/*
 * Copyright 2005-2008 Tim Veil, Jeremy Haile
 *
 * 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.jsecurity.realm.activedirectory;

import org.jsecurity.authc.Account;
import org.jsecurity.authc.AuthenticationToken;
import org.jsecurity.authc.UsernamePasswordToken;
import org.jsecurity.authz.AuthorizingAccount;
import org.jsecurity.authz.SimpleAuthorizingAccount;
import org.jsecurity.realm.Realm;
import org.jsecurity.realm.ldap.AbstractLdapRealm;
import org.jsecurity.realm.ldap.LdapContextFactory;
import org.jsecurity.realm.ldap.LdapUtils;
import org.jsecurity.subject.PrincipalCollection;

import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.SearchControls;
import javax.naming.directory.SearchResult;
import javax.naming.ldap.LdapContext;
import java.util.*;

/**
 * <p>An {@link Realm} that authenticates with an active directory LDAP
 * server to determine the roles for a particular user.  This implementation
 * queries for the user's groups and then maps the group names to roles using the
 * {@link #groupRolesMap}.</p>
 *
 *
 * @since 0.1
 * @author Tim Veil
 * @author Jeremy Haile
 */
public class ActiveDirectoryRealm extends AbstractLdapRealm {

    /*--------------------------------------------
    |             C O N S T A N T S             |
    ============================================*/
    
    private static final String ROLE_NAMES_DELIMETER = ",";

    /*--------------------------------------------
    |    I N S T A N C E   V A R I A B L E S    |
    ============================================*/

    /**
     * Mapping from fully qualified active directory
     * group names (e.g. CN=Group,OU=Company,DC=MyDomain,DC=local)
     * as returned by the active directory LDAP server to role names.
     */
    private Map<String, String> groupRolesMap;

    /*--------------------------------------------
    |         C O N S T R U C T O R S           |
    ============================================*/

    public void setGroupRolesMap(Map<String, String> groupRolesMap) {
        this.groupRolesMap = groupRolesMap;
    }

    /*--------------------------------------------
    |               M E T H O D S               |
    ============================================*/


    /**
     * <p>Builds an {@link org.jsecurity.authc.Account} object by querying the active directory LDAP context for the
     * specified username.  This method binds to the LDAP server using the provided username and password -
     * which if successful, indicates that the password is correct.</p>
     *
     * <p>This method can be overridden by subclasses to query the LDAP server in a more complex way.</p>
     *
     * @param token the authentication token provided by the user.
     * @param ldapContextFactory the factory used to build connections to the LDAP server.
     * @return an {@link org.jsecurity.authc.Account} instance containing information retrieved from LDAP
     * that can be used to build an {@link org.jsecurity.authc.Account} instance to return.
     *
     * @throws NamingException if any LDAP errors occur during the search.
     */
    protected Account queryForLdapAccount(AuthenticationToken token, LdapContextFactory ldapContextFactory) throws NamingException {

        UsernamePasswordToken upToken = (UsernamePasswordToken) token;

        // Binds using the username and password provided by the user.
        LdapContext ctx = null;
        try {
            ctx = ldapContextFactory.getLdapContext( upToken.getUsername(), String.valueOf( upToken.getPassword() ) );
        } finally {
            LdapUtils.closeContext( ctx );
        }

        return createAccount( upToken.getUsername(), upToken.getPassword() );
    }

    protected Account createAccount( String username, char[] password ) {
        return new SimpleAuthorizingAccount( username, password, getName() );
    }


    /**
     * <p>Builds an {@link org.jsecurity.authz.AuthorizingAccount} object by querying the active directory LDAP context for the
     * groups that a user is a member of.  The groups are then translated to role names by using the
     * configured {@link #groupRolesMap}.</p>
     *
     * <p>This implementation expects the <tt>principal</tt> argument to be a String username.
     *
     * <p>Subclasses can override this method to determine authorization data (roles, permissions, etc) in a more
     * complex way.  Note that this default implementation does not support permissions, only roles.</p>
     *
     * @param principals the principal of the Subject whose Account is being retrieved.
     * @param ldapContextFactory the factory used to create LDAP connections.
     * @return the Account for the given Subject principal.
     * @throws NamingException if an error occurs when searching the LDAP server.
     */
    protected AuthorizingAccount queryForLdapAccount( PrincipalCollection principals, LdapContextFactory ldapContextFactory) throws NamingException {

        String username;


        username = (String)principals.fromRealm( getName() ).iterator().next();

        // Perform context search
        LdapContext ldapContext = ldapContextFactory.getSystemLdapContext();

        Set<String> roleNames;

        try {
            roleNames = getRoleNamesForUser(username, ldapContext);
        } finally {
            LdapUtils.closeContext( ldapContext );
        }

        return new SimpleAuthorizingAccount(username, null, getName(), roleNames, null);
    }

    private Set<String> getRoleNamesForUser( String username, LdapContext ldapContext) throws NamingException {
        Set<String> roleNames;
        roleNames = new LinkedHashSet<String>();

        SearchControls searchCtls = new SearchControls();
        searchCtls.setSearchScope(SearchControls.SUBTREE_SCOPE);

        String searchFilter = "(&(objectClass=*)(userPrincipalName=" + username + "))";

        NamingEnumeration answer = ldapContext.search(searchBase, searchFilter, searchCtls);

        while (answer.hasMoreElements()) {
            SearchResult sr = (SearchResult) answer.next();

            if( log.isDebugEnabled() ) {
                log.debug("Retrieving group names for user [" + sr.getName() + "]");
            }

            Attributes attrs = sr.getAttributes();

            if (attrs != null) {
                NamingEnumeration ae = attrs.getAll();
                while( ae.hasMore() ) {
                    Attribute attr = (Attribute) ae.next();

                    if( attr.getID().equals( "memberOf" ) ) {

                        Collection<String> groupNames = LdapUtils.getAllAttributeValues( attr );

                        if (log.isDebugEnabled()) {
                            log.debug("Groups found for user [" + username + "]: " + groupNames );
                        }

                        Collection<String> rolesForGroups = getRoleNamesForGroups(groupNames);
                        roleNames.addAll(rolesForGroups);
                    }
                }
            }
        }
        return roleNames;
    }

    /**
     * This method is called by the default implementation to translate Active Directory group names
     * to role names.  This implementation uses the {@link #groupRolesMap} to map group names to role names.
     * @param groupNames the group names that apply to the current user.
     * @return a collection of roles that are implied by the given role names.
     */
    protected Collection<String> getRoleNamesForGroups(Collection<String> groupNames) {
        Set<String> roleNames = new HashSet<String>( groupNames.size() );

        if( groupRolesMap != null ) {
            for( String groupName : groupNames ) {
                String strRoleNames = groupRolesMap.get( groupName );
                if( strRoleNames != null ) {
                    for( String roleName : strRoleNames.split( ROLE_NAMES_DELIMETER ) ) {

                        if( log.isDebugEnabled() ) {
                            log.debug( "User is member of group [" + groupName + "] so adding role [" + roleName + "]" );
                        }

                        roleNames.add( roleName );

                    }
                }
            }
        }
        return roleNames;
    }


}