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

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

namespace Syntriax.Engine.Serialization;

public class Vector2DConverter : IYamlTypeConverter
{
    public bool Accepts(Type type)
    {
        return type == typeof(Vector2D);
    }

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

        float x = 0f;
        float y = 0f;

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

            if (key.CompareTo(nameof(Vector2D.X)) == 0) x = float.Parse(value);
            if (key.CompareTo(nameof(Vector2D.Y)) == 0) y = float.Parse(value);
        }

        return new Vector2D(x, y);
    }

    public void WriteYaml(IEmitter emitter, object? value, Type type, ObjectSerializer serializer)
    {
        Vector2D vector2D = (Vector2D)value!;

        emitter.Emit(new MappingStart());
        emitter.Emit(new Scalar(nameof(Vector2D.X)));
        emitter.Emit(new Scalar(vector2D.X.ToString()));
        emitter.Emit(new Scalar(nameof(Vector2D.Y)));
        emitter.Emit(new Scalar(vector2D.Y.ToString()));
        emitter.Emit(new MappingEnd());
    }
}

public class EntityConverter : IYamlTypeConverter
{
    private static readonly ISerializer serializer = new SerializerBuilder()
        .WithNamingConvention(PascalCaseNamingConvention.Instance)
        .DisableAliases()
        .Build();

    private static readonly IDeserializer deserializer = new DeserializerBuilder()
        .WithNamingConvention(PascalCaseNamingConvention.Instance)
        .Build();

    public bool Accepts(Type type)
    {
        bool v = typeof(IEntity).IsAssignableFrom(type);
        return v;
    }

    public object? ReadYaml(IParser parser, Type type, ObjectDeserializer rootDeserializer)
    {
        string? id = null;

        parser.Consume<MappingStart>();

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

            if (key.CompareTo(nameof(EntityReference.Id)) == 0)
                id = value;
        }

        return new EntityReference() { Id = id };
    }
    public void WriteYaml(IEmitter emitter, object? value, Type type, ObjectSerializer serializer)
    {
        if (value is not IEntity entity)
            return;

        var typeData = GetTypeData(type);
        emitter.Emit(new MappingStart());

        foreach (var fieldInfo in typeData.Fields)
        {
            if (fieldInfo.GetCustomAttribute<System.Runtime.CompilerServices.CompilerGeneratedAttribute>() != null)
                continue;

            emitter.Emit(new Scalar(fieldInfo.Name));
            var fieldValue = fieldInfo.GetValue(entity);

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

        foreach (var propertyInfo in typeData.Properties)
        {
            emitter.Emit(new Scalar(propertyInfo.Name));
            var propValue = propertyInfo.GetValue(entity);

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

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

        if (value is IEntity singleEntity && !IsEnumerable(declaredType))
        {
            emitter.Emit(new Scalar(singleEntity.Id));
            return;
        }

        if (IsEnumerable(declaredType) && value is System.Collections.IEnumerable list)
        {
            emitter.Emit(new SequenceStart(null, null, false, SequenceStyle.Block));
            foreach (var item in list)
            {
                if (item is IEntity itemEntity)
                    emitter.Emit(new Scalar(itemEntity.Id));
                else
                    serializer(item); // fallback for non-entity items
            }
            emitter.Emit(new SequenceEnd());
            return;
        }

        // fallback
        serializer(value);
    }
    private static TypeData GetTypeData(Type objectType)
    {
        IEnumerable<System.Reflection.EventInfo> eventInfos = objectType.GetEvents(BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public)
            .OrderBy(ei => ei.Name)
            .AsEnumerable();
        IEnumerable<FieldInfo> fieldInfos = objectType.GetFields(BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public)
            .Where(fi => !eventInfos.Any(ei => fi.Name.CompareTo(ei.Name) == 0))
            .OrderBy(ei => ei.Name) //ei => ei.FieldType.IsPrimitive || ei.FieldType == typeof(string))
                                    // .ThenByDescending(ei => ei.Name)
            .AsEnumerable();
        IEnumerable<PropertyInfo> propertyInfos = objectType.GetProperties(BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public)
            .Where(pi => pi.SetMethod is not null)
            .OrderBy(ei => ei.Name)// ei => ei.PropertyType.IsPrimitive || ei.PropertyType == typeof(string))
                                   // .ThenByDescending(ei => ei.Name)
            .AsEnumerable();

        return new TypeData(eventInfos, fieldInfos, propertyInfos);
    }
    private static bool IsEnumerable(Type type)
    {
        return typeof(System.Collections.IEnumerable).IsAssignableFrom(type) && type != typeof(string);
    }
    private record struct TypeData(IEnumerable<System.Reflection.EventInfo> Events, IEnumerable<FieldInfo> Fields, IEnumerable<PropertyInfo> Properties)
    {
        public static implicit operator (IEnumerable<System.Reflection.EventInfo> events, IEnumerable<FieldInfo> fields, IEnumerable<PropertyInfo> properties)(TypeData value) => (value.Events, value.Fields, value.Properties);
        public static implicit operator TypeData((IEnumerable<System.Reflection.EventInfo> events, IEnumerable<FieldInfo> fields, IEnumerable<PropertyInfo> properties) value) => new TypeData(value.events, value.fields, value.properties);
    }
}