using System.Net.WebSockets;
using Microsoft.AspNetCore.Mvc.Testing;
using Vanguard.Shared.Protocol;
using Xunit.Sdk;

namespace Vanguard.Server.Tests;

/// <summary>
/// Минимальный клиент протокола для интеграционных тестов:
/// шлёт интенты, догоняет состояние и проверяет кадры.
/// </summary>
internal sealed class TestGameClient : IAsyncDisposable
{
    private readonly WebSocket _socket;
    private readonly SemaphoreSlim _sendLock = new(1, 1);

    private TestGameClient(WebSocket socket, string playerId)
    {
        _socket = socket;
        PlayerId = playerId;
    }

    public string PlayerId { get; }
    public int Seat { get; private set; }
    public long LastSeq { get; private set; }
    public MatchView View { get; private set; } = null!;

    public static async Task<TestGameClient> ConnectAsync(
        WebApplicationFactory<Program> factory,
        string matchId,
        string ticket,
        string playerId,
        long resumeFromSeq,
        CancellationToken cancellationToken)
    {
        var webSocketClient = factory.Server.CreateWebSocketClient();
        var socket = await webSocketClient.ConnectAsync(
            new Uri($"ws://localhost/game"), cancellationToken);

        var client = new TestGameClient(socket, playerId);

        await client.SendAsync(new ClientHello
        {
            ProtocolVersion = ProtocolConstants.Version,
            Ticket = ticket,
            ClientBuild = "tests",
            ResumeFromSeq = resumeFromSeq,
        }, cancellationToken);

        var hello = await client.ReadUntilAsync<ServerHello>(cancellationToken);
        if (hello.MatchId != matchId)
            throw new XunitException($"Ожидался матч {matchId}, пришёл {hello.MatchId}.");

        client.Seat = hello.PlayerIndex;
        client.LastSeq = hello.EventSeq;

        if (hello.Resumed)
        {
            // после hello сервер присылает события догона и часы
            var events = await client.ReadUntilAsync<ServerEvents>(cancellationToken);
            if (events.ToSeq != hello.EventSeq)
                throw new XunitException($"Догон дошёл до {events.ToSeq}, ожидалось {hello.EventSeq}.");
        }
        else
        {
            var snapshot = await client.ReadUntilAsync<ServerSnapshot>(cancellationToken);
            client.View = snapshot.View;
            client.LastSeq = snapshot.View.EventSeq;
        }

        // после догона нужен снимок, чтобы получить MatchView
        if (client.View is null)
            await client.RequestSnapshotAsync(cancellationToken);

        return client;
    }

    public async Task SendIntentAsync(
        string intentId,
        IntentPayload intent,
        CancellationToken cancellationToken)
    {
        await SendAsync(new ClientIntent
        {
            IntentId = intentId,
            BasedOnSeq = LastSeq,
            Intent = intent,
        }, cancellationToken);
    }

    public async Task SendLeaveAsync(string reason, CancellationToken cancellationToken) =>
        await SendAsync(new ClientLeave { Reason = reason }, cancellationToken);

    public async Task<ServerIntentResult> SubmitAsync(
        string intentId,
        IntentPayload intent,
        CancellationToken cancellationToken)
    {
        await SendIntentAsync(intentId, intent, cancellationToken);
        var result = await ReadUntilAsync<ServerIntentResult>(cancellationToken);

        if (result.IntentId != intentId)
            throw new XunitException($"Ожидался результат {intentId}, пришёл {result.IntentId}.");

        return result;
    }

    public async Task RequestSnapshotAsync(CancellationToken cancellationToken)
    {
        await SendAsync(new ClientResync
        {
            FromSeq = LastSeq + 1,
            FullSnapshot = true,
        }, cancellationToken);

        var snapshot = await ReadUntilAsync<ServerSnapshot>(cancellationToken);
        View = snapshot.View;
        LastSeq = snapshot.View.EventSeq;
    }

