content: /**
   * Copyright (c) 2019 Siemens AG
   * 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;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import at.ac.tuwien.kr.alpha.api.programs.literals.Literal;
  import at.ac.tuwien.kr.alpha.core.programs.rules.InternalRule;
  
  /**
   * A grounding order computed by {@link RuleGroundingInfoImpl} for a specific {@link InternalRule} and a specific starting literal.
   */
  public class RuleGroundingOrderImpl implements RuleGroundingOrder{
  
  	private Literal startingLiteral;
  	private List<Literal> otherLiterals;
  	private int positionLastVarBound;
  	private int stopBindingAtOrderPosition;
  	private final boolean ground;
  	
  	RuleGroundingOrderImpl(Literal startingLiteral, List<Literal> otherLiterals, int positionLastVarBound, boolean isGround) {
  		super();
  		this.startingLiteral = startingLiteral;
  		this.otherLiterals = otherLiterals;
  		this.positionLastVarBound = positionLastVarBound;
  		this.stopBindingAtOrderPosition = otherLiterals.size();
  		this.ground = isGround;
  	}
  	
  	private RuleGroundingOrderImpl(RuleGroundingOrderImpl otherRuleGroundingOrder) {
  		this(otherRuleGroundingOrder.startingLiteral, new ArrayList<>(otherRuleGroundingOrder.otherLiterals), otherRuleGroundingOrder.positionLastVarBound, otherRuleGroundingOrder.ground);
  		this.stopBindingAtOrderPosition = otherRuleGroundingOrder.stopBindingAtOrderPosition;
  	}
  	
  	/**
  	 * Returns the literal at the given position in the grounding order,
  	 * except it is already known that this literal is not able to yield new bindings.
  	 * 
  	 * A literal cannot yield new bindings if it has been copied to the end of the grounding order
  	 * when no bindings could be found, and no bindings for other literals could be found in the meantime.
  	 * 
  	 * @param orderPosition zero-based index into list of literals except the starting literal
  	 * @return the literal at the given position, or {@code null} if it is already known that this literal is not able to yield new bindings
  	 */
  	@Override
  	public Literal getLiteralAtOrderPosition(int orderPosition) {
  		if (orderPosition >= stopBindingAtOrderPosition) {
  			return null;
  		}
  		return otherLiterals.get(orderPosition);
  	}
  
  	/**
  	 * @return the zero-based position from which on all variables are bound in list of literals except the starting literal
  	 */
  	@Override
  	public int getPositionFromWhichAllVarsAreBound() {
  		return positionLastVarBound + 1;
  	}
  
  	public boolean isGround() {
  		return ground;
  	}
  
  	@Override
  	public String toString() {
  		StringBuilder sb = new StringBuilder();
  		sb.append(startingLiteral);
  		sb.append(" : ");
  		for (int i = 0; i < otherLiterals.size(); i++) {
  			if (i == positionLastVarBound + 1) {
  				sb.append("| ");
  			}
  			sb.append(otherLiterals.get(i));
  			if (i < otherLiterals.size() - 1) {
  				sb.append(", ");
  			}
  		}
  		
  		return sb.toString();
  	}
  
  	/**
  	 * "Pushes a literal back" in a grounding order because the literal cannot be used to generate substitutions now but
  	 * maybe later. Pushing back means adding the literal again at the end of the grounding order. Since the literal will
  	 * occur twice in the new grounding order returned by this method, we assume that the grounding order is processed
  	 * from left to right and the literal at {@code orderPosition} will not be considered again.
  	 *
  	 * @param orderPosition the position in the grounding order of the literal to be pushed back.
  	 * @return a new grounding order in which the atom is pushed back,
  	 * or {@code null} if the position of the grounding order after which no new bindings can be found has been reached.
  	 */
  	@Override
  	public RuleGroundingOrderImpl pushBack(int orderPosition) {
  		if (orderPosition >= stopBindingAtOrderPosition - 1) {
  			return null;
  		}
  		RuleGroundingOrderImpl reorderedGroundingOrder = new RuleGroundingOrderImpl(this);
  		reorderedGroundingOrder.otherLiterals.add(otherLiterals.get(orderPosition));
  		return reorderedGroundingOrder;
  	}
  	
  	@Override
  	public void considerUntilCurrentEnd() {
  		this.stopBindingAtOrderPosition = this.otherLiterals.size();
  	}
  
  	@Override
  	public Literal getStartingLiteral() {
  		return this.startingLiteral;
  	}
  
  }
  