization service.  
     */
    public DefaultAuthorizationService() {
        rules            = new ArrayList<AuthorizationRule>();
        userAccessor     = null;
        name             = null;
    }

    /**
     * Sets the user accessor.
     *
     * @param aUserAccessor User accessor.
     */
    public void setUserAccessor(UserAccessor aUserAccessor) {
        userAccessor = aUserAccessor;
    }

    /* (non-Javadoc)
     * @see org.wamblee.security.authorization.AuthorizationService#isAllowed(java.lang.Object, org.wamblee.security.authorization.Operation)
     */
    /**
     * DOCUMENT ME!
     *
     * @param aResource DOCUMENT ME!
     * @param aOperation DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     */
    public boolean isAllowed(Object aResource, Operation aOperation) {
        User user = userAccessor.getCurrentUser();

        for (AuthorizationRule rule : rules) {
            switch (rule.isAllowed(aResource, aOperation, user)) {
                case DENIED:
                    return false;

                case GRANTED:
                    return true;
            }
        }

        return false;
    }

    /* (non-Javadoc)
     * @see org.wamblee.security.authorization.AuthorizationService#check(T, org.wamblee.security.authorization.Operation)
     */
    /**
     * DOCUMENT ME!
     *
     * @param <T> DOCUMENT ME!
     * @param aResource DOCUMENT ME!
     * @param aOperation DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     *
     * @throws AuthorizationException DOCUMENT ME!
     */
    public <T> T check(T aResource, Operation aOperation) {
        if (!isAllowed(aResource, aOperation)) {
            throw new AuthorizationException(aResource, aOperation);
        }

        return aResource;
    }

    /**
     * DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     */
    protected String getName() {
        return name;
    }

    /**
     * DOCUMENT ME!
     *
     * @param aName DOCUMENT ME!
     */
    public void setName(String aName) {
        name = aName;
    }

    /* (non-Javadoc)
     * @see org.wamblee.security.authorization.AuthorizationService#getRules()
     */
    /**
     * DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     */
    public AuthorizationRule[] getRules() {
        return rules.toArray(new AuthorizationRule[0]);
    }

    /* (non-Javadoc)
     * @see org.wamblee.security.authorization.AuthorizationService#appendRule(org.wamblee.security.authorization.AuthorizationRule)
     */
    /**
     * DOCUMENT ME!
     *
     * @param aRule DOCUMENT ME!
     */
    public void appendRule(AuthorizationRule aRule) {
        rules.add(aRule);
    }

    /* (non-Javadoc)
     * @see org.wamblee.security.authorization.AuthorizationService#insertRuleAfter(int, org.wamblee.security.authorization.AuthorizationRule)
     */
    /**
     * DOCUMENT ME!
     *
     * @param aIndex DOCUMENT ME!
     * @param aRule DOCUMENT ME!
     */
    public void insertRuleAfter(int aIndex, AuthorizationRule aRule) {
        rules.add(aIndex, aRule);
    }

    /* (non-Javadoc)
     * @see org.wamblee.security.authorization.AuthorizationService#removeRule(int)
     */
    /**
     * DOCUMENT ME!
     *
     * @param aIndex DOCUMENT ME!
     */
    public void removeRule(int aIndex) {
        rules.remove(aIndex);
    }

    /**
     * For OR mapping.
     *
     * @return The rules.
     */
    protected List<AuthorizationRule> getMappedRules() {
        return rules;
    }

    /**
     * For OR mapping.
     *
     * @param aRules The rules.
     */
    protected void setMappedRules(List<AuthorizationRule> aRules) {
        rules = aRules;
    }
}