using System;
using System.Collections.Generic;
using System.Linq;
using Serilog;
using ZB.MOM.WW.OtOpcUa.Host.Domain;

namespace ZB.MOM.WW.OtOpcUa.Host.OpcUa
{
    /// <summary>
    ///     Builds the tag reference mappings from Galaxy hierarchy and attributes.
    ///     Testable without an OPC UA server. (OPC-002, OPC-003, OPC-004)
    /// </summary>
    public class AddressSpaceBuilder
    {
        private static readonly ILogger Log = Serilog.Log.ForContext<AddressSpaceBuilder>();

        /// <summary>
        ///     Builds an in-memory model of the Galaxy hierarchy and attribute mappings before the OPC UA server materializes
        ///     nodes.
        /// </summary>
        /// <param name="hierarchy">The Galaxy object hierarchy returned by the repository.</param>
        /// <param name="attributes">The Galaxy attribute rows associated with the hierarchy.</param>
        /// <returns>An address-space model containing roots, variables, and tag-reference mappings.</returns>
        public static AddressSpaceModel Build(List<GalaxyObjectInfo> hierarchy, List<GalaxyAttributeInfo> attributes)
        {
            var model = new AddressSpaceModel();
            var objectMap = hierarchy.ToDictionary(h => h.GobjectId);

            var attrsByObject = attributes
                .GroupBy(a => a.GobjectId)
                .ToDictionary(g => g.Key, g => g.ToList());

            // Build parent→children map
            var childrenByParent = hierarchy.GroupBy(h => h.ParentGobjectId)
                .ToDictionary(g => g.Key, g => g.ToList());

            // Find root objects (parent not in hierarchy)
            var knownIds = new HashSet<int>(hierarchy.Select(h => h.GobjectId));

            foreach (var obj in hierarchy)
            {
                var nodeInfo = BuildNodeInfo(obj, attrsByObject, childrenByParent, model);

                if (!knownIds.Contains(obj.ParentGobjectId))
                    model.RootNodes.Add(nodeInfo);
            }

            Log.Information("Address space model: {Objects} objects, {Variables} variables, {Mappings} tag refs",
                model.ObjectCount, model.VariableCount, model.NodeIdToTagReference.Count);

            return model;
        }

        private static NodeInfo BuildNodeInfo(GalaxyObjectInfo obj,
            Dictionary<int, List<GalaxyAttributeInfo>> attrsByObject,
            Dictionary<int, List<GalaxyObjectInfo>> childrenByParent,
            AddressSpaceModel model)
        {
            var node = new NodeInfo
            {
                GobjectId = obj.GobjectId,
                TagName = obj.TagName,
                BrowseName = obj.BrowseName,
                ParentGobjectId = obj.ParentGobjectId,
                IsArea = obj.IsArea
            };

            if (!obj.IsArea)
                model.ObjectCount++;

            if (attrsByObject.TryGetValue(obj.GobjectId, out var attrs))
                foreach (var attr in attrs)
                {
                    node.Attributes.Add(new AttributeNodeInfo
                    {
                        AttributeName = attr.AttributeName,
                        FullTagReference = attr.FullTagReference,
                        MxDataType = attr.MxDataType,
                        IsArray = attr.IsArray,
                        ArrayDimension = attr.ArrayDimension,
                        PrimitiveName = attr.PrimitiveName ?? "",
                        SecurityClassification = attr.SecurityClassification,
                        IsHistorized = attr.IsHistorized,
                        IsAlarm = attr.IsAlarm
                    });

                    model.NodeIdToTagReference[GetNodeIdentifier(attr)] = attr.FullTagReference;
                    model.VariableCount++;
                }

            return node;
        }

        private static string GetNodeIdentifier(GalaxyAttributeInfo attr)
        {
            if (!attr.IsArray)
                return attr.FullTagReference;

            return attr.FullTagReference.EndsWith("[]", StringComparison.Ordinal)
                ? attr.FullTagReference.Substring(0, attr.FullTagReference.Length - 2)
                : attr.FullTagReference;
        }

