using System.Buffers.Binary;
using System.Diagnostics;
using System.Runtime.Versioning;
using System.ServiceModel;
using System.ServiceModel.Channels;
using AVEVA.Historian.Client.Wcf.Contracts;

namespace AVEVA.Historian.Client.Wcf;

[SupportedOSPlatform("windows")]
internal static class HistorianWcfAuthChainHelper
{
    private const int OpenConnection3MinResponseLength = 5;
    private const int CredentialBlockSizeBytes = 1026;
    private const int MaxValClRounds = 8;
    private const string ClientNodeNameFallback = "AVEVA.Historian.Client";
    private const string ClientDataSourceId = "2020.406.2652.2";
    private const string ClientDllVersionString = "2020.406.2652.2";
    private const byte NativeClientType = 4;
    public const uint NativeIntegratedReadOnlyConnectionMode = 0x402;
    public const uint NativeIntegratedEventConnectionMode = 0x501;
    /// <summary>
    /// Process + write-enabled + integrated security. Per native ilspy
    /// (HistorianAccessUtil.SetConnectionMode): Process=1, OR 0x400 for integratedSecurity.
    /// EnsT2 and DelT silently return false with err code 132 (OperationNotEnabled) when
    /// Open2 is opened with 0x402 (read-only); 0x401 unlocks write capability.
    /// </summary>
    public const uint NativeIntegratedWriteEnabledConnectionMode = 0x401;
    private const byte NativeClientCommonInfoFormatVersion = 4;
    private const ushort NativeHcalVersion = 17;
    private const uint NativeClientVersionInt = 999_999;
    private const ushort NativeOpen2ClientVersion = 9;

    /// <summary>
    /// Runs Hist.GetV → Hist.ValCl × N → Hist.Open2 against the configured /Hist endpoint and
    /// returns the transient /Retr client handle decoded from the OpenConnection3 response.
    /// Caller is responsible for opening the matching /Retr channel.
    /// </summary>
    public static uint OpenAuthenticatedConnection(
        HistorianClientOptions options,
        Binding historyBinding,
        EndpointAddress historyEndpoint,
        Guid contextKey,
        CancellationToken cancellationToken,
        uint connectionMode = NativeIntegratedReadOnlyConnectionMode,
        Action<IHistoryServiceContract2, OpenConnectionContext>? additionalSetup = null)
    {
        ChannelFactory<IHistoryServiceContract2> historyFactory = new(historyBinding, historyEndpoint);
        historyFactory.Endpoint.EndpointBehaviors.Add(new HistorianWcfHistAddressingBehavior());
        if (HistorianWcfMessageCaptureBehavior.IsEnabled)
        {
            historyFactory.Endpoint.EndpointBehaviors.Add(new HistorianWcfMessageCaptureBehavior());
        }

        try
        {
            IHistoryServiceContract2 historyChannel = historyFactory.CreateChannel();
            ICommunicationObject historyChannelCo = (ICommunicationObject)historyChannel;
            try
            {
                historyChannel.GetInterfaceVersion(out _);
                RunValClRounds(historyChannel, contextKey, options, cancellationToken);

                byte[] open2Request = BuildOpenConnection3Request(options.Host, contextKey, connectionMode);
                bool open2Success = historyChannel.OpenConnection2(ref open2Request, out byte[] open2Response, out byte[] open2Error);
                open2Response ??= [];
                open2Error ??= [];
                if (!open2Success || open2Response.Length < OpenConnection3MinResponseLength)
                {
                    throw new InvalidOperationException(
                        $"Open2 failed (Success={open2Success}, ResponseLen={open2Response.Length}, ErrorLen={open2Error.Length}).");
                }

                uint clientHandle = BinaryPrimitives.ReadUInt32LittleEndian(open2Response.AsSpan(1, 4));
                Guid storageSessionId = open2Response.Length >= 21
                    ? new Guid(open2Response.AsSpan(5, 16))
                    : Guid.Empty;

                if (additionalSetup is not null)
                {
                    additionalSetup(historyChannel, new OpenConnectionContext(contextKey, clientHandle, storageSessionId));
                }

                return clientHandle;
            }
            finally
            {
                CloseChannelSafely(historyChannelCo);
            }
        }
        finally
        {
            CloseFactorySafely(historyFactory);
        }
    }

    public readonly record struct OpenConnectionContext(Guid ContextKey, uint ClientHandle, Guid StorageSessionId);

    private static void RunValClRounds(IHistoryServiceContract2 channel, Guid contextKey, HistorianClientOptions options, CancellationToken cancellationToken)
    {
        using HistorianSspiClient sspi = options.IntegratedSecurity
            ? new HistorianSspiClient(options.TargetSpn)
            : new HistorianSspiClient(options.TargetSpn, ParseDomain(options.UserName), ParseUserName(options.UserName), options.Password);
        string handle = contextKey.ToString("D").ToUpperInvariant();
        byte[] incoming = [];

        for (int round = 0; round < MaxValClRounds; round++)
        {
            cancellationToken.ThrowIfCancellationRequested();

