WIP: Make Lavalink optional

At the moment, there's a broken instance of the Lavalink system running.
When executing `.play`, our home-hosted `musicbot` will start playing,
but the production TravBot instance will error.

I haven't implemented this as a choice in the setup yet, that's for
another time.
Right now, all I need is for it to be optional.

src/modules/lavalink.ts

@@ -2,48 +2,50 @@ import attachClientToLavalink from "discord.js-lavalink-lib";
 import {Config} from "../structures";
 import {client} from "../index";
 
-// Although the example showed to do "client.music = LavaLink(...)" and "(client as any).music = Lavalink(...)" was done to match that, nowhere in the library is client.music ever actually used nor does the function return anything. In other words, client.music is undefined and is never used.
-attachClientToLavalink(client, {
-    lavalink: {
-        restnode: {
-            host: "localhost",
-            port: 2333,
-            password: "youshallnotpass"
-        },
-        nodes: [
-            {
+if (Config.lavalink) {
+    // Although the example showed to do "client.music = LavaLink(...)" and "(client as any).music = Lavalink(...)" was done to match that, nowhere in the library is client.music ever actually used nor does the function return anything. In other words, client.music is undefined and is never used.
+    attachClientToLavalink(client, {
+        lavalink: {
+            restnode: {
                 host: "localhost",
                 port: 2333,
                 password: "youshallnotpass"
-            }
-        ]
-    },
-    prefix: Config.prefix,
-    helpCmd: "mhelp",
-    admins: ["717352467280691331"]
-});
+            },
+            nodes: [
+                {
+                    host: "localhost",
+                    port: 2333,
+                    password: "youshallnotpass"
+                }
+            ]
+        },
+        prefix: Config.prefix,
+        helpCmd: "mhelp",
+        admins: ["717352467280691331"]
+    });
 
-// Disable the unhandledRejection listener by Lavalink because it captures every single unhandled
-// rejection and adds its message with it. Then replace it with a better, more selective error handler.
-for (const listener of process.listeners("unhandledRejection")) {
-    if (listener.toString().includes("discord.js-lavalink-musicbot")) {
-        process.off("unhandledRejection", listener);
-    }
-}
-
-process.on("unhandledRejection", (reason: any) => {
-    if (reason?.code === "ECONNREFUSED") {
-        // This is console.warn instead of console.error because on development environments, unless Lavalink is being tested, it won't interfere with the bot's functionality.
-        console.warn(
-            `[discord.js-lavalink-musicbot] Caught unhandled rejection: ${reason.stack}\nIf this is causing issues, head to the support server at https://discord.gg/dNN4azK`
-        );
-    }
-});
-
-// It's unsafe to process uncaughtException because after an uncaught exception, the system
-// becomes corrupted. So disable Lavalink from adding a hook to it.
-for (const listener of process.listeners("uncaughtException")) {
-    if (listener.toString().includes("discord.js-lavalink-musicbot")) {
-        process.off("uncaughtException", listener);
+    // Disable the unhandledRejection listener by Lavalink because it captures every single unhandled
+    // rejection and adds its message with it. Then replace it with a better, more selective error handler.
+    for (const listener of process.listeners("unhandledRejection")) {
+        if (listener.toString().includes("discord.js-lavalink-musicbot")) {
+            process.off("unhandledRejection", listener);
+        }
+    }
+
+    process.on("unhandledRejection", (reason: any) => {
+        if (reason?.code === "ECONNREFUSED") {
+            // This is console.warn instead of console.error because on development environments, unless Lavalink is being tested, it won't interfere with the bot's functionality.
+            console.warn(
+                `[discord.js-lavalink-musicbot] Caught unhandled rejection: ${reason.stack}\nIf this is causing issues, head to the support server at https://discord.gg/dNN4azK`
+            );
+        }
+    });
+
+    // It's unsafe to process uncaughtException because after an uncaught exception, the system
+    // becomes corrupted. So disable Lavalink from adding a hook to it.
+    for (const listener of process.listeners("uncaughtException")) {
+        if (listener.toString().includes("discord.js-lavalink-musicbot")) {
+            process.off("uncaughtException", listener);
+        }
     }
 }

src/structures.ts

@@ -13,6 +13,7 @@ class ConfigStructure extends GenericStructure {
     public owner: string;
     public admins: string[];
     public support: string[];
+    public lavalink: boolean | null;
     public systemLogsChannel: string | null;
     public webhooks: {[id: string]: string}; // id-token pairs
 
@@ -23,6 +24,7 @@ class ConfigStructure extends GenericStructure {
         this.owner = select(data.owner, "", String);
         this.admins = select(data.admins, [], String, true);
         this.support = select(data.support, [], String, true);
+        this.lavalink = select(data.lavalink, null, Boolean);
         this.systemLogsChannel = select(data.systemLogsChannel, null, String);
         this.webhooks = {};