/* 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.providers.jaas;

import org.acegisecurity.Authentication;

import org.acegisecurity.context.SecurityContextHolder;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.Map;

import javax.security.auth.Subject;
import javax.security.auth.callback.CallbackHandler;
import javax.security.auth.login.LoginException;
import javax.security.auth.spi.LoginModule;


/**
 * An implementation of {@link LoginModule} that uses an Acegi Security {@link
 * org.acegisecurity.context.SecurityContext SecurityContext} to provide authentication.<p>This LoginModule
 * provides opposite functionality to the {@link JaasAuthenticationProvider} API, and should not really be used in
 * conjunction with it.</p>
 *  <p>The {@link JaasAuthenticationProvider} allows Acegi to authenticate against Jaas.</p>
 *  <p>The SecurityContextLoginModule allows a Jaas based application to authenticate against Acegi. If there is no
 * Authentication in the  {@link SecurityContextHolder} the login() method will throw a LoginException by default.
 * This functionality can be changed with the <tt>ignoreMissingAuthentication</tt> option by setting it to "true".
 * Setting ignoreMissingAuthentication=true will tell the SecurityContextLoginModule to simply return false and be
 * ignored if the authentication is null.</p>
 *
 * @author Brian Moseley
 * @author Ray Krueger
 */
public class SecurityContextLoginModule implements LoginModule {
    //~ Static fields/initializers =====================================================================================

    private static final Log log = LogFactory.getLog(SecurityContextLoginModule.class);

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

    private Authentication authen;
    private Subject subject;
    private boolean ignoreMissingAuthentication = false;

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

    /**
     * Abort the authentication process by forgetting the Acegi Security <code>Authentication</code>.
     *
     * @return true if this method succeeded, or false if this <code>LoginModule</code> should be ignored.
     *
     * @exception LoginException if the abort fails
     */
    public boolean abort() throws LoginException {
        if (authen == null) {
            return false;
        }

        authen = null;

        return true;
    }

    /**
     * Authenticate the <code>Subject</code> (phase two) by adding the Acegi Security
     * <code>Authentication</code> to the <code>Subject</code>'s principals.
     *
     * @return true if this method succeeded, or false if this <code>LoginModule</code> should be ignored.
     *
     * @exception LoginException if the commit fails
     */
    public boolean commit() throws LoginException {
        if (authen == null) {
            return false;
        }

        subject.getPrincipals().add(authen);

        return true;
    }

    Authentication getAuthentication() {
        return authen;
    }

    Subject getSubject() {
        return subject;
    }

    /**
     * Initialize this <code>LoginModule</code>. Ignores the callback handler, since the code establishing the
     * <code>LoginContext</code> likely won't provide one that understands Acegi Security. Also ignores the
     * <code>sharedState</code> and <code>options</code> parameters, since none are recognized.
     *
     * @param subject the <code>Subject</code> to be authenticated. <p>
     * @param callbackHandler is ignored
     * @param sharedState is ignored
     * @param options are ignored
     */
    public void initialize(Subject subject, CallbackHandler callbackHandler, Map sharedState, Map options) {
        this.subject = subject;

        if (options != null) {
            ignoreMissingAuthentication = "true".equals(options.get("ignoreMissingAuthentication"));
        }
    }

    /**
     * Authenticate the <code>Subject</code> (phase one) by extracting the Acegi Security
     * <code>Authentication</code> from the current <code>SecurityContext</code>.
     *
     * @return true if the authentication succeeded, or false if this <code>LoginModule</code> should be ignored.
     *
     * @throws LoginException if the authentication fails
     */
    public boolean login() throws LoginException {
        authen = SecurityContextHolder.getContext().getAuthentication();

        if (authen == null) {
            String msg = "Login cannot complete, authentication not found in security context";

            if (ignoreMissingAuthentication) {
                log.warn(msg);

                return false;
            } else {
                throw new LoginException(msg);
            }
        }

        return true;
    }

    /**
     * Log out the <code>Subject</code>.
     *
     * @return true if this method succeeded, or false if this <code>LoginModule</code> should be ignored.
     *
     * @exception LoginException if the logout fails
     */
    public boolean logout() throws LoginException {
        if (authen == null) {
            return false;
        }

        subject.getPrincipals().remove(authen);
        authen = null;

        return true;
    }
}
