ParsePolygon.ts

import ParseGeoPoint from './ParseGeoPoint';
type Coordinate = [number, number];
type Coordinates = Coordinate[];

/**
 * Creates a new Polygon with any of the following forms:<br>
 *   <pre>
 *   new Polygon([[0,0],[0,1],[1,1],[1,0]])
 *   new Polygon([GeoPoint, GeoPoint, GeoPoint])
 *   </pre>
 *
 * <p>Represents a coordinates that may be associated
 * with a key in a ParseObject or used as a reference point for geo queries.
 * This allows proximity-based queries on the key.</p>
 *
 * <p>Example:<pre>
 *   var polygon = new Parse.Polygon([[0,0],[0,1],[1,1],[1,0]]);
 *   var object = new Parse.Object("PlaceObject");
 *   object.set("area", polygon);
 *   object.save();</pre></p>
 *
 * @alias Parse.Polygon
 */
class ParsePolygon {
  _coordinates: Coordinates;

  /**
   * @param {(Coordinates | Parse.GeoPoint[])} coordinates An Array of coordinate pairs
   */
  constructor(coordinates: Coordinates | ParseGeoPoint[]) {
    this._coordinates = ParsePolygon._validate(coordinates);
  }

  /**
   * Coordinates value for this Polygon.
   * Throws an exception if not valid type.
   *
   * @property {(Coordinates | Parse.GeoPoint[])} coordinates list of coordinates
   * @returns {Coordinates}
   */
  get coordinates(): Coordinates {
    return this._coordinates;
  }

  set coordinates(coords: Coordinates | ParseGeoPoint[]) {
    this._coordinates = ParsePolygon._validate(coords);
  }

  /**
   * Returns a JSON representation of the Polygon, suitable for Parse.
   *
   * @returns {object}
   */
  toJSON(): { __type: string; coordinates: Coordinates } {
    ParsePolygon._validate(this._coordinates);
    return {
      __type: 'Polygon',
      coordinates: this._coordinates,
    };
  }

  /**
   * Checks if two polygons are equal
   *
   * @param {(Parse.Polygon | object)} other
   * @returns {boolean}
   */
  equals(other: ParsePolygon | any): boolean {
    if (!(other instanceof ParsePolygon) || this.coordinates.length !== other.coordinates.length) {
      return false;
    }
    let isEqual = true;

    for (let i = 1; i < this._coordinates.length; i += 1) {
      if (
        this._coordinates[i][0] != other.coordinates[i][0] ||
        this._coordinates[i][1] != other.coordinates[i][1]
      ) {
        isEqual = false;
        break;
      }
    }
    return isEqual;
  }

  /**
   *
   * @param {Parse.GeoPoint} point
   * @returns {boolean} Returns if the point is contained in the polygon
   */
  containsPoint(point: ParseGeoPoint): boolean {
    let minX = this._coordinates[0][0];
    let maxX = this._coordinates[0][0];
    let minY = this._coordinates[0][1];
    let maxY = this._coordinates[0][1];

    for (let i = 1; i < this._coordinates.length; i += 1) {
      const p = this._coordinates[i];
      minX = Math.min(p[0], minX);
      maxX = Math.max(p[0], maxX);
      minY = Math.min(p[1], minY);
      maxY = Math.max(p[1], maxY);
    }

    const outside =
      point.latitude < minX ||
      point.latitude > maxX ||
      point.longitude < minY ||
      point.longitude > maxY;
    if (outside) {
      return false;
    }

    let inside = false;
    for (let i = 0, j = this._coordinates.length - 1; i < this._coordinates.length; j = i++) {
      const startX = this._coordinates[i][0];
      const startY = this._coordinates[i][1];
      const endX = this._coordinates[j][0];
      const endY = this._coordinates[j][1];

      const intersect =
        startY > point.longitude != endY > point.longitude &&
        point.latitude < ((endX - startX) * (point.longitude - startY)) / (endY - startY) + startX;

      if (intersect) {
        inside = !inside;
      }
    }
    return inside;
  }

  /**
   * Validates that the list of coordinates can form a valid polygon
   *
   * @param {Array} coords the list of coordinates to validate as a polygon
   * @throws {TypeError}
   * @returns {number[][]} Array of coordinates if validated.
   */
  static _validate(coords: Coordinates | ParseGeoPoint[]): Coordinates {
    if (!Array.isArray(coords)) {
      throw new TypeError('Coordinates must be an Array');
    }
    if (coords.length < 3) {
      throw new TypeError('Polygon must have at least 3 GeoPoints or Points');
    }
    const points: Coordinates = [];
    for (let i = 0; i < coords.length; i += 1) {
      const coord = coords[i];
      let geoPoint;
      if (coord instanceof ParseGeoPoint) {
        geoPoint = coord;
      } else if (Array.isArray(coord) && coord.length === 2) {
        geoPoint = new ParseGeoPoint(coord[0], coord[1]);
      } else {
        throw new TypeError('Coordinates must be an Array of GeoPoints or Points');
      }
      points.push([geoPoint.latitude, geoPoint.longitude]);
    }
    return points;
  }
}

export default ParsePolygon;