/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.
 */
/*
 * $Id$
 */

package org.apache.xalan.xsltc.compiler;

import java.util.Iterator;
import java.util.Vector;

import org.apache.bcel.generic.BranchHandle;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.InstructionList;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 */
public final class FlowList {
    private Vector _elements;

    public FlowList() {
	_elements = null;
    }

    public FlowList(InstructionHandle bh) {
	_elements = new Vector();
	_elements.addElement(bh);
    }

    public FlowList(FlowList list) {
	_elements = list._elements;
    }

    public FlowList add(InstructionHandle bh) {
	if (_elements == null) {
	    _elements = new Vector();
	}
	_elements.addElement(bh);
	return this;
    }

    public FlowList append(FlowList right) {
	if (_elements == null) {
	    _elements = right._elements;
	}
	else {
	    final Vector temp = right._elements;
	    if (temp != null) {
		final int n = temp.size();
		for (int i = 0; i < n; i++) {
		    _elements.addElement(temp.elementAt(i));
		}
	    }
	}
	return this;
    }

    /**
     * Back patch a flow list. All instruction handles must be branch handles.
     */
    public void backPatch(InstructionHandle target) {
	if (_elements != null) {
	    final int n = _elements.size();
	    for (int i = 0; i < n; i++) {
		BranchHandle bh = (BranchHandle)_elements.elementAt(i);
		bh.setTarget(target);
	    }
	    _elements.clear();		// avoid backpatching more than once
	}
    }

    /**
     * Redirect the handles from oldList to newList. "This" flow list
     * is assumed to be relative to oldList.
     */
    public FlowList copyAndRedirect(InstructionList oldList, 
	InstructionList newList) 
    {
	final FlowList result = new FlowList();
	if (_elements == null) {
	    return result;
	}

	final int n = _elements.size();
	final Iterator oldIter = oldList.iterator();
	final Iterator newIter = newList.iterator();
	
	while (oldIter.hasNext()) {
	    final InstructionHandle oldIh = (InstructionHandle) oldIter.next();
	    final InstructionHandle newIh = (InstructionHandle) newIter.next();

	    for (int i = 0; i < n; i++) {
		if (_elements.elementAt(i) == oldIh) {
		    result.add(newIh);
		}
	    }
	}
	return result;
    }
}