"use strict";

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

var zoom = d3.behavior.zoom()
    .translate([0, 0])
    .scale(1)
    .scaleExtent([.5, 8])
    .on("zoom", zoomed);

var path = d3.geo.path()
    .pointRadius(3)
    .projection(null);

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

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

var g = svg.append("g");

svg.call(zoom)
    .call(zoom.event);

d3.json("railroads.json", function(error, rr) {
  window.rr = rr;
  g.append("g")
      .attr("class", "feature feature--state")
    .selectAll("path")
      .data(topojson.feature(rr, rr.objects.states).features)
    .enter().append("path")
      .attr("d", path)
      .on("click", clicked);

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

  g.append("g")
      .attr("class", "feature feature--railroad")
    .selectAll("path")
      .data(topojson.feature(rr, rr.objects.railroads).features)
    .enter().append("path")
      .attr("d", path);

  g.append("g")
      .attr("class", "feature feature--station")
    .selectAll("path")
      .data(topojson.feature(rr, rr.objects.stations).features)
    .enter().append("path")
      .attr("d", path)
      .on("click", clicked);

  svg.call(zoom.scale(0.5).event);
});

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 = Math.min(.9 / Math.max(dx / width, dy / height), zoom.scaleExtent()[1]),
      translate = [width / 2 - scale * x, height / 2 - scale * y];

  svg.transition()
      .duration(750)
      .call(zoom.translate(translate).scale(scale).event);
}

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

  svg.transition()
      .duration(750)
      .call(zoom.translate([0, 0]).scale(.5).event);
}

function zoomed() {
  g.style("stroke-width", 1.0 / d3.event.scale + "px");
  g.attr("transform", "translate(" + d3.event.translate + ")scale(" + d3.event.scale + ")");

  path.pointRadius(5 / (d3.event.scale + .45));
  g.selectAll("g.feature--station path").attr("d", path);
  g.selectAll("g.boundary--states").style("stroke-width", .8 / d3.event.scale + "px");
}

function stopped() {
  if (d3.event.defaultPrevented) d3.event.stopPropagation();
}