'use strict';

var meta = require('@turf/meta');
var helpers = require('@turf/helpers');

/**
 * Smooths a {@link Polygon} or {@link MultiPolygon}. Based on [Chaikin's algorithm](http://graphics.cs.ucdavis.edu/education/CAGDNotes/Chaikins-Algorithm/Chaikins-Algorithm.html).
 * Warning: may create degenerate polygons.
 *
 * @name polygonSmooth
 * @param {FeatureCollection|Feature<Polygon|MultiPolygon>} inputPolys (Multi)Polygon(s) to smooth
 * @param {Object} [options={}] Optional parameters
 * @param {string} [options.iterations=1] THe number of times to smooth the polygon. A higher value means a smoother polygon.
 * @returns {FeatureCollection<Polygon>} FeatureCollection containing the smoothed polygon/poylgons
 * @example
 * var polygon = turf.polygon([[[11, 0], [22, 4], [31, 0], [31, 11], [21, 15], [11, 11], [11, 0]]]);
 *
 * var smoothed = turf.polygonSmooth(polygon, {iterations: 3})
 *
 * //addToMap
 * var addToMap = [smoothed, polygon];
 */
function polygonSmooth(inputPolys, options) {
  var outPolys = [];
  // Optional parameters
  var iterations = options.iterations || 1;
  if (!inputPolys) throw new Error("inputPolys is required");

  meta.geomEach(inputPolys, function (geom, geomIndex, properties) {
    var outCoords;
    var poly;
    var tempOutput;

    switch (geom.type) {
      case "Polygon":
        outCoords = [[]];
        for (var i = 0; i < iterations; i++) {
          tempOutput = [[]];
          poly = geom;
          if (i > 0) poly = helpers.polygon(outCoords).geometry;
          processPolygon(poly, tempOutput);
          outCoords = tempOutput.slice(0);
        }
        outPolys.push(helpers.polygon(outCoords, properties));
        break;
      case "MultiPolygon":
        outCoords = [[[]]];
        for (var y = 0; y < iterations; y++) {
          tempOutput = [[[]]];
          poly = geom;
          if (y > 0) poly = helpers.multiPolygon(outCoords).geometry;
          processMultiPolygon(poly, tempOutput);
          outCoords = tempOutput.slice(0);
        }
        outPolys.push(helpers.multiPolygon(outCoords, properties));
        break;
      default:
        throw new Error("geometry is invalid, must be Polygon or MultiPolygon");
    }
  });
  return helpers.featureCollection(outPolys);
}

/**
 * @param {poly} poly to process
 * @param {poly} tempOutput to place the results in
 * @private
 */
function processPolygon(poly, tempOutput) {
  var prevGeomIndex = 0;
  var subtractCoordIndex = 0;

  meta.coordEach(
    poly,
    function (
      currentCoord,
      coordIndex,
      featureIndex,
      multiFeatureIndex,
      geometryIndex
    ) {
      if (geometryIndex > prevGeomIndex) {
        prevGeomIndex = geometryIndex;
        subtractCoordIndex = coordIndex;
        tempOutput.push([]);
      }
      var realCoordIndex = coordIndex - subtractCoordIndex;
      var p1 = poly.coordinates[geometryIndex][realCoordIndex + 1];
      var p0x = currentCoord[0];
      var p0y = currentCoord[1];
      var p1x = p1[0];
      var p1y = p1[1];
      tempOutput[geometryIndex].push([
        0.75 * p0x + 0.25 * p1x,
        0.75 * p0y + 0.25 * p1y,
      ]);
      tempOutput[geometryIndex].push([
        0.25 * p0x + 0.75 * p1x,
        0.25 * p0y + 0.75 * p1y,
      ]);
    },
    true
  );
  tempOutput.forEach(function (ring) {
    ring.push(ring[0]);
  });
}

/**
 * @param {poly} poly to process
 * @param {poly} tempOutput to place the results in
 * @private
 */
function processMultiPolygon(poly, tempOutput) {
  var prevGeomIndex = 0;
  var subtractCoordIndex = 0;
  var prevMultiIndex = 0;

  meta.coordEach(
    poly,
    function (
      currentCoord,
      coordIndex,
      featureIndex,
      multiFeatureIndex,
      geometryIndex
    ) {
      if (multiFeatureIndex > prevMultiIndex) {
        prevMultiIndex = multiFeatureIndex;
        subtractCoordIndex = coordIndex;
        tempOutput.push([[]]);
      }
      if (geometryIndex > prevGeomIndex) {
        prevGeomIndex = geometryIndex;
        subtractCoordIndex = coordIndex;
        tempOutput[multiFeatureIndex].push([]);
      }
      var realCoordIndex = coordIndex - subtractCoordIndex;
      var p1 =
        poly.coordinates[multiFeatureIndex][geometryIndex][realCoordIndex + 1];
      var p0x = currentCoord[0];
      var p0y = currentCoord[1];
      var p1x = p1[0];
      var p1y = p1[1];
      tempOutput[multiFeatureIndex][geometryIndex].push([
        0.75 * p0x + 0.25 * p1x,
        0.75 * p0y + 0.25 * p1y,
      ]);
      tempOutput[multiFeatureIndex][geometryIndex].push([
        0.25 * p0x + 0.75 * p1x,
        0.25 * p0y + 0.75 * p1y,
      ]);
    },
    true
  );

  tempOutput.forEach(function (poly) {
    poly.forEach(function (ring) {
      ring.push(ring[0]);
    });
  });
}

module.exports = polygonSmooth;
module.exports.default = polygonSmooth;