refactor(ShardClientUtil): use BigInt for shard calculation

.eslintrc.json

@@ -2,10 +2,10 @@
   "extends": ["eslint:recommended", "plugin:prettier/recommended"],
   "plugins": ["import"],
   "parserOptions": {
-    "ecmaVersion": 2019
+    "ecmaVersion": 2020
   },
   "env": {
-    "es6": true,
+    "es2020": true,
     "node": true
   },
   "overrides": [{ "files": ["*.browser.js"], "env": { "browser": true } }],

src/errors/Messages.js

@@ -29,6 +29,8 @@ const Messages = {
   SHARDING_READY_DISCONNECTED: id => `Shard ${id}'s Client disconnected before becoming ready.`,
   SHARDING_READY_DIED: id => `Shard ${id}'s process exited before its Client became ready.`,
   SHARDING_NO_CHILD_EXISTS: id => `Shard ${id} has no active process or worker.`,
+  SHARDING_SHARD_MISCALCULATION: (shard, guild, count) =>
+    `Calculated invalid shard ${shard} for guild ${guild} with ${count} shards.`,
 
   COLOR_RANGE: 'Color must be within the range 0 - 16777215 (0xFFFFFF).',
   COLOR_CONVERT: 'Unable to convert color to a number.',

src/sharding/ShardClientUtil.js

@@ -1,7 +1,6 @@
 'use strict';
 
 const { Events } = require('../util/Constants');
-const Snowflake = require('../util/Snowflake');
 const Util = require('../util/Util');
 
 /**
@@ -235,9 +234,9 @@ class ShardClientUtil {
    * @returns {number}
    */
   static shardIdForGuildId(guildId, shardCount) {
-    // This performs (guild_id >> 22) % num_shards, but with a string Snowflake
-    const timestamp = Snowflake.deconstruct(guildId).timestamp;
-    return (timestamp - Snowflake.epoch) % shardCount;
+    const shard = Number(BigInt(guildId) >> 22n) % shardCount;
+    if (shard < 0 || shard >= shardCount) throw new Error('SHARDING_SHARD_MISCALCULATION', guildId, shardCount, shard);
+    return shard;
   }
 }