/* 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.access.intercept;

import java.util.Collection;

import org.aopalliance.intercept.MethodInvocation;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.security.access.AccessDeniedException;
import org.springframework.security.access.ConfigAttribute;
import org.springframework.security.core.Authentication;
import org.springframework.util.Assert;


/**
 * Allows users to determine whether they have "before invocation" privileges for a given method invocation.
 * <p>
 * Of course, if an {@link org.springframework.security.access.intercept.AfterInvocationManager} is used to authorize the
 * <em>result</em> of a method invocation, this class cannot assist determine whether or not the
 * <code>AfterInvocationManager</code> will enable
 * access. Instead this class aims to allow applications to determine whether or not the current principal would be
 * allowed to at least attempt to invoke the method, irrespective of the "after" invocation handling.</p>
 *
 * @author Ben Alex
 */
public class MethodInvocationPrivilegeEvaluator implements InitializingBean {
    //~ Static fields/initializers =====================================================================================

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

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

    private AbstractSecurityInterceptor securityInterceptor;

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

    public void afterPropertiesSet() throws Exception {
        Assert.notNull(securityInterceptor, "SecurityInterceptor required");
    }

    public boolean isAllowed(MethodInvocation mi, Authentication authentication) {
        Assert.notNull(mi, "MethodInvocation required");
        Assert.notNull(mi.getMethod(), "MethodInvocation must provide a non-null getMethod()");

        Collection<ConfigAttribute> attrs = securityInterceptor.obtainSecurityMetadataSource().getAttributes(mi);

        if (attrs == null) {
            if (securityInterceptor.isRejectPublicInvocations()) {
                return false;
            }

            return true;
        }

        if (authentication == null || authentication.getAuthorities().isEmpty()) {
            return false;
        }

        try {
            securityInterceptor.getAccessDecisionManager().decide(authentication, mi, attrs);
        } catch (AccessDeniedException unauthorized) {
            if (logger.isDebugEnabled()) {
                logger.debug(mi.toString() + " denied for " + authentication.toString(), unauthorized);
            }

            return false;
        }

        return true;
    }

    public void setSecurityInterceptor(AbstractSecurityInterceptor securityInterceptor) {
        Assert.notNull(securityInterceptor, "AbstractSecurityInterceptor cannot be null");
        Assert.isTrue(MethodInvocation.class.equals(securityInterceptor.getSecureObjectClass()),
            "AbstractSecurityInterceptor does not support MethodInvocations");
        Assert.notNull(securityInterceptor.getAccessDecisionManager(),
            "AbstractSecurityInterceptor must provide a non-null AccessDecisionManager");
        this.securityInterceptor = securityInterceptor;
    }
}
