/**
 * ObjectId from Mongodb
 */
function encodeInt(data: number, bits: number, forceBigEndian: boolean) {
  var max = Math.pow(2, bits);
  if (data >= max || data < -(max / 2)) {
    // console.warn("encodeInt::overflow");
    data = 0;
  }

  if (data < 0) {
    data += max;
  }

  for (var r: string[] = []; data; r[r.length] = String.fromCharCode(data % 256), data = Math.floor(data / 256));

  for (bits = -(-bits >> 3) - r.length; bits--; r[r.length] = "\0");

  return (forceBigEndian ? r.reverse() : r).join("");
};

/**
 * Machine id.
 *
 * Create a random 3-byte value (i.e. unique for this
 * process). Other drivers use a md5 of the machine id here, but
 * that would mean an asyc call to gethostname, so we don't bother.
 */

var MACHINE_ID = parseInt((Math.random() * 0xFFFFFF).toString(), 10);

export class ObjectId {
  constructor(
    public id?: string
  ) {
    // Throw an error if it's not a valid setup
    if (
      id != null &&
      (id.length != 12 && id.length != 24)
    ) throw new Error("Argument passed in must be a single String of 12 bytes or a string of 24 hex characters in hex format");
    // Generate id based on the input
    if (null == id) {
      this.id = this.generate();
    } else if (/^[0-9a-fA-F]{24}$/.test(id)) {
      var result = '', str, num;

      for (var index = 0; index < 24; index += 2) {
        str = id.substr(index, 2);
        num = parseInt(str, 16);
        result += encodeInt(num, 8, false);
      }
      this.id = result;
    } else {
      this.id = id;
    }
  }

  public generate(): string {
    var unixTime = parseInt((Date.now() / 1000).toString(), 10);
    var time4Bytes = encodeInt(unixTime, 32, true);
    var machine3Bytes = encodeInt(MACHINE_ID, 24, false);
    var pid2Bytes = encodeInt(process.pid, 24, false);
    var index3Bytes = encodeInt(this.get_inc(), 16, true);
    return time4Bytes + machine3Bytes + pid2Bytes + index3Bytes;
  }

  get_inc() {
    var self = <typeof ObjectId>this.constructor;
    return self.index = (self.index + 1) % 0xFFFF;
  };

  toHexString() {
    var hexString = '', num, value;

    for (var index = 0, len = this.id.length; index < len; index++) {
      value = this.id.charCodeAt(index);
      num = value <= 15
        ? '0' + value.toString(16)
        : value.toString(16);
      hexString = hexString + num;
    }
    return hexString;
  }

  public static index = 0;
}