            HistorianSspiStepResult step = sspi.Next(incoming);
            byte[] outgoing = step.Token;
            HistorianWcfAuthenticationProtocol.TryApplyNativeNtlmNegotiateVersionFlag(outgoing);
            byte[] wrapped = HistorianWcfAuthenticationProtocol.WrapValidateClientCredentialToken(round == 0, outgoing);

            bool serverSuccess = channel.ValidateClientCredential(handle, wrapped, out byte[] serverOutput, out byte[] errorBuffer);
            serverOutput ??= [];
            errorBuffer ??= [];

            if (!serverSuccess)
            {
                throw new InvalidOperationException($"ValCl round {round} rejected (errorLen={errorBuffer.Length}).");
            }

            ValidateClientCredentialResponse? response = HistorianWcfAuthenticationProtocol.TryReadValidateClientCredentialResponse(serverOutput);
            if (response is null || !response.Continue)
            {
                return;
            }

            incoming = response.Token;
            if (step.IsCompleted && incoming.Length == 0)
            {
                return;
            }
        }

        throw new InvalidOperationException($"ValCl exceeded {MaxValClRounds} rounds without terminal success.");
    }

    private static string ParseDomain(string userName)
    {
        if (string.IsNullOrEmpty(userName)) return string.Empty;
        int slash = userName.IndexOf('\\');
        return slash > 0 ? userName[..slash] : string.Empty;
    }

    private static string ParseUserName(string userName)
    {
        if (string.IsNullOrEmpty(userName)) return string.Empty;
        int slash = userName.IndexOf('\\');
        return slash > 0 ? userName[(slash + 1)..] : userName;
    }

    private static byte[] BuildOpenConnection3Request(string host, Guid contextKey, uint connectionMode)
    {
        Process current = Process.GetCurrentProcess();
        string machineName = Environment.MachineName;
        string processName = string.IsNullOrEmpty(current.ProcessName) ? ClientNodeNameFallback : current.ProcessName;
        _ = host; // host reserved for remote-orchestrator extension

        HistorianOpen2Request open2 = new(
            HostName: machineName,
            ProcessName: string.Empty,
            ProcessId: checked((uint)current.Id),
            UserName: string.Empty,
            Password: [],
            ClientType: NativeClientType,
            ClientVersion: NativeOpen2ClientVersion,
            ConnectionMode: connectionMode,
            MetadataNamespace: HistorianMetadataNamespace.Empty);

        HistorianClientCommonInfo commonInfo = new(
            FormatVersion: NativeClientCommonInfoFormatVersion,
            ServerNodeName: machineName,
            ClientNodeName: processName,
            ProcessId: checked((uint)current.Id),
            HcalVersion: NativeHcalVersion,
            ProcessName: string.Empty,
            Proxy: string.Empty,
            DataSourceId: ClientDataSourceId,
            ShardId: Guid.Empty,
            ClientVersion: NativeClientVersionInt,
            ClientTimestamp: (ulong)DateTime.UtcNow.ToFileTimeUtc(),
            ClientDllVersion: ClientDllVersionString);

        return HistorianOpen2Protocol.SerializeNativeOpenConnection3Version6(
            open2,
            commonInfo,
            contextKey,
            credentialBlock: new byte[CredentialBlockSizeBytes]);
    }

    private static void CloseChannelSafely(ICommunicationObject channel)
    {
        try
        {
            if (channel.State == CommunicationState.Faulted) channel.Abort();
            else channel.Close();
        }
        catch { try { channel.Abort(); } catch { } }
    }

    private static void CloseFactorySafely<TChannel>(ChannelFactory<TChannel> factory)
    {
        try
        {
            if (factory.State == CommunicationState.Faulted) factory.Abort();
            else factory.Close();
        }
        catch { try { factory.Abort(); } catch { } }
    }
}