/*
    * #%L
    * prolobjectlink-jpi-jtrolog
    * %%
    * Copyright (C) 2012 - 2018 WorkLogic Project
    * %%
    * This program is free software: you can redistribute it and/or modify
    * it under the terms of the GNU Lesser General Public License as
    * published by the Free Software Foundation, either version 2.1 of the
   * License, or (at your option) any later version.
   * 
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Lesser Public License for more details.
   * 
   * You should have received a copy of the GNU General Lesser Public
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-2.1.html>.
   * #L%
   */
  package jTrolog.engine;
  
  import jTrolog.terms.*;
  
  import java.io.*;
  import java.util.*;
  
  /**
   * Sorts the result into a Solution object. Arranges the bindings into a
   * LinkedHashMap.
   * 
   * @author janerist@stud.ntnu.no
   * @author ivar.orstavik@hist.no
   */
  @SuppressWarnings({ "rawtypes", "unchecked","serial" })
  class SolutionManager implements Serializable {
  
  	private static HashMap setupResultTable(BindingsTable result, Struct query) {
  		// 1. stringToStructList a new goal object based on the results and
  		// query
  		HashMap bindings = new HashMap();
  		if (query.getVarList() == null)
  			return bindings;
  		// 2. stringToStructList a simple HashMap based on only the query vars.
  		for (int i = 0; i < query.getVarList().length; i++) {
  			Var var = query.getVarList()[i];
  			Term link = result.flatCopy(var, 0);
  			if (link.equals(var))
  				link = null;
  			bindings.put(var, link);
  		}
  		bindings = replaceUnknownManInTheMiddle(bindings);
  		bindings = reverseAnyNullLinks(bindings);
  		return bindings;
  	}
  
  	private static HashMap reverseAnyNullLinks(HashMap bindings) {
  		LinkedHashMap almostACopy = new LinkedHashMap();
  		for (Iterator it = bindings.keySet().iterator(); it.hasNext();) {
  			Term key1 = (Term) it.next();
  			Object link1 = bindings.get(key1);
  			if (link1 == null && bindings.containsValue(key1)) {
  				// key1 is not linked, find another key2 that links to key1
  				for (Iterator iterator = bindings.keySet().iterator(); iterator.hasNext();) {
  					Term key2 = (Term) iterator.next();
  					Term link2 = (Term) bindings.get(key2);
  					// key2 links to key1, return key2
  					if (key1.equals(link2)) {
  						almostACopy.put(key1.toString(), key2);
  						break;
  					}
  				}
  			} else
  				almostACopy.put(key1.toString(), link1);
  		}
  		return almostACopy;
  	}
  
  	private static HashMap replaceUnknownManInTheMiddle(HashMap bindings) {
  		Collection linked = bindings.values();
  		for (Iterator it = linked.iterator(); it.hasNext();) {
  			Term isLinked = (Term) it.next();
  			if (!(isLinked instanceof Var))
  				continue;
  			if (bindings.keySet().contains(isLinked))
  				continue;
  			int howOftenIsIsLinkedLinked = Collections.frequency(linked, isLinked);
  			if (howOftenIsIsLinkedLinked <= 1)
  				continue;
  			// isLinked is manInTheMiddle
  			LinkedList keys = new LinkedList();
  			for (Iterator it2 = bindings.keySet().iterator(); it2.hasNext();) {
  				Term varName = (Term) it2.next();
  				if (isLinked.equals(bindings.get(varName)))
  					keys.add(varName);
  			}
  			for (int i = 0; i < keys.size(); i++) {
  				Var key = (Var) keys.get(i);
 				if (i == keys.size() - 1)
 					bindings.put(key, null);
 				else
 					bindings.put(key, (Var) keys.getLast());
 			}
 		}
 		return bindings;
 	}
 
 	static Solution prepareSolution(Struct query, BindingsTable result) {
 		if (result == null)
 			return new Solution(null);
 
 		HashMap bindings = SolutionManager.setupResultTable(result, query);
 		Term goal = result.flatCopy(query, 0);
 		return new Solution(bindings, goal);
 	}
 }