(function () {
  'use strict';

  angular.module('app.service')
    .service('indicator', ['$document', function ($document) {
      this.busy = false;
      this.list = [];

      var normalizeId = function (id) {
        return 'string' === typeof id ? id : null;
      };

      this.has = function (id) {
        return -1 !== this.list.indexOf(normalizeId(id));
      };

      this.refreshBusy = function () {
        this.busy = this.list.length > 0;
        $document[0].documentElement.style.cursor = this.busy ? 'progress' : '';
        return this;
      };

      this.start = function (id) {
        this.list.push(normalizeId(id));
        this.refreshBusy();
        return this;
      };

      this.stop = function (id) {
        var idx = this.list.lastIndexOf(normalizeId(id));
        if (-1 !== idx) {
          this.list.splice(idx, 1);
        }
        this.refreshBusy();
        return this;
      };

    }]);

})();