var canvasAny = d3.select("canvas#any"),
  ctxAny = canvasAny.node().getContext("2d"),
  canvasAnyWidth = +canvasAny.attr("width"),
  canvasAnyHeight = +canvasAny.attr("height");

var projectionAny = d3
  .geoMercator()
  .rotate([-160, 0, -23.4])
  .fitSize([canvasAnyWidth, canvasAnyHeight], {
    type: "Sphere"
  });

var geoPathGeneratorAny = d3
  .geoPath()
  .projection(projectionAny)
  .context(ctxAny);

var canvasOrtho = d3.select("canvas#ortho"),
  ctxOrtho = canvasOrtho.node().getContext("2d"),
  canvasOrthoWidth = +canvasOrtho.attr("width"),
  canvasOrthoHeight = +canvasOrtho.attr("height");

var projectionOrtho = d3
  .geoOrthographic()
  .rotate([-160, 0, -23.4])
  .fitSize([canvasOrthoWidth, canvasOrthoHeight], {
    type: "Sphere"
  });

var geoPathGeneratorOrtho = d3
  .geoPath()
  .projection(projectionOrtho)
  .context(ctxOrtho);

var selectElement = document.querySelector("select#projectionChoice");
selectElement.addEventListener("change", function(evt) {
  changeProjection(evt.target.value);
});

var axialTilt = -23.4;

var axialTiltElement = document.querySelector("input#axialTilt");
axialTiltElement.addEventListener("change", function(evt) {
  changeAxialTilt(evt.target.checked);
});

var geoCircles = {
  type: "GeometryCollection",
  geometries: []
};

for (var longitude = -180; longitude < 180; longitude += 15) {
  for (var latitude = -90; latitude <= 90; latitude += 15) {
    geoCircles.geometries.push(
      d3
        .geoCircle()
        .center([longitude, latitude])
        .radius(1)()
    );
  }
}

drawSphereAndCircles(geoCircles);

d3
  .json("https://unpkg.com/world-atlas@1.1.4/world/110m.json")
  .then(function(loadedTopoJson) {
    var topology = topojson.presimplify(loadedTopoJson);
    topology = topojson.simplify(topology, 1.1);
    var worldGeoJson = topojson.feature(
      topology,
      topology.objects.land
    );

    d3.timer(function(elapsed) {
      geoPathGeneratorAny
        .projection()
        .rotate([elapsed * 0.005 - 160, 0, axialTilt]);

      geoPathGeneratorOrtho
        .projection()
        .rotate([elapsed * 0.005 - 160, 0, axialTilt]);

      ctxOrtho.clearRect(0, 0, canvasOrthoWidth, canvasOrthoHeight);
      ctxAny.clearRect(0, 0, canvasAnyWidth, canvasAnyHeight);

      drawWorld(worldGeoJson);

      drawSphereAndCircles(geoCircles);
    });

    var totalOptions = selectElement.options.length;
    var intervalTimer = d3.interval(function() {
      if (selectElement.selectedIndex === totalOptions - 1) {
        selectElement.selectedIndex = 1;
      } else {
        selectElement.selectedIndex++;
      }
      selectElement.dispatchEvent(new Event("change"));
    }, 2500);

    selectElement.addEventListener("focus", function() {
      intervalTimer.stop();
    });
  });

function drawWorld(worldGeoJson) {
  ctxOrtho.beginPath();
  ctxOrtho.fillStyle = "#b2df8a";
  geoPathGeneratorOrtho(worldGeoJson);
  ctxOrtho.fill();
  ctxOrtho.closePath();

  ctxAny.beginPath();
  ctxAny.fillStyle = "#b2df8a";
  geoPathGeneratorAny(worldGeoJson);
  ctxAny.fill();
  ctxAny.closePath();
}

function drawSphereAndCircles(geoCircles) {
  ctxOrtho.beginPath();
  ctxOrtho.fillStyle = "#1f78b4";
  geoPathGeneratorOrtho(geoCircles);
  ctxOrtho.fill();
  ctxOrtho.closePath();

  ctxOrtho.beginPath();
  ctxOrtho.strokeStyle = "#1f78b4";
  geoPathGeneratorOrtho({ type: "Sphere" });
  ctxOrtho.stroke();
  ctxOrtho.closePath();

  ctxAny.beginPath();
  ctxAny.fillStyle = "#1f78b4";
  geoPathGeneratorAny(geoCircles);
  ctxAny.fill();
  ctxAny.closePath();

  ctxAny.beginPath();
  ctxAny.strokeStyle = "#1f78b4";
  geoPathGeneratorAny({ type: "Sphere" });
  ctxAny.stroke();
  ctxAny.closePath();
}

function changeProjection(d3ProjectionName) {
  var newProjection = d3[d3ProjectionName]().fitSize(
    [canvasAnyWidth, canvasAnyHeight],
    {
      type: "Sphere"
    }
  );

  geoPathGeneratorAny.projection(newProjection);
}

function changeAxialTilt(checked) {
  var newAxialTilt = checked ? -23.4 : 0;

  d3
    .select({})
    .transition()
    .duration(1250)
    .tween(null, function() {
      var interpolator = d3.interpolate(axialTilt, newAxialTilt);
      return function(t) {
        axialTilt = interpolator(t);
      };
    });
}