'use strict';

const MAX_ATLAS = 255;
const MAX_TILE = 1048575;
const MAX_ROT = 3;
const MAX_U32 = 0xFFFFFFFF;

function checkInt(name, value, min, max) {
  if (!Number.isInteger(value) || value < min || value > max) {
    throw new RangeError(`${name} ${value} out of range [${min},${max}]`);
  }
}

function encodeGid(atlas, tile, rotation = 0) {
  checkInt('atlas', atlas, 0, MAX_ATLAS);
  checkInt('tile', tile, 0, MAX_TILE);
  checkInt('rotation', rotation, 0, MAX_ROT);
  return ((atlas << 24) | (tile << 4) | (rotation << 2)) >>> 0;
}

function decodeGid(gid) {
  checkInt('gid', gid, 0, MAX_U32);
  return {
    atlas: (gid >>> 24) & 0xFF,
    tile: (gid >>> 4) & 0xFFFFF,
    rotation: (gid >>> 2) & 0x3,
  };
}

module.exports = { encodeGid, decodeGid, MAX_ATLAS, MAX_TILE, MAX_ROT };