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// Copyright 2017, Yahoo Holdings Inc.
// Licensed under the terms of the Apache License 2.0. Please see LICENSE file in project root for terms.
package com.yahoo.maha.parrequest2;

import org.apache.commons.lang3.ObjectUtils;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.PriorityQueue;

import scala.Tuple2;

/**
 * Created by hiral on 6/26/14.
 */
public class CollectionsUtil {

    public static  List emptyList() {
        return (List) Collections.emptyList();
    }

    public static  Map emptyMap() {
        return (Map) Collections.emptyMap();
    }

    public static > Map sortMapByValue(Map map) {
        List> list = new LinkedList<>(map.entrySet());

        Collections.sort(list, new Comparator>() {
            public int compare(Map.Entry e1, Map.Entry e2) {
                return ObjectUtils.compare(e1.getValue(), e2.getValue());
            }
        });

        Map result = new LinkedHashMap<>();
        for (Map.Entry entry : list) {
            result.put(entry.getKey(), entry.getValue());
        }

        return result;
    }

    public static  Map getTopNByValue(Map map, int topN, final Comparator comparator) {
        Map result = new LinkedHashMap<>();
        if (topN <= 0) {
            return result;
        }
        // min heap
        PriorityQueue> queue = new PriorityQueue<>(topN, new Comparator>() {
            public int compare(Map.Entry e1, Map.Entry e2) {
                return (-1) * comparator.compare(e1.getValue(), e2.getValue());
            }
        });

        for (Map.Entry entry : map.entrySet()) {
            if (queue.size() < topN) {
                queue.offer(entry);
            } else if (comparator.compare(queue.peek().getValue(), entry.getValue()) > 0) {
                queue.poll();
                queue.offer(entry);
            }
        }

        List> list = new ArrayList<>();
        while (!queue.isEmpty()) {
            Map.Entry entry = queue.poll();
            list.add(entry);
        }
        // reverse
        for (int i = list.size() - 1; i >= 0; i--) {
            result.put(list.get(i).getKey(), list.get(i).getValue());
        }
        return result;
    }

    public static  Map sortMapByValue(Map map, final Comparator comparator) {
        List> list = new LinkedList<>(map.entrySet());

        Collections.sort(list, new Comparator>() {
            public int compare(Map.Entry e1, Map.Entry e2) {
                return comparator.compare(e1.getValue(), e2.getValue());
            }
        });

        Map result = new LinkedHashMap<>();
        for (Map.Entry entry : list) {
            result.put(entry.getKey(), entry.getValue());
        }

        return result;
    }

    public static  Map> combine2Map(Map map1, Map map2) {
        HashSet combinedKeySet = new HashSet();
        Map> combinedMap = new HashMap<>();
        if (map1 != null && !map1.isEmpty()) {
            combinedKeySet.addAll(map1.keySet());
        }
        if (map2 != null && !map2.isEmpty()) {
            combinedKeySet.addAll(map2.keySet());
        }
        for (K key : combinedKeySet) {
            V1 val1 = null;
            if (map1 != null) {
                val1 = map1.get(key);
            }
            V2 val2 = null;
            if (map2 != null) {
                val2 = map2.get(key);
            }
            combinedMap.put(key, new Tuple2(val1, val2));
        }
        return combinedMap;
    }
}