'use strict';

import Util = require('../util/util');

// Discord epoch (2015-01-01T00:00:00.000Z)
const EPOCH = 1420070400000;
let INCREMENT = 0;

/**
 * A container for useful snowflake-related methods.
 */
export default class SnowflakeUtil {
  constructor() {
    throw new Error(`The ${this.constructor.name} class may not be instantiated.`);
  }

  /**
   * A Twitter snowflake, except the epoch is 2015-01-01T00:00:00.000Z
   * ```
   * If we have a snowflake '266241948824764416' we can represent it as binary:
   *
   * 64                                          22     17     12          0
   *  000000111011000111100001101001000101000000  00001  00000  000000000000
   *       number of ms since Discord epoch       worker  pid    increment
   * ```
   * @typedef {string} Snowflake
   */

  /**
   * Generates a Discord snowflake.
   * <info>This hardcodes the worker ID as 1 and the process ID as 0.</info>
   * @param {number|Date} [timestamp=Date.now()] Timestamp or date of the snowflake to generate
   * @returns {Snowflake} The generated snowflake
   */
  static generate(timestamp: number | Date = Date.now()): Snowflake {
    if (timestamp instanceof Date) timestamp = timestamp.getTime();
    if (typeof timestamp !== 'number' || isNaN(timestamp)) {
      throw new TypeError(
        `"timestamp" argument must be a number (received ${isNaN(timestamp) ? 'NaN' : typeof timestamp})`,
      );
    }
    if (INCREMENT >= 4095) INCREMENT = 0;
    // eslint-disable-next-line max-len
    const BINARY = `${(timestamp - EPOCH).toString(2).padStart(42, '0')}0000100000${(INCREMENT++)
      .toString(2)
      .padStart(12, '0')}`;
    return Util.binaryToID(BINARY);
  }

  /**
   * A deconstructed snowflake.
   * @typedef {Object} DeconstructedSnowflake
   * @property {number} timestamp Timestamp the snowflake was created
   * @property {Date} date Date the snowflake was created
   * @property {number} workerID Worker ID in the snowflake
   * @property {number} processID Process ID in the snowflake
   * @property {number} increment Increment in the snowflake
   * @property {string} binary Binary representation of the snowflake
   */

  /**
   * Deconstructs a Discord snowflake.
   * @param {Snowflake} snowflake Snowflake to deconstruct
   * @returns {DeconstructedSnowflake} Deconstructed snowflake
   */
  static deconstruct(snowflake: Snowflake): DeconstructedSnowflake {
    const BINARY = Util.idToBinary(snowflake)
      .toString()
      .padStart(64, '0');
    const res = {
      timestamp: parseInt(BINARY.substring(0, 42), 2) + EPOCH,
      workerID: parseInt(BINARY.substring(42, 47), 2),
      processID: parseInt(BINARY.substring(47, 52), 2),
      increment: parseInt(BINARY.substring(52, 64), 2),
      binary: BINARY,
    };
    Object.defineProperty(res, 'date', {
      get: function get() {
        return new Date(this.timestamp);
      },
      enumerable: true,
    });
    return res as DeconstructedSnowflake;
  }
}

type DeconstructedSnowflake = {
  timestamp: number,
  workerID: number,
  processID: number,
  increment: number,
  binary: string,
  readonly date: Date
}

type Snowflake = string