using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Proxy.Ipc;
using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Shared.Contracts;
using IpcHostConnectivityStatus = ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Shared.Contracts.HostConnectivityStatus;

namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Proxy;

/// <summary>
///     <see cref="IDriver"/> implementation that forwards every capability over the Galaxy IPC
///     channel to the out-of-process Host. Implements the full Phase 2 capability surface;
///     bodies that depend on the deferred Host-side MXAccess code lift will surface
///     <see cref="GalaxyIpcException"/> with code <c>not-implemented</c> until the Host's
///     <c>IGalaxyBackend</c> is wired to the real <c>MxAccessClient</c>.
/// </summary>
public sealed class GalaxyProxyDriver(GalaxyProxyOptions options)
    : IDriver,
      ITagDiscovery,
      IReadable,
      IWritable,
      ISubscribable,
      IAlarmSource,
      IHistoryProvider,
      IRediscoverable,
      IHostConnectivityProbe,
      IDisposable
{
    private GalaxyIpcClient? _client;
    private long _sessionId;
    private DriverHealth _health = new(DriverState.Unknown, null, null);

    private IReadOnlyList<Core.Abstractions.HostConnectivityStatus> _hostStatuses = [];

    public string DriverInstanceId => options.DriverInstanceId;
    public string DriverType => "Galaxy";

    public event EventHandler<DataChangeEventArgs>? OnDataChange;
    public event EventHandler<AlarmEventArgs>? OnAlarmEvent;
    public event EventHandler<RediscoveryEventArgs>? OnRediscoveryNeeded;
    public event EventHandler<HostStatusChangedEventArgs>? OnHostStatusChanged;

    public async Task InitializeAsync(string driverConfigJson, CancellationToken cancellationToken)
    {
        _health = new DriverHealth(DriverState.Initializing, null, null);
        try
        {
            _client = await GalaxyIpcClient.ConnectAsync(
                options.PipeName, options.SharedSecret, options.ConnectTimeout, cancellationToken);

            var resp = await _client.CallAsync<OpenSessionRequest, OpenSessionResponse>(
                MessageKind.OpenSessionRequest,
                new OpenSessionRequest { DriverInstanceId = DriverInstanceId, DriverConfigJson = driverConfigJson },
                MessageKind.OpenSessionResponse,
                cancellationToken);

            if (!resp.Success)
                throw new InvalidOperationException($"Galaxy.Host OpenSession failed: {resp.Error}");

            _sessionId = resp.SessionId;
            _health = new DriverHealth(DriverState.Healthy, DateTime.UtcNow, null);
        }
        catch (Exception ex)
        {
            _health = new DriverHealth(DriverState.Faulted, null, ex.Message);
            throw;
        }
    }

    public async Task ReinitializeAsync(string driverConfigJson, CancellationToken cancellationToken)
    {
        await ShutdownAsync(cancellationToken);
        await InitializeAsync(driverConfigJson, cancellationToken);
    }

    public async Task ShutdownAsync(CancellationToken cancellationToken)
    {
        if (_client is null) return;

        try
        {
            await _client.SendOneWayAsync(
                MessageKind.CloseSessionRequest,
                new CloseSessionRequest { SessionId = _sessionId },
                cancellationToken);
        }
        catch { /* shutdown is best effort */ }

        await _client.DisposeAsync();
        _client = null;
        _health = new DriverHealth(DriverState.Unknown, _health.LastSuccessfulRead, null);
    }

    public DriverHealth GetHealth() => _health;
    public long GetMemoryFootprint() => 0;
    public Task FlushOptionalCachesAsync(CancellationToken cancellationToken) => Task.CompletedTask;

    // ---- ITagDiscovery ----

    public async Task DiscoverAsync(IAddressSpaceBuilder builder, CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(builder);
        var client = RequireClient();

        var resp = await client.CallAsync<DiscoverHierarchyRequest, DiscoverHierarchyResponse>(
            MessageKind.DiscoverHierarchyRequest,
            new DiscoverHierarchyRequest { SessionId = _sessionId },
            MessageKind.DiscoverHierarchyResponse,
            cancellationToken);

        if (!resp.Success)
            throw new InvalidOperationException($"Galaxy.Host DiscoverHierarchy failed: {resp.Error}");

        foreach (var obj in resp.Objects)
        {
            var folder = builder.Folder(obj.ContainedName, obj.ContainedName);
            foreach (var attr in obj.Attributes)
            {
                var fullName = $"{obj.TagName}.{attr.AttributeName}";
                var handle = folder.Variable(
                    attr.AttributeName,
                    attr.AttributeName,
                    new DriverAttributeInfo(
                        FullName: fullName,
                        DriverDataType: MapDataType(attr.MxDataType),
                        IsArray: attr.IsArray,
                        ArrayDim: attr.ArrayDim,
                        SecurityClass: MapSecurity(attr.SecurityClassification),
                        IsHistorized: attr.IsHistorized,
                        IsAlarm: attr.IsAlarm));

