using Akka.Actor;
using Akka.Cluster.Tools.PublishSubscribe;
using Akka.Event;
using Microsoft.EntityFrameworkCore;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Redundancy;
using ZB.MOM.WW.OtOpcUa.Commons.Observability;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;
using ZB.MOM.WW.OtOpcUa.Commons.Types;
using ZB.MOM.WW.OtOpcUa.Configuration;
using ZB.MOM.WW.OtOpcUa.OpcUaServer;
using ZB.MOM.WW.OtOpcUa.Runtime.Drivers;

namespace ZB.MOM.WW.OtOpcUa.Runtime.OpcUa;

/// <summary>
///     Single-threaded bridge between Akka messages and the OPC UA SDK address space. Hosted on
///     the pinned <c>opcua-synchronized-dispatcher</c> (Task 19 HOCON) so the OPC UA SDK sees
///     only one thread per actor instance — its session/subscription locks expect strict
///     single-threaded access.
///
///     Address-space writes route through <see cref="IOpcUaAddressSpaceSink"/>; ServiceLevel
///     writes route through <see cref="IServiceLevelPublisher"/>. Production binds SDK-backed
///     implementations; dev/Mac/tests bind the Null* defaults so the actor stays decoupled from
///     <c>Opc.Ua.Server</c>. The remaining piece is wiring those bindings to a real
///     <c>StandardServer</c> address space — tracked as F10b.
/// </summary>
public sealed class OpcUaPublishActor : ReceiveActor
{
    public const string DispatcherId = "opcua-synchronized-dispatcher";
    public const string RedundancyStateTopic = "redundancy-state";

    public sealed record AttributeValueUpdate(string NodeId, object? Value, OpcUaQuality Quality, DateTime TimestampUtc);
    public sealed record AlarmStateUpdate(string AlarmNodeId, bool Active, bool Acknowledged, DateTime TimestampUtc);
    /// <summary>
    ///     Triggers an address-space rebuild. <paramref name="DeploymentId"/> is the deployment
    ///     just applied by the host; the rebuild loads THAT artifact so materialisation matches the
    ///     applied config + the SubscribeBulk pass. It is null only for legacy/dev callers, which
    ///     fall back to the latest sealed deployment (lags a not-yet-sealed apply by one revision).
    /// </summary>
    public sealed record RebuildAddressSpace(CorrelationId Correlation, DeploymentId? DeploymentId = null);
    public sealed record ServiceLevelChanged(byte ServiceLevel);

    private readonly IOpcUaAddressSpaceSink _sink;
    private readonly IServiceLevelPublisher _serviceLevel;
    private readonly bool _subscribeRedundancyTopic;
    private readonly NodeId? _localNode;
    private readonly IDbContextFactory<OtOpcUaConfigDbContext>? _dbFactory;
    private readonly Phase7Applier? _applier;
    private readonly ILoggingAdapter _log = Context.GetLogger();

    private int _writes;
    private byte _lastServiceLevel;
    private Phase7CompositionResult _lastApplied = new(
        Array.Empty<UnsAreaProjection>(),
        Array.Empty<UnsLineProjection>(),
        Array.Empty<EquipmentNode>(),
        Array.Empty<DriverInstancePlan>(),
        Array.Empty<ScriptedAlarmPlan>(),
        Array.Empty<GalaxyTagPlan>());

    /// <summary>Gets the number of writes performed.</summary>
    public int WriteCount => _writes;
    /// <summary>Gets the last published service level.</summary>
    public byte LastServiceLevel => _lastServiceLevel;

