/*
 * Copyright (C) 2011 eXo Platform SAS.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.exoplatform.web.controller.router;

/**
 * A bit stack optimized for speed.
 *
 * @author <a href="mailto:julien.viet@exoplatform.com">Julien Viet</a>
 */
class BitStack
{

   private static class Frame
   {

      /** . */
      private Frame previous;

      /** . */
      private Frame next;

      /** . */
      private long bits;

      /** . */
      private int cardinality;

      private Frame()
      {
         this(0, 0);
      }

      private Frame(long bits, int cardinality)
      {
         this.previous = null;
         this.next = null;
         this.bits = bits;
         this.cardinality = cardinality;
      }
   }

   /** . */
   private Frame head;

   /** . */
   private Frame current;

   /** . */
   private int depth;

   /** . */
   private int size;

   BitStack()
   {
      this.current = null;
      this.depth = 0;
      this.size = 0;
   }

   void init(int size)
   {
      if (depth > 0)
      {
         throw new IllegalStateException();
      }
      if (size < 0)
      {
         throw new IllegalArgumentException();
      }
      this.size = size;
   }

   void reset()
   {
      if (depth > 0)
      {
         throw new IllegalStateException();
      }
      this.size = 0;
   }

   void push()
   {
      if (current == null)
      {
         if (head == null)
         {
            head = new Frame();
         }
         current = head;
         depth++;
      }
      else
      {
         if (current.next == null)
         {
            Frame next = new Frame(current.bits, current.cardinality);
            current.next = next;
            next.previous = current;
            current = next;
            depth++;
         }
         else
         {
            Frame next = current.next;
            next.bits = current.bits;
            next.cardinality = current.cardinality;
            current = next;
            depth++;
         }
      }
   }

   void pop()
   {
      if (depth == 0)
      {
         throw new IllegalStateException();
      }
      current = current.previous;
      depth--;
   }

   int getDepth()
   {
      return depth;
   }

   void set(int index)
   {
      if (index > 63)
      {
         throw new IllegalArgumentException("Index " + index + "  > 63 not allowed");
      }
      if (depth < 1)
      {
         throw new IllegalStateException();
      }
      if (index > size)
      {
         throw new IllegalArgumentException();
      }
      long pre = current.bits;
      current.bits |= 1L << index;
      if (current.bits != pre)
      {
         current.cardinality++;
      }
   }

   boolean get(int index)
   {
      if (index > 63)
      {
         throw new IllegalArgumentException("Index " + index + "  > 63 not allowed");
      }
      if (depth < 1)
      {
         throw new IllegalStateException();
      }
      if (index > size)
      {
         throw new IllegalArgumentException();
      }
      return (current.bits & (1L << index)) != 0;
   }

   boolean isEmpty()
   {
      if (depth < 1)
      {
         throw new IllegalStateException();
      }
      return current.cardinality == size;
   }
}
