using System.Runtime.Versioning;
using System.ServiceModel;
using System.ServiceModel.Channels;
using AVEVA.Historian.Client.Models;
using AVEVA.Historian.Client.Wcf.Contracts;

namespace AVEVA.Historian.Client.Wcf;

internal static class HistorianWcfStatusClient
{
    public static Task<string?> GetSystemParameterAsync(
        HistorianClientOptions options,
        string parameterName,
        CancellationToken cancellationToken)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(parameterName);
        return Task.Run(() => GetSystemParameter(options, parameterName), cancellationToken);
    }

    /// <summary>Diagnostic: the GETRP return code / error description from the last
    /// <see cref="GetRuntimeParameterAsync"/> call (set only when the server rejects it).</summary>
    public static string? LastRuntimeParameterError { get; private set; }

    public static Task<string?> GetRuntimeParameterAsync(
        HistorianClientOptions options,
        string parameterName,
        CancellationToken cancellationToken)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(parameterName);
        return Task.Run(() => GetRuntimeParameter(options, parameterName), cancellationToken);
    }

    public static Task<HistorianConnectionStatus> GetConnectionStatusAsync(
        HistorianClientOptions options,
        CancellationToken cancellationToken)
    {
        return Task.Run(() => SynthesizeConnectionStatus(options), cancellationToken);
    }

    public static Task<HistorianStoreForwardStatus> GetStoreForwardStatusAsync(
        HistorianClientOptions options,
        CancellationToken cancellationToken)
    {
        return Task.Run(() => SynthesizeStoreForwardStatus(options), cancellationToken);
    }

    private static string? GetSystemParameter(HistorianClientOptions options, string parameterName)
    {
        Guid contextKey = Guid.NewGuid();
        var (histBinding, histEndpoint, _, _) = HistorianWcfBindingFactory.CreateBindingPair(options);
        Binding statusBinding = HistorianWcfBindingFactory.CreateAuxiliaryBinding(options);
        EndpointAddress statusEndpoint = HistorianWcfBindingFactory.CreateAuxiliaryEndpointAddress(options, HistorianWcfServiceNames.Status);

        string? value = null;
        HistorianWcfAuthChainHelper.OpenAuthenticatedConnection(
            options, histBinding, histEndpoint, contextKey, CancellationToken.None,
            additionalSetup: (_, context) => value = QuerySystemParameter(statusBinding, statusEndpoint, context.ClientHandle, parameterName));
        return value;
    }

    private static string? GetRuntimeParameter(HistorianClientOptions options, string parameterName)
    {
        Guid contextKey = Guid.NewGuid();
        var (histBinding, histEndpoint, _, _) = HistorianWcfBindingFactory.CreateBindingPair(options);
        Binding statusBinding = HistorianWcfBindingFactory.CreateAuxiliaryBinding(options);
        EndpointAddress statusEndpoint = HistorianWcfBindingFactory.CreateAuxiliaryEndpointAddress(options, HistorianWcfServiceNames.Status);

        string? value = null;
        LastRuntimeParameterError = null;
        HistorianWcfAuthChainHelper.OpenAuthenticatedConnection(
            options, histBinding, histEndpoint, contextKey, CancellationToken.None,
            additionalSetup: (_, context) => value = QueryRuntimeParameter(statusBinding, statusEndpoint, context.StorageSessionId, parameterName));
        return value;
    }

    private static string? QueryRuntimeParameter(Binding statusBinding, EndpointAddress statusEndpoint, Guid storageSessionId, string parameterName)
    {
        // GETRP takes the storage-session GUID as a string handle, formatted exactly as the
        // native client sends it: uppercase, dash-separated, no braces.
        string handle = storageSessionId.ToString("D").ToUpperInvariant();
        byte[] requestBuffer = HistorianRuntimeParameterProtocol.SerializeRequest(parameterName);

