Discord.Net/src/Discord.Net.Modules/ModuleManager.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;

namespace Discord
{
    public class ModuleManager
	{
		public event EventHandler<ServerEventArgs> ServerEnabled;
		public event EventHandler<ServerEventArgs> ServerDisbled;
		public event EventHandler<ServerEventArgs> ChannelEnabled;
		public event EventHandler<ServerEventArgs> ChannelDisbled;

		public event EventHandler<ServerEventArgs> LeftServer;
		public event EventHandler<ServerEventArgs> ServerUpdated;
		public event EventHandler<ServerEventArgs> ServerUnavailable;
		public event EventHandler<ServerEventArgs> ServerAvailable;

		public event EventHandler<BanEventArgs> UserBanned;
		public event EventHandler<BanEventArgs> UserUnbanned;

		public event EventHandler<ChannelEventArgs> ChannelCreated;
		public event EventHandler<ChannelEventArgs> ChannelDestroyed;
		public event EventHandler<ChannelEventArgs> ChannelUpdated;

		public event EventHandler<RoleEventArgs> RoleCreated;
		public event EventHandler<RoleEventArgs> RoleUpdated;
		public event EventHandler<RoleEventArgs> RoleDeleted;

		public event EventHandler<UserEventArgs> UserJoined;
		public event EventHandler<UserEventArgs> UserLeft;
		public event EventHandler<UserEventArgs> UserUpdated;
		public event EventHandler<UserEventArgs> UserPresenceUpdated;
		public event EventHandler<UserEventArgs> UserVoiceStateUpdated;
		public event EventHandler<UserChannelEventArgs> UserIsTypingUpdated;
		public event EventHandler<UserIsSpeakingEventArgs> UserIsSpeakingUpdated;

		public event EventHandler<MessageEventArgs> MessageReceived;
		public event EventHandler<MessageEventArgs> MessageSent;
		public event EventHandler<MessageEventArgs> MessageDeleted;
		public event EventHandler<MessageEventArgs> MessageUpdated;
		public event EventHandler<MessageEventArgs> MessageReadRemotely;
		
		private readonly bool _allowServerWhitelist, _allowChannelWhitelist, _allowPrivate;
		private readonly ConcurrentDictionary<string, Server> _enabledServers;
		private readonly ConcurrentDictionary<string, Channel> _enabledChannels;
		private readonly ConcurrentDictionary<string, int> _indirectServers;

		public IEnumerable<Server> EnabledServers => _enabledServers.Select(x => x.Value);
		public IEnumerable<Channel> EnabledChannels => _enabledChannels.Select(x => x.Value);

		internal ModuleManager(DiscordClient client, FilterType type)
		{
			_allowServerWhitelist = type.HasFlag(FilterType.Server);
			_allowChannelWhitelist = type.HasFlag(FilterType.Channel);
			_allowPrivate = type.HasFlag(FilterType.AllowPrivate);

			_enabledServers = new ConcurrentDictionary<string, Server>();
			_enabledChannels = new ConcurrentDictionary<string, Channel>();
			_indirectServers = new ConcurrentDictionary<string, int>();

			if (_allowServerWhitelist) //Server-only events
			{
				client.LeftServer += (s, e) => { if (LeftServer != null && HasIndirectServer(e.Server)) DisableServer(e.Server); LeftServer(s, e); };
				client.ServerUpdated += (s, e) => { if (ServerUpdated != null && HasIndirectServer(e.Server)) ServerUpdated(s, e); };
				client.ServerUnavailable += (s, e) => { if (ServerUnavailable != null && HasIndirectServer(e.Server)) ServerUnavailable(s, e); };
				client.ServerAvailable += (s, e) => { if (ServerAvailable != null && HasIndirectServer(e.Server)) ServerAvailable(s, e); };

				client.UserBanned += (s, e) => { if (UserBanned != null && HasIndirectServer(e.Server)) UserBanned(s, e); };
				client.UserUnbanned += (s, e) => { if (UserUnbanned != null && HasIndirectServer(e.Server)) UserUnbanned(s, e); };

				client.ChannelCreated += (s, e) => { if (ChannelCreated != null && HasServer(e.Server)) ChannelCreated(s, e); };
				client.ChannelDestroyed += (s, e) => { if (ChannelDestroyed != null && HasChannel(e.Channel)) ChannelDestroyed(s, e); };
				client.ChannelUpdated += (s, e) => { if (ChannelUpdated != null && HasChannel(e.Channel)) ChannelUpdated(s, e); };

				client.RoleCreated += (s, e) => { if (RoleCreated != null && HasIndirectServer(e.Server)) RoleCreated(s, e); };
				client.RoleUpdated += (s, e) => { if (RoleUpdated != null && HasIndirectServer(e.Server)) RoleUpdated(s, e); };
				client.RoleDeleted += (s, e) => { if (RoleDeleted != null && HasIndirectServer(e.Server)) RoleDeleted(s, e); };

