var GaugeChart = {
  init: function(svg, html_tag_attr, min, current, max){
    console.log(min, current, max);
    var startAngle = -Math.PI/2,
        tau = Math.PI/2,
        C = tau/max;
        console.log(tau, max, C, (current*C));
        
    var width = $(html_tag_attr).width(),
        height = $(html_tag_attr).height(),
        coeff = height / 2,
        size = 15,
        g = svg.append("g").attr("transform", "translate(" + ((width / 2) - size) + "," + (height - height/2) + ")");
    
    var arc = d3.arc()
        .innerRadius(height - coeff)
        .outerRadius(height - coeff - size)
        .startAngle(startAngle);
  
    // Add the background arc, from 0 to 100% (tau).
    var background = g.append("path")
        .datum({endAngle: tau})
        .style("fill", "#ddd")
        .attr("d", arc);
    
    // Add the foreground arc in orange, currently showing 12.7%.
    var foreground = g.append("path")
        .datum({endAngle: (current/max*C)/startAngle })
        .style("fill", "orange")
        .attr("d", arc);
  },
};