content: /**
   * Copyright (c) 2020, the Alpha Team.
   * All rights reserved.
   *
   * 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.grounder.instantiation;
  
  import at.ac.tuwien.kr.alpha.api.programs.atoms.Atom;
  import at.ac.tuwien.kr.alpha.api.programs.literals.Literal;
  import at.ac.tuwien.kr.alpha.commons.substitutions.Instance;
  import at.ac.tuwien.kr.alpha.core.grounder.WorkingMemory;
  
  /**
   * A very basic implementation of {@link AbstractLiteralInstantiationStrategy} that determines truth of an atom solely based on the atom's
   * presence in a working memory. Atoms that have a corresponding positive instance in the working memory have {@link AssignmentStatus#TRUE},
   * all other atoms have {@link AssignmentStatus#FALSE}. A negated literal lit is true iff
   * <code>getAssignmentStatusForAtom(lit.getAtom()) == AssignmentStatus.FALSE</code>, false otherwise.
   * 
   * Copyright (c) 2020, the Alpha Team.
   */
  public class WorkingMemoryBasedInstantiationStrategy extends AbstractLiteralInstantiationStrategy {
  
  	private final WorkingMemory workingMemory;
  
  	public WorkingMemoryBasedInstantiationStrategy(WorkingMemory workingMemory) {
  		this.workingMemory = workingMemory;
  	}
  
  	@Override
  	protected Iterable<Instance> computeCandidateInstances(Atom partiallyGroundAtom) {
  		return this.workingMemory.get(partiallyGroundAtom, true).getInstancesFromPartiallyGroundAtom(partiallyGroundAtom);
  	}
  
  	@Override
  	protected AssignmentStatus getAssignmentStatusForAtom(Atom atom) {
  		return this.workingMemory.get(atom, true).containsInstance(Instance.fromAtom(atom)) ? AssignmentStatus.TRUE : AssignmentStatus.FALSE;
  	}
  
  	@Override
  	protected AssignmentStatus getAssignmentStatusForNegatedGroundLiteral(Literal negatedGroundLiteral) {
  		return this.getAssignmentStatusForAtom(negatedGroundLiteral.getAtom()) == AssignmentStatus.TRUE ? AssignmentStatus.FALSE : AssignmentStatus.TRUE;
  	}
  
  	@Override
  	protected boolean assignmentStatusAccepted(AssignmentStatus assignmentStatus) {
  		return assignmentStatus == AssignmentStatus.TRUE;
  	}
  
  }
  