mcdiscordbot/MinecraftDiscordBot/Program.cs

using Discord;
using Discord.Rest;
using Discord.WebSocket;
using Fleck;
using Newtonsoft.Json;
using System.Collections.Concurrent;

namespace MinecraftDiscordBot;

public class Program {
    private const string WebSocketSource = "WebSocket";
    private readonly object _logLock = new();
    private readonly DiscordSocketClient _client = new(new() {
        LogLevel = LogSeverity.Verbose
    });
    private readonly WebSocketServer _wssv;
    private readonly BotConfiguration _config;
    private readonly HashSet<ulong> _whitelistedChannels;
    private readonly ConcurrentDictionary<Guid, IWebSocketConnection> _connections = new();

    public Program(BotConfiguration config) {
        _config = config;
        _client.Log += Log;
        _client.MessageReceived += MessageReceived;
        _wssv = new WebSocketServer($"ws://0.0.0.0:{config.Port}") {
            RestartAfterListenError = true
        };
        _whitelistedChannels = config.Channels.ToHashSet();
    }

    public static Task<int> Main(string[] args)
        => JsonConvert.DeserializeObject<BotConfiguration>(File.ReadAllText("config.json")) is BotConfiguration config
            ? new Program(config).RunAsync()
            : throw new InvalidProgramException("Configuration file missing!");

    public async Task<int> RunAsync() {
        _wssv.Start(socket => {
            socket.OnOpen = async () => await SocketOpened(socket);
            socket.OnClose = async () => await SocketClosed(socket);
            socket.OnMessage = async message => await SocketReceived(socket, message);
        });
        await _client.LoginAsync(TokenType.Bot, _config.Token);
        await _client.StartAsync();
        await VerifyTextChannels();

        // Block this task until the program is closed.
        await Task.Delay(-1);
        return 0;
    }

    private async Task VerifyTextChannels() {
        var channels = await Task.WhenAll(_whitelistedChannels.Select(id => _client.GetChannelAsync(id).AsTask()).ToArray());
        await Task.WhenAll(channels.Where(i => i is ITextChannel { Guild: RestGuild }).Select(i => ((RestGuild)((ITextChannel)i).Guild).UpdateAsync()));
        foreach (var channel in channels) {
            if (channel is ITextChannel tchannel) Console.WriteLine($"Whitelisted in channel: {channel.Name} [{channel.Id}] on server {tchannel.Guild.Name} [{tchannel.Guild.Id}]");
            else throw new InvalidProgramException($"Cannot use this bot on non-text channel {channel.Name} [{channel.Id}]!");
        }
    }

    private async Task SocketReceived(IWebSocketConnection socket, string message)
        => await Log(new LogMessage(LogSeverity.Info, WebSocketSource, $"[{socket.ConnectionInfo.Id}] Received: {message}")).ConfigureAwait(false);

    private async Task SocketClosed(IWebSocketConnection socket) {
        if (!_connections.TryRemove(socket.ConnectionInfo.Id, out _))
            throw new InvalidProgramException("Could not remove non-existing client!");
        await Log(new LogMessage(LogSeverity.Info, WebSocketSource, $"[{socket.ConnectionInfo.Id}] Client disconnected!")).ConfigureAwait(false);
    }

    private async Task SocketOpened(IWebSocketConnection socket) {
        if (!_connections.TryAdd(socket.ConnectionInfo.Id, socket))
            throw new InvalidProgramException("Could not add already-existing client!");
        await Log(new LogMessage(LogSeverity.Info, WebSocketSource, $"[{socket.ConnectionInfo.Id}] Client connected from {socket.ConnectionInfo.ClientIpAddress}:{socket.ConnectionInfo.ClientPort}!")).ConfigureAwait(false);
    }

    private async Task MessageReceived(SocketMessage arg) {
        if (arg.Author.IsBot) return;
        if (IsChannelWhitelisted(arg.Channel))
            await Log(new LogMessage(LogSeverity.Info, "Discord", $"[{arg.Author.Username}] {arg.Content}")).ConfigureAwait(false);
        await SendToAll(JsonConvert.SerializeObject(new TextMessage(arg)));
    }

    private bool IsChannelWhitelisted(ISocketMessageChannel channel)
        => _whitelistedChannels.Contains(channel.Id);

    private async Task SendToAll(string message) {
        async Task SendToClient(KeyValuePair<Guid, IWebSocketConnection> cp) {
            try {
                await cp.Value.Send(message);
            } catch (Exception e) {
                await Log(new LogMessage(LogSeverity.Warning, WebSocketSource, $"[{cp.Key}] Sending message failed!", e)).ConfigureAwait(false);
            }
        }
        await Task.WhenAll(_connections.Select(SendToClient).ToArray());
    }

    private async Task Log(LogMessage msg) {
        lock (_logLock)
            Console.WriteLine(msg.ToString());
        await Task.CompletedTask;
    }
}