using System.Buffers.Binary;
using System.Net;
using System.Reflection;
using System.Text;
using AcDream.Core.CharGen;
using AcDream.Core.Net;
using AcDream.Core.Net.Messages;
using AcDream.Core.Net.Packets;
using AcDream.Runtime;
using AcDream.Runtime.Session;
using AcDream.Runtime.Tests.CharGen;

namespace AcDream.Runtime.Tests.Session;

/// <summary>
/// Campaign CC slice CC3: <see cref="LiveSessionController"/>'s
/// character-creation integration — the wire send (via a REAL
/// <see cref="WorldSession"/> + <c>GameMessageCapture</c>, the same seam
/// <c>WorldSessionCharacterCreationTests</c> uses in Core.Net) and the
/// Ok-response round trip (roster append reusing
/// <see cref="RuntimeCharacterSelectionState.ApplyRoster"/>, the reused
/// <c>EnterSelectedCore</c> log-straight-in, and the new
/// <see cref="ILiveSessionLifecycleHost.ApplyCharacterCreated"/>/
/// <see cref="ILiveSessionLifecycleHost.ApplyCreationFailed"/> hooks) via a
/// real inbound <c>0xF643</c> packet through <c>WorldSession.ProcessDatagram</c>
/// (reflection — the same private test seam Core.Net's own creation tests
/// use).
/// </summary>
public sealed class LiveSessionControllerCharacterCreationTests
{
    private sealed class TestTransport : IWorldSessionTransport
    {
        public void Send(ReadOnlySpan<byte> datagram) { }
        public void Send(IPEndPoint remote, ReadOnlySpan<byte> datagram) { }
        public int Receive(Span<byte> destination, TimeSpan timeout, out IPEndPoint? from)
        {
            from = null;
            return -1;
        }
        public ValueTask<NetReceiveResult> ReceiveAsync(
            Memory<byte> destination,
            CancellationToken cancellationToken) =>
            throw new OperationCanceledException(cancellationToken);
        public void Dispose() { }
    }

    private sealed class TestOperations : ILiveSessionOperations
    {
        public List<WorldSession> Sessions { get; } = [];
        public int EnterWorldCount { get; private set; }

        public IPEndPoint ResolveEndpoint(string host, int port) =>
            new(IPAddress.Loopback, port);

        public WorldSession CreateSession(IPEndPoint endpoint)
        {
            var session = new WorldSession(endpoint, new TestTransport());
            Sessions.Add(session);
            return session;
        }

        public void Connect(WorldSession session, string user, string password) { }

        public void StartCharacterSelectionReceive(WorldSession session) { }

        public CharacterList.Parsed? GetCharacters(WorldSession session) => new(
            0u,
            [new CharacterList.Character(0x50000001u, "Existing", 0u)],
            [],
            SlotCount: 11,
            AccountName: "testaccount",
            true,
            true);

        public void EnterWorld(WorldSession session, int activeCharacterIndex) =>
            EnterWorldCount++;

        public void Tick(WorldSession session) { }

        public void DisposeSession(WorldSession session) { }
    }

    private sealed class TestHost : ILiveSessionLifecycleHost
    {
        public List<LiveSessionRosterReport> Rosters { get; } = [];
        public List<LiveSessionCharacterSelection> EnteredWorld { get; } = [];
        public List<RuntimeCharacterCreationIdentity> Created { get; } = [];
        public List<RuntimeCharacterCreationRejection> Failed { get; } = [];

        public LiveSessionBinding BindSession(WorldSession session) =>
            new(session, activateCommands: () => { }, deactivateCommands: () => { }, detachEvents: () => { });
        public void ResetSessionState(RuntimeGenerationToken retiringGeneration) { }
        public void ReportConnecting(string host, int port, string user) { }
        public void ReportConnected() { }
        public void ReportRoster(LiveSessionRosterReport roster) => Rosters.Add(roster);
        public void ApplySelectedCharacter(LiveSessionCharacterSelection selection) { }
        public void ApplyEnteredWorld(LiveSessionCharacterSelection selection) =>
            EnteredWorld.Add(selection);
        public void DetachSession(WorldSession session) { }
        public void ApplyCharacterCreated(RuntimeCharacterCreationIdentity identity) =>
            Created.Add(identity);
        public void ApplyCreationFailed(RuntimeCharacterCreationRejection rejection) =>
            Failed.Add(rejection);
    }

