var margin = {top: 20, right: 20, bottom: 30, left: 50},
    width = 600 - margin.left - margin.right,
    height = 300 - margin.top - margin.bottom;


var data = ['profile.json', 'profile_short.json', 'profile_long_flat.json', 'profile_long_not_flat.json'];

d3.json(data[0], function(data) {
            drawChart(data);
        });
function drawChart(data) {
    d3.select("#chart").html("");

    var x = d3.scale.linear()
        .range([0, width]);

    var y = d3.scale.linear()
        .range([height, 0]);

    var xAxis = d3.svg.axis()
        .scale(x)
        .orient("bottom");

    var yAxis = d3.svg.axis()
        .scale(y)
        .orient("left");

    var area = d3.svg.area()
        .x(function(d) { return x(d.dist); })
        .y0(height)
        .y1(function(d) { return y(d.alts.DTM25); });

    var svg = d3.select("#chart").append("svg")
        .attr("width", width + margin.left + margin.right)
        .attr("height", height + margin.top + margin.bottom)
      .append("g")
        .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

  var xDomain = d3.extent(data, function(d) { return d.dist; });
  x.domain(xDomain);

  var yDomain = [d3.min(data, function(d) { return d.alts.DTM25; }),
                 d3.max(data, function(d) { return d.alts.DTM25; })];

  y.domain(yDomain);

  var xResolution = (xDomain[1] - xDomain[0]) / width;
  var yResolution = (yDomain[1] - yDomain[0]) / height;
  var ratioXY = yResolution / xResolution;


  var ratios = [0.05, 0.1, 0.2];
  // determine the more appropriate ratio
  for (var i = 0; i < ratios.length; i++) {
      if (ratioXY <= ratios[i]) {
          ratioXY = ratios[i];
          break;
      }
  }

  // change the domain accordingly
  var mean = (yDomain[1] - yDomain[0])  / 2 + yDomain[0];
  y.domain([mean - (xResolution * ratioXY) * height / 2,
           mean + (xResolution * ratioXY) * height / 2]);

  svg.append("path")
      .datum(data)
      .attr("class", "area")
      .attr("d", area);

  svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);

  svg.append("g")
      .attr("class", "y axis")
      .call(yAxis);

  d3.select('#ratio').text(1 / ratioXY);
}