var LRU = require("./algorithm/LRU");
var LFU = require("./algorithm/LFU");

var lastAlgo = null, lastMaxsize = null;
var generateQueue = function (name, maxsize) {
    var algorithm = {
        "LRU": LRU,
        "LFU": LFU
    }
    lastAlgo = name || "LRU";
    lastMaxsize = maxsize;
    var Queue = algorithm[name];
    return Queue.createQueue(maxsize);
}
// 加入缓存
var set = function (key, value, expire) {
    var _cache = this.cache;
    var _queue = this.queue;
    // 如果已经存在该值，则重新赋值
    if (_cache[key]) {
        // 重新赋值或重设过期时间
		value?(_cache[key].value = value):'';
        _cache[key].expire = expire;
		_cache[key].insertTime= +new Date(),
        _queue.update(_cache[key].node);
    // 如果为新插入
    } else {
		if(!key || !value){
			return ;
		}
        // 更新索引
        var returnNode = _queue.insert(key);
        _cache[key] = {
            value: value,
            expire: expire,
            insertTime: +new Date(),
            node: returnNode.node
        }        
        returnNode.delArr.forEach(function (k) {
            _cache[k] = null;
        });
    }
}

var get = function (key) {
    var _cache = this.cache;
    var _queue = this.queue;
    // 如果存在该值
    if (_cache[key]) {
        var insertTime = _cache[key].insertTime;
        var expire = _cache[key].expire;
        var node = _cache[key].node;
        var curTime = +new Date();
        // 如果不存在过期时间 或者 存在过期时间但尚未过期
        if (!expire || (expire && curTime - insertTime < expire)) {
            // 已经使用过，更新队列
            _queue.update(node);
            var temp = _cache[key].value;
            return temp;
        // 如果已经过期
        } else if (expire && curTime - insertTime > expire) {
            // 从队列中删除
            _queue.del(node);
            return null
        }
    } else {
        return null;
    }
}

var clear = function () {
    this.cache = {};
    this.queue = generateQueue(lastMaxsize, lastAlgo);
}
var del = function(key){
    var _cache = this.cache;
    var _queue = this.queue;
    if(key && _cache[key]){
        var node = _cache[key].node;
       _queue.del(node);
       _cache[key] = null;
    }
}
var print = function () {
    var queue = this.queue;
    return queue.print();
}
// 应用类
var createCache = function (alg_name, maxsize) {
    if (!alg_name) alg_name = "LRU";
    if (!maxsize) maxsize = 100 * 100 * 10;
    var obj =  {
        cache: {},
        queue: generateQueue(alg_name, maxsize),
        set: set,
        get: get,
        clear: clear,
        print: print,
        del : del
    }
    setInterval(function () {
        var cache = obj.cache;
        var queue = obj.queue;
        for (var key in cache) {
            if (!cache[key]) continue;
            var insertTime = cache[key].insertTime;
            var expire = cache[key].expire;
            var curTime = +new Date();
            var node = cache[key]["node"];
            // 如果过期时间存在并且已经过期
            if (expire && curTime - insertTime > expire) {
                queue.del(node);
                cache[key] = null;
            }            
        }
    }, 1000);
    return obj;
}
exports.createCache = createCache;
/* 使用
var Cache = require("node-cache");
var cache = Cache.createCache("LRU", 100 * 100 * 10);
cache.set('use', {},2000);
*/