    private static LiveSessionConnectOptions LiveOptions() => new(
        Enabled: true,
        "127.0.0.1",
        9000,
        "testaccount",
        "password",
        Character: null,
        Probe: false,
        AwaitCharacterSelection: true);

    private static (LiveSessionController Controller, TestOperations Operations, TestHost Host, RuntimeGenerationToken Generation)
        StartAwaitingSelection()
    {
        var operations = new TestOperations();
        var host = new TestHost();
        var controller = new LiveSessionController(
            operations,
            timeProvider: null,
            RuntimeCharacterCreationStateFixture.Build());

        LiveSessionStartResult result = controller.Start(LiveOptions(), host);
        Assert.Equal(LiveSessionStartStatus.AwaitingCharacterSelection, result.Status);

        return (controller, operations, host, controller.Generation);
    }

    private static void BuildReadyCharacter(LiveSessionController controller, RuntimeGenerationToken generation)
    {
        Assert.True(controller.SelectHeritage(generation, RuntimeCharacterCreationStateFixture.AluvianId).Accepted);
        Assert.True(controller.SelectGender(generation, RuntimeCharacterCreationStateFixture.MaleGenderKey).Accepted);
        Assert.True(controller.SelectTemplate(generation, RuntimeCharacterCreationStateFixture.PresetTemplateIndex).Accepted);
        Assert.True(controller.SetName(generation, "NewChar").Accepted);
    }

    [Fact]
    public void Finish_SendsExactly55SkillSlotsAndTheCorrectAttributesAndName()
    {
        (LiveSessionController controller, TestOperations operations, _, RuntimeGenerationToken generation) =
            StartAwaitingSelection();
        BuildReadyCharacter(controller, generation);

        WorldSession session = operations.Sessions[0];
        byte[]? captured = null;
        GameMessageGroup? capturedGroup = null;
        session.GameMessageCapture = (body, group) =>
        {
            captured = body;
            capturedGroup = group;
        };

        RuntimeCommandResult result = controller.Finish(generation);

        Assert.True(result.Accepted);
        Assert.NotNull(captured);
        Assert.Equal(GameMessageGroup.LoginQueue, capturedGroup);

        CapturedCreateRequest decoded = DecodeCreateRequest(captured!);
        Assert.Equal("testaccount", decoded.AccountName);
        Assert.Equal(RuntimeCharacterCreationStateFixture.AluvianId, decoded.Heritage);
        Assert.Equal(RuntimeCharacterCreationStateFixture.MaleGenderKey, decoded.Gender);
        Assert.Equal(RuntimeCharacterCreationStateFixture.PresetTemplateIndex, decoded.Template);
        Assert.Equal(16u, decoded.Strength);
        Assert.Equal("NewChar", decoded.Name);
        Assert.Equal((uint)CharacterCreate.SkillAdvancementClassCount, decoded.NumSkills);
        Assert.Equal(CharacterCreate.SkillAdvancementClassCount, decoded.SkillAdvancementClasses.Length);
        Assert.Equal(
            (uint)ChargenSkillAdvancementClass.Trained,
            decoded.SkillAdvancementClasses[RuntimeCharacterCreationStateFixture.SkillTrainSpecialize]);
        Assert.Equal(
            (uint)ChargenSkillAdvancementClass.Specialized,
            decoded.SkillAdvancementClasses[RuntimeCharacterCreationStateFixture.SkillPresetPrimary]);
    }

    [Fact]
    public void Finish_ThenOkResponse_AppendsToRosterAndLogsStraightIn()
    {
        (LiveSessionController controller, TestOperations operations, TestHost host, RuntimeGenerationToken generation) =
            StartAwaitingSelection();
        BuildReadyCharacter(controller, generation);
        WorldSession session = operations.Sessions[0];
        session.GameMessageCapture = (_, _) => { };

        Assert.True(controller.Finish(generation).Accepted);

