/*
 *  RapidMiner
 *
 *  Copyright (C) 2001-2014 by RapidMiner and the contributors
 *
 *  Complete list of developers available at our web site:
 *
 *       http://rapidminer.com
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero General Public License as published by
 *  the Free Software Foundation, either version 3 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 Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/.
 */
package com.rapidminer.operator.learner.associations;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

import com.rapidminer.operator.Operator;
import com.rapidminer.operator.OperatorDescription;
import com.rapidminer.operator.OperatorException;
import com.rapidminer.operator.ports.PortPairExtender;
import com.rapidminer.operator.ports.metadata.MetaData;
import com.rapidminer.tools.container.Tupel;
/**
 * This operator compares a number of FrequentItemSet sets and removes every
 * not unique FrequentItemSet.
 * 
 * @author Sebastian Land
 */
public class FrequentItemSetUnificator extends Operator {

    private static class FrequencyIgnoringSetComparator implements Comparator<FrequentItemSet> {
        @Override
        public int compare(FrequentItemSet o1, FrequentItemSet o2) {
            // compare size
            Collection<Item> items = o1.getItems();
            Collection<Item> hisItems = o2.getItems();
            if (items.size() < hisItems.size()) {
                return -1;
            } else if (items.size() > hisItems.size()) {
                return 1;
            } else {
                // compare items
                Iterator<Item> iterator = hisItems.iterator();
                for (Item myCurrentItem : items) {
                    int relation = myCurrentItem.toString().compareTo(iterator.next().toString());
                    if (relation != 0) {
                        return relation;
                    }
                }
                // equal sets
                return 0;
            }
        }

    }

    private static class TupelComparator implements Comparator<Tupel<FrequentItemSet, Iterator<FrequentItemSet>>> {

        @Override
        public int compare(Tupel<FrequentItemSet, Iterator<FrequentItemSet>> o1, Tupel<FrequentItemSet, Iterator<FrequentItemSet>> o2) {
            FrequencyIgnoringSetComparator comparator = new FrequencyIgnoringSetComparator();
            return comparator.compare(o1.getFirst(), o2.getFirst());
        }

    }

    private PortPairExtender portExtender = new PortPairExtender("frequent item sets", getInputPorts(), getOutputPorts(), new MetaData(FrequentItemSets.class));

    public FrequentItemSetUnificator(OperatorDescription description) {
        super(description);

        portExtender.ensureMinimumNumberOfPorts(2);
        getTransformer().addRule(portExtender.makePassThroughRule());
        portExtender.start();

    }

    @Override
    public void doWork() throws OperatorException {
        List<FrequentItemSets> sets = portExtender.getData(FrequentItemSets.class);
        for (FrequentItemSets set: sets) {
            set.sortSets(new FrequencyIgnoringSetComparator());
            sets.add(set);
        }

        ArrayList<Tupel<FrequentItemSet, Iterator<FrequentItemSet>>> iteratorTupels = new ArrayList<Tupel<FrequentItemSet, Iterator<FrequentItemSet>>>(2);
        for (FrequentItemSets classSets: sets) {
            Iterator<FrequentItemSet> iterator = classSets.iterator();
            iteratorTupels.add(new Tupel<FrequentItemSet, Iterator<FrequentItemSet>>(iterator.next(), iterator));
        }
        // running through iterators
        while(haveNext(iteratorTupels)) {
            // filling set to test if all frequent item sets are equal
            Set<FrequentItemSet> currentSets = new TreeSet<FrequentItemSet>(new FrequencyIgnoringSetComparator());
            for (Tupel<FrequentItemSet, Iterator<FrequentItemSet>> tupel: iteratorTupels) {
                currentSets.add(tupel.getFirst());
            }
            if (currentSets.size() == 1) {
                // not unique: deletion
                ArrayList<Tupel<FrequentItemSet, Iterator<FrequentItemSet>>> newTupels = new ArrayList<Tupel<FrequentItemSet, Iterator<FrequentItemSet>>>(2);
                for (Tupel<FrequentItemSet, Iterator<FrequentItemSet>> tupel: iteratorTupels) {
                    Iterator<FrequentItemSet> currentIterator = tupel.getSecond();
                    currentIterator.remove();
                    if (currentIterator.hasNext())
                        newTupels.add(new Tupel<FrequentItemSet, Iterator<FrequentItemSet>>(currentIterator.next(), currentIterator));
                }
                iteratorTupels = newTupels;
            } else {
                // unique: no deletion but forward smallest iterator
                Collections.sort(iteratorTupels, new TupelComparator());
                Iterator<FrequentItemSet> currentIterator = iteratorTupels.get(0).getSecond();
                if (currentIterator.hasNext())
                    iteratorTupels.add(new Tupel<FrequentItemSet, Iterator<FrequentItemSet>>(currentIterator.next(), currentIterator));
                iteratorTupels.remove(0);
            }
        }

        portExtender.deliver(sets);
    }

    private boolean haveNext(ArrayList<Tupel<FrequentItemSet, Iterator<FrequentItemSet>>> iterators) {
        boolean hasNext = iterators.size() > 0;
        for (Tupel<FrequentItemSet, Iterator<FrequentItemSet>> iterator: iterators) {
            hasNext = hasNext || iterator.getSecond().hasNext();
        }
        return hasNext;
    }
}