        ChannelFactory<IStatusServiceContract2> factory = new(statusBinding, statusEndpoint);
        IStatusServiceContract2 channel = factory.CreateChannel();
        ICommunicationObject co = (ICommunicationObject)channel;
        try
        {
            bool ok = channel.GetRuntimeParameter(handle, requestBuffer, out byte[] responseBuffer, out byte[] errorBuffer);
            if (!ok)
            {
                LastRuntimeParameterError = $"GETRP returned false (responseLen={responseBuffer?.Length ?? 0}, errorLen={errorBuffer?.Length ?? 0}).";
                return null;
            }

            return HistorianRuntimeParameterProtocol.ParseSingleStringResult(responseBuffer ?? []);
        }
        finally
        {
            try { if (co.State == CommunicationState.Faulted) co.Abort(); else co.Close(); } catch { try { co.Abort(); } catch { } }
            try { if (factory.State == CommunicationState.Faulted) factory.Abort(); else factory.Close(); } catch { try { factory.Abort(); } catch { } }
        }
    }

    private static string? QuerySystemParameter(Binding statusBinding, EndpointAddress statusEndpoint, uint clientHandle, string parameterName)
    {
        ChannelFactory<IStatusServiceContract2> factory = new(statusBinding, statusEndpoint);
        IStatusServiceContract2 channel = factory.CreateChannel();
        ICommunicationObject co = (ICommunicationObject)channel;
        try
        {
            bool ok = channel.GetSystemParameter(clientHandle, parameterName, out string parameterValue, out _, out _);
            return ok ? parameterValue : null;
        }
        finally
        {
            try { if (co.State == CommunicationState.Faulted) co.Abort(); else co.Close(); } catch { try { co.Abort(); } catch { } }
            try { if (factory.State == CommunicationState.Faulted) factory.Abort(); else factory.Close(); } catch { try { factory.Abort(); } catch { } }
        }
    }

    /// <remarks>
    /// AVEVA's native <c>HistorianAccess.GetConnectionStatus</c> reads local C++
    /// <c>HistorianClient</c> state (no WCF op exists for it). We synthesize an equivalent
    /// by attempting an authenticated session open: a successful auth+open implies
    /// <c>ConnectedToServer = true</c>. Store-forward and partner-connection state are not
    /// observable from a single client probe and remain false.
    /// </remarks>
    private static HistorianConnectionStatus SynthesizeConnectionStatus(HistorianClientOptions options)
    {
        bool connected;
        string? error = null;
        try
        {
            Guid contextKey = Guid.NewGuid();
            var (histBinding, histEndpoint, _, _) = HistorianWcfBindingFactory.CreateBindingPair(options);
            HistorianWcfAuthChainHelper.OpenAuthenticatedConnection(
                options, histBinding, histEndpoint, contextKey, CancellationToken.None);
            connected = true;
        }
        catch (Exception ex)
        {
            connected = false;
            error = $"{ex.GetType().Name}: {ex.Message}";
        }

        return new HistorianConnectionStatus(
            ServerName: options.Host,
            Pending: false,
            ErrorOccurred: !connected,
            Error: error,
            ConnectedToServer: connected,
            ConnectedToServerStorage: connected,
            ConnectedToStoreForward: false,
            ConnectionKind: HistorianConnectionKind.Process);
    }

    /// <remarks>
    /// Native <c>HistorianAccess.GetStoreForwardStatus</c> is also client-side state.
    /// Without a local store-forward sidecar to probe, we report defaults: not pending,
    /// no error, no data stored, not actively storing. Connection kind is Process by
    /// convention (event-only sessions are uncommon for this status helper).
    /// </remarks>
    private static HistorianStoreForwardStatus SynthesizeStoreForwardStatus(HistorianClientOptions options)
    {
        return new HistorianStoreForwardStatus(
            ServerName: options.Host,
            Pending: false,
            ErrorOccurred: false,
            Error: null,
            DataStored: false,
            Storing: false,
            ConnectionKind: HistorianConnectionKind.Process);
    }
}