    /// <summary>Production Props — pins the OPC UA dispatcher + subscribes to the
    /// <c>redundancy-state</c> DPS topic so cluster transitions drive the local ServiceLevel
    /// publish path. When <paramref name="dbFactory"/> + <paramref name="applier"/> are supplied,
    /// <see cref="RebuildAddressSpace"/> reads the latest deployment artifact + drives the
    /// applier through the sink.</summary>
    /// <param name="sink">The OPC UA address space sink.</param>
    /// <param name="serviceLevel">The service level publisher.</param>
    /// <param name="localNode">The local cluster node ID.</param>
    /// <param name="dbFactory">The optional database context factory.</param>
    /// <param name="applier">The optional Phase 7 applier.</param>
    public static Props Props(
        IOpcUaAddressSpaceSink? sink = null,
        IServiceLevelPublisher? serviceLevel = null,
        NodeId? localNode = null,
        IDbContextFactory<OtOpcUaConfigDbContext>? dbFactory = null,
        Phase7Applier? applier = null) =>
        Akka.Actor.Props.Create(() => new OpcUaPublishActor(
            sink ?? NullOpcUaAddressSpaceSink.Instance,
            serviceLevel ?? NullServiceLevelPublisher.Instance,
            subscribeRedundancyTopic: true,
            localNode,
            dbFactory,
            applier)).WithDispatcher(DispatcherId);

    /// <summary>Test-only Props that omits the pinned-dispatcher requirement and skips the
    /// DPS subscribe so unit tests can spin up the actor on a vanilla TestKit cluster.</summary>
    /// <param name="sink">The OPC UA address space sink.</param>
    /// <param name="serviceLevel">The service level publisher.</param>
    /// <param name="subscribeRedundancyTopic">Whether to subscribe to the redundancy topic.</param>
    /// <param name="localNode">The local cluster node ID.</param>
    /// <param name="dbFactory">The optional database context factory.</param>
    /// <param name="applier">The optional Phase 7 applier.</param>
    public static Props PropsForTests(
        IOpcUaAddressSpaceSink? sink = null,
        IServiceLevelPublisher? serviceLevel = null,
        bool subscribeRedundancyTopic = false,
        NodeId? localNode = null,
        IDbContextFactory<OtOpcUaConfigDbContext>? dbFactory = null,
        Phase7Applier? applier = null) =>
        Akka.Actor.Props.Create(() => new OpcUaPublishActor(
            sink ?? NullOpcUaAddressSpaceSink.Instance,
            serviceLevel ?? NullServiceLevelPublisher.Instance,
            subscribeRedundancyTopic,
            localNode,
            dbFactory,
            applier));

    /// <summary>Initializes a new instance of the <see cref="OpcUaPublishActor"/> class.</summary>
    /// <param name="sink">The OPC UA address space sink.</param>
    /// <param name="serviceLevel">The service level publisher.</param>
    /// <param name="subscribeRedundancyTopic">Whether to subscribe to the redundancy topic.</param>
    /// <param name="localNode">The local cluster node ID.</param>
    /// <param name="dbFactory">The optional database context factory.</param>
    /// <param name="applier">The optional Phase 7 applier.</param>
    public OpcUaPublishActor(
        IOpcUaAddressSpaceSink sink,
        IServiceLevelPublisher serviceLevel,
        bool subscribeRedundancyTopic,
        NodeId? localNode,
        IDbContextFactory<OtOpcUaConfigDbContext>? dbFactory = null,
        Phase7Applier? applier = null)
    {
        _sink = sink;
        _serviceLevel = serviceLevel;
        _subscribeRedundancyTopic = subscribeRedundancyTopic;
        _localNode = localNode;
        _dbFactory = dbFactory;
        _applier = applier;

        Receive<AttributeValueUpdate>(HandleAttributeUpdate);
        Receive<AlarmStateUpdate>(HandleAlarmUpdate);
        Receive<RebuildAddressSpace>(HandleRebuild);
        Receive<ServiceLevelChanged>(HandleServiceLevelChanged);
        Receive<RedundancyStateChanged>(HandleRedundancyStateChanged);
        Receive<SubscribeAck>(_ => { /* PubSub ack */ });
    }

