using System.Text.Json;
using System.Text.Json.Serialization;

namespace Prefab.Base;

/// <summary>
/// Creates JSON converters that serialize Prefab enums using their logical names.
/// </summary>
public sealed class PrefabEnumJsonConverterFactory : JsonConverterFactory
{
    /// <inheritdoc />
    public override bool CanConvert(Type typeToConvert)
    {
        if (!typeToConvert.IsClass)
        {
            return false;
        }

        var baseType = typeToConvert;
        while (baseType is not null)
        {
            if (baseType.IsGenericType && baseType.GetGenericTypeDefinition() == typeof(PrefabEnum<>))
            {
                return true;
            }

            baseType = baseType.BaseType;
        }

        return false;
    }

    /// <inheritdoc />
    public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializerOptions options)
    {
        var converterType = typeof(PrefabEnumJsonConverter<>).MakeGenericType(typeToConvert);
        return (JsonConverter)Activator.CreateInstance(converterType)!;
    }

    /// <summary>
    /// Converter used for concrete Prefab enum types.
    /// </summary>
    private sealed class PrefabEnumJsonConverter<TEnum> : JsonConverter<TEnum> where TEnum : PrefabEnum<TEnum>
    {
        /// <inheritdoc />
        public override TEnum? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
        {
            if (reader.TokenType == JsonTokenType.String)
            {
                var name = reader.GetString() ?? string.Empty;
                return PrefabEnum<TEnum>.FromName(name);
            }

            if (reader.TokenType == JsonTokenType.Number && reader.TryGetInt32(out var value))
            {
                return PrefabEnum<TEnum>.FromValue(value);
            }

            throw new JsonException($"Unexpected token {reader.TokenType} when parsing {typeof(TEnum).Name}.");
        }

        /// <inheritdoc />
        public override void Write(Utf8JsonWriter writer, TEnum value, JsonSerializerOptions options) => writer.WriteStringValue(value.Name);
    }
}