#nullable enable
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using Speckle.ConnectorUnity.Utils;
using Speckle.Core.Logging;
using Speckle.Core.Models;
using Speckle.Core.Models.GraphTraversal;
using UnityEngine;

namespace Speckle.ConnectorUnity.Components
{
    /// <summary>
    /// Struct that encapsulates the result of a <see cref="RecursiveConverter"/> ToNative conversion of a single Speckle Object (<see cref="Base"/>)
    /// </summary>
    public readonly struct ConversionResult
    {
        /// <summary>
        /// The context that was converted ToNative
        /// </summary>
        public readonly TraversalContext traversalContext;

        /// <summary>
        /// The result of conversion a successful conversion
        /// </summary>
        public readonly GameObject? converted;

        /// <summary>
        /// The result of conversion a failed conversion
        /// </summary>
        public readonly Exception? exception;

        /// <summary>
        /// Constructor used for Successful conversions
        /// </summary>
        /// <param name="traversalContext">The current traversal context</param>
        /// <param name="converted">The resultant ToNative conversion of <see cref="TraversalContext.current"/> context object</param>
        /// <exception cref="ArgumentNullException"/>
        public ConversionResult(TraversalContext traversalContext, [NotNull] GameObject? converted)
            : this(traversalContext, converted, null)
        {
            if (converted is null)
                throw new ArgumentNullException(nameof(converted));
        }

        /// <summary>
        /// Constructor used for Failed conversions
        /// </summary>
        /// <param name="traversalContext">The current conversion</param>
        /// <param name="exception">The operation halting exception that occured</param>
        /// <param name="converted">Optional converted GameObject</param>
        /// <exception cref="ArgumentNullException"/>
        public ConversionResult(
            TraversalContext traversalContext,
            [NotNull] Exception? exception,
            GameObject? converted = null
        )
            : this(traversalContext, converted, exception)
        {
            if (exception is null)
                throw new ArgumentNullException(nameof(exception));
        }

        private ConversionResult(
            TraversalContext traversalContext,
            GameObject? converted,
            Exception? exception
        )
        {
            this.traversalContext = traversalContext;
            this.converted = converted;
            this.exception = exception;
        }

        /// <summary>
        ///
        /// </summary>
        /// <param name="converted">The converted <see cref="GameObject"/></param>
        /// <param name="exception">The <see cref="exception"/> that occured during conversion</param>
        /// <returns>True if the conversion was successful</returns>
        public bool WasSuccessful(
            [NotNullWhen(true)] out GameObject? converted,
            [NotNullWhen(false)] out Exception? exception
        )
        {
            converted = this.converted;
            exception = this.exception;
            return WasSuccessful();
        }

        public bool WasSuccessful() => this.exception == null;

        public Base SpeckleObject => traversalContext.Current;
    }

    public partial class RecursiveConverter
    {
        /// <inheritdoc cref="RecursivelyConvertToNative_Enumerable"/>
        /// <remarks>Calling this function will perform the conversion process synchronously</remarks>
        /// <returns>The conversion result</returns>
        public List<ConversionResult> RecursivelyConvertToNative_Sync(
            Base rootObject,
            Transform? parent,
            Predicate<TraversalContext>? predicate = null
        )
        {
            return RecursivelyConvertToNative_Enumerable(rootObject, parent, predicate).ToList();
        }

        /// <inheritdoc cref="RecursivelyConvertToNative_Enumerable"/>
        /// <remarks>Calling this function will start a coroutine to complete later on the coroutine loop</remarks>
        /// <returns>The started Coroutine</returns>
        public Coroutine RecursivelyConvertToNative_Coroutine(
            Base rootObject,
            Transform? parent,
            Predicate<TraversalContext>? predicate = null
        )
        {
            return StartCoroutine(
                RecursivelyConvertToNative_Enumerable(rootObject, parent, predicate).GetEnumerator()
            );
        }