    /// <inheritdoc />
    protected override void PreStart()
    {
        if (_subscribeRedundancyTopic)
        {
            DistributedPubSub.Get(Context.System).Mediator.Tell(new Subscribe(RedundancyStateTopic, Self));
        }
    }

    private void HandleAttributeUpdate(AttributeValueUpdate msg)
    {
        try
        {
            _sink.WriteValue(msg.NodeId, msg.Value, msg.Quality, msg.TimestampUtc);
            Interlocked.Increment(ref _writes);
            OtOpcUaTelemetry.OpcUaSinkWrite.Add(1, new KeyValuePair<string, object?>("kind", "value"));
        }
        catch (Exception ex)
        {
            _log.Warning(ex, "OpcUaPublish: sink.WriteValue threw for {Node}", msg.NodeId);
        }
    }

    private void HandleAlarmUpdate(AlarmStateUpdate msg)
    {
        try
        {
            _sink.WriteAlarmState(msg.AlarmNodeId, msg.Active, msg.Acknowledged, msg.TimestampUtc);
            Interlocked.Increment(ref _writes);
            OtOpcUaTelemetry.OpcUaSinkWrite.Add(1, new KeyValuePair<string, object?>("kind", "alarm"));
        }
        catch (Exception ex)
        {
            _log.Warning(ex, "OpcUaPublish: sink.WriteAlarmState threw for {Node}", msg.AlarmNodeId);
        }
    }

    private void HandleRebuild(RebuildAddressSpace msg)
    {
        using var span = OtOpcUaTelemetry.StartAddressSpaceRebuildSpan();
        span?.SetTag("otopcua.correlation_id", msg.Correlation.ToString());

        // Two modes: when dbFactory + applier are wired, do a real diff-and-apply pass against
        // the latest deployment artifact. Without them, fall back to a raw sink rebuild — the
        // F10b/dev path before the integration completes.
        if (_dbFactory is null || _applier is null)
        {
            try
            {
                _sink.RebuildAddressSpace();
                OtOpcUaTelemetry.OpcUaSinkWrite.Add(1, new KeyValuePair<string, object?>("kind", "rebuild"));
            }
            catch (Exception ex)
            {
                _log.Error(ex, "OpcUaPublish: sink.RebuildAddressSpace threw (correlation={Correlation})",
                    msg.Correlation);
            }
            return;
        }

        try
        {
            // Prefer the artifact of the deployment the host just applied — at apply time it is not
            // yet Sealed, so LoadLatestArtifact would return the PREVIOUS revision and materialise a
            // stale composition (variables that don't match the SubscribeBulk refs). Fall back to
            // latest-sealed only for legacy callers that don't carry a DeploymentId.
            var artifact = msg.DeploymentId is { } depId
                ? LoadArtifact(depId)
                : LoadLatestArtifact();
            var composition = DeploymentArtifact.ParseComposition(artifact);
            var plan = Phase7Planner.Compute(_lastApplied, composition);

            if (plan.IsEmpty)
            {
                _log.Debug("OpcUaPublish: rebuild requested but plan is empty (correlation={Correlation})",
                    msg.Correlation);
                return;
            }

            var outcome = _applier.Apply(plan);
            _lastApplied = composition;

            // #85 — after the plan diff lands, rebuild the UNS folder hierarchy so OPC UA
            // clients see Area/Line/Equipment as proper folders. Idempotent; Phase7Applier
            // skips folders that already exist with the same node id.
            _applier.MaterialiseHierarchy(composition);
            // Galaxy / SystemPlatform tags get their own pass: ensures their FolderPath folder
            // + Variable node exist so clients can browse them. The Galaxy driver fills values
            // on a future SubscribeBulk pass; until then variables show BadWaitingForInitialData.
            _applier.MaterialiseGalaxyTags(composition);

