/*******************************************************************************
    * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
    *
    * All rights reserved. This program and the accompanying materials
    * are made available under the terms of the Eclipse Public License v1.0
    * which accompanies this distribution, and is available at
    * http://www.eclipse.org/legal/epl-v10.html
    *
    * Alternatively, the contents of this file may be used under the terms of
   * either the GNU Lesser General Public License Version 2.1 or later (the
   * "LGPL"), in which case the provisions of 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 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 LGPL. If you do not delete the provisions above, a recipient
   * may use your version of this file under the terms of the EPL or the LGPL.
   * 
   * Based on the original MiniSat specification from:
   * 
   * An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
   * Sixth International Conference on Theory and Applications of Satisfiability
   * Testing, LNCS 2919, pp 502-518, 2003.
   *
   * See www.minisat.se for the original solver in C++.
   * 
   *******************************************************************************/
  package org.sat4j.minisat.constraints.cnf;
  
  import java.io.Serializable;
  
  import org.sat4j.minisat.core.Constr;
  import org.sat4j.minisat.core.ILits;
  import org.sat4j.minisat.core.Undoable;
  import org.sat4j.minisat.core.UnitPropagationListener;
  import org.sat4j.specs.IVecInt;
  
  /**
   * @author leberre
   * @since 2.1
   */
  public class CBClause implements Constr, Undoable, Serializable {
  
  	private static final long serialVersionUID = 1L;
  
  	protected int falsified;
  
  	private boolean learnt;
  
  	protected final int[] lits;
  
  	protected final ILits voc;
  
  	private double activity;
  
  	public static CBClause brandNewClause(UnitPropagationListener s, ILits voc,
  			IVecInt literals) {
  		CBClause c = new CBClause(literals, voc);
  		c.register();
  		return c;
  	}
  
  	/**
       * 
       */
  	public CBClause(IVecInt ps, ILits voc, boolean learnt) {
  		this.learnt = learnt;
  		this.lits = new int[ps.size()];
  		this.voc = voc;
  		ps.moveTo(this.lits);
  	}
  
  	public CBClause(IVecInt ps, ILits voc) {
  		this(ps, voc, false);
  	}
  
  	/**
  	 * @since 2.1
  	 */
  	public void remove(UnitPropagationListener upl) {
  		for (int i = 0; i < lits.length; i++) {
  			voc.watches(lits[i] ^ 1).remove(this);
  		}
  	}
  
  	/*
  	 * (non-Javadoc)
  	 * 
  	 * @seeorg.sat4j.minisat.core.Constr#propagate(org.sat4j.minisat.core.
  	 * UnitPropagationListener, int)
  	 */
  	public boolean propagate(UnitPropagationListener s, int p) {
  		voc.undos(p).push(this);
  		falsified++;
  		assert falsified != lits.length;
  		if (falsified == lits.length - 1) {
  			// find unassigned literal
  			for (int i = 0; i < lits.length; i++) {
  				if (!voc.isFalsified(lits[i])) {
 					return s.enqueue(lits[i], this);
 				}
 			}
 			// one of the variable in to be propagated to false.
 			// (which explains why the falsified counter has not
 			// been increased yet)
 			return false;
 		}
 		return true;
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#simplify()
 	 */
 	public boolean simplify() {
 		for (int p : lits) {
 			if (voc.isSatisfied(p)) {
 				return true;
 			}
 		}
 		return false;
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#undo(int)
 	 */
 	public void undo(int p) {
 		falsified--;
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#calcReason(int,
 	 * org.sat4j.specs.VecInt)
 	 */
 	public void calcReason(int p, IVecInt outReason) {
 		assert outReason.size() == 0;
 		for (int q : lits) {
 			assert voc.isFalsified(q) || q == p;
 			if (voc.isFalsified(q)) {
 				outReason.push(q ^ 1);
 			}
 		}
 		assert (p == ILits.UNDEFINED) || (outReason.size() == lits.length - 1);
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#learnt()
 	 */
 	public boolean learnt() {
 		return learnt;
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#incActivity(double)
 	 */
 	public void incActivity(double claInc) {
 		if (learnt) {
 			activity += claInc;
 		}
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#getActivity()
 	 */
 	public double getActivity() {
 		return activity;
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#locked()
 	 */
 	public boolean locked() {
 		return voc.getReason(lits[0]) == this;
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#setLearnt()
 	 */
 	public void setLearnt() {
 		learnt = true;
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#register()
 	 */
 	public void register() {
 		for (int p : lits) {
 			voc.watch(p ^ 1, this);
 		}
 		if (learnt) {
 			for (int p : lits) {
 				if (voc.isFalsified(p)) {
 					voc.undos(p ^ 1).push(this);
 					falsified++;
 				}
 			}
 			assert falsified == lits.length - 1;
 		}
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#rescaleBy(double)
 	 */
 	public void rescaleBy(double d) {
 		activity *= d;
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#size()
 	 */
 	public int size() {
 		return lits.length;
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see org.sat4j.minisat.core.Constr#get(int)
 	 */
 	public int get(int i) {
 		return lits[i];
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * 
 	 * @see
 	 * org.sat4j.minisat.core.Constr#assertConstraint(org.sat4j.minisat.core
 	 * .UnitPropagationListener)
 	 */
 	public void assertConstraint(UnitPropagationListener s) {
 		assert voc.isUnassigned(lits[0]);
 		boolean ret = s.enqueue(lits[0], this);
 		assert ret;
 	}
 
 	@Override
 	public String toString() {
 		StringBuffer stb = new StringBuffer();
 		for (int i = 0; i < lits.length; i++) {
 			stb.append(lits[i]);
 			stb.append("["); //$NON-NLS-1$
 			stb.append(voc.valueToString(lits[i]));
 			stb.append("]"); //$NON-NLS-1$
 			stb.append(" "); //$NON-NLS-1$
 		}
 		return stb.toString();
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public void forwardActivity(double claInc) {
 		if (!learnt) {
 			activity += claInc;
 		}
 	}
 }