content: /**
   * Copyright (c) 2018-2019 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.solver.heuristics;
  
  import at.ac.tuwien.kr.alpha.core.common.NoGood;
  import at.ac.tuwien.kr.alpha.core.solver.learning.GroundConflictNoGoodLearner.ConflictAnalysisResult;
  
  import static at.ac.tuwien.kr.alpha.commons.util.Util.oops;
  
  import java.util.*;
  
  /**
   * A "chained" list of branching heuristics in which the entry at position n+1 is used as a fallback if the entry at position n cannot make a decision. 
   */
  public class ChainedBranchingHeuristics implements BranchingHeuristic {
  	
  	private List<BranchingHeuristic> chain = new LinkedList<>();
  	private int[] decisionCounters;
  	
  	private ChainedBranchingHeuristics(BranchingHeuristic... branchingHeuristics) {
  		for (BranchingHeuristic element : branchingHeuristics) {
  			add(element);
  		}
  		this.decisionCounters = new int[chain.size()];
  	}
  	
  	@Override
  	public void violatedNoGood(NoGood violatedNoGood) {
  		for (BranchingHeuristic element : chain) {
  			element.violatedNoGood(violatedNoGood);
  		}
  	}
  
  	@Override
  	public void analyzedConflict(ConflictAnalysisResult analysisResult) {
  		for (BranchingHeuristic element : chain) {
  			element.analyzedConflict(analysisResult);
  		}
  	}
  
  	@Override
  	public void newNoGood(NoGood newNoGood) {
  		for (BranchingHeuristic element : chain) {
  			element.newNoGood(newNoGood);
  		}
  	}
  	
  	@Override
  	public int chooseLiteral() {
  		for (int i = 0; i < chain.size(); i++) {
  			BranchingHeuristic element = chain.get(i);
  			int chosenLiteral = element.chooseLiteral();
  			if (chosenLiteral != DEFAULT_CHOICE_LITERAL) {
  				decisionCounters[i]++;
  				return chosenLiteral;
  			}
  		}
  		return DEFAULT_CHOICE_LITERAL;
  	}
  
  	@Override
  	public void growForMaxAtomId(int maxAtomId) {
  		for (BranchingHeuristic element : chain) {
  			element.growForMaxAtomId(maxAtomId);
  		}
  	}
  
  	public void add(BranchingHeuristic element) {
  		if (chain.contains(element)) {
  			throw oops("Cycle detected in chain of branching heuristics");
  		}
  		chain.add(element);
  		if (decisionCounters != null) {
  			decisionCounters = Arrays.copyOf(decisionCounters, decisionCounters.length + 1);
  		}
  	}
  
  	public BranchingHeuristic getLastElement() {
  		return chain.get(chain.size() - 1);
  	}
  	
  	public static ChainedBranchingHeuristics chainOf(BranchingHeuristic... branchingHeuristics) {
  		return new ChainedBranchingHeuristics(branchingHeuristics);
  	}
  
  	/**
  	 * Returns a mapping from individual heuristics to number of decisions made by them.
  	 */
  	public Map<BranchingHeuristic, Integer> getNumberOfDecisions() {
  		Map<BranchingHeuristic, Integer> map = new HashMap<>();
  		for (int i = 0; i < chain.size(); i++) {
  			map.put(chain.get(i), decisionCounters[i]);
  		}
  		return map;
  	}
  	
  	@Override
  	public String toString() {
  		return this.getClass().getSimpleName() + chain;
  	}
  
  }
  