Add snowflake utils (#1064)

* snowflakes

* use proper binary for snowflake example

* fix jsdoc errors

* remove dupe

src/util/Snowflake.js

@@ -0,0 +1,62 @@
+const Long = require('long');
+
+// Discord epoch (2015-01-01T00:00:00.000Z)
+const EPOCH = 1420070400000;
+let INCREMENT = 0;
+
+function pad(v, n, c = '0') {
+  return String(v).length >= n ? String(v) : (String(c).repeat(n) + v).slice(-n);
+}
+
+ /**
+  * A deconstructed snowflake
+  * @typedef {Object} DeconstructedSnowflake
+  * @property {Date} date Date in the snowflake
+  * @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
+  */
+
+  /**
+   * 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
+   * ```
+   * Note: this generator hardcodes the worker id as 1 and the process id as 0
+   * @typedef {string} Snowflake
+   * @class Snowflake
+   */
+class Snowflake {
+  /**
+   * Generate a Discord snowflake
+   * @returns {Snowflake} The generated snowflake
+   */
+  static generate() {
+    if (INCREMENT >= 4095) INCREMENT = 0;
+    const BINARY = `${pad((Date.now() - EPOCH).toString(2), 42)}0000100000${pad((INCREMENT++).toString(2), 12)}`;
+    return Long.fromString(BINARY, 2).toString();
+  }
+
+  /**
+   * Deconstruct a Discord snowflake
+   * @param {Snowflake} snowflake Snowflake to deconstruct
+   * @returns {DeconstructedSnowflake} Deconstructed snowflake
+   */
+  static deconstruct(snowflake) {
+    const BINARY = pad(Long.fromString(snowflake).toString(2), 64);
+    return {
+      date: new Date(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,
+    };
+  }
+}
+
+module.exports = Snowflake;