                // PR 15: when Galaxy flags the attribute as alarm-bearing (AlarmExtension
                // primitive), register an alarm-condition sink so the generic node manager
                // can route OnAlarmEvent payloads for this tag to the concrete address-space
                // builder. Severity default Medium — the live severity arrives through
                // AlarmEventArgs once MxAccessGalaxyBackend's tracker starts firing.
                if (attr.IsAlarm)
                {
                    handle.MarkAsAlarmCondition(new AlarmConditionInfo(
                        SourceName: fullName,
                        InitialSeverity: AlarmSeverity.Medium,
                        InitialDescription: null));
                }
            }
        }
    }

    // ---- IReadable ----

    public async Task<IReadOnlyList<DataValueSnapshot>> ReadAsync(
        IReadOnlyList<string> fullReferences, CancellationToken cancellationToken)
    {
        var client = RequireClient();
        var resp = await client.CallAsync<ReadValuesRequest, ReadValuesResponse>(
            MessageKind.ReadValuesRequest,
            new ReadValuesRequest { SessionId = _sessionId, TagReferences = [.. fullReferences] },
            MessageKind.ReadValuesResponse,
            cancellationToken);

        if (!resp.Success)
            throw new InvalidOperationException($"Galaxy.Host ReadValues failed: {resp.Error}");

        var byRef = resp.Values.ToDictionary(v => v.TagReference);
        var result = new DataValueSnapshot[fullReferences.Count];
        for (var i = 0; i < fullReferences.Count; i++)
        {
            result[i] = byRef.TryGetValue(fullReferences[i], out var v)
                ? ToSnapshot(v)
                : new DataValueSnapshot(null, StatusBadInternalError, null, DateTime.UtcNow);
        }
        return result;
    }

    // ---- IWritable ----

    public async Task<IReadOnlyList<WriteResult>> WriteAsync(
        IReadOnlyList<WriteRequest> writes, CancellationToken cancellationToken)
    {
        var client = RequireClient();
        var resp = await client.CallAsync<WriteValuesRequest, WriteValuesResponse>(
            MessageKind.WriteValuesRequest,
            new WriteValuesRequest
            {
                SessionId = _sessionId,
                Writes = [.. writes.Select(FromWriteRequest)],
            },
            MessageKind.WriteValuesResponse,
            cancellationToken);

        return [.. resp.Results.Select(r => new WriteResult(r.StatusCode))];
    }

    // ---- ISubscribable ----

    public async Task<ISubscriptionHandle> SubscribeAsync(
        IReadOnlyList<string> fullReferences, TimeSpan publishingInterval, CancellationToken cancellationToken)
    {
        var client = RequireClient();
        var resp = await client.CallAsync<SubscribeRequest, SubscribeResponse>(
            MessageKind.SubscribeRequest,
            new SubscribeRequest
            {
                SessionId = _sessionId,
                TagReferences = [.. fullReferences],
                RequestedIntervalMs = (int)publishingInterval.TotalMilliseconds,
            },
            MessageKind.SubscribeResponse,
            cancellationToken);

        if (!resp.Success)
            throw new InvalidOperationException($"Galaxy.Host Subscribe failed: {resp.Error}");

        return new GalaxySubscriptionHandle(resp.SubscriptionId);
    }

    public async Task UnsubscribeAsync(ISubscriptionHandle handle, CancellationToken cancellationToken)
    {
        var client = RequireClient();
        var sid = ((GalaxySubscriptionHandle)handle).SubscriptionId;
        await client.SendOneWayAsync(
            MessageKind.UnsubscribeRequest,
            new UnsubscribeRequest { SessionId = _sessionId, SubscriptionId = sid },
            cancellationToken);
    }

    /// <summary>
    ///     Internal entry point used by the IPC client when the Host pushes an
    ///     <see cref="MessageKind.OnDataChangeNotification"/> frame. Surfaces it as a managed
    ///     <see cref="OnDataChange"/> event.
    /// </summary>
    internal void RaiseDataChange(OnDataChangeNotification notif)
    {
        var handle = new GalaxySubscriptionHandle(notif.SubscriptionId);
        // ISubscribable.OnDataChange fires once per changed attribute — fan out the batch.
        foreach (var v in notif.Values)
            OnDataChange?.Invoke(this, new DataChangeEventArgs(handle, v.TagReference, ToSnapshot(v)));
    }

