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 java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import at.ac.tuwien.kr.alpha.api.programs.atoms.Atom;
  import at.ac.tuwien.kr.alpha.commons.util.IntIdGenerator;
  import at.ac.tuwien.kr.alpha.commons.util.Util;
  import at.ac.tuwien.kr.alpha.core.programs.atoms.RuleAtom;
  import at.ac.tuwien.kr.alpha.core.solver.AtomCounter;
  
  /**
   * This class stores ground atoms and provides the translation from an (integer) atomId to a (structured) predicate instance.
   */
  public class AtomStoreImpl implements AtomStore {
  	private final List<Atom> atomIdsToInternalBasicAtoms = new ArrayList<>();
  	private final Map<Atom, Integer> predicateInstancesToAtomIds = new HashMap<>();
  	private final IntIdGenerator atomIdGenerator = new IntIdGenerator(1);
  	private final AtomCounter atomCounter = new AtomCounter();
  
  	private final List<Integer> releasedAtomIds = new ArrayList<>();	// contains atomIds ready to be garbage collected if necessary.
  
  	public AtomStoreImpl() {
  		// Create atomId for falsum (currently not needed, but it gets atomId 0, which cannot represent a negated literal).
  		atomIdsToInternalBasicAtoms.add(null);
  	}
  
  	@Override
  	public int putIfAbsent(Atom groundAtom) {
  		if (!groundAtom.isGround()) {
  			throw new IllegalArgumentException("Atom must be ground: " + groundAtom);
  		}
  
  		Integer id = predicateInstancesToAtomIds.get(groundAtom);
  
  		if (id == null) {
  			id = atomIdGenerator.getNextId();
  			predicateInstancesToAtomIds.put(groundAtom, id);
  			atomIdsToInternalBasicAtoms.add(id, groundAtom);
  			atomCounter.add(groundAtom);
  		}
  
  		return id;
  	}
  
  	@Override
  	public boolean contains(Atom groundAtom) {
  		return predicateInstancesToAtomIds.containsKey(groundAtom);
  	}
  
  	/**
  	 * Removes the given atom from the AtomStoreImpl.
  	 * @param atomId
  	 */
  	public void releaseAtomId(int atomId) {
  		releasedAtomIds.add(atomId);
  		// HINT: Additionally removing the terms used in the instance might be beneficial in some cases.
  	}
  
  	public String printAtomIdTermMapping() {
  		StringBuilder ret = new StringBuilder();
  		for (Map.Entry<Atom, Integer> entry : predicateInstancesToAtomIds.entrySet()) {
  			ret.append(entry.getValue()).append(" <-> ").append(entry.getKey().toString()).append(System.lineSeparator());
  		}
  		return ret.toString();
  	}
  
  	@Override
  	public String atomToString(int atomId) {
  		return get(atomId).toString();
  	}
  
  	@Override
  	public boolean isAtomChoicePoint(int atom) {
  		return get(atom) instanceof RuleAtom;
  	}
  
  	@Override
  	public int getMaxAtomId() {
  		return atomIdsToInternalBasicAtoms.size() - 1;
  	}
  
  	@Override
  	public Atom get(int atom) {
  		try {
  			return atomIdsToInternalBasicAtoms.get(atom);
  		} catch (IndexOutOfBoundsException e) {
  			throw Util.oops("Unknown atom ID encountered: " + atom, e);
  		}
  	}
  
  	@Override
  	public int get(Atom atom) {
  		return predicateInstancesToAtomIds.get(atom);
  	}
  
  	@Override
  	public AtomCounter getAtomCounter() {
  		return atomCounter;
  	}
  }