				client.UserJoined += (s, e) => { if (UserJoined != null && HasIndirectServer(e.Server)) UserJoined(s, e); };
				client.UserLeft += (s, e) => { if (UserLeft != null && HasIndirectServer(e.Server)) UserLeft(s, e); };
				client.UserUpdated += (s, e) => { if (UserUpdated != null && HasIndirectServer(e.Server)) UserUpdated(s, e); };
				client.UserPresenceUpdated += (s, e) => { if (UserPresenceUpdated != null && HasIndirectServer(e.Server)) UserPresenceUpdated(s, e); };
				client.UserVoiceStateUpdated += (s, e) => { if (UserVoiceStateUpdated != null && HasServer(e.Server)) UserVoiceStateUpdated(s, e); };
				client.UserIsTypingUpdated += (s, e) => { if (UserIsSpeakingUpdated != null && HasChannel(e.Channel)) UserIsTypingUpdated(s, e); };
				client.UserIsSpeakingUpdated += (s, e) => { if (UserIsSpeakingUpdated != null && HasServer(e.Server)) UserIsSpeakingUpdated(s, e); };

				client.MessageReceived += (s, e) => { if (MessageReceived != null && HasChannel(e.Channel)) MessageReceived(s, e); };
				client.MessageSent += (s, e) => { if (MessageSent != null && HasChannel(e.Channel)) MessageSent(s, e); };
				client.MessageDeleted += (s, e) => { if (MessageDeleted != null && HasChannel(e.Channel)) MessageDeleted(s, e); };
				client.MessageUpdated += (s, e) => { if (MessageUpdated != null && HasChannel(e.Channel)) MessageUpdated(s, e); };
				client.MessageReadRemotely += (s, e) => { if (MessageReadRemotely != null && HasChannel(e.Channel)) MessageReadRemotely(s, e); };
				client.MessageReceived += (s, e) => { if (MessageReceived != null && HasChannel(e.Channel)) MessageReceived(s, e); };
			}
        }

		public bool EnableServer(Server server)
		{
			if (server == null) throw new ArgumentNullException(nameof(server));
			if (!_allowServerWhitelist) throw new InvalidOperationException("This module is not configured to use a server whitelist.");

			if (_enabledServers.TryAdd(server.Id, server))
			{
				if (ServerEnabled != null)
					ServerEnabled(this, new ServerEventArgs(server));
				return true;
			}
			return false;
		}
		public bool DisableServer(Server server)
		{
			if (server == null) throw new ArgumentNullException(nameof(server));
			if (!_allowServerWhitelist) throw new InvalidOperationException("This module is not configured to use a server whitelist.");

			if (_enabledServers.TryRemove(server.Id, out server))
			{
				if (ServerDisbled != null)
					ServerDisbled(this, new ServerEventArgs(server));
				return true;
			}
			return false;
		}
		public void DisableAllServers()
		{
			if (!_allowServerWhitelist) throw new InvalidOperationException("This module is not configured to use a server whitelist.");

			_enabledServers.Clear();
		}

		public void EnableChannel(Channel channel)
		{
			if (channel == null) throw new ArgumentNullException(nameof(channel));
            if (!_allowChannelWhitelist) throw new InvalidOperationException("This module is not configured to use a channel whitelist.");

			lock (this)
			{
				_enabledChannels[channel.Id] = channel;
				var server = channel.Server;
				if (server != null)
				{
					int value = 0;
					_indirectServers.TryGetValue(server.Id, out value);
					value++;
					_indirectServers[server.Id] = value;
				}
			}
		}
		public bool DisableChannel(Channel channel)
		{
			if (channel == null) throw new ArgumentNullException(nameof(channel));
			if (!_allowChannelWhitelist) throw new InvalidOperationException("This module is not configured to use a channel whitelist.");

			lock (this)
			{
				Channel ignored;
				if (_enabledChannels.TryRemove(channel.Id, out ignored))
				{
					var server = channel.Server;
					if (server != null)
					{
						int value = 0;
						_indirectServers.TryGetValue(server.Id, out value);
						value--;
						if (value <= 0)
							_indirectServers.TryRemove(server.Id, out value);
						else
							_indirectServers[server.Id] = value;
					}
					return true;
				}
				return false;
			}
		}
		public void DisableAllChannels()
		{
			if (!_allowChannelWhitelist) throw new InvalidOperationException("This module is not configured to use a channel whitelist.");

			lock (this)
			{
				_enabledChannels.Clear();
				_indirectServers.Clear();
			}
		}

		public void DisableAll()
		{
			if (_allowServerWhitelist)
				DisableAllServers();
			if (_allowChannelWhitelist)
				DisableAllChannels();
		}

		private bool HasServer(Server server) => 
			_allowServerWhitelist && _enabledServers.ContainsKey(server.Id);
		private bool HasIndirectServer(Server server) => 
			(_allowServerWhitelist && _enabledServers.ContainsKey(server.Id)) || 
			(_allowChannelWhitelist && _indirectServers.ContainsKey(server.Id));
		private bool HasChannel(Channel channel)
		{
			if (channel.IsPrivate) return _allowPrivate;

			if (_allowChannelWhitelist && _enabledChannels.ContainsKey(channel.Id)) return true;
			if (_allowServerWhitelist)
			{
				var server = channel.Server;
				if (server == null) return false;
				if (_enabledServers.ContainsKey(server.Id)) return true;
			}
			return false;
		}
	}
}