#nullable enable
using System;
using System.Buffers;
using System.Collections.Generic;

namespace ShrinkNetwork
{
    public interface IShrinkMessageCodec<T>
    {
        void Write(IBufferWriter<byte> writer, T value);
        T Read(ReadOnlyMemory<byte> payload);
    }

    /// <summary>Explicit codecs work with AOT and external modules without runtime generic reflection.</summary>
    public class ShrinkRegisteredNetworkSerializer : IShrinkNetworkBufferSerializer
    {
        private interface ICodec
        {
            void Write(IBufferWriter<byte> writer, object value);
            object Read(ReadOnlyMemory<byte> payload);
        }
        private sealed class Codec<T> : ICodec
        {
            private readonly IShrinkMessageCodec<T> _codec;
            public Codec(IShrinkMessageCodec<T> codec) => _codec = codec;
            public void Write(IBufferWriter<byte> writer, object value) => _codec.Write(writer, (T)value);
            public object Read(ReadOnlyMemory<byte> payload) => _codec.Read(payload)!;
        }
        private readonly Dictionary<Type, ICodec> _codecs = new();
        public void Register<T>(IShrinkMessageCodec<T> codec)
        {
            if (codec == null) throw new ArgumentNullException(nameof(codec));
            _codecs.Add(typeof(T), new Codec<T>(codec));
        }
        public bool Unregister<T>() => _codecs.Remove(typeof(T));
        private ICodec Resolve(Type type) => _codecs.TryGetValue(type, out var codec) ? codec :
            throw new InvalidOperationException($"SHRINK-NET-CODEC: No codec registered for {type.FullName}. Register a generated formatter before binding the transport.");
        public void Serialize(IBufferWriter<byte> writer, object value) => Resolve(value.GetType()).Write(writer, value);
        public object Deserialize(ReadOnlyMemory<byte> payload, Type type) => Resolve(type).Read(payload);
        public byte[] Serialize(object value)
        {
            using var writer = new ShrinkBufferWriter();
            Serialize(writer, value);
            return writer.WrittenMemory.ToArray();
        }
        public object Deserialize(byte[] payload, Type type) => Deserialize((ReadOnlyMemory<byte>)payload, type);
        public T Deserialize<T>(byte[] payload) => (T)Deserialize(payload, typeof(T));
    }
}