using System.Net.WebSockets;
using System.Text;
using System.Text.Json;
using MessagePack;
using Microsoft.Extensions.Logging.Abstractions;
using NUnit.Framework;
using SVSim.BattleNode.Bridge;
using SVSim.BattleNode.Protocol;
using SVSim.BattleNode.Sessions;
using SVSim.BattleNode.Sessions.Participants;
using SVSim.BattleNode.Wire;
using SVSim.UnitTests.BattleNode.Infrastructure;

namespace SVSim.UnitTests.BattleNode.Sessions.Participants;

/// <summary>
/// Regression tests for the <c>"hand"</c> SIO event handler. The active bug at
/// <c>docs/audits/battle-node-sio-events-2026-06-02.md</c> §"Active bug" was:
/// client-stocked <c>SELECT_SKILL_URI</c> / <c>SLIDE_OBJECT_URI</c> hand emits arrive
/// with an ack-id; without a server ack, the client's <c>stockEmitMessageMgr</c> deadlocks
/// behind them and every subsequent emit (PlayActions, TurnEndActions, TurnEnd) is queued
/// but never transmitted. These tests drive a hand frame through the WS read loop and
/// inspect the outbound text-frame queue for the SIO ack.
/// </summary>
[TestFixture]
public class RealParticipantHandEventTests
{
    // Any 32-char ASCII string is a valid AES key for NodeCrypto — DecryptForNode reads the
    // key from the first 32 chars of the encrypted blob.
    private const string TestKey = "abcdefghijklmnopqrstuvwxyz012345";

    [Test]
    public async Task Stocked_hand_event_acks_with_body_pubSeq()
    {
        var ws = new TestWebSocket();
        var p = new RealParticipant(ws, viewerId: 906_243_102L, FixtureCtx(),
            NullLogger<RealParticipant>.Instance);

        // Client-shape hand body for a SELECT_SKILL emit: StockHandData[0] = uri_int
        // (HAND_URI_TYPE.SELECT_SKILL_URI = 2), top-level "try" + "pubSeq" added by
        // EmitMsgUriPack. The handler reads top-level "pubSeq" — body contents otherwise
        // don't matter for ack semantics.
        const long expectedPubSeq = 42L;
        var body = $"{{\"StockHandData\":[2,906243102,\"u\",1,0,{expectedPubSeq}],\"try\":0,\"pubSeq\":{expectedPubSeq}}}";
        EnqueueHandFrame(ws, ackId: 26, body: body);
        ws.CompleteIncoming();

        await p.RunAsync(CancellationToken.None);

        var ackFrame = FindAckFrame(ws, ackId: 26);
        Assert.That(ackFrame, Is.Not.Null,
            $"Expected an SIO Ack frame for ackId=26 in outbound sends; got: [{string.Join(", ", AllTextSends(ws))}]");
        Assert.That(ackFrame, Does.Contain($"[{expectedPubSeq}]"),
            "Ack arg must echo the body's pubSeq so the client's stockEmitMessageMgr.GetSelectData lookup succeeds.");
    }

    [Test]
    public async Task Hand_event_without_ackId_is_swallowed_silently_no_ack_sent()
    {
        // Fire-and-forget hand emits (TOUCH_URI, SELECT_OBJECT_URI, TURN_END_READY_URI) arrive
        // without an ack-id and don't block the client's emit queue. We should swallow them
        // without trying to decode or ack.
        var ws = new TestWebSocket();
        var p = new RealParticipant(ws, viewerId: 1, FixtureCtx(),
            NullLogger<RealParticipant>.Instance);

        var body = "{\"StockHandData\":[1,1,\"u\",0],\"try\":0}";
        EnqueueHandFrame(ws, ackId: null, body: body);
        ws.CompleteIncoming();

        await p.RunAsync(CancellationToken.None);