    /// <summary>Случайный бот: играет легальными интентами до конца партии.</summary>
    public async Task PlayRandomlyAsync(int seed, CancellationToken cancellationToken)
    {
        var random = new Random(seed);
        var deadline = DateTime.UtcNow.AddSeconds(90);

        while (!View.IsFinished)
        {
            if (DateTime.UtcNow > deadline)
                throw new XunitException(
                    $"Тест не доиграл партию за 90 секунд (seat {Seat}).");

            if (View.ActivePlayer == Seat)
            {
                var choices = View.LegalIntents
                    .Where(intent => intent is not ConcedeIntent)
                    .ToList();

                if (choices.Count == 0)
                    throw new XunitException(
                        $"Нет легальных интентов для seat {Seat}, " +
                        $"фаза {View.Phase}, шаг {View.Step}.");

                var intent = choices[random.Next(choices.Count)];
                var intentId = Guid.NewGuid().ToString("N");

                var result = await SubmitAsync(intentId, intent, cancellationToken);
                if (result.Duplicate)
                    throw new XunitException($"Неожиданный duplicate для {intentId}.");

                if (!result.Accepted)
                    throw new XunitException(
                        $"Интент {intent.GetType().Name} отклонён: {result.Code} {result.Reason}");

                // держимся ниже лимита 16 интентов в секунду
                await Task.Delay(75, cancellationToken);
            }

            await RequestSnapshotAsync(cancellationToken);

            if (!View.IsFinished && View.ActivePlayer != Seat)
                await Task.Delay(20, cancellationToken);
        }
    }

    public async Task<T> ReadUntilAsync<T>(CancellationToken cancellationToken)
        where T : ServerFrame
    {
        for (var i = 0; i < 2000; i++)
        {
            var frame = await ReadFrameAsync(cancellationToken);

            if (frame is T typed)
                return typed;

            if (frame is ServerError error)
                throw new XunitException(
                    $"Сервер ответил ошибкой {error.Code}: {error.Message}");
        }

        throw new XunitException($"Не дождались кадра {typeof(T).Name}.");
    }

    public async Task SendAsync(ClientFrame frame, CancellationToken cancellationToken)
    {
        var bytes = ProtocolSerializer.Encode(frame);

        await _sendLock.WaitAsync(cancellationToken);
        try
        {
            await _socket.SendAsync(
                bytes.AsMemory(),
                WebSocketMessageType.Binary,
                endOfMessage: true,
                cancellationToken);
        }
        finally
        {
            _sendLock.Release();
        }
    }

    private async Task<ServerFrame> ReadFrameAsync(CancellationToken cancellationToken)
    {
        var buffer = new byte[16 * 1024];
        using var stream = new MemoryStream();

        while (true)
        {
            var result = await _socket.ReceiveAsync(buffer.AsMemory(), cancellationToken);

            if (result.MessageType == WebSocketMessageType.Close)
                throw new XunitException(
                    $"Сокет закрыт: {_socket.CloseStatus} {_socket.CloseStatusDescription}");

            if (result.MessageType != WebSocketMessageType.Binary)
                throw new XunitException("Сервер прислал текстовый кадр.");

            stream.Write(buffer, 0, result.Count);

            if (stream.Length > ProtocolConstants.MaxFrameBytes)
                throw new XunitException("Кадр сервера слишком велик.");

            if (result.EndOfMessage)
                break;
        }

        return ProtocolSerializer.DecodeServer(stream.ToArray());
    }

    public async ValueTask DisposeAsync()
    {
        try
        {
            if (_socket.State == WebSocketState.Open)
                await _socket.CloseOutputAsync(
                    WebSocketCloseStatus.NormalClosure,
                    "bye",
                    CancellationToken.None);
        }
        catch (Exception)
        {
            // тестовый клиент мог уже отвалиться
        }

        _socket.Dispose();
        _sendLock.Dispose();
    }
}