using CommandLine;
using Discord;
using Discord.Commands;
using Discord.Rest;
using Discord.WebSocket;
using Fleck;
using Newtonsoft.Json;
using System.Collections.Concurrent;
using System.Reflection;
using System.Runtime.CompilerServices;

namespace MinecraftDiscordBot;

public class Program : IDisposable {
    public const string WebSocketSource = "WebSocket";
    public const string BotSource = "Bot";
    private static readonly object LogLock = new();
    private readonly DiscordSocketClient _client = new(new() {
        LogLevel = LogSeverity.Verbose,
        GatewayIntents = GatewayIntents.AllUnprivileged & ~(GatewayIntents.GuildScheduledEvents | GatewayIntents.GuildInvites)
    });
    private readonly WebSocketServer _wssv;
    private readonly BotConfiguration _config;
    private readonly HashSet<ulong> _whitelistedChannels;
    private readonly ConcurrentDictionary<Guid, ConnectedComputer> _connections = new();
    private static readonly char[] WhiteSpace = new char[] { '\t', '\n', ' ', '\r' };
    public ITextChannel[] _channels = Array.Empty<ITextChannel>();
    private RefinedStorageComputer? _rsSystem = null;
    private bool disposedValue;

    public RefinedStorageComputer? RsSystem {
        get => _rsSystem; set {
            if (_rsSystem != value) {
                _rsSystem = value;
                _ = Task.Run(() => Broadcast(i => i.SendMessageAsync(value is null
                    ? $"The Refined Storage went offline. Please check the server!"
                    : $"The Refined Storage is back online!")));
            }
        }
    }

    private async Task Broadcast(Func<ITextChannel, Task<IUserMessage>> message) => _ = await Task.WhenAll(_channels.Select(message));
    public Program(BotConfiguration config) {
        _config = config;
        _client.Log += LogAsync;
        _client.MessageReceived += (msg) => DiscordMessageReceived(msg);
        _wssv = new WebSocketServer($"ws://0.0.0.0:{config.Port}") {
            RestartAfterListenError = true
        };
        FleckLog.LogAction = LogWebSocket;
        _whitelistedChannels = config.Channels.ToHashSet();
    }

    private void LogWebSocket(LogLevel level, string message, Exception exception) => Log(new(level switch {
        LogLevel.Debug => LogSeverity.Debug,
        LogLevel.Info => LogSeverity.Info,
        LogLevel.Warn => LogSeverity.Warning,
        LogLevel.Error => LogSeverity.Error,
        _ => LogSeverity.Critical // Unknown logging states should behave critical
    }, WebSocketSource, message, exception));


    public static Task<int> Main(string[] args)
        => Parser.Default.ParseArguments<BotConfiguration, ConfigFile>(args)
        .MapResult<BotConfiguration, ConfigFile, Task<int>>(
            RunWithConfig,
            RunWithConfig,
            errs => Task.FromResult(1));

    private static Task<int> RunWithConfig(IBotConfigurator arg) => new Program(arg.Config).RunAsync();

    public async Task<int> RunAsync() {
        await _client.LoginAsync(TokenType.Bot, _config.Token);
        await _client.StartAsync();
        if (!await HasValidChannels())
            return 1;
        StartWebSocketServer();

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

    private async Task<bool> HasValidChannels() {
        if (await GetValidChannels(_whitelistedChannels).ToArrayAsync() is not { Length: > 0 } channels) {
            await LogErrorAsync(BotSource, new InvalidOperationException("No valid textchannel was whitelisted!"));
            return false;
        }
        _channels = channels;
        return true;
    }

    private void StartWebSocketServer() => _wssv.Start(socket => {
        socket.OnOpen = async () => await SocketOpened(socket);
        socket.OnClose = async () => await SocketClosed(socket);
        socket.OnMessage = async message => await SocketReceived(socket, message);
    });

    private async IAsyncEnumerable<ITextChannel> GetValidChannels(IEnumerable<ulong> ids) {
        foreach (var channelId in ids) {
            var channel = await _client.GetChannelAsync(channelId);
            if (channel is not ITextChannel textChannel) {
                if (channel is null) await LogWarningAsync(BotSource, $"Channel with id [{channelId}] does not exist!");
                else await LogWarningAsync(BotSource, $"Channel is not a text channels and will not be used: {channel.Name} [{channel.Id}]!");
                continue;
            }

            if (textChannel.Guild is RestGuild guild) {
                await guild.UpdateAsync();
                await LogInfoAsync(BotSource, $"Whitelisted in channel: {channel.Name} [{channel.Id}] on server {guild.Name} [{guild.Id}]");
            } else {
                await LogWarningAsync(BotSource, $"Whitelisted in channel: {channel.Name} [{channel.Id}] on unknown server!");
            }
            yield return textChannel;
        }
    }

    private async Task SocketReceived(IWebSocketConnection socket, string message) {
        if (JsonConvert.DeserializeObject<CapabilityMessage>(message) is not CapabilityMessage capability) return;

