Add anti AFK component (#177)

Keep members from taking up voice slots by moving them to AFK if they
linger in a self-deafened state.

Author: michael-kenzel

src/components/anti-afk.ts

@@ -0,0 +1,60 @@
+import { strict as assert } from "assert";
+
+import * as Discord from "discord.js";
+
+import { SECOND } from "../common.js";
+import { BotComponent } from "../bot-component.js";
+import { clear_timeout, set_timeout } from "../utils/node.js";
+
+export default class AntiAFK extends BotComponent {
+    private countdown = new Map<string, NodeJS.Timeout>();
+
+    private check_voice_state(old_state: Discord.VoiceState, new_state: Discord.VoiceState) {
+        if ((!new_state.selfDeaf || new_state.channel != old_state.channel) && this.countdown.has(new_state.id)) {
+            clear_timeout(this.countdown.get(new_state.id));
+            this.countdown.delete(new_state.id);
+        }
+        if (
+            new_state.channel != null &&
+            new_state.channelId != this.wheatley.guild.afkChannelId &&
+            new_state.selfDeaf
+        ) {
+            assert(new_state.member);
+            const member = new_state.member;
+            const timeout = set_timeout(
+                () => {
+                    member.voice
+                        .fetch()
+                        .then(async current_state => {
+                            if (current_state.selfDeaf && current_state.channelId != this.wheatley.guild.afkChannelId) {
+                                await member.voice.setChannel(this.wheatley.guild.afkChannel);
+                            }
+                        })
+                        .catch(this.wheatley.critical_error.bind(this.wheatley));
+                    this.countdown.delete(new_state.id);
+                },
+                (this.wheatley.guild.afkTimeout + 30) * SECOND,
+            );
+            this.countdown.set(new_state.id, timeout);
+        }
+    }
+
+    override async on_voice_state_update(old_state: Discord.VoiceState, new_state: Discord.VoiceState) {
+        this.check_voice_state(old_state, new_state);
+    }
+
+    override async on_ready() {
+        await Promise.all(
+            this.wheatley.guild.channels.cache
+                .filter(c => c.isVoiceBased())
+                .map(async channel => {
+                    await Promise.all(
+                        channel.members.map(async member => {
+                            const voice_state = await member.voice.fetch();
+                            this.check_voice_state(voice_state, voice_state);
+                        }),
+                    );
+                }),
+        );
+    }
+}