        /// <summary>
        /// Will recursively traverse the given <paramref name="rootObject"/> and convert convertable child objects
        /// where the given <see cref="predicate"/>
        /// </summary>
        /// <param name="rootObject">The Speckle object to traverse and convert all convertable children</param>
        /// <param name="parent">Optional parent <see cref="Transform"/> for the created root <see cref="GameObject"/>s</param>
        /// <param name="predicate">A filter function to allow for selectively excluding certain objects from being converted</param>
        /// <returns>An unevaluated <see cref="IEnumerable"/> of all created <see cref="GameObject"/>s</returns>
        public IEnumerable<ConversionResult> RecursivelyConvertToNative_Enumerable(
            Base rootObject,
            Transform? parent,
            Predicate<TraversalContext>? predicate = null
        )
        {
            var userPredicate = predicate ?? (_ => true);

            var traversalFunc = DefaultTraversal.CreateBIMTraverseFunc(ConverterInstance);

            var objectsToConvert = traversalFunc
                .Traverse(rootObject)
                .Where(x => ConverterInstance.CanConvertToNative(x.Current))
                .Where(x => userPredicate(x));

            Dictionary<Base, GameObject?> created = new();
            foreach (var conversionResult in ConvertTree(objectsToConvert, parent, created))
            {
                if (!isActiveAndEnabled)
                    throw new InvalidOperationException(
                        $"Cannot convert objects while {GetType()} is disabled"
                    );

                yield return conversionResult;
            }
        }

        /// <summary>
        /// Converts a objectTree (see <see cref="GraphTraversal"/>) to unevaluated enumerable.
        /// As this enumerable is iterated through, each context <see cref="Base"/> object will be converted to <see cref="GameObject"/> (if successful)
        /// or <see langword="null"/> if not.
        /// </summary>
        /// <remarks>
        /// You may enumerate over multiple frames (e.g. coroutine) but you must ensure the output eventually gets fully enumerated (exactly once)
        /// </remarks>
        /// <param name="objectTree"></param>
        /// <param name="parent"></param>
        /// <param name="outCreatedObjects"></param>
        /// <returns></returns>
        protected IEnumerable<ConversionResult> ConvertTree(
            IEnumerable<TraversalContext> objectTree,
            Transform? parent,
            IDictionary<Base, GameObject?> outCreatedObjects
        )
        {
            InitializeAssetCache();
            AssetCache.BeginWrite();

            foreach (TraversalContext tc in objectTree)
            {
                ConversionResult result;
                try
                {
                    Transform? currentParent = GetParent(tc, outCreatedObjects) ?? parent;

                    var converted = ConvertToNative(tc.Current, currentParent);
                    result = new ConversionResult(tc, converted);
                    outCreatedObjects.TryAdd(tc.Current, result.converted);
                }
                catch (Exception ex)
                {
                    result = new ConversionResult(tc, ex);
                }

                yield return result;
            }

            AssetCache.FinishWrite();
        }

        protected static Transform? GetParent(
            TraversalContext? tc,
            IDictionary<Base, GameObject?> createdObjects
        )
        {
            if (tc == null)
                return null; //We've reached the root object, and still not found a converted parent

            if (createdObjects.TryGetValue(tc.Current, out GameObject? p) && p != null)
                return p.transform;

            //Go one level up, and repeat!
            return GetParent(tc.Parent, createdObjects);
        }

        protected GameObject ConvertToNative(Base speckleObject, Transform? parentTransform)
        {
            GameObject? go = ConverterInstance.ConvertToNative(speckleObject) as GameObject;
            if (go == null)
                throw new SpeckleException("Conversion Returned Null");

            go.transform.SetParent(parentTransform, true);

            //Set some common for all created GameObjects
            //TODO add support for more unity specific props
            if (go.name == "New Game Object" || string.IsNullOrWhiteSpace(go.name))
                go.name = CoreUtils.GenerateObjectName(speckleObject);
            if (speckleObject["physicsLayer"] is string layerName)
            {
                int layer = LayerMask.NameToLayer(layerName); //TODO: check how this can be interoperable with Unreal and Blender
                if (layer > -1)
                    go.layer = layer;
            }
            //if (baseObject["tag"] is string t) go.tag = t;
            //if (baseObject["isStatic"] is bool isStatic) go.isStatic = isStatic;
            return go;
        }

        #region deprecated conversion functions
        [Obsolete("Use " + nameof(RecursivelyConvertToNative_Coroutine))]
        public IEnumerator ConvertCoroutine(
            Base rootObject,
            Transform? parent,
            List<GameObject> outCreatedObjects
        ) =>
            ConvertCoroutine(
                rootObject,
                parent,
                outCreatedObjects,
                b => ConverterInstance.CanConvertToNative(b)
            );