    // ---- IAlarmSource ----

    public async Task<IAlarmSubscriptionHandle> SubscribeAlarmsAsync(
        IReadOnlyList<string> sourceNodeIds, CancellationToken cancellationToken)
    {
        var client = RequireClient();
        await client.SendOneWayAsync(
            MessageKind.AlarmSubscribeRequest,
            new AlarmSubscribeRequest { SessionId = _sessionId },
            cancellationToken);
        return new GalaxyAlarmSubscriptionHandle($"alarm-{_sessionId}");
    }

    public Task UnsubscribeAlarmsAsync(IAlarmSubscriptionHandle handle, CancellationToken cancellationToken)
        => Task.CompletedTask;

    public async Task AcknowledgeAsync(
        IReadOnlyList<AlarmAcknowledgeRequest> acknowledgements, CancellationToken cancellationToken)
    {
        var client = RequireClient();
        foreach (var ack in acknowledgements)
        {
            await client.SendOneWayAsync(
                MessageKind.AlarmAckRequest,
                new AlarmAckRequest
                {
                    SessionId = _sessionId,
                    EventId = ack.ConditionId,
                    Comment = ack.Comment ?? string.Empty,
                },
                cancellationToken);
        }
    }

    internal void RaiseAlarmEvent(GalaxyAlarmEvent ev)
    {
        var handle = new GalaxyAlarmSubscriptionHandle($"alarm-{_sessionId}");
        OnAlarmEvent?.Invoke(this, new AlarmEventArgs(
            SubscriptionHandle: handle,
            SourceNodeId: ev.ObjectTagName,
            ConditionId: ev.EventId,
            AlarmType: ev.AlarmName,
            Message: ev.Message,
            Severity: MapSeverity(ev.Severity),
            SourceTimestampUtc: DateTimeOffset.FromUnixTimeMilliseconds(ev.UtcUnixMs).UtcDateTime));
    }

    // ---- IHistoryProvider ----

    public async Task<HistoryReadResult> ReadRawAsync(
        string fullReference, DateTime startUtc, DateTime endUtc, uint maxValuesPerNode,
        CancellationToken cancellationToken)
    {
        var client = RequireClient();
        var resp = await client.CallAsync<HistoryReadRequest, HistoryReadResponse>(
            MessageKind.HistoryReadRequest,
            new HistoryReadRequest
            {
                SessionId = _sessionId,
                TagReferences = [fullReference],
                StartUtcUnixMs = new DateTimeOffset(startUtc, TimeSpan.Zero).ToUnixTimeMilliseconds(),
                EndUtcUnixMs = new DateTimeOffset(endUtc, TimeSpan.Zero).ToUnixTimeMilliseconds(),
                MaxValuesPerTag = maxValuesPerNode,
            },
            MessageKind.HistoryReadResponse,
            cancellationToken);

        if (!resp.Success)
            throw new InvalidOperationException($"Galaxy.Host HistoryRead failed: {resp.Error}");

        var first = resp.Tags.FirstOrDefault();
        IReadOnlyList<DataValueSnapshot> samples = first is null
            ? Array.Empty<DataValueSnapshot>()
            : [.. first.Values.Select(ToSnapshot)];
        return new HistoryReadResult(samples, ContinuationPoint: null);
    }

    public async Task<HistoryReadResult> ReadProcessedAsync(
        string fullReference, DateTime startUtc, DateTime endUtc, TimeSpan interval,
        HistoryAggregateType aggregate, CancellationToken cancellationToken)
    {
        var client = RequireClient();
        var column = MapAggregateToColumn(aggregate);

        var resp = await client.CallAsync<HistoryReadProcessedRequest, HistoryReadProcessedResponse>(
            MessageKind.HistoryReadProcessedRequest,
            new HistoryReadProcessedRequest
            {
                SessionId = _sessionId,
                TagReference = fullReference,
                StartUtcUnixMs = new DateTimeOffset(startUtc, TimeSpan.Zero).ToUnixTimeMilliseconds(),
                EndUtcUnixMs = new DateTimeOffset(endUtc, TimeSpan.Zero).ToUnixTimeMilliseconds(),
                IntervalMs = (long)interval.TotalMilliseconds,
                AggregateColumn = column,
            },
            MessageKind.HistoryReadProcessedResponse,
            cancellationToken);

        if (!resp.Success)
            throw new InvalidOperationException($"Galaxy.Host HistoryReadProcessed failed: {resp.Error}");