        // Only the EIO Open handshake should be in Sends; no Ack frame.
        var ackFrames = AllTextSends(ws).Where(s => s.StartsWith("43")).ToList();
        Assert.That(ackFrames, Is.Empty,
            $"No-ack-id hand frame must not produce an Ack; got: [{string.Join(", ", ackFrames)}]");
    }

    [Test]
    public async Task Hand_event_with_missing_pubSeq_falls_back_to_ack_arg_0()
    {
        // If a stocked hand frame ever arrives without a pubSeq, we still ack so the
        // client doesn't softlock — but with arg=0 (the client's GetSelectData lookup
        // will miss and OnAck fires with null selectData, which is the same path as a
        // normal cache-miss; not great, but not a deadlock).
        var ws = new TestWebSocket();
        var p = new RealParticipant(ws, viewerId: 1, FixtureCtx(),
            NullLogger<RealParticipant>.Instance);

        var body = "{\"StockHandData\":[2,1,\"u\"],\"try\":0}"; // no pubSeq
        EnqueueHandFrame(ws, ackId: 99, body: body);
        ws.CompleteIncoming();

        await p.RunAsync(CancellationToken.None);

        var ackFrame = FindAckFrame(ws, ackId: 99);
        Assert.That(ackFrame, Is.Not.Null,
            "Missing-pubSeq fallback should still ack (arg=0), not silently swallow.");
        Assert.That(ackFrame, Does.Contain("[0]"),
            "Fallback ack arg should be 0.");
    }

    // -----------------------------------------------------------------------
    // Helpers
    // -----------------------------------------------------------------------

    /// <summary>
    /// Enqueue an SIO BinaryEvent("hand", {placeholder}) text frame followed by its single
    /// binary attachment (NodeCrypto-encrypted msgpack-string of <paramref name="body"/>).
    /// Wire format mirrors what <c>EmitFrontStockData:717-720</c> emits.
    /// </summary>
    private static void EnqueueHandFrame(TestWebSocket ws, int? ackId, string body)
    {
        // Text frame: 4 (EIO Message) + 5 (SIO BinaryEvent) + 1- (1 attachment) + ackId + json
        var ackPart = ackId.HasValue ? ackId.Value.ToString() : "";
        var text = $"451-{ackPart}[\"hand\",{{\"_placeholder\":true,\"num\":0}}]";
        ws.EnqueueIncoming(Encoding.UTF8.GetBytes(text), WebSocketMessageType.Text);

        // Binary attachment: EIO Message prefix (0x04) + msgpack-string(NodeCrypto.Encrypt(json)).
        var encrypted = NodeCrypto.EncryptForNode(body, TestKey);
        var msgpackBytes = MessagePackSerializer.Serialize(encrypted);
        var prefixed = new byte[msgpackBytes.Length + 1];
        prefixed[0] = (byte)EngineIoPacketType.Message;
        Buffer.BlockCopy(msgpackBytes, 0, prefixed, 1, msgpackBytes.Length);
        ws.EnqueueIncoming(prefixed, WebSocketMessageType.Binary);
    }

    private static IEnumerable<string> AllTextSends(TestWebSocket ws) =>
        ws.Sends
            .Where(f => f.Type == WebSocketMessageType.Text)
            .Select(f => Encoding.UTF8.GetString(f.Payload));

    /// <summary>
    /// SIO Ack wire form: EIO Message (4) + SIO Ack (3) + ackId + [arg]. Filter the text
    /// sends for that shape.
    /// </summary>
    private static string? FindAckFrame(TestWebSocket ws, int ackId) =>
        AllTextSends(ws).FirstOrDefault(s => s.StartsWith($"43{ackId}["));

    private static MatchContext FixtureCtx() => new(
        SelfDeckCardIds: Enumerable.Range(1, 30).Select(_ => 100_011_010L).ToList(),
        ClassId: "1", CharaId: "1", CardMasterName: "card_master_node_10015",
        CountryCode: "KOR", UserName: "Player", SleeveId: "3000011",
        EmblemId: "701441011", DegreeId: "300003", FieldId: 43, IsOfficial: 0,
        BattleType: 11);
}