Angular directive to navigate around table cells and edit them

clickToEdit.js

angular.module("app").directive("clickToEdit", function()
{
	return {
		restrict: "A",
		link: function link(scope, element)
		{
			var LEFT = 37, UP = 38, RIGHT = 39, DOWN = 40, ENTER = 13;
			var navKeys = [ LEFT, UP, RIGHT, DOWN, ENTER ];
			element.attr("contenteditable", true);
			element.on("focus", function(e)
			{
				var currentRow = [].slice.call(e.target.offsetParent.rows).indexOf(e.target.parentElement);
				var currentCell = [].slice.call(e.target.parentElement.cells).indexOf(e.target);
				var begin = (e.target.innerText !== undefined) ? e.target.innerHTML.indexOf(e.target.innerText) : 0;
				var end = (e.target.innerText !== undefined) ? begin + e.target.innerText.length : e.target.innerHTML.length;
				var empty = (begin === end);

				// http://stackoverflow.com/a/13641884
				var range = document.createRange();
				range.selectNodeContents(e.target);
				var sel = window.getSelection();
				sel.removeAllRanges();
				sel.addRange(range);

				angular.element(e.target).on("keydown", function(e)
				{
					if (navKeys.indexOf(e.keyCode) !== -1)
					{
						var caretOffset = 0;
						// http://stackoverflow.com/a/4812022
						if (typeof window.getSelection !== "undefined")
						{
							var range = window.getSelection().getRangeAt(0);
							var selected = range.toString().length;
							var preCaretRange = range.cloneRange();
							preCaretRange.selectNodeContents(e.target);
							preCaretRange.setEnd(range.endContainer, range.endOffset);

							if (selected)
							{
								caretOffset = preCaretRange.toString().length - selected;
							}
							else
							{
								caretOffset = preCaretRange.toString().length;
							}
						}

						switch(e.keyCode)
						{
							case UP:
							{
								var next = e.target.offsetParent.rows[currentRow - 1].cells[currentCell];
								if (next)
								{
									next.focus();
								}
								break;
							}
							case DOWN:
							{
								var next = e.target.offsetParent.rows[currentRow + 1].cells[currentCell];
								if (next)
								{
									next.focus();
								}
								break;
							}
							case ENTER:
							{
								var move = (e.shiftKey) ? -1 : 1;
								var next = e.target.offsetParent.rows[currentRow + move].cells[currentCell];
								if (next)
								{
									next.focus();
								}
								e.preventDefault();
								break;
							}
							case LEFT:
							{
								if (empty || caretOffset === begin)
								{
									var next = e.target.offsetParent.rows[currentRow].cells[currentCell - 1];
									if (next)
									{
										next.focus();
									}
								}
								break;
							}
							case RIGHT:
							{
								if (empty || caretOffset === end)
								{
									var next = e.target.offsetParent.rows[currentRow].cells[currentCell + 1];
									if (next)
									{
										next.focus();
									}
								}
								break;
							}
						}
					}
				});
			});

			element.on("blur", function(e)
			{
				angular.element(e.target).off("keydown");
			});
		}
	};
});