using System.Collections;
using System.Reflection;
using Syntriax.Engine.Core;
using Syntriax.Engine.Core.Factory;

using YamlDotNet.Core;
using YamlDotNet.Core.Events;
using YamlDotNet.Serialization;

namespace Syntriax.Engine.Serialization;

public class EntityConverter(IReadOnlyDictionary<string, IEntity> entities) : IYamlTypeConverter
{
    private readonly IReadOnlyDictionary<string, IEntity> Entities = entities;
    private readonly HashSet<IEntity> entitiesVisited = [];

    public bool Accepts(Type type) => typeof(IEntity).IsAssignableFrom(type);

    public object? ReadYaml(IParser parser, Type type, ObjectDeserializer rootDeserializer)
    {
        parser.Consume<MappingStart>();

        TypeContainer typeContainer = (TypeContainer)rootDeserializer(typeof(TypeContainer))!;

        object instance = TypeFactory.Get(typeContainer.Type);

        while (!parser.TryConsume<MappingEnd>(out _))
        {
            string key = parser.Consume<Scalar>().Value;

            if (type.GetField(key, BindingFlags.Instance | BindingFlags.NonPublic) is FieldInfo fieldInfo)
            {
                object? fieldValue = rootDeserializer(fieldInfo.FieldType);
                fieldInfo.SetValue(instance, fieldValue);
            }
            else if (type.GetProperty(key) is PropertyInfo propertyInfo)
            {
                object? propertyValue = rootDeserializer(propertyInfo.PropertyType);
                propertyInfo.SetValue(instance, propertyValue);
            }
            else
                parser.SkipThisAndNestedEvents();
        }

        parser.TryConsume<MappingEnd>(out _);

        return instance;
    }

    public void WriteYaml(IEmitter emitter, object? value, Type type, ObjectSerializer serializer)
    {
        if (type.HasAttribute<IgnoreSerializationAttribute>())
        {
            emitter.Emit(new Scalar(""));
            return;
        }

        IEntity entity = (IEntity)value!;
        if (!entitiesVisited.Add(entity))
        {
            emitter.Emit(new Scalar(entity.Id));
            return;
        }

        emitter.Emit(new MappingStart());
        serializer(new TypeContainer(value), typeof(TypeContainer));

        TypeData typeData = Utils.GetTypeData(type);

        foreach (PropertyInfo propertyInfo in typeData.Properties)
        {
            if (propertyInfo.HasAttribute<IgnoreSerializationAttribute>())
                continue;

            emitter.Emit(new Scalar(propertyInfo.Name));
            object? propertyValue = propertyInfo.GetValue(value);

            EmitValue(propertyValue, propertyInfo.PropertyType, emitter, serializer);
        }

        foreach (FieldInfo fieldInfo in typeData.Fields)
        {
            if (fieldInfo.HasAttribute<System.Runtime.CompilerServices.CompilerGeneratedAttribute>())
                continue;

            if (fieldInfo.HasAttribute<IgnoreSerializationAttribute>())
                continue;

            // if (!fieldInfo.HasAttribute<SerializeAttribute>())
            //     continue;

            emitter.Emit(new Scalar(fieldInfo.Name));
            object? fieldValue = fieldInfo.GetValue(value);

            EmitValue(fieldValue, fieldInfo.FieldType, emitter, serializer);
        }

        emitter.Emit(new MappingEnd());
    }

    private static void EmitValue(object? value, Type declaredType, IEmitter emitter, ObjectSerializer serializer)
    {
        if (value is null)
        {
            emitter.Emit(new Scalar(""));
            return;
        }

        if (value is IEntity entity)
        {
            emitter.Emit(new Scalar(entity.Id));
            return;
        }

        bool isSequence = Utils.IsEnumerable(declaredType);

        if (!isSequence)
        {
            serializer(value);
            return;
        }

        IEnumerable sequence = (IEnumerable)value;

        emitter.Emit(new SequenceStart(null, null, false, SequenceStyle.Block));
        foreach (object? item in sequence)
            if (value is IEntity sequenceEntity)
                emitter.Emit(new Scalar(sequenceEntity.Id));
            else
                serializer(item);
        emitter.Emit(new SequenceEnd());
    }
}