        IReadOnlyList<DataValueSnapshot> samples = [.. resp.Values.Select(ToSnapshot)];
        return new HistoryReadResult(samples, ContinuationPoint: null);
    }

    public async Task<HistoryReadResult> ReadAtTimeAsync(
        string fullReference, IReadOnlyList<DateTime> timestampsUtc, CancellationToken cancellationToken)
    {
        var client = RequireClient();
        var resp = await client.CallAsync<HistoryReadAtTimeRequest, HistoryReadAtTimeResponse>(
            MessageKind.HistoryReadAtTimeRequest,
            new HistoryReadAtTimeRequest
            {
                SessionId = _sessionId,
                TagReference = fullReference,
                TimestampsUtcUnixMs = [.. timestampsUtc.Select(t => new DateTimeOffset(t, TimeSpan.Zero).ToUnixTimeMilliseconds())],
            },
            MessageKind.HistoryReadAtTimeResponse,
            cancellationToken);

        if (!resp.Success)
            throw new InvalidOperationException($"Galaxy.Host HistoryReadAtTime failed: {resp.Error}");

        // ReadAtTime returns one sample per requested timestamp in the same order — the Host
        // pads with bad-quality snapshots when a timestamp can't be interpolated, so response
        // length matches request length exactly. We trust that contract rather than
        // re-aligning here, because the Host is the source-of-truth for interpolation policy.
        IReadOnlyList<DataValueSnapshot> samples = [.. resp.Values.Select(ToSnapshot)];
        return new HistoryReadResult(samples, ContinuationPoint: null);
    }

    public async Task<HistoricalEventsResult> ReadEventsAsync(
        string? sourceName, DateTime startUtc, DateTime endUtc, int maxEvents, CancellationToken cancellationToken)
    {
        var client = RequireClient();
        var resp = await client.CallAsync<HistoryReadEventsRequest, HistoryReadEventsResponse>(
            MessageKind.HistoryReadEventsRequest,
            new HistoryReadEventsRequest
            {
                SessionId = _sessionId,
                SourceName = sourceName,
                StartUtcUnixMs = new DateTimeOffset(startUtc, TimeSpan.Zero).ToUnixTimeMilliseconds(),
                EndUtcUnixMs = new DateTimeOffset(endUtc, TimeSpan.Zero).ToUnixTimeMilliseconds(),
                MaxEvents = maxEvents,
            },
            MessageKind.HistoryReadEventsResponse,
            cancellationToken);

        if (!resp.Success)
            throw new InvalidOperationException($"Galaxy.Host HistoryReadEvents failed: {resp.Error}");

        IReadOnlyList<HistoricalEvent> events = [.. resp.Events.Select(ToHistoricalEvent)];
        return new HistoricalEventsResult(events, ContinuationPoint: null);
    }

    internal static HistoricalEvent ToHistoricalEvent(GalaxyHistoricalEvent wire) => new(
        EventId: wire.EventId,
        SourceName: wire.SourceName,
        EventTimeUtc: DateTimeOffset.FromUnixTimeMilliseconds(wire.EventTimeUtcUnixMs).UtcDateTime,
        ReceivedTimeUtc: DateTimeOffset.FromUnixTimeMilliseconds(wire.ReceivedTimeUtcUnixMs).UtcDateTime,
        Message: wire.DisplayText,
        Severity: wire.Severity);

    /// <summary>
    ///     Maps the OPC UA Part 13 aggregate enum onto the Wonderware Historian
    ///     AnalogSummaryQuery column names consumed by <c>HistorianDataSource.ReadAggregateAsync</c>.
    ///     Kept on the Proxy side so Galaxy.Host stays OPC-UA-free.
    /// </summary>
    internal static string MapAggregateToColumn(HistoryAggregateType aggregate) => aggregate switch
    {
        HistoryAggregateType.Average => "Average",
        HistoryAggregateType.Minimum => "Minimum",
        HistoryAggregateType.Maximum => "Maximum",
        HistoryAggregateType.Count => "ValueCount",
        HistoryAggregateType.Total => throw new NotSupportedException(
            "HistoryAggregateType.Total is not supported by the Wonderware Historian AnalogSummary " +
            "query — use Average × Count on the caller side, or switch to Average/Minimum/Maximum/Count."),
        _ => throw new NotSupportedException($"Unknown HistoryAggregateType {aggregate}"),
    };

