loopback-datasource-juggler/lib/geo.js

// Copyright IBM Corp. 2013,2016. All Rights Reserved.
// Node module: loopback-datasource-juggler
// This file is licensed under the MIT License.
// License text available at https://opensource.org/licenses/MIT

'use strict';

const assert = require('assert');

/*!
 * Get a near filter from a given where object. For connector use only.
 */

exports.nearFilter = function nearFilter(where) {
  const nearResults = [];
  nearSearch(where);
  return (!nearResults.length ? false : nearResults);

  function nearSearch(clause, parentKeys) {
    if (typeof clause !== 'object') {
      return false;
    }
    parentKeys = parentKeys || [];

    Object.keys(clause).forEach(function(clauseKey) {
      if (typeof clause[clauseKey] !== 'object' || !clause[clauseKey]) return;
      if (Array.isArray(clause[clauseKey])) {
        clause[clauseKey].forEach(function(el, index) {
          const ret = nearSearch(el, parentKeys.concat(clauseKey).concat(index));
          if (ret) return ret;
        });
      } else {
        if (clause[clauseKey].hasOwnProperty('near')) {
          const result = clause[clauseKey];
          nearResults.push({
            near: result.near,
            maxDistance: result.maxDistance,
            minDistance: result.minDistance,
            unit: result.unit,
            // If key is at root, define a single string, otherwise append it to the full path array
            mongoKey: parentKeys.length ? parentKeys.concat(clauseKey) : clauseKey,
            key: clauseKey,
          });
        }
      }
    });
  }
};

/*!
 * Filter a set of results using the given filters returned by `nearFilter()`.
 * Can support multiple locations, but will include results from all of them.
 *
 * WARNING: "or" operator with GeoPoint does not work as expected, eg:
 * {where: {or: [{location: {near: (29,-90)}},{name:'Sean'}]}}
 * Will actually work as if you had used "and".  This is because geo filtering
 * takes place outside of the SQL query, so the result set of "name = Sean" is
 * returned by the database, and then the location filtering happens in the app
 * logic.  So the "near" operator is always an "and" of the SQL filters, and "or"
 * of other GeoPoint filters.
 *
 * Additionally, since this step occurs after the SQL result set is returned,
 * if using GeoPoints with pagination the result set may be smaller than the
 * page size.  The page size is enforced at the DB level, and then we may
 * remove results at the Geo-app level.  If we "limit: 25", but 4 of those results
 * do not have a matching geopoint field, the request will only return 21 results.
 * This may make it erroneously look like a given page is the end of the result set.
 */

exports.filter = function(rawResults, filters) {
  const distances = {};
  const results = [];

  filters.forEach(function(filter) {
    const origin = filter.near;
    const max = filter.maxDistance > 0 ? filter.maxDistance : false;
    const min = filter.minDistance > 0 ? filter.minDistance : false;
    const unit = filter.unit;
    const key = filter.key;

    // create distance index
    rawResults.forEach(function(result) {
      let loc = result[key];

      // filter out results without locations
      if (!loc) return;

      if (!(loc instanceof GeoPoint)) loc = GeoPoint(loc);

      if (typeof loc.lat !== 'number') return;
      if (typeof loc.lng !== 'number') return;

      const d = GeoPoint.distanceBetween(origin, loc, {type: unit});

      // filter result if distance is either < minDistance or > maxDistance
      if ((min && d < min) || (max && d > max)) return;

      distances[result.id] = d;
      results.push(result);
    });

    results.sort(function(resA, resB) {
      const a = resA[key];
      const b = resB[key];

      if (a && b) {
        const da = distances[resA.id];
        const db = distances[resB.id];

        if (db === da) return 0;
        return da > db ? 1 : -1;
      } else {
        return 0;
      }
    });
  });

  return results;
};

exports.GeoPoint = GeoPoint;

/**
 * The GeoPoint object represents a physical location.
 *
 * For example:
 *
 * ```js
 * var loopback = require(‘loopback’);
 * var here = new loopback.GeoPoint({lat: 10.32424, lng: 5.84978});
 * ```
 *
 * Embed a latitude / longitude point in a model.
 *
 * ```js
 * var CoffeeShop = loopback.createModel('coffee-shop', {
 *   location: 'GeoPoint'
 * });
 * ```
 *
 * You can query LoopBack models with a GeoPoint property and an attached data source using geo-spatial filters and
 * sorting. For example, the following code finds the three nearest coffee shops.
 *
 * ```js
 * CoffeeShop.attachTo(oracle);
 * var here = new GeoPoint({lat: 10.32424, lng: 5.84978});
 * CoffeeShop.find( {where: {location: {near: here}}, limit:3}, function(err, nearbyShops) {
 *   console.info(nearbyShops); // [CoffeeShop, ...]
 * });
 * ```
 * @class GeoPoint
 * @property {Number} lat The latitude in degrees.
 * @property {Number} lng The longitude in degrees.
 *
 * @options {Object} Options Object with two Number properties: lat and long.
 * @property {Number} lat The latitude point in degrees. Range: -90 to 90.
 * @property {Number} lng The longitude point in degrees. Range: -180 to 180.
 *
 * @options {Array} Options Array with two Number entries: [lat,long].
 * @property {Number} lat The latitude point in degrees. Range: -90 to 90.
 * @property {Number} lng The longitude point in degrees. Range: -180 to 180.
 */

