content: /**
   * Copyright (c) 2016-2019, 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.common;
  
  import static at.ac.tuwien.kr.alpha.core.programs.atoms.Literals.atomOf;
  import static at.ac.tuwien.kr.alpha.core.programs.atoms.Literals.isNegated;
  
  import java.util.Set;
  
  import at.ac.tuwien.kr.alpha.core.solver.Antecedent;
  import at.ac.tuwien.kr.alpha.core.solver.ThriceTruth;
  
  public interface Assignment {
  	Entry get(int atom);
  
  	/**
  	 * Returns the truth value assigned to an atom.
  	 * @param atom the id of the atom.
  	 * @return the truth value; null if atomId is not assigned.
  	 */
  	default ThriceTruth getTruth(int atom) {
  		final Entry entry = get(atom);
  		return entry == null ? null : entry.getTruth();
  	}
  
  	/**
  	 * Returns the weak decision level of the atom if it is assigned.
  	 * @param atom the atom.
  	 * @return the weak decision level of the atom if it is assigned; otherwise any value may be returned.
  	 */
  	int getWeakDecisionLevel(int atom);
  
  	/**
  	 * Returns the strong decision level of the atom.
  	 * @param atom the atom.
  	 * @return the strong decision level of the atom or -1.
  	 */
  	int getStrongDecisionLevel(int atom);
  
  	boolean isAssigned(int atom);
  
  	/**
  	 * Returns the NoGood that implied the atom.
  	 * @param atom the atom.
  	 * @return the implying Antecedent.
  	 */
  	Antecedent getImpliedBy(int atom);
  
  	/**
  	 * Determines if the given {@code noGood} is undefined in the current assignment.
  	 *
  	 * @param noGood
  	 * @return {@code true} iff at least one literal in {@code noGood} is unassigned.
  	 */
  	default boolean isUndefined(NoGood noGood) {
  		for (Integer literal : noGood) {
  			if (!isAssigned(atomOf(literal))) {
  				return true;
  			}
  		}
  		return false;
  	}
  
  	/**
  	 * Returns an iterator over all newly assigned atoms. New assignments are only returned once.
  	 * @return an iterator over all atoms newly assigned to TRUE or MBT.
  	 */
  	IntIterator getNewPositiveAssignmentsIterator();
  
  	/**
  	 * Returns the new assignments to process.
  	 * @return a Pollable that yields the atoms that were newly assigned.
  	 */
  	Pollable getAssignmentsToProcess();
  
  	/**
  	 * Returns the weak decision level of the atom considering also out-of-order assignments.
  	 * @param atom the atom.
  	 * @return the weakDecisionLevel of the atom if it is not an out-of-order assignment, otherwise the lowest
  	 * decision level at which it will be re-assigned.
  	 */
  	int getRealWeakDecisionLevel(int atom);
  
  	interface Pollable {
  		int peek();
  		int remove();
  		boolean isEmpty();
  	}
  
  	interface Entry {
  		ThriceTruth getTruth();
  		int getAtom();
  		int getDecisionLevel();
  		Antecedent getImpliedBy();
  
  		boolean hasPreviousMBT();
  		int getMBTDecisionLevel();
  
  	}
  
  	int getDecisionLevel();
  
  	default boolean isViolated(int literal) {
  		final int atom = atomOf(literal);
  		final ThriceTruth truth = getTruth(atom);
  
  		// For unassigned atoms, any literal is not violated.
  		return truth != null && isNegated(literal) != truth.toBoolean();
  
  	}
  
  	default boolean violates(NoGood noGood) {
  		// Check each NoGood, if it is violated
  		for (Integer noGoodLiteral : noGood) {
  			if (!isAssigned(atomOf(noGoodLiteral)) || !isViolated(noGoodLiteral)) {
  				return false;
  			}
  		}
  		return true;
  	}
  
  	/**
  	 * Returns all atomIds that are assigned TRUE in the current assignment.
  	 * @return a list of all true assigned atoms.
  	 */
  	Set<Integer> getTrueAssignments();
  
  	/**
  	 * Reports how many atoms are assigned to must-be-true currently. If this method returns
  	 * zero, the assignment is guaranteed to be free of must-be-true values (i.e. it only
  	 * contains assignments to either true or false).
  	 * @return the count of must-be-true values in the asignment.
  	 */
  	int getMBTCount();
  
  	/**
  	 * Grows all internal data structures to accommodate for all atoms known.
  	 */
  	void growForMaxAtomId();
  	
  	/**
  	 * @return the number of atoms assigned since the last decision
  	 */
  	int getNumberOfAtomsAssignedSinceLastDecision();
  
  	/**
  	 * Obtain a BasicAtom that is currently assigned MBT (but not TRUE).
  	 * @return some BasicAtom that is assigned MBT.
  	 */
  	int getBasicAtomAssignedMBT();
  }
  