/*
 * ARX: Powerful Data Anonymization
 * Copyright 2012 - 2017 Fabian Prasser, Florian Kohlmayer and contributors
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.deidentifier.arx.aggregates.classification;

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import org.deidentifier.arx.DataHandleInternal;

/**
 * Implements a classifier
 * @author Fabian Prasser
 */
public class MultiClassZeroR implements ClassificationMethod {

    /** Counts */
    private final Map<Integer, Integer>           counts = new HashMap<>();
    /** Result */
    private Integer                               result = null;
    /** Index */
    private final ClassificationDataSpecification specification;
    
    /**
     * Creates a new instance
     * @param specification
     */
    public MultiClassZeroR(ClassificationDataSpecification specification) {
        this.specification = specification;
    }

    @Override
    public ClassificationResult classify(DataHandleInternal handle, int row) {
        if (result == null) {
            result = getIndexWithMostCounts();
        }
        return new MultiClassZeroRClassificationResult(result, specification.classMap);
    }

    @Override
    public void close() {
        // Nothing to do
    }

    @Override
    public void train(DataHandleInternal features, DataHandleInternal clazz, int row) {
        Integer key = specification.classMap.get(clazz.getValue(row, specification.classIndex, true));
        Integer count = counts.get(key);
        count = count == null ? 1 : count + 1;
        counts.put(key, count);
        result = null;
    }

    /**
     * Returns the index of the most frequent element
     * @return
     */
    private Integer getIndexWithMostCounts() {
        int max = Integer.MIN_VALUE;
        Integer result = null;
        for (Entry<Integer, Integer> entry : counts.entrySet()) {
            int count = entry.getValue();
            int index = entry.getKey();
            if (count > max) {
                max = count;
                result = index;
            }
        }
        return result;
    }
}