        InvokeProcessDatagram(session, BuildResponsePacket(
            (uint)CharGenVerificationResponse.Code.Ok, 0x50001234u, "NewChar"));

        Assert.Single(host.Created);
        Assert.Equal(0x50001234u, host.Created[0].Guid);
        Assert.Equal("NewChar", host.Created[0].Name);
        Assert.Empty(host.Failed);

        // The roster report following the Ok reply has BOTH the pre-existing
        // character and the newly created one.
        LiveSessionRosterReport lastReport = host.Rosters[^1];
        Assert.Contains(lastReport.Entries, e => e.Id == 0x50001234u && e.Name == "NewChar");
        Assert.Contains(lastReport.Entries, e => e.Id == 0x50000001u);

        // gmCharGenMainUI::Update @ 0x004E8460's log-straight-in, reused via
        // EnterSelectedCore — the controller is now in-world as the new
        // character, no second selection/EnterWorld call needed.
        Assert.True(controller.IsInWorld);
        Assert.Equal(1, operations.EnterWorldCount);
        Assert.Single(host.EnteredWorld);
        Assert.Equal(0x50001234u, host.EnteredWorld[0].CharacterId);
    }

    [Fact]
    public void Finish_ThenNameInUseResponse_SurfacesRejectionAndStaysAwaitingSelection()
    {
        (LiveSessionController controller, TestOperations operations, TestHost host, RuntimeGenerationToken generation) =
            StartAwaitingSelection();
        BuildReadyCharacter(controller, generation);
        WorldSession session = operations.Sessions[0];
        session.GameMessageCapture = (_, _) => { };

        Assert.True(controller.Finish(generation).Accepted);

        InvokeProcessDatagram(session, BuildResponsePacket(
            (uint)CharGenVerificationResponse.Code.NameInUse, 0u, string.Empty));

        Assert.Single(host.Failed);
        Assert.Equal(CharGenVerificationResponse.Code.NameInUse, host.Failed[0].Code);
        Assert.Equal("NewChar", host.Failed[0].AttemptedName);
        Assert.Empty(host.Created);
        Assert.False(controller.IsInWorld);
        Assert.Equal(0, operations.EnterWorldCount);
        Assert.Empty(host.EnteredWorld);
        // No roster append on a rejection.
        Assert.DoesNotContain(host.Rosters, r => r.Entries.Any(e => e.Name == "NewChar"));
    }

    [Fact]
    public void Finish_RefusedLocallyWithUnspentAttributeCredits_NeverTouchesTheWire()
    {
        (LiveSessionController controller, TestOperations operations, _, RuntimeGenerationToken generation) =
            StartAwaitingSelection();
        Assert.True(controller.SelectHeritage(generation, RuntimeCharacterCreationStateFixture.AluvianId).Accepted);
        Assert.True(controller.SelectGender(generation, RuntimeCharacterCreationStateFixture.MaleGenderKey).Accepted);
        Assert.True(controller.SelectTemplate(generation, RuntimeCharacterCreationStateFixture.CustomTemplateIndex).Accepted);
        Assert.True(controller.SetName(generation, "NewChar").Accepted);
        WorldSession session = operations.Sessions[0];
        bool sent = false;
        session.GameMessageCapture = (_, _) => sent = true;

        RuntimeCommandResult result = controller.Finish(generation);

        Assert.False(result.Accepted);
        Assert.False(sent);
    }

    private static void InvokeProcessDatagram(WorldSession session, byte[] datagram)
    {
        MethodInfo method = typeof(WorldSession).GetMethod(
            "ProcessDatagram",
            BindingFlags.NonPublic | BindingFlags.Instance)!;
        method.Invoke(session, [new ReadOnlyMemory<byte>(datagram), null, true]);
    }

    private static byte[] BuildResponseBody(uint code, uint guid, string name)
    {
        var w = new PacketWriter();
        w.WriteUInt32(CharGenVerificationResponse.ResponseOpcode);
        w.WriteUInt32(code);
        if (code == (uint)CharGenVerificationResponse.Code.Ok)
        {
            w.WriteUInt32(guid);
            w.WriteString16L(name);
            w.WriteUInt32(0u);
        }
        return w.ToArray();
    }