            OtOpcUaTelemetry.OpcUaSinkWrite.Add(1, new KeyValuePair<string, object?>("kind", "rebuild"));
            _log.Info("OpcUaPublish: applied rebuild (correlation={Correlation}, added={Added}, removed={Removed}, changed={Changed}, rebuild={Rebuild})",
                msg.Correlation, outcome.AddedNodes, outcome.RemovedNodes, outcome.ChangedNodes, outcome.RebuildCalled);
        }
        catch (Exception ex)
        {
            _log.Error(ex, "OpcUaPublish: rebuild pipeline threw (correlation={Correlation})", msg.Correlation);
        }
    }

    /// <summary>Read a specific deployment's artifact blob from ConfigDb (the one just applied,
    /// which may not be Sealed yet). Empty array on any failure — parser treats it as "no composition".</summary>
    private byte[] LoadArtifact(DeploymentId deploymentId)
    {
        try
        {
            using var db = _dbFactory!.CreateDbContext();
            return db.Deployments.AsNoTracking()
                .Where(d => d.DeploymentId == deploymentId.Value)
                .Select(d => d.ArtifactBlob)
                .FirstOrDefault() ?? Array.Empty<byte>();
        }
        catch (Exception ex)
        {
            _log.Warning(ex, "OpcUaPublish: failed to load artifact for deployment {Id}; rebuild becomes no-op", deploymentId);
            return Array.Empty<byte>();
        }
    }

    /// <summary>Read the most recent <c>Sealed</c> deployment's artifact blob from ConfigDb.
    /// Empty array on any failure — the parser treats empty blob as "no composition".</summary>
    private byte[] LoadLatestArtifact()
    {
        try
        {
            using var db = _dbFactory!.CreateDbContext();
            return db.Deployments.AsNoTracking()
                .Where(d => d.Status == Configuration.Enums.DeploymentStatus.Sealed)
                .OrderByDescending(d => d.SealedAtUtc)
                .Select(d => d.ArtifactBlob)
                .FirstOrDefault() ?? Array.Empty<byte>();
        }
        catch (Exception ex)
        {
            _log.Warning(ex, "OpcUaPublish: failed to load latest deployment artifact; rebuild becomes no-op");
            return Array.Empty<byte>();
        }
    }

    private void HandleServiceLevelChanged(ServiceLevelChanged msg)
    {
        if (msg.ServiceLevel == _lastServiceLevel) return;
        _lastServiceLevel = msg.ServiceLevel;
        try
        {
            _serviceLevel.Publish(msg.ServiceLevel);
            OtOpcUaTelemetry.ServiceLevelChange.Add(1,
                new KeyValuePair<string, object?>("level", msg.ServiceLevel));
            _log.Debug("OpcUaPublish: ServiceLevel={Level}", msg.ServiceLevel);
        }
        catch (Exception ex)
        {
            _log.Warning(ex, "OpcUaPublish: ServiceLevel publisher threw at level {Level}", msg.ServiceLevel);
        }
    }

    /// <summary>
    ///     Compute a coarse ServiceLevel from the cluster snapshot and forward to the
    ///     <see cref="IServiceLevelPublisher"/>. This is a placeholder for F10b's full health
    ///     aggregation — for now we surface "primary-leader → 240, secondary → 100, detached → 0"
    ///     so the local SDK at least reflects role state. The full <see cref="ServiceLevelCalculator"/>
    ///     path (with DB-reachable, OPC UA probe inputs) lives in <c>RedundancyStateActor</c> on
    ///     admin nodes; this driver-side mirror exists so each node's own SDK exposes a sensible
    ///     ServiceLevel without round-tripping back through the admin singleton.
    /// </summary>
    private void HandleRedundancyStateChanged(RedundancyStateChanged msg)
    {
        if (_localNode is null) return;

        var local = msg.Nodes.FirstOrDefault(n => n.NodeId == _localNode.Value);
        if (local is null) return;

        byte level = local.Role switch
        {
            RedundancyRole.Primary when local.IsRoleLeaderForDriver => 240,
            RedundancyRole.Primary => 200,
            RedundancyRole.Secondary => 100,
            RedundancyRole.Detached => 0,
            _ => 0,
        };
        Self.Tell(new ServiceLevelChanged(level));
    }
}