Port VoiceRoleSync from legacy

Since it was recently rewritten, the code was copied over nearly as-is from
the legacy branch without any other major changes considered.

RegexBot-Modules/VoiceRoleSync/ModuleConfig.cs

@@ -0,0 +1,42 @@
+using System.Collections.ObjectModel;
+
+namespace RegexBot.Modules.VoiceRoleSync;
+/// <summary>
+/// Dictionary wrapper. Key = voice channel ID, Value = role.
+/// </summary>
+class ModuleConfig {
+    private readonly ReadOnlyDictionary<ulong, ulong> _values;
+
+    public ModuleConfig(JObject config) {
+        // Configuration format is expected to be an object that contains other objects.
+        // The objects themselves should have their name be the voice channel,
+        // and the value be the role to be applied.
+
+        // TODO Make it accept names; currently only accepts ulongs
+
+        var values = new Dictionary<ulong, ulong>();
+
+        foreach (var item in config.Properties()) {
+            if (!ulong.TryParse(item.Name, out var voice)) throw new ModuleLoadException($"{item.Name} is not a voice channel ID.");
+            var valstr = item.Value.Value<string>();
+            if (!ulong.TryParse(valstr, out var role)) throw new ModuleLoadException($"{valstr} is not a role ID.");
+
+            values[voice] = role;
+        }
+
+        _values = new ReadOnlyDictionary<ulong, ulong>(values);
+    }
+
+    public SocketRole? GetAssociatedRoleFor(SocketVoiceChannel voiceChannel) {
+        if (voiceChannel == null) return null;
+        if (_values.TryGetValue(voiceChannel.Id, out var roleId)) return voiceChannel.Guild.GetRole(roleId);
+        return null;
+    }
+
+    public IEnumerable<SocketRole> GetTrackedRoles(SocketGuild guild) {
+        foreach (var pair in _values) {
+            var r = guild.GetRole(pair.Value);
+            if (r != null) yield return r;
+        }
+    }
+}

RegexBot-Modules/VoiceRoleSync/VoiceRoleSync.cs

@@ -0,0 +1,53 @@
+namespace RegexBot.Modules.VoiceRoleSync;
+/// <summary>
+/// Synchronizes a user's state in a voice channel with a role.
+/// In other words: applies a role to a user entering a voice channel. Removes the role when exiting.
+/// </summary>
+[RegexbotModule]
+public class VoiceRoleSync : RegexbotModule {
+    // TODO wishlist? specify multiple definitions - multiple channels associated with multiple roles.
+
+    public VoiceRoleSync(RegexbotClient bot) : base(bot) {
+        DiscordClient.UserVoiceStateUpdated += Client_UserVoiceStateUpdated;
+    }
+
+    private async Task Client_UserVoiceStateUpdated(SocketUser argUser, SocketVoiceState before, SocketVoiceState after) {
+        // Gather data.
+        if (argUser is not SocketGuildUser user) return; // not a guild user
+        var settings = GetGuildState<ModuleConfig>(user.Guild.Id);
+        if (settings == null) return; // not enabled here
+
+        async Task RemoveAllAssociatedRoles()
+            => await user.RemoveRolesAsync(settings.GetTrackedRoles(user.Guild).Intersect(user.Roles));
+
+        if (after.VoiceChannel == null) {
+            // Not in any voice channel. Remove all roles being tracked by this instance. Clear.
+            await RemoveAllAssociatedRoles();
+        } else {
+            // In a voice channel, and...
+            if (after.IsDeafened || after.IsSelfDeafened) {
+                // Is defeaned, which is like not being in a voice channel for our purposes. Clear.
+                await RemoveAllAssociatedRoles();
+            } else {
+                var targetRole = settings.GetAssociatedRoleFor(after.VoiceChannel);
+                if (targetRole == null) {
+                    // In an untracked voice channel. Clear.
+                    await RemoveAllAssociatedRoles();
+                } else {
+                    // In a tracked voice channel: Clear all except target, add target if needed.
+                    await user.RemoveRolesAsync(settings.GetTrackedRoles(user.Guild)
+                        .Where(role => role.Id != targetRole.Id)
+                        .Intersect(user.Roles));
+                    if (!user.Roles.Contains(targetRole)) await user.AddRoleAsync(targetRole);
+                }
+            }
+        }
+    }
+
+    public override Task<object?> CreateGuildStateAsync(ulong guildID, JToken config) {
+        if (config == null) return Task.FromResult<object?>(null);
+        if (config.Type != JTokenType.Object)
+            throw new ModuleLoadException("Configuration for this section is invalid.");
+        return Task.FromResult<object?>(new ModuleConfig((JObject)config));
+    }
+}