    private static byte[] BuildResponsePacket(uint code, uint guid, string name)
    {
        byte[] message = BuildResponseBody(code, guid, name);
        var fragments = new byte[MessageFragmentHeader.Size + message.Length];
        GameMessageFragment.WriteSingleFragment(fragments.AsSpan(), fragmentSequence: 1u, GameMessageGroup.UIQueue, message);
        return PacketCodec.Encode(
            new PacketHeader { Sequence = 1u, Flags = PacketHeaderFlags.BlobFragments },
            fragments,
            outboundIsaac: null);
    }

    private readonly record struct CapturedCreateRequest(
        string AccountName,
        uint Heritage,
        uint Gender,
        uint Template,
        uint Strength,
        string Name,
        uint NumSkills,
        uint[] SkillAdvancementClasses);

    /// <summary>Manual mirror of <see cref="CharacterCreate.BuildRequestBody"/>'s
    /// exact field order — see that class's doc comment for the full
    /// layout.</summary>
    private static CapturedCreateRequest DecodeCreateRequest(ReadOnlySpan<byte> body)
    {
        int pos = 0;
        uint opcode = ReadU32(body, ref pos);
        Assert.Equal(CharacterCreate.Opcode, opcode);
        string accountName = ReadString16L(body, ref pos);
        uint constant = ReadU32(body, ref pos);
        Assert.Equal(1u, constant);
        uint heritage = ReadU32(body, ref pos);
        uint gender = ReadU32(body, ref pos);
        _ = ReadU32(body, ref pos); // eyesStrip
        _ = ReadU32(body, ref pos); // noseStrip
        _ = ReadU32(body, ref pos); // mouthStrip
        _ = ReadU32(body, ref pos); // hairColor
        _ = ReadU32(body, ref pos); // eyeColor
        _ = ReadU32(body, ref pos); // hairStyle
        _ = ReadU32(body, ref pos); // headgearStyle
        _ = ReadU32(body, ref pos); // headgearColor
        _ = ReadU32(body, ref pos); // shirtStyle
        _ = ReadU32(body, ref pos); // shirtColor
        _ = ReadU32(body, ref pos); // trousersStyle
        _ = ReadU32(body, ref pos); // trousersColor
        _ = ReadU32(body, ref pos); // footwearStyle
        _ = ReadU32(body, ref pos); // footwearColor
        for (int i = 0; i < 6; i++)
            _ = ReadF64(body, ref pos); // six shades
        uint template = ReadU32(body, ref pos);
        uint strength = ReadU32(body, ref pos);
        _ = ReadU32(body, ref pos); // endurance
        _ = ReadU32(body, ref pos); // coordination
        _ = ReadU32(body, ref pos); // quickness
        _ = ReadU32(body, ref pos); // focus
        _ = ReadU32(body, ref pos); // self
        _ = ReadU32(body, ref pos); // slot
        _ = ReadU32(body, ref pos); // classId
        uint numSkills = ReadU32(body, ref pos);
        var skills = new uint[numSkills];
        for (int i = 0; i < numSkills; i++)
            skills[i] = ReadU32(body, ref pos);
        string name = ReadString16L(body, ref pos);
        // startArea, isAdmin, isEnvoy, checksum follow — not needed here.
        return new CapturedCreateRequest(
            accountName, heritage, gender, template, strength, name, numSkills, skills);
    }

    private static uint ReadU32(ReadOnlySpan<byte> body, ref int pos)
    {
        uint value = BinaryPrimitives.ReadUInt32LittleEndian(body.Slice(pos));
        pos += 4;
        return value;
    }

    private static double ReadF64(ReadOnlySpan<byte> body, ref int pos)
    {
        double value = BinaryPrimitives.ReadDoubleLittleEndian(body.Slice(pos));
        pos += 8;
        return value;
    }

    private static string ReadString16L(ReadOnlySpan<byte> body, ref int pos)
    {
        ushort len = BinaryPrimitives.ReadUInt16LittleEndian(body.Slice(pos));
        string value = Encoding.ASCII.GetString(body.Slice(pos + 2, len));
        int recordSize = 2 + len;
        int padding = (4 - (recordSize & 3)) & 3;
        pos += recordSize + padding;
        return value;
    }
}