/*
 *  RapidMiner
 *
 *  Copyright (C) 2001-2011 by Rapid-I and the contributors
 *
 *  Complete list of developers available at our web site:
 *
 *       http://rapid-i.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.preprocessing;

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.rapidminer.example.Attribute;
import com.rapidminer.example.ExampleSet;
import com.rapidminer.example.Statistics;
import com.rapidminer.example.table.NominalMapping;
import com.rapidminer.operator.OperatorDescription;
import com.rapidminer.operator.OperatorException;
import com.rapidminer.operator.ports.metadata.AttributeMetaData;
import com.rapidminer.operator.ports.metadata.ExampleSetMetaData;
import com.rapidminer.operator.ports.metadata.SetRelation;
import com.rapidminer.operator.preprocessing.RemoveUnusedNominalValuesModel.MappingTranslation;
import com.rapidminer.parameter.ParameterType;
import com.rapidminer.parameter.ParameterTypeBoolean;
import com.rapidminer.parameter.UndefinedParameterError;
import com.rapidminer.tools.Ontology;

/**
 * This operator will remove each unused (=not occurring) nominal value from the mapping.
 * 
 * @author Sebastian Land
 */
public class RemoveUnusedNominalValuesOperator extends PreprocessingOperator {

    private static final String PARAMETER_SORT_MAPPING_ALPHABETICALLY = "sort_alphabetically";

    public RemoveUnusedNominalValuesOperator(OperatorDescription description) {
        super(description);
    }

    @Override
    protected Collection<AttributeMetaData> modifyAttributeMetaData(ExampleSetMetaData emd, AttributeMetaData amd) throws UndefinedParameterError {
        amd.setValueSetRelation(SetRelation.SUBSET);
        return Collections.singleton(amd);
    }

    @Override
    public PreprocessingModel createPreprocessingModel(ExampleSet exampleSet) throws OperatorException {
        boolean sortMappings = getParameterAsBoolean(PARAMETER_SORT_MAPPING_ALPHABETICALLY);

        Map<String, MappingTranslation> translations = new HashMap<String, MappingTranslation>();

        exampleSet.recalculateAllAttributeStatistics();
        for (Attribute attribute: exampleSet.getAttributes()) {
            MappingTranslation translation = new MappingTranslation((NominalMapping)attribute.getMapping().clone());
            if (attribute.isNominal()) {
                for (String value: attribute.getMapping().getValues()) {
                    double count = exampleSet.getStatistics(attribute, Statistics.COUNT, value);
                    if (count > 0) {
                        translation.newMapping.mapString(value);
                    }
                }
                if (translation.newMapping.size() < attribute.getMapping().size()) {
                    if (sortMappings)
                        translation.newMapping.sortMappings();
                    translations.put(attribute.getName(), translation);
                }
            }
        }
        return new RemoveUnusedNominalValuesModel(exampleSet, translations);
    }

    @Override
    protected int[] getFilterValueTypes() {
        return new int[] { Ontology.NOMINAL };
    }

    @Override
    public Class<? extends PreprocessingModel> getPreprocessingModelClass() {
        return RemoveUnusedNominalValuesModel.class;
    }

    @Override
    public List<ParameterType> getParameterTypes() {
        List<ParameterType> types = super.getParameterTypes();

        types.add(new ParameterTypeBoolean(PARAMETER_SORT_MAPPING_ALPHABETICALLY, "If checked, the resulting mapping will be sorted alphabetically.", true, false));

        return types;
    }
}