atriusmaps-node-sdk/dist/cjs/src/extModules/geohasher.js

This project provides an API to Atrius Personal Wayfinder maps within a Node environment. See the README.md for more information

'use strict';

// Ported from https://github.com/JacksonTian/geohasher
// to ESM as it was not bundling properly via Rollup as a CJS

// Geohash library for Javascript
// (c) 2008 David Troy
// (c) 2010 Chris Williams
// (c) 2013 Jackson Tian
// Distributed under the MIT License

const BITS = [16, 8, 4, 2, 1];

const BASE32 = '0123456789bcdefghjkmnpqrstuvwxyz';

const NEIGHBORS = {
  right: { even: 'bc01fg45238967deuvhjyznpkmstqrwx' },
  left: { even: '238967debc01fg45kmstqrwxuvhjyznp' },
  top: { even: 'p0r21436x8zb9dcf5h7kjnmqesgutwvy' },
  bottom: { even: '14365h7k9dcfesgujnmqp0r2twvyx8zb' }
};

const BORDERS = {
  right: { even: 'bcfguvyz' },
  left: { even: '0145hjnp' },
  top: { even: 'prxz' },
  bottom: { even: '028b' }
};

NEIGHBORS.bottom.odd = NEIGHBORS.left.even;
NEIGHBORS.top.odd = NEIGHBORS.right.even;
NEIGHBORS.left.odd = NEIGHBORS.bottom.even;
NEIGHBORS.right.odd = NEIGHBORS.top.even;

BORDERS.bottom.odd = BORDERS.left.even;
BORDERS.top.odd = BORDERS.right.even;
BORDERS.left.odd = BORDERS.bottom.even;
BORDERS.right.odd = BORDERS.top.even;

function calculateAdjacent (srcHash, dir) {
  srcHash = srcHash.toLowerCase();
  const lastChr = srcHash.charAt(srcHash.length - 1);
  const type = (srcHash.length % 2) ? 'odd' : 'even';
  let base = srcHash.substring(0, srcHash.length - 1);
  if (BORDERS[dir][type].indexOf(lastChr) !== -1) {
    base = calculateAdjacent(base, dir);
  }
  return base + BASE32[NEIGHBORS[dir][type].indexOf(lastChr)]
}

function encode (latitude, longitude, precision) {
  let isEven = 1;
  const lat = [-90, 90.0];
  const lng = [-180, 180.0];
  let bit = 0;
  let ch = 0;
  precision = precision || 12;

  let geohash = '';
  while (geohash.length < precision) {
    let mid;
    if (isEven) {
      mid = (lng[0] + lng[1]) / 2;
      if (longitude > mid) {
        ch |= BITS[bit];
        lng[0] = mid;
      } else {
        lng[1] = mid;
      }
    } else {
      mid = (lat[0] + lat[1]) / 2;
      if (latitude > mid) {
        ch |= BITS[bit];
        lat[0] = mid;
      } else {
        lat[1] = mid;
      }
    }

    isEven = !isEven;
    if (bit < 4) {
      bit++;
    } else {
      geohash += BASE32[ch];
      bit = 0;
      ch = 0;
    }
  }
  return geohash
}

exports.calculateAdjacent = calculateAdjacent;
exports.encode = encode;