        /// <summary>
        ///     Node info for the address space tree.
        /// </summary>
        public class NodeInfo
        {
            /// <summary>
            ///     Gets or sets the Galaxy object identifier represented by this address-space node.
            /// </summary>
            public int GobjectId { get; set; }

            /// <summary>
            ///     Gets or sets the runtime tag name used to tie the node back to Galaxy metadata.
            /// </summary>
            public string TagName { get; set; } = "";

            /// <summary>
            ///     Gets or sets the browse name exposed to OPC UA clients for this hierarchy node.
            /// </summary>
            public string BrowseName { get; set; } = "";

            /// <summary>
            ///     Gets or sets the parent Galaxy object identifier used to assemble the tree.
            /// </summary>
            public int ParentGobjectId { get; set; }

            /// <summary>
            ///     Gets or sets a value indicating whether the node represents a Galaxy area folder.
            /// </summary>
            public bool IsArea { get; set; }

            /// <summary>
            ///     Gets or sets the attribute nodes published beneath this object.
            /// </summary>
            public List<AttributeNodeInfo> Attributes { get; set; } = new();

            /// <summary>
            ///     Gets or sets the child nodes that appear under this branch of the Galaxy hierarchy.
            /// </summary>
            public List<NodeInfo> Children { get; set; } = new();
        }

        /// <summary>
        ///     Lightweight description of an attribute node that will become an OPC UA variable.
        /// </summary>
        public class AttributeNodeInfo
        {
            /// <summary>
            ///     Gets or sets the Galaxy attribute name published under the object.
            /// </summary>
            public string AttributeName { get; set; } = "";

            /// <summary>
            ///     Gets or sets the fully qualified runtime reference used for reads, writes, and subscriptions.
            /// </summary>
            public string FullTagReference { get; set; } = "";

            /// <summary>
            ///     Gets or sets the Galaxy data type code used to pick the OPC UA variable type.
            /// </summary>
            public int MxDataType { get; set; }

            /// <summary>
            ///     Gets or sets a value indicating whether the attribute is modeled as an array.
            /// </summary>
            public bool IsArray { get; set; }

            /// <summary>
            ///     Gets or sets the declared array length when the attribute is a fixed-size array.
            /// </summary>
            public int? ArrayDimension { get; set; }

            /// <summary>
            ///     Gets or sets the primitive name that groups the attribute under a sub-object node.
            ///     Empty for root-level attributes.
            /// </summary>
            public string PrimitiveName { get; set; } = "";

            /// <summary>
            ///     Gets or sets the Galaxy security classification that determines OPC UA write access.
            /// </summary>
            public int SecurityClassification { get; set; } = 1;

            /// <summary>
            ///     Gets or sets a value indicating whether the attribute is historized.
            /// </summary>
            public bool IsHistorized { get; set; }

            /// <summary>
            ///     Gets or sets a value indicating whether the attribute is an alarm.
            /// </summary>
            public bool IsAlarm { get; set; }
        }

        /// <summary>
        ///     Result of building the address space model.
        /// </summary>
        public class AddressSpaceModel
        {
            /// <summary>
            ///     Gets or sets the root nodes that become the top-level browse entries in the Galaxy namespace.
            /// </summary>
            public List<NodeInfo> RootNodes { get; set; } = new();

            /// <summary>
            ///     Gets or sets the mapping from OPC UA node identifiers to runtime tag references.
            /// </summary>
            public Dictionary<string, string> NodeIdToTagReference { get; set; } =
                new(StringComparer.OrdinalIgnoreCase);

            /// <summary>
            ///     Gets or sets the number of non-area Galaxy objects included in the model.
            /// </summary>
            public int ObjectCount { get; set; }

            /// <summary>
            ///     Gets or sets the number of variable nodes created from Galaxy attributes.
            /// </summary>
            public int VariableCount { get; set; }
        }
    }
}