// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
namespace Roslyn.LanguageServer.Protocol;
 
using System;
using System.Text.Json;
using System.Text.Json.Serialization;
 
/// <summary>
/// Converter used to serialize and deserialize classes extending types defined in the
/// Microsoft.VisualStudio.LanguageServer.Protocol package.
/// </summary>
/// <typeparam name="TBase">Base class that is specified in the
/// Microsoft.VisualStudio.LanguageServer.Protocol package.</typeparam>
/// <typeparam name="TExtension">Extension class that extends TBase.</typeparam>
internal sealed class VSExtensionConverter<TBase, TExtension> : JsonConverter<TBase>
where TExtension : TBase
{
    private JsonSerializerOptions? _trimmedOptions;
 
    public override TBase? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        return JsonSerializer.Deserialize<TExtension>(ref reader, options);
    }
 
    public override void Write(Utf8JsonWriter writer, TBase value, JsonSerializerOptions options)
    {
        // System.Text.Json doesn't serialize properties from derived classes by default, and there's no 'readonly' converters
        // like Newtonsoft has.
        if (value is TExtension extension)
        {
            JsonSerializer.Serialize(writer, extension, options);
        }
        else
        {
            // There's no ability to fallback to a 'default' serialization, so we clone our options
            // and exclude this converter from it to prevent a stack overflow.
            JsonSerializer.Serialize(writer, (object)value!, DropConverter(options));
        }
    }
 
    private JsonSerializerOptions DropConverter(JsonSerializerOptions options)
    {
        if (_trimmedOptions != null)
        {
            return _trimmedOptions;
        }
 
        lock (this)
        {
            options = new System.Text.Json.JsonSerializerOptions(options);
            options.Converters.Remove(this);
            _trimmedOptions = options;
            return options;
        }
    }
}