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/*
 ***** BEGIN LICENSE BLOCK *****
 * Version: EPL 1.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Eclipse Public
 * License Version 1.0 (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.eclipse.org/legal/epl-v10.html
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * Copyright (C) 2001-2002 Jan Arne Petersen 
 * Copyright (C) 2001-2002 Benoit Cerrina 
 * Copyright (C) 2002 Anders Bengtsson 
 * Copyright (C) 2004 Thomas E Enebo 
 * 
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the EPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the EPL, the GPL or the LGPL.
 ***** END LICENSE BLOCK *****/
package org.jruby.ast;

import java.util.List;

import org.jruby.Ruby;
import org.jruby.RubyMatchData;
import org.jruby.RubyRegexp;
import org.jruby.RubyString;
import org.jruby.ast.visitor.NodeVisitor;
import org.jruby.lexer.yacc.ISourcePosition;
import org.jruby.runtime.Block;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;
import org.jruby.util.ByteList;
import org.jruby.util.DefinedMessage;

/**
 *	Regexp back reference:
 *    - $& last successful match
 *    - $+ highest numbered group matched in last successful match.
 *    - $` what precedes the last successful match
 *    - $' what follows the last successful match
 */
public class BackRefNode extends Node {
    /**
     * the character which generated the back reference
     **/
    private final char type;
    
    /** ByteList for the name of this backref global */
    private final DefinedMessage definedMessage;

    public BackRefNode(ISourcePosition position, int type) {
        super(position);
        this.type = (char) type;
        this.definedMessage = DefinedMessage.byText("$" + (char)type);
    }

    public NodeType getNodeType() {
        return NodeType.BACKREFNODE;
    }

    /**
     * Accept for the visitor pattern.
     * @param iVisitor the visitor
     **/
    public Object accept(NodeVisitor iVisitor) {
        return iVisitor.visitBackRefNode(this);
    }

    /**
     * Gets the type 
     * 
     * @return the character which generates the back reference
     */
    public char getType() {
        return type;
    }
    
    public List childNodes() {
        return EMPTY_LIST;
    }
    
    @Override
    public IRubyObject interpret(Ruby runtime, ThreadContext context, IRubyObject self, Block aBlock) {
        IRubyObject backref = context.getBackRef();
        
        switch (type) {
        case '&':
            return RubyRegexp.last_match(backref);
        case '`':
            return RubyRegexp.match_pre(backref);
        case '\'':
            return RubyRegexp.match_post(backref);
        case '+':
            return RubyRegexp.match_last(backref);
        default:
            assert false: "backref with invalid type";
            return null;
        }        
    }
    
    @Override
    public RubyString definition(Ruby runtime, ThreadContext context, IRubyObject self, Block aBlock) {
        IRubyObject backref = context.getBackRef();

        if (backref instanceof RubyMatchData) {
            return runtime.getDefinedMessage(runtime.is1_9() ? DefinedMessage.GLOBAL_VARIABLE : definedMessage);
        }
        return null;
    }
}