content: /**
   * Copyright (c) 2016, the Alpha Team.
   * All rights reserved.
   *
   * Additional changes made by Siemens.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1) Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2) Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  package at.ac.tuwien.kr.alpha.core.solver;
  
  import static at.ac.tuwien.kr.alpha.core.programs.atoms.Literals.atomOf;
  import static at.ac.tuwien.kr.alpha.core.programs.atoms.Literals.isPositive;
  
  import at.ac.tuwien.kr.alpha.core.common.Assignment;
  import at.ac.tuwien.kr.alpha.core.common.NoGood;
  
  public interface WritableAssignment extends Assignment {
  	/**
  	 * Delete all information stored in the assignment.
  	 */
  	void clear();
  
  	/**
  	 * Backtracks the most recent decision level.
  	 */
  	void backtrack();
  
  	/**
  	 * Backtracks to the indicated decision level. Every assignment on a higher decisionLevel is removed.
  	 * All assignments below (or equal to) decisionLevel are kept. Note that for atoms being TRUE this may require
  	 * setting the assigned value to MBT during backtracking.
  	 * @param decisionLevel the decision level to backjump to (this decision level is the highest that is kept).
  	 */
  	void backjump(int decisionLevel);
  
  	/**
  	 * Assigns an atom some value on the indicated decision level.
  	 * @param atom the atom to assign
  	 * @param value the truth value to assign the atom
  	 * @param impliedBy the antecedent that is implying the atom.
  	 * @param decisionLevel the decision level on which the assignment is to take effect.
  	 * @return null if the assignment is consistent or a ConflictCause otherwise.
  	 */
  	ConflictCause assign(int atom, ThriceTruth value, Antecedent impliedBy, int decisionLevel);
  
  	default ConflictCause assign(int atom, ThriceTruth value, Antecedent impliedBy) {
  		return assign(atom, value, impliedBy, getDecisionLevel());
  	}
  
  	default ConflictCause assign(int atom, ThriceTruth value) {
  		return assign(atom, value, null);
  	}
  
  	ConflictCause choose(int atom, ThriceTruth value);
  
  	void registerCallbackOnChange(int atom);
  
  	void setCallback(ChoiceManager choiceManager);
  
  	default ConflictCause choose(int atom, boolean value) {
  		return choose(atom, ThriceTruth.valueOf(value));
  	}
  
  	default int minimumConflictLevel(NoGood noGood) {
  		int minimumConflictLevel = -1;
  		for (Integer literal : noGood) {
  			ThriceTruth atomTruth = getTruth(atomOf(literal));
  			if (atomTruth == null || isPositive(literal) != atomTruth.toBoolean()) {
  				return -1;
  			}
  			int literalDecisionLevel = getWeakDecisionLevel(atomOf(literal));
  			if (literalDecisionLevel > minimumConflictLevel) {
  				minimumConflictLevel = literalDecisionLevel;
  			}
  		}
  		return minimumConflictLevel;
  	}
  
  	/**
  	 * Assigns all unassigned atoms to FALSE.
  	 * @return true if any atom was assigned.
  	 */
  	boolean closeUnassignedAtoms();
  
  	/**
  	 * Returns whether the assignment did change since this method was last called.
  	 * @return true if the assignment changed since this method was last called.
  	 */
  	boolean didChange();
  }
  