import {hasOwnProperty} from "./object.js";

// Computes the bounding box of the specified hash of GeoJSON objects.
export default function(objects) {
  var x0 = Infinity,
      y0 = Infinity,
      x1 = -Infinity,
      y1 = -Infinity;

  function boundGeometry(geometry) {
    if (geometry != null && hasOwnProperty.call(boundGeometryType, geometry.type)) boundGeometryType[geometry.type](geometry);
  }

  var boundGeometryType = {
    GeometryCollection: function(o) { o.geometries.forEach(boundGeometry); },
    Point: function(o) { boundPoint(o.coordinates); },
    MultiPoint: function(o) { o.coordinates.forEach(boundPoint); },
    LineString: function(o) { boundLine(o.arcs); },
    MultiLineString: function(o) { o.arcs.forEach(boundLine); },
    Polygon: function(o) { o.arcs.forEach(boundLine); },
    MultiPolygon: function(o) { o.arcs.forEach(boundMultiLine); }
  };

  function boundPoint(coordinates) {
    var x = coordinates[0],
        y = coordinates[1];
    if (x < x0) x0 = x;
    if (x > x1) x1 = x;
    if (y < y0) y0 = y;
    if (y > y1) y1 = y;
  }

  function boundLine(coordinates) {
    coordinates.forEach(boundPoint);
  }

  function boundMultiLine(coordinates) {
    coordinates.forEach(boundLine);
  }

  for (var key in objects) {
    boundGeometry(objects[key]);
  }

  return x1 >= x0 && y1 >= y0 ? [x0, y0, x1, y1] : undefined;
}