using System.Globalization;
using Microsoft.Extensions.Logging;
using Opc.Ua;
using Opc.Ua.Server;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using DriverWriteRequest = ZB.MOM.WW.OtOpcUa.Core.Abstractions.WriteRequest;

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

/// <summary>
///     Concrete <see cref="CustomNodeManager2"/> that materializes the driver's address space
///     into OPC UA nodes. Implements <see cref="IAddressSpaceBuilder"/> itself so
///     <c>GenericDriverNodeManager.BuildAddressSpaceAsync</c> can stream nodes directly into the
///     OPC UA server's namespace. PR 15's <c>MarkAsAlarmCondition</c> hook creates a sibling
///     <see cref="AlarmConditionState"/> node per alarm-flagged variable; subsequent driver
///     <c>OnAlarmEvent</c> pushes land through the returned sink to drive Activate /
///     Acknowledge / Deactivate transitions.
/// </summary>
/// <remarks>
///     Read / Subscribe / Write are routed to the driver's capability interfaces — the node
///     manager holds references to <see cref="IReadable"/>, <see cref="ISubscribable"/>, and
///     <see cref="IWritable"/> when present. Nodes with no driver backing (plain folders) are
///     served directly from the internal PredefinedNodes table.
/// </remarks>
public sealed class DriverNodeManager : CustomNodeManager2, IAddressSpaceBuilder
{
    private readonly IDriver _driver;
    private readonly IReadable? _readable;
    private readonly IWritable? _writable;
    private readonly ILogger<DriverNodeManager> _logger;

    /// <summary>The driver whose address space this node manager exposes.</summary>
    public IDriver Driver => _driver;

    private FolderState? _driverRoot;
    private readonly Dictionary<string, BaseDataVariableState> _variablesByFullRef = new(StringComparer.OrdinalIgnoreCase);

    // Active building folder — set per Folder() call so Variable() lands under the right parent.
    // A stack would support nested folders; we use a single current folder because IAddressSpaceBuilder
    // returns a child builder per Folder call and the caller threads nesting through those references.
    private FolderState _currentFolder = null!;

    public DriverNodeManager(IServerInternal server, ApplicationConfiguration configuration,
        IDriver driver, ILogger<DriverNodeManager> logger)
        : base(server, configuration, namespaceUris: $"urn:OtOpcUa:{driver.DriverInstanceId}")
    {
        _driver = driver;
        _readable = driver as IReadable;
        _writable = driver as IWritable;
        _logger = logger;
    }

    protected override NodeStateCollection LoadPredefinedNodes(ISystemContext context) => new();

    public override void CreateAddressSpace(IDictionary<NodeId, IList<IReference>> externalReferences)
    {
        lock (Lock)
        {
            _driverRoot = new FolderState(null)
            {
                SymbolicName = _driver.DriverInstanceId,
                ReferenceTypeId = ReferenceTypeIds.Organizes,
                TypeDefinitionId = ObjectTypeIds.FolderType,
                NodeId = new NodeId(_driver.DriverInstanceId, NamespaceIndex),
                BrowseName = new QualifiedName(_driver.DriverInstanceId, NamespaceIndex),
                DisplayName = new LocalizedText(_driver.DriverInstanceId),
                EventNotifier = EventNotifiers.None,
            };

            // Link under Objects folder so clients see the driver subtree at browse root.
            if (!externalReferences.TryGetValue(ObjectIds.ObjectsFolder, out var references))
            {
                references = new List<IReference>();
                externalReferences[ObjectIds.ObjectsFolder] = references;
            }
            references.Add(new NodeStateReference(ReferenceTypeIds.Organizes, false, _driverRoot.NodeId));

            AddPredefinedNode(SystemContext, _driverRoot);
            _currentFolder = _driverRoot;
        }
    }

    // ------- IAddressSpaceBuilder implementation (PR 15 contract) -------

    public IAddressSpaceBuilder Folder(string browseName, string displayName)
    {
        lock (Lock)
        {
            var folder = new FolderState(_currentFolder)
            {
                SymbolicName = browseName,
                ReferenceTypeId = ReferenceTypeIds.Organizes,
                TypeDefinitionId = ObjectTypeIds.FolderType,
                NodeId = new NodeId($"{_currentFolder.NodeId.Identifier}/{browseName}", NamespaceIndex),
                BrowseName = new QualifiedName(browseName, NamespaceIndex),
                DisplayName = new LocalizedText(displayName),
            };
            _currentFolder.AddChild(folder);
            AddPredefinedNode(SystemContext, folder);
            return new NestedBuilder(this, folder);
        }
    }

