var width = 960,
    height = 500,
    active = d3.select(null);

var projection = d3.geo.albersUsa()
    .scale(1000)
    .translate([width / 2, height / 2]);

var path = d3.geo.path()
    .projection(projection);

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);

svg.append("rect")
    .attr("class", "background")
    .attr("width", width)
    .attr("height", height)
    .on("click", reset);

var g = svg.append("g")
    .style("stroke-width", "1.5px");

d3.json("us.json", function(error, us) {
  if (error) throw error;

  g.selectAll("path")
      .data(topojson.feature(us, us.objects.states).features)
    .enter().append("path")
      .attr("d", path)
      .attr("class", "feature")
      .on("click", clicked);

  g.append("path")
      .datum(topojson.mesh(us, us.objects.states, function(a, b) { return a !== b; }))
      .attr("class", "mesh")
      .attr("d", path);
});


d3.json("https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_week.geojson", function(raw) {

  // strips the data into a much simpler flat format and removes
  // data points outside the US (ie. outside the clipping bounds of the projection)
  var data = raw["features"].map(function(d) {
    return {"magnitude": d["properties"]["mag"], "coordinates": d["geometry"]["coordinates"].slice(0,-1)}
  }).filter(function(d) {
    return projection(d.coordinates) !== null;
  })

  var scale = d3.scale.linear()
      .domain([1,10])
      .range([0,60]);

  var circles = svg.selectAll("circle")
       .data(data)
     .enter().append("circle");

  circles
      .attr("cx", function(d,i) {
        return projection(d.coordinates)[0];
      })
      .attr("cy", function(d,i) {
        return projection(d.coordinates)[1];
      })
      .attr("r", function(d,i) {
        return scale(d.magnitude);
      })
      .style("fill", "steelblue")
      .style("fill-opacity", 0.5);

});




function clicked(d) {
  if (active.node() === this) return reset();
  active.classed("active", false);
  active = d3.select(this).classed("active", true);

  var bounds = path.bounds(d),
      dx = bounds[1][0] - bounds[0][0],
      dy = bounds[1][1] - bounds[0][1],
      x = (bounds[0][0] + bounds[1][0]) / 2,
      y = (bounds[0][1] + bounds[1][1]) / 2,
      scale = .9 / Math.max(dx / width, dy / height),
      translate = [width / 2 - scale * x, height / 2 - scale * y];

  g.transition()
      .duration(750)
      .style("stroke-width", 1.5 / scale + "px")
      .attr("transform", "translate(" + translate + ")scale(" + scale + ")");
}

function reset() {
  active.classed("active", false);
  active = d3.select(null);

  g.transition()
      .duration(750)
      .style("stroke-width", "1.5px")
      .attr("transform", "");
}