package com.terra.proxy.controller;

import java.util.Date;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 简单对象缓存管理
 * Created by lxb on 2018/7/1
 */
public class CacheManager {

    private static final long DEFAULT_TIMEOUT = 30000;
    private long cacheTimeout;
    private static CacheManager defaultInstance;
    private static Map<String, CacheData> CACHE_DATA = new ConcurrentHashMap<String, CacheData>();


    private CacheManager(long timeout) {

        this.cacheTimeout = timeout;

        new ClearThread().start();

    }

    private class ClearThread extends Thread {
        ClearThread() {
            setName("clear cache thread");
        }

        public void run() {
            while (true) {
                try {
                    long now = System.currentTimeMillis();
                    Object[] keys = CACHE_DATA.keySet().toArray();
                    for (Object key : keys) {
                        CacheData data = CACHE_DATA.get(key);
                        if (data != null && (data.getExpire() > 0 && data.getSaveTime() < new Date().getTime())) {
                            synchronized (CACHE_DATA) {
                                CACHE_DATA.remove(key);
                            }
                        }
                    }

                    Thread.sleep(cacheTimeout);

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static synchronized final CacheManager getDefault() {
        if (defaultInstance == null) {
            defaultInstance = new CacheManager(DEFAULT_TIMEOUT);
        }
        return defaultInstance;

    }

    private class CacheData<T> {
        CacheData(T t, int expire) {
            this.data = t;
            this.expire = expire <= 0 ? 0 : expire * 1000;
            this.saveTime = new Date().getTime() + this.expire;
        }

        private T data;
        private long saveTime; // 存活时间
        private long expire; // 过期时间 小于等于0标识永久存活

        public T getData() {
            return data;
        }

        public long getExpire() {
            return expire;
        }

        public long getSaveTime() {
            return saveTime;
        }
    }


    public <T> T getData(String key, Load<T> load, int expire) {
        T data = getData(key);
        if (data == null && load != null) {
            data = load.load();
            if (data != null) {
                setData(key, data, expire);
            }
        }
        return data;
    }

    public <T> T getData(String key) {
        CacheData<T> data = CACHE_DATA.get(key);
        if (data != null && (data.getExpire() <= 0 || data.getSaveTime() >= new Date().getTime())) {
            return data.getData();
        }
        return null;
    }

    public <T> void setData(String key, T data, int expire) {
        CACHE_DATA.put(key, new CacheData(data, expire));
    }

    public void clear(String key) {
        CACHE_DATA.remove(key);
    }

    public void clearAll() {
        CACHE_DATA.clear();
    }

    public interface Load<T> {
        T load();
    }

}