    public IVariableHandle Variable(string browseName, string displayName, DriverAttributeInfo attributeInfo)
    {
        lock (Lock)
        {
            var v = new BaseDataVariableState(_currentFolder)
            {
                SymbolicName = browseName,
                ReferenceTypeId = ReferenceTypeIds.Organizes,
                TypeDefinitionId = VariableTypeIds.BaseDataVariableType,
                NodeId = new NodeId(attributeInfo.FullName, NamespaceIndex),
                BrowseName = new QualifiedName(browseName, NamespaceIndex),
                DisplayName = new LocalizedText(displayName),
                DataType = MapDataType(attributeInfo.DriverDataType),
                ValueRank = attributeInfo.IsArray ? ValueRanks.OneDimension : ValueRanks.Scalar,
                AccessLevel = AccessLevels.CurrentReadOrWrite,
                UserAccessLevel = AccessLevels.CurrentReadOrWrite,
                Historizing = attributeInfo.IsHistorized,
            };
            _currentFolder.AddChild(v);
            AddPredefinedNode(SystemContext, v);
            _variablesByFullRef[attributeInfo.FullName] = v;

            v.OnReadValue = OnReadValue;
            v.OnWriteValue = OnWriteValue;
            return new VariableHandle(this, v, attributeInfo.FullName);
        }
    }

    public void AddProperty(string browseName, DriverDataType dataType, object? value)
    {
        lock (Lock)
        {
            var p = new PropertyState(_currentFolder)
            {
                SymbolicName = browseName,
                ReferenceTypeId = ReferenceTypeIds.HasProperty,
                TypeDefinitionId = VariableTypeIds.PropertyType,
                NodeId = new NodeId($"{_currentFolder.NodeId.Identifier}/{browseName}", NamespaceIndex),
                BrowseName = new QualifiedName(browseName, NamespaceIndex),
                DisplayName = new LocalizedText(browseName),
                DataType = MapDataType(dataType),
                ValueRank = ValueRanks.Scalar,
                Value = value,
            };
            _currentFolder.AddChild(p);
            AddPredefinedNode(SystemContext, p);
        }
    }

    private ServiceResult OnReadValue(ISystemContext context, NodeState node, NumericRange indexRange,
        QualifiedName dataEncoding, ref object? value, ref StatusCode statusCode, ref DateTime timestamp)
    {
        if (_readable is null)
        {
            statusCode = StatusCodes.BadNotReadable;
            return ServiceResult.Good;
        }

        try
        {
            var fullRef = node.NodeId.Identifier as string ?? "";
            var result = _readable.ReadAsync([fullRef], CancellationToken.None).GetAwaiter().GetResult();
            if (result.Count == 0)
            {
                statusCode = StatusCodes.BadNoData;
                return ServiceResult.Good;
            }
            var snap = result[0];
            value = snap.Value;
            statusCode = snap.StatusCode;
            timestamp = snap.ServerTimestampUtc;
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "OnReadValue failed for {NodeId}", node.NodeId);
            statusCode = StatusCodes.BadInternalError;
        }
        return ServiceResult.Good;
    }

    private static NodeId MapDataType(DriverDataType t) => t switch
    {
        DriverDataType.Boolean => DataTypeIds.Boolean,
        DriverDataType.Int32 => DataTypeIds.Int32,
        DriverDataType.Float32 => DataTypeIds.Float,
        DriverDataType.Float64 => DataTypeIds.Double,
        DriverDataType.String => DataTypeIds.String,
        DriverDataType.DateTime => DataTypeIds.DateTime,
        _ => DataTypeIds.BaseDataType,
    };

    /// <summary>
    ///     Nested builder returned by <see cref="Folder"/>. Temporarily retargets the parent's
    ///     <see cref="_currentFolder"/> during each call so Variable/Folder calls land under the
    ///     correct subtree. Not thread-safe if callers drive Discovery concurrently — but
    ///     <c>GenericDriverNodeManager</c> discovery is sequential per driver.
    /// </summary>
    private sealed class NestedBuilder(DriverNodeManager owner, FolderState folder) : IAddressSpaceBuilder
    {
        public IAddressSpaceBuilder Folder(string browseName, string displayName)
        {
            var prior = owner._currentFolder;
            owner._currentFolder = folder;
            try { return owner.Folder(browseName, displayName); }
            finally { owner._currentFolder = prior; }
        }

        public IVariableHandle Variable(string browseName, string displayName, DriverAttributeInfo attributeInfo)
        {
            var prior = owner._currentFolder;
            owner._currentFolder = folder;
            try { return owner.Variable(browseName, displayName, attributeInfo); }
            finally { owner._currentFolder = prior; }
        }

        public void AddProperty(string browseName, DriverDataType dataType, object? value)
        {
            var prior = owner._currentFolder;
            owner._currentFolder = folder;
            try { owner.AddProperty(browseName, dataType, value); }
            finally { owner._currentFolder = prior; }
        }
    }

    private sealed class VariableHandle : IVariableHandle
    {
        private readonly DriverNodeManager _owner;
        private readonly BaseDataVariableState _variable;
        public string FullReference { get; }

        public VariableHandle(DriverNodeManager owner, BaseDataVariableState variable, string fullRef)
        {
            _owner = owner;
            _variable = variable;
            FullReference = fullRef;
        }

