d3.helper = {};

d3.helper.tooltip = function (accessor) {
  return function (selection) {
    var tooltipDiv;
    var bodyNode = d3.select('body').node();
    selection.on("mouseover", function (d, i) {
      // Clean up lost tooltips
      d3.select('body').selectAll('div.tooltip').remove();
      // Append tooltip
      tooltipDiv = d3.select('body').append('div').attr('class', 'tooltip');
      var absoluteMousePos = d3.mouse(bodyNode);
      tooltipDiv.style('left', (absoluteMousePos[0] + 10) + 'px')
        .style('top', (absoluteMousePos[1] - 15) + 'px')
        .style('position', 'absolute')
        .style('z-index', 1001);
      // Add text using the accessor function
      var tooltipText = accessor(d, i) || '';
      // Crop text arbitrarily
      //tooltipDiv.style('width', function(d, i){return (tooltipText.length > 80) ? '300px' : null;})
      //    .html(tooltipText);
    })
      .on('mousemove', function (d, i) {
      // Move tooltip
      var absoluteMousePos = d3.mouse(bodyNode);
      tooltipDiv.style('left', (absoluteMousePos[0] + 10) + 'px')
        .style('top', (absoluteMousePos[1] - 15) + 'px');
      var tooltipText = accessor(d, i) || '';
      tooltipDiv.html(tooltipText);
    })
      .on("mouseout", function (d, i) {
      // Remove tooltip
      tooltipDiv.remove();
    });

  };
};