/*
 * Copyright (C) 2006-2008 Alfresco Software Limited.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 * As a special exception to the terms and conditions of version 2.0 of 
 * the GPL, you may redistribute this Program in connection with Free/Libre 
 * and Open Source Software ("FLOSS") applications as described in Alfresco's 
 * FLOSS exception.  You should have recieved a copy of the text describing 
 * the FLOSS exception, and it is also available here: 
 * http://www.alfresco.com/legal/licensing"
 */

package org.alfresco.jlan.server.auth.acl;

import org.springframework.extensions.config.ConfigElement;

/**
 * Access Control Parser Class
 * 
 * <p>Creates an AccessControl instance by parsing a set of name/value parameters.
 *
 * @author gkspencer
 */
public abstract class AccessControlParser {

	//	Constants
	//
	//	Standard parameter names
	
	public final static String ParameterAccess	=	"access";
	
	//	Access control type names
	
	private final static String[] _accessTypes = { "None", "Read", "Write"};
	
	/**
	 * Return the access control type name that uniquely identifies this type of access control.
	 * 
	 * @return String
	 */
	public abstract String getType();
	
	/**
	 * Create an AccessControl instance by parsing the set of name/value parameters
	 *
	 * @param params ConfigElement
	 * @return AccessControl
	 * @exception ACLParseException
	 */
	public abstract AccessControl createAccessControl(ConfigElement params)
		throws ACLParseException;
		
	/**
	 * Find the access parameter and parse the value
	 * 
	 * @param params ConfigElement
	 * @return int
	 * @exception ACLParseException
	 */
	protected final int parseAccessType(ConfigElement params)
		throws ACLParseException {

		//	Check if the parameter list is valid
		
		if ( params == null)
			throw new ACLParseException("Empty parameter list");
			
		//	Find the access type parameter
		
		String accessParam = params.getAttribute(ParameterAccess);
		if ( accessParam == null || accessParam.length() == 0)
			throw new ACLParseException("Required parameter 'access' missing");
			
		//	Parse the access type value
		
		return parseAccessTypeString(accessParam);
	}
	
	/**
	 * Parse the access level type and validate
	 * 
	 * @param accessType String
	 * @return int
	 * @exception ACLParseException
	 */
	public static final int parseAccessTypeString(String accessType)
		throws ACLParseException {

		//	Check if the access type is valid
		
		if ( accessType == null || accessType.length() == 0)
			throw new ACLParseException("Empty access type string");
			
		//	Parse the access type value

		int access = -1;
		
		for ( int i = 0; i < _accessTypes.length; i++) {
			
			//	Check if the access type matches the current type
			
			if ( accessType.equalsIgnoreCase(_accessTypes[i]))
				access = i;
		}

		//	Check if we found a valid access type
		
		if ( access == -1)
			throw new ACLParseException("Invalid access type, " + accessType);
			
		//	Return the access type
		
		return access;		
	}
	
	/**
	 * Return the parser details as a string
	 * 
	 * @return String
	 */
	public String toString() {
		StringBuffer str = new StringBuffer();
		
		str.append("[");
		str.append(getType());
		str.append("]");
		
		return str.toString();
	}
}