/**
 * Decodes an encoded Polyline string into an array of [lng, lat] coordinates.
 * @param str The encoded polyline string
 * @param precision The precision of the coordinates (default 5 for Google Polyline)
 * @returns Array of [lng, lat] coordinates
 */
export function decodePolyline(str: string, precision: number = 5): [number, number][] {
  let index = 0;
  let lat = 0;
  let lng = 0;
  const coordinates: [number, number][] = [];
  let shift = 0;
  let result = 0;
  let byte: number | null = null;
  let latitude_change: number;
  let longitude_change: number;
  const factor = Math.pow(10, precision);

  while (index < str.length) {
    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));
    lat += latitude_change;

    shift = 0;
    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));
    lng += longitude_change;

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

  return coordinates;
}