spatialreference/dist/index.js

A helper library for translating spatial reference systems

var request = require('request')
var fixWkt = require('./fixwkt')
var esriCodes = require('@esri/proj-codes')

/**
 * Define the SpatialReference class
 */
var SpatialReference = function SpatialReference (options) {
  // If a db was passed in, ensure it has required methods, then add to instance
  if (options.db && options.db.getWKT && options.db.insertWKT) {
    this.db = options.db
  } else if (options.db) {
    throw new Error('Passed in db does not support getWKT or insertWKT')
  }
  // Add optional logger to instance
  this.logger = options.logger
};

/**
 * Convert a wkid to a wkt, by 1) looking in db, 2) check ESRI lookups, 3) asking epsg.io
 * @param {integer} wkid
 * @param {function} callback
 */
SpatialReference.prototype.wkidToWkt = function wkidToWkt (wkid, callback) {
    var this$1 = this;

  // If a db used, check there first
  if (this.db) {
    getFromDB.call(this, wkid)
      .then(function (wkt) {
        if (wkt) {
          return callback(null, fixWkt(wkt))
        }
        // If wkt was not found in db, check Esri lookup
        wkt = getWktFromEsri(wkid)
        if (wkt) { return wkt }

        // If wkt was not found in Esri lookup, check EPSG
        return getFromApi(wkid)
      })
      .then(function (wkt) {
        // If the wkt
        if (!wkt) { return }

        // Insert into DB
        return this$1.db.insertWKT(wkid, wkt, function (err) {
          if (err) { log.call(this$1, 'error', 'Failed to insert WKT into database: ' + wkid + ' ' + wkt + ', ' + err.message) }
          // Log DB insertion error, but pass on wkt to callback
          callback(null, fixWkt(wkt))
        })
      })
      .catch(function (err) {
        log(this$1, 'error', err.message)
        return callback(err)
      })
  } else {
    // No db, look in Esri first
    var wkt = getWktFromEsri(wkid)

    // If wkt found in Esri, execute callback and end here
    if (wkt) { return callback(null, fixWkt(wkt)) }

    // If not found in Esri, look in EPSG
    getFromApi(wkid)
      .then(function (wkt) {
        return callback(null, fixWkt(wkt))
      })
      .catch(function (err) {
        log(this$1, 'error', err.message)
        return callback(err)
      })
  }
};

/**
 * Wrapper around ESRI lookup
 * @param {integer} wkid
 * @param {function} callback
 */
SpatialReference.prototype.esriLookup = function esriLookup (wkid, callback) {
  var wkt = getWktFromEsri(wkid)
  if (!wkt) {
    log.call(this, 'error', 'WKT not found for WKID: ' + wkid)
    return callback(new Error('WKT not found'))
  }
  callback(null, wkt)
};

/**
 * Check the DB to see if it already contains the wkid
 * @param {integer} wkid
 */
function getFromDB (wkid) {
  var this$1 = this;

  return new Promise(function (resolve, reject) {
    this$1.db.getWKT(wkid, function (err, wkt) {
      if (err) { reject(err) }
      if (!wkt) { resolve() }
      resolve(wkt)
    })
  })
}

/**
 * Request WKT for a wkid from epsg.io
 * @param {integer} wkid
 */
function getFromApi (wkid) {
  var url = 'http://epsg.io/' + wkid + '.wkt'
  return new Promise(function (resolve, reject) {
    request.get(url, function (err, res, body) {
      if (err) { reject(err) }
      if (res.statusCode >= 400) { reject(new Error(("Request to " + url + " returned with status " + (res.statusCode) + "."))) }
      resolve(body)
    })
  })
}

/**
 * Look in current and deprecated ESRI projection codes
 * @param {integer} wkid
 */
function getWktFromEsri (wkid) {
  var result = esriCodes.lookup(wkid)
  if (result) { return result.wkt }
}

/**
 * Log messages
 * @param {string} level
 * @param {string} message
 */
function log (level, message) {
  if (!this.logger) { return console.error(message) }
  this.logger.log(level, message)
}

module.exports = SpatialReference