        public IAlarmConditionSink MarkAsAlarmCondition(AlarmConditionInfo info)
        {
            lock (_owner.Lock)
            {
                var alarm = new AlarmConditionState(_variable)
                {
                    SymbolicName = _variable.BrowseName.Name + "_Condition",
                    ReferenceTypeId = ReferenceTypeIds.HasComponent,
                    NodeId = new NodeId(FullReference + ".Condition", _owner.NamespaceIndex),
                    BrowseName = new QualifiedName(_variable.BrowseName.Name + "_Condition", _owner.NamespaceIndex),
                    DisplayName = new LocalizedText(info.SourceName),
                };
                alarm.Create(_owner.SystemContext, alarm.NodeId, alarm.BrowseName, alarm.DisplayName, false);
                alarm.SourceName.Value = info.SourceName;
                alarm.Severity.Value = (ushort)MapSeverity(info.InitialSeverity);
                alarm.Message.Value = new LocalizedText(info.InitialDescription ?? info.SourceName);
                alarm.EnabledState.Value = new LocalizedText("Enabled");
                alarm.EnabledState.Id.Value = true;
                alarm.Retain.Value = false;
                alarm.AckedState.Value = new LocalizedText("Acknowledged");
                alarm.AckedState.Id.Value = true;
                alarm.ActiveState.Value = new LocalizedText("Inactive");
                alarm.ActiveState.Id.Value = false;

                _variable.AddChild(alarm);
                _owner.AddPredefinedNode(_owner.SystemContext, alarm);

                return new ConditionSink(_owner, alarm);
            }
        }

        private static int MapSeverity(AlarmSeverity s) => s switch
        {
            AlarmSeverity.Low => 250,
            AlarmSeverity.Medium => 500,
            AlarmSeverity.High => 700,
            AlarmSeverity.Critical => 900,
            _ => 500,
        };
    }

    private sealed class ConditionSink(DriverNodeManager owner, AlarmConditionState alarm)
        : IAlarmConditionSink
    {
        public void OnTransition(AlarmEventArgs args)
        {
            lock (owner.Lock)
            {
                alarm.Severity.Value = (ushort)MapSeverity(args.Severity);
                alarm.Time.Value = args.SourceTimestampUtc;
                alarm.Message.Value = new LocalizedText(args.Message);

                // Map the driver's transition type to OPC UA Part 9 state. The driver uses
                // AlarmEventArgs but the state transition kind is encoded in AlarmType by
                // convention — Galaxy's GalaxyAlarmTracker emits "Active"/"Acknowledged"/"Inactive".
                switch (args.AlarmType)
                {
                    case "Active":
                        alarm.SetActiveState(owner.SystemContext, true);
                        alarm.SetAcknowledgedState(owner.SystemContext, false);
                        alarm.Retain.Value = true;
                        break;
                    case "Acknowledged":
                        alarm.SetAcknowledgedState(owner.SystemContext, true);
                        break;
                    case "Inactive":
                        alarm.SetActiveState(owner.SystemContext, false);
                        // Retain stays true until the condition is both Inactive and Acknowledged
                        // so alarm clients keep the record in their condition refresh snapshot.
                        if (alarm.AckedState.Id.Value) alarm.Retain.Value = false;
                        break;
                }

                alarm.ClearChangeMasks(owner.SystemContext, true);
                alarm.ReportEvent(owner.SystemContext, alarm);
            }
        }

        private static int MapSeverity(AlarmSeverity s) => s switch
        {
            AlarmSeverity.Low => 250,
            AlarmSeverity.Medium => 500,
            AlarmSeverity.High => 700,
            AlarmSeverity.Critical => 900,
            _ => 500,
        };
    }

    /// <summary>
    ///     Per-variable write hook wired on each <see cref="BaseDataVariableState"/>. Routes the
    ///     value into the driver's <see cref="IWritable"/> and surfaces its per-tag status code.
    /// </summary>
    private ServiceResult OnWriteValue(ISystemContext context, NodeState node, NumericRange indexRange,
        QualifiedName dataEncoding, ref object? value, ref StatusCode statusCode, ref DateTime timestamp)
    {
        if (_writable is null) return StatusCodes.BadNotWritable;
        var fullRef = node.NodeId.Identifier as string;
        if (string.IsNullOrEmpty(fullRef)) return StatusCodes.BadNodeIdUnknown;

        try
        {
            var results = _writable.WriteAsync(
                [new DriverWriteRequest(fullRef!, value)],
                CancellationToken.None).GetAwaiter().GetResult();
            if (results.Count > 0 && results[0].StatusCode != 0)
            {
                statusCode = results[0].StatusCode;
                return ServiceResult.Good;
            }
            return ServiceResult.Good;
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "Write failed for {FullRef}", fullRef);
            return new ServiceResult(StatusCodes.BadInternalError);
        }
    }

    // Diagnostics hook for tests — number of variables registered in this node manager.
    internal int VariableCount => _variablesByFullRef.Count;
    internal bool TryGetVariable(string fullRef, out BaseDataVariableState? v)
        => _variablesByFullRef.TryGetValue(fullRef, out v!);
}