;
!(function () {
    BI.LRU = function (limit) {
        this.size = 0;
        this.limit = limit;
        this.head = this.tail = undefined;
        this._keymap = {};
    };

    var p = BI.LRU.prototype;

    p.put = function (key, value) {
        var removed;
        if (this.size === this.limit) {
            removed = this.shift();
        }

        var entry = this.get(key, true);
        if (!entry) {
            entry = {
                key: key
            };
            this._keymap[key] = entry;
            if (this.tail) {
                this.tail.newer = entry;
                entry.older = this.tail
            } else {
                this.head = entry
            }
            this.tail = entry;
            this.size++;
        }
        entry.value = value;

        return removed;
    };

    p.shift = function () {
        var entry = this.head;
        if (entry) {
            this.head = this.head.newer;
            this.head.older = undefined;
            entry.newer = entry.older = undefined;
            this._keymap[entry.key] = undefined;
            this.size--;
        }
        return entry;
    };


    p.get = function (key, returnEntry) {
        var entry = this._keymap[key];
        if (entry === undefined) return;
        if (entry === this.tail) {
            return returnEntry
                ? entry
                : entry.value
        }
        // HEAD--------------TAIL
        //   <.older   .newer>
        //  <--- add direction --
        //   A  B  C  <D>  E
        if (entry.newer) {
            if (entry === this.head) {
                this.head = entry.newer
            }
            entry.newer.older = entry.older; // C <-- E.
        }
        if (entry.older) {
            entry.older.newer = entry.newer; // C. --> E
        }
        entry.newer = undefined; // D --x
        entry.older = this.tail; // D. --> E
        if (this.tail) {
            this.tail.newer = entry; // E. <-- D
        }
        this.tail = entry;
        return returnEntry
            ? entry
            : entry.value
    };

    p.has = function (key) {
        return this._keymap[key] != null;
    }
})();