    // ---- IRediscoverable ----

    /// <summary>
    ///     Triggered by the IPC client when the Host pushes a deploy-watermark notification
    ///     (Galaxy <c>time_of_last_deploy</c> changed per decision #54).
    /// </summary>
    internal void RaiseRediscoveryNeeded(string reason, string? scopeHint = null) =>
        OnRediscoveryNeeded?.Invoke(this, new RediscoveryEventArgs(reason, scopeHint));

    // ---- IHostConnectivityProbe ----

    public IReadOnlyList<Core.Abstractions.HostConnectivityStatus> GetHostStatuses() => _hostStatuses;

    internal void OnHostConnectivityUpdate(IpcHostConnectivityStatus update)
    {
        var translated = new Core.Abstractions.HostConnectivityStatus(
            HostName: update.HostName,
            State: ParseHostState(update.RuntimeStatus),
            LastChangedUtc: DateTimeOffset.FromUnixTimeMilliseconds(update.LastObservedUtcUnixMs).UtcDateTime);

        var prior = _hostStatuses.FirstOrDefault(h => h.HostName == translated.HostName);
        _hostStatuses = [
            .. _hostStatuses.Where(h => h.HostName != translated.HostName),
            translated
        ];

        if (prior is null || prior.State != translated.State)
        {
            OnHostStatusChanged?.Invoke(this, new HostStatusChangedEventArgs(
                translated.HostName, prior?.State ?? HostState.Unknown, translated.State));
        }
    }

    private static HostState ParseHostState(string s) => s switch
    {
        "Running" => HostState.Running,
        "Stopped" => HostState.Stopped,
        "Faulted" => HostState.Faulted,
        _ => HostState.Unknown,
    };

    // ---- helpers ----

    private GalaxyIpcClient RequireClient() =>
        _client ?? throw new InvalidOperationException("Driver not initialized");

    private const uint StatusBadInternalError = 0x80020000u;

    private static DataValueSnapshot ToSnapshot(GalaxyDataValue v) => new(
        Value: v.ValueBytes,
        StatusCode: v.StatusCode,
        SourceTimestampUtc: v.SourceTimestampUtcUnixMs > 0
            ? DateTimeOffset.FromUnixTimeMilliseconds(v.SourceTimestampUtcUnixMs).UtcDateTime
            : null,
        ServerTimestampUtc: DateTimeOffset.FromUnixTimeMilliseconds(v.ServerTimestampUtcUnixMs).UtcDateTime);

    private static GalaxyDataValue FromWriteRequest(WriteRequest w) => new()
    {
        TagReference = w.FullReference,
        ValueBytes = MessagePack.MessagePackSerializer.Serialize(w.Value),
        ValueMessagePackType = 0,
        StatusCode = 0,
        SourceTimestampUtcUnixMs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(),
        ServerTimestampUtcUnixMs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(),
    };

    private static DriverDataType MapDataType(int mxDataType) => mxDataType switch
    {
        0 => DriverDataType.Boolean,
        1 => DriverDataType.Int32,
        2 => DriverDataType.Float32,
        3 => DriverDataType.Float64,
        4 => DriverDataType.String,
        5 => DriverDataType.DateTime,
        _ => DriverDataType.String,
    };

    private static SecurityClassification MapSecurity(int mxSec) => mxSec switch
    {
        0 => SecurityClassification.FreeAccess,
        1 => SecurityClassification.Operate,
        2 => SecurityClassification.SecuredWrite,
        3 => SecurityClassification.VerifiedWrite,
        4 => SecurityClassification.Tune,
        5 => SecurityClassification.Configure,
        6 => SecurityClassification.ViewOnly,
        _ => SecurityClassification.FreeAccess,
    };

    private static AlarmSeverity MapSeverity(int sev) => sev switch
    {
        <= 250 => AlarmSeverity.Low,
        <= 500 => AlarmSeverity.Medium,
        <= 800 => AlarmSeverity.High,
        _ => AlarmSeverity.Critical,
    };

    public void Dispose() => _client?.DisposeAsync().AsTask().GetAwaiter().GetResult();
}

internal sealed record GalaxySubscriptionHandle(long SubscriptionId) : ISubscriptionHandle
{
    public string DiagnosticId => $"galaxy-sub-{SubscriptionId}";
}

internal sealed record GalaxyAlarmSubscriptionHandle(string Id) : IAlarmSubscriptionHandle
{
    public string DiagnosticId => Id;
}

public sealed class GalaxyProxyOptions
{
    public required string DriverInstanceId { get; init; }
    public required string PipeName { get; init; }
    public required string SharedSecret { get; init; }
    public TimeSpan ConnectTimeout { get; init; } = TimeSpan.FromSeconds(10);
}