"use strict";
  
  Object.defineProperty(exports, "__esModule", {
      value: true
  });
  exports.default = DLL;
  // Simple doubly linked list (https://en.wikipedia.org/wiki/Doubly_linked_list) implementation
  // used for queues. This implementation assumes that the node provided by the user can be modified
  // to adjust the next and last properties. We implement only the minimal functionality
  // for queue support.
  function DLL() {
      this.head = this.tail = null;
      this.length = 0;
  }
  
  function setInitial(dll, node) {
      dll.length = 1;
      dll.head = dll.tail = node;
  }
  
  DLL.prototype.removeLink = function (node) {
      if (node.prev) node.prev.next = node.next;else this.head = node.next;
      if (node.next) node.next.prev = node.prev;else this.tail = node.prev;
  
      node.prev = node.next = null;
      this.length -= 1;
      return node;
  };
  
  DLL.prototype.empty = function () {
      while (this.head) this.shift();
      return this;
  };
  
  DLL.prototype.insertAfter = function (node, newNode) {
      newNode.prev = node;
      newNode.next = node.next;
      if (node.next) node.next.prev = newNode;else this.tail = newNode;
      node.next = newNode;
      this.length += 1;
  };
  
  DLL.prototype.insertBefore = function (node, newNode) {
      newNode.prev = node.prev;
      newNode.next = node;
      if (node.prev) node.prev.next = newNode;else this.head = newNode;
      node.prev = newNode;
      this.length += 1;
  };
  
  DLL.prototype.unshift = function (node) {
      if (this.head) this.insertBefore(this.head, node);else setInitial(this, node);
  };
  
  DLL.prototype.push = function (node) {
      if (this.tail) this.insertAfter(this.tail, node);else setInitial(this, node);
  };
  
  DLL.prototype.shift = function () {
      return this.head && this.removeLink(this.head);
  };
  
  DLL.prototype.pop = function () {
      return this.tail && this.removeLink(this.tail);
  };
  
  DLL.prototype.toArray = function () {
      var arr = Array(this.length);
      var curr = this.head;
      for (var idx = 0; idx < this.length; idx++) {
          arr[idx] = curr.data;
          curr = curr.next;
      }
      return arr;
  };
  
  DLL.prototype.remove = function (testFn) {
      var curr = this.head;
      while (!!curr) {
          var next = curr.next;
          if (testFn(curr)) {
              this.removeLink(curr);
          }
          curr = next;
      }
      return this;
  };
  module.exports = exports["default"];