/**

  * Back 2 Browser Bytecode Translator

  * Copyright (C) 2012 Jaroslav Tulach <jaroslav.tulach@apidesign.org>

  *

  * 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, version 2 of the License.

  *

  * 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. Look for COPYING file in the top folder.

  * If not, see http://opensource.org/licenses/GPL-2.0.

  */

 package org.apidesign.vm4brwsr;

 public final class StackToVariableMapper {

     private static final String VAR_NAME_PREFIX = "stack";

     private int stackSize;

     private StringBuilder varNameBuilder;

     private int maxStackSize;

     public StackToVariableMapper() {

         varNameBuilder = new StringBuilder(VAR_NAME_PREFIX);

     }

     public void reset(final int newStackSize) {

         stackSize = newStackSize;

         if (maxStackSize < stackSize) {

             maxStackSize = stackSize;

         }

     }

     public void push(final int numOfElements) {

         stackSize += numOfElements;

         if (maxStackSize < stackSize) {

             maxStackSize = stackSize;

         }

     }

     public String push() {

         push(1);

         return get(0);

     }

     public void pop(final int numOfElements) {

         if (numOfElements > stackSize) {

             throw new IllegalStateException("Stack underflow");

         }

         stackSize -= numOfElements;

     }

     public String pop() {

         final String variableName = get(0);

         pop(1);

         return variableName;

     }

     public String get(final int indexFromTop) {

         if (indexFromTop >= stackSize) {

             throw new IllegalStateException("Stack underflow");

         }

         return constructVariableName(stackSize - indexFromTop - 1);

     }

     public String top() {

         return get(0);

     }

     public String bottom() {

         if (stackSize == 0) {

             throw new IllegalStateException("Stack underflow");

         }

         return constructVariableName(0);

     }

     public int getMaxStackSize() {

         return maxStackSize;

     }

     public String constructVariableName(final int index) {

         varNameBuilder.setLength(VAR_NAME_PREFIX.length());

         varNameBuilder.append(index);

         return varNameBuilder.toString();

     }

 }