content: /**
   * Copyright (c) 2019 Siemens AG
   * All rights reserved.
   * <p>
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   * <p>
   * 1) Redistributions of source code must retain the above copyright notice, this
   * list of conditions and the following disclaimer.
   * <p>
   * 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.
   * <p>
   * 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.api.config;
  
  /**
   * Contains configuration parameters for heuristics used by the grounder.
   *
   * Both parameters {@link #toleranceConstraints} and {@link #toleranceRules} are interpreted as follows:
   * A rule (or constraint) is grounded if the following conditions are satisfied:
   * <ul>
   * 	<li>All variables in the rule are bound (either by positive body literals that are already
   *      satisfied, or because the whole rule is ground).</li>
   * 	<li>No atom occurring positively in the body is assigned F.</li>
   * 	<li>No atom occurring negatively in the body is true as a fact.
   * 		(Note: The rule is still grounded if an atom occurring negatively in the body is assigned true without
   * 		being a fact, because the alternative would necessitate triggering re-grounding during backtracking.)</li>
   * 	<li>At most {@code N} atoms occurring positively in the body are still unassigned.</li>
   * </ul>
   *
   * The parameter {@link #toleranceConstraints} specifies {@code N} for constraints, while {@link #toleranceRules}
   * specifies {@code N} for all other rules. Infinity is represented by the value {@code -1}.
   * The default value for both parameters is {@code 0}, which means that only those rules and constraints are
   * grounded whose positive body is already satisfied.
   *
   * The additional parameter {@link #accumulatorEnabled} is a switch for the accumulator grounding strategy
   * which disables the removal of instances from the grounder memory in certain cases.
   */
  public class GrounderHeuristicsConfiguration {
  
  	public static final String STRICT_STRING = "strict";
  	public static final int STRICT_INT = 0;
  	public static final String PERMISSIVE_STRING = "permissive";
  	public static final int PERMISSIVE_INT = -1;
  
  	private int toleranceConstraints;
  	private int toleranceRules;
  	private boolean accumulatorEnabled;
  
  	public GrounderHeuristicsConfiguration() {
  		super();
  		this.toleranceConstraints = STRICT_INT;
  		this.toleranceRules = STRICT_INT;
  	}
  
  	/**
  	 * @param toleranceConstraints
  	 * @param toleranceRules
  	 */
  	private GrounderHeuristicsConfiguration(int toleranceConstraints, int toleranceRules) {
  		super();
  		this.toleranceConstraints = toleranceConstraints;
  		this.toleranceRules = toleranceRules;
  	}
  
  	/**
  	 * @return the tolerance for constraints
  	 */
  	public int getToleranceConstraints() {
  		return toleranceConstraints;
  	}
  
  	/**
  	 * @return the tolerance for rules that are not constraints
  	 */
  	public int getToleranceRules() {
  		return toleranceRules;
  	}
  
  	/**
  	 * @param ruleIsConstraint {@code true} iff the parameter for constraints shall be returned
  	 * @return {@link #getToleranceConstraints()} if {@code ruleIsConstraint}, otherwise {@link #getToleranceRules()}
  	 */
  	public int getTolerance(boolean ruleIsConstraint) {
  		return ruleIsConstraint ? getToleranceConstraints() : getToleranceRules();
  	}
  
  	/**
  	 * @param ruleIsConstraint {@code true} iff the parameter for constraints shall be returned
  	 * @return {@code true} iff the tolerance is not 0
  	 */
  	public boolean isPermissive(boolean ruleIsConstraint) {
  		return getTolerance(ruleIsConstraint) != STRICT_INT;
  	}
  
  	public boolean isAccumulatorEnabled() {
  		return accumulatorEnabled;
  	}
  
  	public void setAccumulatorEnabled(boolean accumulatorEnabled) {
  		this.accumulatorEnabled = accumulatorEnabled;
  	}
  
  	public static GrounderHeuristicsConfiguration strict() {
  		return new GrounderHeuristicsConfiguration(STRICT_INT, STRICT_INT);
  	}
  
  	public static GrounderHeuristicsConfiguration permissive() {
  		return new GrounderHeuristicsConfiguration(PERMISSIVE_INT, PERMISSIVE_INT);
  	}
  
  	public static GrounderHeuristicsConfiguration getInstance(int toleranceConstraints, int toleranceRules) {
  		return new GrounderHeuristicsConfiguration(toleranceConstraints, toleranceRules);
  	}
  
  	public static GrounderHeuristicsConfiguration getInstance(String toleranceConstraints, String toleranceRules) {
  		return getInstance(parseTolerance(toleranceConstraints), parseTolerance(toleranceRules));
  	}
  
  	private static int parseTolerance(String tolerance) {
  		if (STRICT_STRING.equalsIgnoreCase(tolerance)) {
  			return STRICT_INT;
  		} else if (PERMISSIVE_STRING.equalsIgnoreCase(tolerance)) {
  			return PERMISSIVE_INT;
  		} else {
  			return Integer.parseInt(tolerance);
  		}
  	}
  
  	@Override
  	public String toString() {
  		return this.getClass().getSimpleName() + "(toleranceConstraints=" + toleranceConstraints + ",toleranceRules=" + toleranceRules + ",disableInstanceRemoval=" + accumulatorEnabled + ")";
  	}
  
  }
  