        [Obsolete("Use " + nameof(RecursivelyConvertToNative_Coroutine))]
        public IEnumerator ConvertCoroutine(
            Base rootObject,
            Transform? parent,
            List<GameObject> outCreatedObjects,
            Func<Base, bool> predicate
        )
        {
            foreach (string propertyName in GetPotentialChildren(rootObject))
            {
                ConvertChild(rootObject[propertyName], parent, predicate, outCreatedObjects);
                yield return null;
            }
        }

        /// <summary>
        /// Given <paramref name="o"/>,
        /// will recursively convert any objects in the tree
        /// </summary>
        /// <param name="o">The object to convert (<see cref="Base"/> or <see cref="List{T}"/> of)</param>
        /// <param name="parent">Optional parent transform for the created root <see cref="GameObject"/>s</param>
        /// <returns> A list of all created <see cref="GameObject"/>s</returns>
        [Obsolete("Use " + nameof(RecursivelyConvertToNative_Sync))]
        public virtual List<GameObject> RecursivelyConvertToNative(object? o, Transform? parent) =>
            RecursivelyConvertToNative(o, parent, b => ConverterInstance.CanConvertToNative(b));

        /// <inheritdoc cref="RecursivelyConvertToNative(object, Transform)"/>
        /// <param name="predicate">A function to determine if an object should be converted</param>
        [Obsolete("Use " + nameof(RecursivelyConvertToNative_Sync))]
        public virtual List<GameObject> RecursivelyConvertToNative(
            object? o,
            Transform? parent,
            Func<Base, bool> predicate
        )
        {
            InitializeAssetCache();

            var createdGameObjects = new List<GameObject>();
            try
            {
                AssetCache.BeginWrite();
                ConvertChild(o, parent, predicate, createdGameObjects);
            }
            finally
            {
                AssetCache.FinishWrite();
            }

            //TODO track event?


            return createdGameObjects;
        }

        private void InitializeAssetCache()
        {
            //Ensure we have A native cache
            if (AssetCache.nativeCaches.Any(x => x == null))
            {
                AssetCache.nativeCaches = NativeCacheFactory.GetStandaloneCacheSetup();
            }
            ConverterInstance.SetContextDocument(AssetCache);
        }

        [Obsolete]
        public virtual void RecurseTreeToNative(
            Base baseObject,
            Transform? parent,
            Func<Base, bool> predicate,
            IList<GameObject> outCreatedObjects
        )
        {
            object? converted = null;
            if (predicate(baseObject))
            {
                try
                {
                    converted = ConverterInstance.ConvertToNative(baseObject);
                }
                catch (Exception ex) when (!ex.IsFatal())
                {
                    Debug.LogWarning(
                        $"Failed to convert {baseObject.speckle_type} - {baseObject.id}\n{ex}"
                    );
                }
            }

            // Handle new GameObjects
            Transform? nextParent = parent;
            if (converted is GameObject go)
            {
                outCreatedObjects.Add(go);
                nextParent = go.transform;

                go.transform.SetParent(parent, true);

                //Set some common for all created GameObjects
                //TODO add support for more unity specific props
                if (go.name == "New Game Object" || string.IsNullOrWhiteSpace(go.name))
                    go.name = CoreUtils.GenerateObjectName(baseObject);
                //if (baseObject["tag"] is string t) go.tag = t;
                if (baseObject["physicsLayer"] is string layerName)
                {
                    int layer = LayerMask.NameToLayer(layerName); //TODO: check how this can be interoperable with Unreal and Blender
                    if (layer > -1)
                        go.layer = layer;
                }
                //if (baseObject["isStatic"] is bool isStatic) go.isStatic = isStatic;
            }

            // For geometry, only traverse `elements` prop, otherwise, try and convert everything
            IEnumerable<string> potentialChildren = GetPotentialChildren(baseObject);

            // Convert Children
            foreach (string propertyName in potentialChildren)
            {
                ConvertChild(baseObject[propertyName], nextParent, predicate, outCreatedObjects);
            }
        }

        [Obsolete]
        private IEnumerable<string> GetPotentialChildren(Base baseObject)
        {
            return ConverterInstance.CanConvertToNative(baseObject)
                ? new[] { "elements" }
                : baseObject.GetMembers().Keys;
        }

        [Obsolete]
        protected virtual void ConvertChild(
            object? value,
            Transform? parent,
            Func<Base, bool> predicate,
            IList<GameObject> outCreatedObjects
        )
        {
            foreach (Base b in GraphTraversal.TraverseMember(value))
            {
                RecurseTreeToNative(b, parent, predicate, outCreatedObjects);
            }
        }
        #endregion
    }
}