function GeoPoint(data) {
  if (!(this instanceof GeoPoint)) {
    return new GeoPoint(data);
  }

  if (arguments.length === 2) {
    data = {
      lat: arguments[0],
      lng: arguments[1],
    };
  }

  assert(Array.isArray(data) || typeof data === 'object' || typeof data === 'string',
    'must provide valid geo-coordinates array [lat, lng] or object or a "lat, lng" string');

  if (typeof data === 'string') {
    try {
      data = JSON.parse(data);
    } catch (err) {
      data = data.split(/,\s*/);
      assert(data.length === 2, 'must provide a string "lat,lng" creating a GeoPoint with a string');
    }
  }
  if (Array.isArray(data)) {
    data = {
      lat: Number(data[0]),
      lng: Number(data[1]),
    };
  } else {
    data.lng = Number(data.lng);
    data.lat = Number(data.lat);
  }

  assert(typeof data === 'object', 'must provide a lat and lng object when creating a GeoPoint');
  assert(typeof data.lat === 'number' && !isNaN(data.lat), 'lat must be a number when creating a GeoPoint');
  assert(typeof data.lng === 'number' && !isNaN(data.lng), 'lng must be a number when creating a GeoPoint');
  assert(data.lng <= 180, 'lng must be <= 180');
  assert(data.lng >= -180, 'lng must be >= -180');
  assert(data.lat <= 90, 'lat must be <= 90');
  assert(data.lat >= -90, 'lat must be >= -90');

  this.lat = data.lat;
  this.lng = data.lng;
}

/**
 * Determine the spherical distance between two GeoPoints.
 *
 * @param  {GeoPoint} pointA Point A
 * @param  {GeoPoint} pointB Point B
 * @options  {Object} options Options object with one key, 'type'.  See below.
 * @property {String} type Unit of measurement, one of:
 *
 * - `miles` (default)
 * - `radians`
 * - `kilometers`
 * - `meters`
 * - `miles`
 * - `feet`
 * - `degrees`
 */

GeoPoint.distanceBetween = function distanceBetween(a, b, options) {
  if (!(a instanceof GeoPoint)) {
    a = GeoPoint(a);
  }
  if (!(b instanceof GeoPoint)) {
    b = GeoPoint(b);
  }

  const x1 = a.lat;
  const y1 = a.lng;

  const x2 = b.lat;
  const y2 = b.lng;

  return geoDistance(x1, y1, x2, y2, options);
};

/**
 * Determine the spherical distance to the given point.
 * Example:
 * ```js
 * var loopback = require(‘loopback’);
 *
 * var here = new loopback.GeoPoint({lat: 10, lng: 10});
 * var there = new loopback.GeoPoint({lat: 5, lng: 5});
 *
 * loopback.GeoPoint.distanceBetween(here, there, {type: 'miles'}) // 438
 * ```
 * @param {Object} point GeoPoint object to which to measure distance.
 * @options  {Object} options Options object with one key, 'type'.  See below.
 * @property {String} type Unit of measurement, one of:
 *
 * - `miles` (default)
 * - `radians`
 * - `kilometers`
 * - `meters`
 * - `miles`
 * - `feet`
 * - `degrees`
 */

GeoPoint.prototype.distanceTo = function(point, options) {
  return GeoPoint.distanceBetween(this, point, options);
};

/**
 * Simple serialization.
 */

GeoPoint.prototype.toString = function() {
  return this.lat + ',' + this.lng;
};

/**
 * @property {Number} DEG2RAD - Factor to convert degrees to radians.
 * @property {Number} RAD2DEG - Factor to convert radians to degrees.
 * @property {Object} EARTH_RADIUS - Radius of the earth.
*/

// factor to convert degrees to radians
const DEG2RAD = 0.01745329252;

// factor to convert radians degrees to degrees
const RAD2DEG = 57.29577951308;

// radius of the earth
const EARTH_RADIUS = {
  kilometers: 6370.99056,
  meters: 6370990.56,
  miles: 3958.75,
  feet: 20902200,
  radians: 1,
  degrees: RAD2DEG,
};

function geoDistance(x1, y1, x2, y2, options) {
  const type = (options && options.type) || 'miles';

  // Convert to radians
  x1 = x1 * DEG2RAD;
  y1 = y1 * DEG2RAD;
  x2 = x2 * DEG2RAD;
  y2 = y2 * DEG2RAD;

  // use the haversine formula to calculate distance for any 2 points on a sphere.
  // ref http://en.wikipedia.org/wiki/Haversine_formula
  const haversine = function(a) {
    return Math.pow(Math.sin(a / 2.0), 2);
  };

  const f = Math.sqrt(haversine(x2 - x1) + Math.cos(x2) * Math.cos(x1) * haversine(y2 - y1));

  return 2 * Math.asin(f) * EARTH_RADIUS[type];
}