/*
    * #%L
    * prolobjectlink-jpi-jtrolog
    * %%
    * Copyright (C) 2012 - 2018 WorkLogic Project
    * %%
    * This program 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 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 Lesser Public License for more details.
   * 
   * You should have received a copy of the GNU General Lesser Public
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-2.1.html>.
   * #L%
   */
  package jTrolog.engine;
  
  import jTrolog.terms.Term;
  
  /**
   * @author ivar.orstavik@hist.no
   */
  class LinkTable {
  
  	private int depth = 8;
  	private int width = Engine.STARTUP_STACK_SIZE;
  
  	// Links are stored in a set of two dimensional arrays.
  	// The terms and their ctx id are stored as individual dimensions.
  	// The negative duplicates are used for terms with ctx id that are generated
  	// by library methods.
  	private Term[][] linkToTerm = new Term[depth][width];
  	private int[][] linkToCtx = new int[depth][width];
  
  	LinkTable() {
  		for (int i = 0; i < depth; i++) {
  			linkToTerm[i] = new Term[width];
  			linkToCtx[i] = new int[width];
  		}
  	}
  
  	final Term getTerm(final int vNr, final int vCtx) {
  		return vNr >= depth || vCtx >= width ? null : linkToTerm[vNr][vCtx];
  	}
  
  	final int getCtx(final int vNr, final int vCtx) {
  		return linkToCtx[vNr][vCtx];
  	}
  
  	final void put(final int vNr, int vCtx, final Term link, final int linkCtx) {
  		if (vNr >= depth)
  			expandLinkTableDepth(vNr * 2);
  
  		// mark vNr and vCtx under the given execCtx
  		linkToTerm[vNr][vCtx] = link;
  		linkToCtx[vNr][vCtx] = linkCtx;
  	}
  
  	private void expandLinkTableDepth(final int newSize) {
  		linkToTerm = LinkTable.expandMap(linkToTerm, newSize);
  		linkToCtx = LinkTable.expandMap(linkToCtx, newSize);
  		for (int i = depth; i < newSize; i++) {
  			linkToTerm[i] = new Term[width];
  			linkToCtx[i] = new int[width];
  		}
  		depth = newSize;
  	}
  
  	final void reset(int vNr, int vCtx) {
  		linkToTerm[vNr][vCtx] = null;
  		linkToCtx[vNr][vCtx] = 0;
  	}
  
  	final void doubleWidth(final int newSize) {
  		for (int i = 0; i < depth; i++) {
  			linkToTerm[i] = LinkTable.expandArray(linkToTerm[i], newSize);
  			linkToCtx[i] = LinkTable.expandArray(linkToCtx[i], newSize);
  		}
  		width = newSize;
  	}
  
  	public int getWidth() {
  		return width;
  	}
  
  	static int[][] expandMap(final int[][] array, final int newSize) {
  		int[][] newArray = new int[newSize][];
  		System.arraycopy(array, 0, newArray, 0, array.length);
  		return newArray;
  	}
  
  	static int[] expandArray(int[] array, final int newSize) {
  		int[] newArray = new int[newSize];
 		System.arraycopy(array, 0, newArray, 0, array.length);
 		return newArray;
 	}
 
 	static Term[][] expandMap(final Term[][] array, final int newSize) {
 		Term[][] newArray = new Term[newSize][];
 		System.arraycopy(array, 0, newArray, 0, array.length);
 		return newArray;
 	}
 
 	static Term[] expandArray(Term[] array, final int newSize) {
 		Term[] newArray = new Term[newSize];
 		System.arraycopy(array, 0, newArray, 0, array.length);
 		return newArray;
 	}
 }