        try {
            var pc = capability.Role switch {
                RefinedStorageComputer.Role => new RefinedStorageComputer(socket),
                string role => throw new ArgumentException($"Invalid role '{role}'!")
            };
            AddComputerSocket(socket, pc);
            await LogInfoAsync(WebSocketSource, $"[{socket.ConnectionInfo.Id}] Presented capability as {pc.GetType().Name}");
        } catch (ArgumentException e) {
            await LogErrorAsync(WebSocketSource, e);
        }
    }

    private void AddComputerSocket(IWebSocketConnection socket, ConnectedComputer pc) {
        if (pc is RefinedStorageComputer rs) RsSystem = rs;
    }

    private void RemoveComputerSocket(IWebSocketConnection socket) {
        if (RsSystem?.ConnectionInfo.Id == socket.ConnectionInfo.Id) RsSystem = null;
    }

    private async Task SocketClosed(IWebSocketConnection socket) {
        RemoveComputerSocket(socket);
        await LogInfoAsync(WebSocketSource, $"[{socket.ConnectionInfo.Id}] Client disconnected!");
    }

    private static async Task SocketOpened(IWebSocketConnection socket)
        => await LogInfoAsync(WebSocketSource, $"[{socket.ConnectionInfo.Id}] Client connected from {socket.ConnectionInfo.ClientIpAddress}:{socket.ConnectionInfo.ClientPort}!");

    private async Task DiscordMessageReceived(SocketMessage arg, int timeout = 10000) {
        if (arg is not SocketUserMessage message) return;
        if (message.Author.IsBot) return;
        if (!IsChannelWhitelisted(arg.Channel)) return;

        var cts = new CancellationTokenSource(timeout);

        if (IsCommand(message, out var argPos)) {
            var parameters = message.Content[argPos..].Split(WhiteSpace, StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
            _ = Task.Run(() => HandleCommand(message, parameters, cts.Token));
            return;
        }

        await LogInfoAsync("Discord", $"[{arg.Author.Username}] {arg.Content}");
        // TODO: Relay Message to Chat Receiver   
    }

    private Task HandleCommand(SocketUserMessage message, string[] parameters, CancellationToken ct)
        => parameters is { Length: > 0 }
            ? parameters[0].ToLower() switch {
                RefinedStorageComputer.Role => HandleRefinedStorageCommand(message, parameters[1..], ct),
                _ => message.ReplyAsync($"What the fuck do you mean by '{parameters[0]}'?")
            }
            : message.ReplyAsync($"You really think an empty command works?");

    private Task HandleRefinedStorageCommand(SocketUserMessage message, string[] parameters, CancellationToken ct)
        => RsSystem is RefinedStorageComputer rs
            ? rs.HandleCommand(message, parameters, ct)
            : message.ReplyAsync("The Refined Storage system is currently unavailable!");

    private bool IsCommand(SocketUserMessage message, out int argPos) {
        argPos = 0;
        return message.HasStringPrefix(_config.Prefix, ref argPos);
    }
    private bool IsChannelWhitelisted(ISocketMessageChannel channel)
        => _whitelistedChannels.Contains(channel.Id);

    public static ConfiguredTaskAwaitable LogInfoAsync(string source, string message) => LogAsync(new(LogSeverity.Info, source, message)).ConfigureAwait(false);
    public static ConfiguredTaskAwaitable LogWarningAsync(string source, string message) => LogAsync(new(LogSeverity.Warning, source, message)).ConfigureAwait(false);
    public static ConfiguredTaskAwaitable LogErrorAsync(string source, Exception exception) => LogAsync(new(LogSeverity.Error, source, exception?.Message, exception)).ConfigureAwait(false);
    public static void LogInfo(string source, string message) => Log(new(LogSeverity.Info, source, message));
    public static void LogWarning(string source, string message) => Log(new(LogSeverity.Warning, source, message));
    public static void LogError(string source, Exception exception) => Log(new(LogSeverity.Error, source, exception?.Message, exception));

    private static async Task LogAsync(LogMessage msg) {
        Log(msg);
        await Task.CompletedTask;
    }

    public static void Log(LogMessage msg) {
        lock (LogLock)
            Console.WriteLine(msg.ToString());
    }

    protected virtual void Dispose(bool disposing) {
        if (!disposedValue) {
            if (disposing) {
                // TODO: dispose managed state (managed objects)
                _wssv.Dispose();
                _client.Dispose();
            }

            // TODO: free unmanaged resources (unmanaged objects) and override finalizer
            // TODO: set large fields to null
            disposedValue = true;
        }
    }

    // // TODO: override finalizer only if 'Dispose(bool disposing)' has code to free unmanaged resources
    // ~Program()
    // {
    //     // Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
    //     Dispose(disposing: false);
    // }

    public void Dispose() {
        // Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
        Dispose(disposing: true);
        GC.SuppressFinalize(this);
    }
}