(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('vega-dataflow'), require('vega-util'), require('d3-delaunay')) :
  typeof define === 'function' && define.amd ? define(['exports', 'vega-dataflow', 'vega-util', 'd3-delaunay'], factory) :
  (global = global || self, factory((global.vega = global.vega || {}, global.vega.transforms = {}), global.vega, global.vega, global.d3));
}(this, (function (exports, vegaDataflow, vegaUtil, d3Delaunay) { 'use strict';

  function Voronoi(params) {
    vegaDataflow.Transform.call(this, null, params);
  }

  Voronoi.Definition = {
    'type': 'Voronoi',
    'metadata': {'modifies': true},
    'params': [
      { 'name': 'x', 'type': 'field', 'required': true },
      { 'name': 'y', 'type': 'field', 'required': true },
      { 'name': 'size', 'type': 'number', 'array': true, 'length': 2 },
      { 'name': 'extent', 'type': 'array', 'array': true, 'length': 2,
        'default': [[-1e5, -1e5], [1e5, 1e5]],
        'content': {'type': 'number', 'array': true, 'length': 2} },
      { 'name': 'as', 'type': 'string', 'default': 'path' }
    ]
  };

  const prototype = vegaUtil.inherits(Voronoi, vegaDataflow.Transform);

  const defaultExtent = [-1e5, -1e5, 1e5, 1e5];

  prototype.transform = function(_, pulse) {
    const as = _.as || 'path',
          data = pulse.source;

    // nothing to do if no data
    if (!data || !data.length) return pulse;

    // configure and construct voronoi diagram
    let s = _.size;
    s = s ? [0, 0, s[0], s[1]]
      : (s = _.extent) ? [s[0][0], s[0][1], s[1][0], s[1][1]]
      : defaultExtent;

    const voronoi = this.value = d3Delaunay.Delaunay.from(data, _.x, _.y).voronoi(s);

    // map polygons to paths
    for (let i=0, n=data.length; i<n; ++i) {
      const polygon = voronoi.cellPolygon(i);
      data[i][as] = polygon ? toPathString(polygon) : null;
    }

    return pulse.reflow(_.modified()).modifies(as);
  };

  // suppress duplicated end point vertices
  function toPathString(p) {
    const x = p[0][0],
          y = p[0][1];

    let n = p.length - 1;
    for (; p[n][0] === x && p[n][1] === y; --n);

    return 'M' + p.slice(0, n + 1).join('L') + 'Z';
  }

  exports.voronoi = Voronoi;

  Object.defineProperty(exports, '__esModule', { value: true });

})));