export function decodePolyline(str: string, precision: number): number[][] {
  let index = 0,
    lat = 0,
    lng = 0,
    coordinates = [],
    shift = 0,
    result = 0,
    byte = null,
    latitude_change,
    longitude_change,
    factor = Math.pow(10, Number.isInteger(precision) ? precision : 5)

  // Coordinates have variable length when encoded, so just keep
  // track of whether we've hit the end of the string. In each
  // loop iteration, a single coordinate is decoded.
  while (index < str.length) {
    // Reset shift, result, and byte
    byte = null
    shift = 0
    result = 0

    do {
      byte = str.charCodeAt(index++) - 63
      result |= (byte & 0x1f) << shift
      shift += 5
    } while (byte >= 0x20)

    latitude_change = result & 1 ? ~(result >> 1) : result >> 1

    shift = result = 0

    do {
      byte = str.charCodeAt(index++) - 63
      result |= (byte & 0x1f) << shift
      shift += 5
    } while (byte >= 0x20)

    longitude_change = result & 1 ? ~(result >> 1) : result >> 1

    lat += latitude_change
    lng += longitude_change

    coordinates.push([lat / factor, lng / factor])
  }

  return coordinates
}