package com.xxl.job.admin.scheduler.route.strategy;

import com.xxl.job.admin.scheduler.route.ExecutorRouter;
import com.xxl.job.core.biz.model.ReturnT;
import com.xxl.job.core.biz.model.TriggerParam;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * 单个JOB对应的每个执行器，使用频率最低的优先被选举
 *      a(*)、LFU(Least Frequently Used)：最不经常使用，频率/次数
 *      b、LRU(Least Recently Used)：最近最久未使用，时间
 *
 * Created by xuxueli on 17/3/10.
 */
public class ExecutorRouteLFU extends ExecutorRouter {

    private static ConcurrentMap<Integer, HashMap<String, Integer>> jobLfuMap = new ConcurrentHashMap<Integer, HashMap<String, Integer>>();
    private static long CACHE_VALID_TIME = 0;

    public String route(int jobId, List<String> addressList) {

        // cache clear
        if (System.currentTimeMillis() > CACHE_VALID_TIME) {
            jobLfuMap.clear();
            CACHE_VALID_TIME = System.currentTimeMillis() + 1000*60*60*24;
        }

        // lfu item init
        HashMap<String, Integer> lfuItemMap = jobLfuMap.get(jobId);     // Key排序可以用TreeMap+构造入参Compare；Value排序暂时只能通过ArrayList；
        if (lfuItemMap == null) {
            lfuItemMap = new HashMap<String, Integer>();
            jobLfuMap.putIfAbsent(jobId, lfuItemMap);   // 避免重复覆盖
        }

        // put new
        for (String address: addressList) {
            if (!lfuItemMap.containsKey(address) || lfuItemMap.get(address) >1000000 ) {
                lfuItemMap.put(address, new Random().nextInt(addressList.size()));  // 初始化时主动Random一次，缓解首次压力
            }
        }
        // remove old
        List<String> delKeys = new ArrayList<>();
        for (String existKey: lfuItemMap.keySet()) {
            if (!addressList.contains(existKey)) {
                delKeys.add(existKey);
            }
        }
        if (delKeys.size() > 0) {
            for (String delKey: delKeys) {
                lfuItemMap.remove(delKey);
            }
        }

        // load least userd count address
        List<Map.Entry<String, Integer>> lfuItemList = new ArrayList<Map.Entry<String, Integer>>(lfuItemMap.entrySet());
        Collections.sort(lfuItemList, new Comparator<Map.Entry<String, Integer>>() {
            @Override
            public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
                return o1.getValue().compareTo(o2.getValue());
            }
        });

        Map.Entry<String, Integer> addressItem = lfuItemList.get(0);
        String minAddress = addressItem.getKey();
        addressItem.setValue(addressItem.getValue() + 1);

        return addressItem.getKey();
    }

    @Override
    public ReturnT<String> route(TriggerParam triggerParam, List<String> addressList) {
        String address = route(triggerParam.getJobId(), addressList);
        return ReturnT.ofSuccess(address);
    }

}
