(function ($) {
  // register namespace
  $.extend(true, window, {
    "Slick": {
      "CellRangeSelector": CellRangeSelector
    }
  });

  function CellRangeSelector(options) {
    var _grid;
    var _currentlySelectedRange;
    var _canvas;
    var _gridOptions;
    var _$activeCanvas;
    var _dragging;
    var _decorator;
    var _self = this;
    var _handler = new Slick.EventHandler();
    var _defaults = {
      selectionCss: {
        "border": "2px dashed blue"
      }
    };

    // Frozen row & column variables
    var _rowOffset;
    var _columnOffset;
    var _isRightCanvas;
    var _isBottomCanvas;

    // Scrollings
    var _scrollTop = 0;
    var _scrollLeft = 0;

    function init(grid) {
      options = $.extend(true, {}, _defaults, options);
      _decorator = options.cellDecorator || new Slick.CellRangeDecorator(grid, options);
      _grid = grid;
      _canvas = _grid.getCanvasNode();
      _gridOptions = _grid.getOptions();
      _handler
        .subscribe(_grid.onScroll, handleScroll)
        .subscribe(_grid.onDragInit, handleDragInit)
        .subscribe(_grid.onDragStart, handleDragStart)
        .subscribe(_grid.onDrag, handleDrag)
        .subscribe(_grid.onDragEnd, handleDragEnd);
    }

    function destroy() {
      _handler.unsubscribeAll();
    }

    function getCellDecorator() {
      return _decorator;
    }

    function handleScroll(e, args) {
      _scrollTop = args.scrollTop;
      _scrollLeft = args.scrollLeft;
    }

    function handleDragInit(e, dd) {
      // Set the active canvas node because the decorator needs to append its
      // box to the correct canvas
      _$activeCanvas = $(_grid.getActiveCanvasNode(e));

      var c = _$activeCanvas.offset();

      _rowOffset = 0;
      _columnOffset = 0;
      _isBottomCanvas = _$activeCanvas.hasClass('grid-canvas-bottom');

      if (_gridOptions.frozenRow > -1 && _isBottomCanvas) {
        _rowOffset = (_gridOptions.frozenBottom) ? $('.grid-canvas-bottom').height() : $('.grid-canvas-top').height();
      }

      _isRightCanvas = _$activeCanvas.hasClass('grid-canvas-right');

      if (_gridOptions.frozenColumn > -1 && _isRightCanvas) {
        _columnOffset = $('.grid-canvas-left').width();
      }

      // prevent the grid from cancelling drag'n'drop by default
      e.stopImmediatePropagation();
    }

    function handleDragStart(e, dd) {
      var cell = _grid.getCellFromEvent(e);
      if (_self.onBeforeCellRangeSelected.notify(cell) !== false) {
        if (_grid.canCellBeSelected(cell.row, cell.cell)) {
          _dragging = true;
          e.stopImmediatePropagation();
        }
      }
      if (!_dragging) {
        return;
      }

      _grid.focus();

      var startX = dd.startX - $(_canvas).offset().left;
      if (_gridOptions.frozenColumn >= 0 && _isRightCanvas) {
        startX += _scrollLeft;
      }

      var startY = dd.startY - $(_canvas).offset().top;
      if (_gridOptions.frozenRow >= 0 && _isBottomCanvas) {
        startY += _scrollTop;
      }

      var start = _grid.getCellFromPoint(startX, startY);

      dd.range = { start: start, end: {} };
      _currentlySelectedRange = dd.range;
      return _decorator.show(new Slick.Range(start.row, start.cell));
    }

    function handleDrag(e, dd) {
      if (!_dragging) {
        return;
      }
      e.stopImmediatePropagation();

      var end = _grid.getCellFromPoint(
        e.pageX - _$activeCanvas.offset().left + _columnOffset,
        e.pageY - _$activeCanvas.offset().top + _rowOffset
      );

      // ... frozen column(s), 
      if ( _gridOptions.frozenColumn >= 0 && (!_isRightCanvas && (end.cell > _gridOptions.frozenColumn)) || (_isRightCanvas && (end.cell <= _gridOptions.frozenColumn)) ) {
        return;
      }

      // ... or frozen row(s)
      if ( _gridOptions.frozenRow >= 0 && (!_isBottomCanvas && (end.row >= _gridOptions.frozenRow)) || (_isBottomCanvas && (end.row < _gridOptions.frozenRow)) ) {
        return;
      }

      // ... or regular grid (without any frozen options)
      if (!_grid.canCellBeSelected(end.row, end.cell)) {
        return;
      }

      dd.range.end = end;

      _decorator.show(new Slick.Range(dd.range.start.row, dd.range.start.cell, end.row, end.cell));
    }

    function handleDragEnd(e, dd) {
      if (!_dragging) {
        return;
      }

      _dragging = false;
      e.stopImmediatePropagation();

      _decorator.hide();
      _self.onCellRangeSelected.notify({
        range: new Slick.Range(
          dd.range.start.row,
          dd.range.start.cell,
          dd.range.end.row,
          dd.range.end.cell
        )
      });
    }
    
    function getCurrentRange() {
      return _currentlySelectedRange;
    }

    $.extend(this, {
      "init": init,
      "destroy": destroy,
      "getCellDecorator": getCellDecorator,
      "getCurrentRange": getCurrentRange,

      "onBeforeCellRangeSelected": new Slick.Event(),
      "onCellRangeSelected": new Slick.Event()
    });
  }
})(jQuery);