using Sandbox;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace ExtendedEditor;

public class TypeJsonConverter : JsonConverter<Type>
{
    public const string TypePropertyName = "$type";
    public const string GenericArgsPropertyName = "$args";

    public override Type? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        if(typeToConvert != typeof(Type))
        {
            Log.Warning($"Can't deserialize Type to {typeToConvert.FullName}.");
            return null!;
        }

        if(reader.TokenType == JsonTokenType.Null)
            return null!;

        if(reader.TokenType != JsonTokenType.String && reader.TokenType != JsonTokenType.StartObject)
        {
            Log.Warning($"Invalid JSON format for {nameof(TypeJsonConverter)}. Expected one of [{JsonTokenType.Null}, {JsonTokenType.String}, {JsonTokenType.StartObject}].");
            return default!;
        }

        if(reader.TokenType == JsonTokenType.String)
        {
            var type = TypeLibrary.GetType(reader.GetString());
            if(type is null)
            {
                Log.Warning($"Type {reader.GetString()} is not allowed to be deserialized by whitelist.");
                return null!;
            }

            return type.TargetType;
        }

        TypeDescription? genericTypeDefinition = null;
        List<Type?> args = [];

        while(reader.Read() && reader.TokenType != JsonTokenType.EndObject)
        {
            if(reader.TokenType != JsonTokenType.PropertyName)
                Log.Warning($"Invalid JSON format for {nameof(TypeJsonConverter)}. Expected {JsonTokenType.PropertyName}.");

            var name = reader.ValueSpan;

            if(name.SequenceEqual("$type"u8))
            {
                if(!reader.Read() || (reader.TokenType != JsonTokenType.String))
                {
                    Log.Warning($"Invalid JSON format for {nameof(TypeJsonConverter)}. Expected {JsonTokenType.String}.");
                    return null!;
                }

                var type = TypeLibrary.GetType(reader.GetString());
                if(type is null)
                {
                    Log.Warning($"Type {reader.GetString()} is not allowed to be deserialized by whitelist.");
                    return null!;
                }

                genericTypeDefinition = type;
            }
            else if(name.SequenceEqual("$args"u8))
            {
                if(!reader.Read() || reader.TokenType != JsonTokenType.StartArray)
                {
                    Log.Warning($"Invalid JSON format for {nameof(TypeJsonConverter)}. Expected {JsonTokenType.StartArray}.");
                    return null!;
                }

                while(reader.Read() && reader.TokenType != JsonTokenType.EndArray)
                {
                    var argType = Read(ref reader, typeof(Type), options);
                    args.Add(argType);
                }

                if(reader.TokenType != JsonTokenType.EndArray)
                {
                    Log.Warning($"Invalid JSON format for {nameof(TypeJsonConverter)}. Expected {JsonTokenType.EndArray}.");
                    return null;
                }
            }
            else
            {
                reader.Skip();
                Log.Warning($"Invalid JSON format for {nameof(TypeJsonConverter)}. Unknown property '{reader.GetString()}' in {nameof(TypeJsonConverter)}.");
            }
        }

        if(reader.TokenType != JsonTokenType.EndObject)
        {
            Log.Warning($"Invalid JSON format for {nameof(TypeJsonConverter)}. Expected {JsonTokenType.EndObject}.");
            return null;
        }

        if(genericTypeDefinition is null)
        {
            Log.Warning($"Invalid JSON format for {nameof(TypeJsonConverter)}. Generic type definition not found or not generic type definition.");
            return null;
        }

        if(args.Count == 0)
        {
            Log.Warning($"Invalid JSON format for {nameof(TypeJsonConverter)}. Generic arguments not found.");
            return null;
        }

        if(args.Any(x => x is null))
            return genericTypeDefinition.TargetType;

        var result = genericTypeDefinition.MakeGenericType([.. args]);
        if(result is null)
            Log.Warning($"Type {genericTypeDefinition.FullName} is not allowed to be deserialized by constraints or by whitelist with theese generic arguments: {string.Join(", ", args.Select(x => x?.FullName ?? "null"))}.");

        return result;
    }

    public override void Write(Utf8JsonWriter writer, Type value, JsonSerializerOptions options)
    {
        if(value is null)
        {
            writer.WriteNullValue();
            return;
        }

        if(value.IsGenericType)
        {
            var typeDescription = TypeLibrary.GetType(value);
            if(typeDescription is null)
            {
                Log.Warning($"Type {value} is not allowed to be serialized by whitelist.");
                return;
            }

            var genericTypeDefinition = typeDescription.TargetType;
            var isGenericTypeDefinition = genericTypeDefinition == value;

            if(isGenericTypeDefinition)
            {
                writer.WriteStringValue(genericTypeDefinition.FullName);
            }
            else
            {
                writer.WriteStartObject();
                writer.WriteString(TypePropertyName, genericTypeDefinition.FullName);
                writer.WritePropertyName(GenericArgsPropertyName);

                writer.WriteStartArray();
                foreach(var parameterType in TypeLibrary.GetGenericArguments(value))
                    Write(writer, parameterType, options);
                writer.WriteEndArray();
                writer.WriteEndObject();
            }
        }
        else
        {
            writer.WriteStringValue(value.FullName);
        }
    }
}