index.js

'use strict';

var extent = require('turf-extent');
var featurecollection = require('turf-featurecollection');
var inside = require('turf-inside');
var random = require('turf-random');

/**
 * Takes a number and a feature and {@link Polygon} or {@link MultiPolygon} and returns {@link Points} that reside inside the polygon. The polygon can
 * be convex or concave. The function accounts for holes.
 *
 * * Given a {Number}, the number of points to be randomly generated.
 * * Given a {@link Polygon} or {@link MultiPolygon}, the boundary of the random points
 *
 *
 * @module turf-random-points-on-polygon
 * @category measurement
 * @param {Number} number of points to be generated
 * @param {Feature<(Polygon|MultiPolygon)>} polygon input polygon or multipolygon
 * @param {Object} [properties={}] properties to be appended to the point features
 * @param {Boolean} [fc=false] if true returns points as a {@link FeatureCollection}
 * @return {Array} || {FeatureCollection<Points>} an array or feature collection of the random points inside the polygon
**/

function randomPointsOnPolygon(number, polygon, properties, fc) {
  if (typeof properties === 'boolean') {
    fc = properties;
    properties = {};
  }

  if (number < 1) {
    return new Error('Number must be >= 1');
  }

  if(polygon.type !== 'Feature') {
    return new Error('Polygon parameter must be a Feature<(Polygon|MultiPolygon)>');

    if (polygon.geomtry.type !== 'Polygon' || polygon.geomtry.type !== 'MutliPolygon') {
      return new Error('Polygon parameter must be a Feature<(Polygon|MultiPolygon)>')
    }
  }

  if (this instanceof randomPointsOnPolygon) {
    return new randomPointsOnPolygon(number, polygon, properties);
  }

  properties = properties || {};
  fc = fc || false;
  var points = [];
  var bbox = extent(polygon);
  var count = Math.round(parseFloat(number));

  for (var i = 0; i <= count; i++) {
    if (i === count) {
      if (fc) {
        return featurecollection(points);
      }

      return points;
    }

    var point = random('point', 1, { bbox: bbox });

    if (inside(point.features[0], polygon) === false) {
      i = --i;
    }

    if (inside(point.features[0], polygon) === true) {
      point.features[0].properties = properties;
      points.push(point.features[0]);
    }
  }

}

module.exports = randomPointsOnPolygon;