Provide non-generic ISerializer, IAsyncSerializer, IDeserializer, IAsyncDeserializer

[horato]

Description

I am using one consumer to consume multiple topics with different avro schemas. I created a deserializer, but for the lack of non-generic IDeserializer, I had to resort to all kind of weird hacks.

Non-generic I(Async)Deserializer would reduce this code

public class TopicSpecificAvroDeserializer : IDeserializer<ISpecificRecord>
{
	private readonly ConcurrentDictionary<string, object> _deserializers = new ConcurrentDictionary<string, object>();
	private readonly ISchemaRegistryClient _schemaRegistryClient;

	private static readonly IDictionary<string, Type> Configuration = new Dictionary<string, Type>
	{
		{ "topic.A", typeof(TopicA) },
		{ "topic.B", typeof(TopicB) },
	};

	private delegate object DeserializeDelegate(ReadOnlySpan<byte> data, bool isNull, SerializationContext context);

	public TopicSpecificAvroDeserializer(ISchemaRegistryClient schemaRegistryClient)
	{
		_schemaRegistryClient = schemaRegistryClient ?? throw new ArgumentNullException(nameof(schemaRegistryClient));
	}

	public ISpecificRecord Deserialize(ReadOnlySpan<byte> data, bool isNull, SerializationContext context)
	{
		var deserializer = _deserializers.GetOrAdd(context.Topic, CreateDeserializer);
		return CallDeserialize(deserializer, data, isNull, context);
	}
	
	private ISpecificRecord CallDeserialize(object deserializer, ReadOnlySpan<byte> data, bool isNull, SerializationContext context)
	{
		var instance = Expression.Constant(deserializer);
		var dataParameter = Expression.Parameter(typeof(ReadOnlySpan<byte>), "data");
		var isNullParameter = Expression.Parameter(typeof(bool), "isNull");
		var contextParameter = Expression.Parameter(typeof(SerializationContext), "context");

		var method = deserializer.GetType().GetMethod(nameof(IDeserializer<object>.Deserialize));
		var call = Expression.Call(instance, method, dataParameter, isNullParameter, contextParameter);
		var expression = Expression.Lambda<DeserializeDelegate>(call, dataParameter, isNullParameter, contextParameter);
		var func = expression.Compile();
		return (ISpecificRecord)func(data, isNull, context);
	}

	private object CreateDeserializer(string topic)
	{
		if (!Configuration.TryGetValue(topic, out var type))
			throw new InvalidOperationException($"Missing message type for topic {topic}");

		var deserializerType = typeof(AvroDeserializer<>).MakeGenericType(type);
		var deserializerInstance = Activator.CreateInstance(deserializerType, _schemaRegistryClient, null);
		if (deserializerInstance == null)
			throw new InvalidOperationException($"Failed to create instance of {typeof(AvroDeserializer<>)} with generic argument {type}");

		var syncDeserializerType = typeof(SyncOverAsyncDeserializer<>).MakeGenericType(type);
		var syncDeserializerInstance = Activator.CreateInstance(syncDeserializerType, deserializerInstance);
		if (syncDeserializerInstance == null)
			throw new InvalidOperationException($"Failed to create instance of {typeof(SyncOverAsyncDeserializer<>)} with generic argument {type}");

		return syncDeserializerInstance;
	}

to this code

public class TopicSpecificAvroDeserializer : IDeserializer<ISpecificRecord>
{
	private readonly ConcurrentDictionary<string, IDeserializer> _deserializers = new ConcurrentDictionary<string, IDeserializer>();
	private readonly ISchemaRegistryClient _schemaRegistryClient;

	private static readonly IDictionary<string, Type> Configuration = new Dictionary<string, Type>
	{
		{ "topic.A", typeof(TopicA) },
		{ "topic.B", typeof(TopicB) },
	};
	
	public TopicSpecificAvroDeserializer(ISchemaRegistryClient schemaRegistryClient)
	{
		_schemaRegistryClient = schemaRegistryClient ?? throw new ArgumentNullException(nameof(schemaRegistryClient));
	}

	public ISpecificRecord Deserialize(ReadOnlySpan<byte> data, bool isNull, SerializationContext context)
	{
		var deserializer = _deserializers.GetOrAdd(context.Topic, CreateDeserializer);
		return (ISpecificRecord)deserializer.Deserialize(data, isNull, context);
	}

	private IDeserializer CreateDeserializer(string topic)
	{
		if (!Configuration.TryGetValue(topic, out var type))
			throw new InvalidOperationException($"Missing message type for topic {topic}");

		var deserializerType = typeof(AvroDeserializer<>).MakeGenericType(type);
		var deserializerInstance = (IAsyncDeserializer)Activator.CreateInstance(deserializerType, _schemaRegistryClient, null);
		if (deserializerInstance == null)
			throw new InvalidOperationException($"Failed to create instance of {typeof(AvroDeserializer<>)} with generic argument {type}");

		return deserializerInstance.AsSyncOverAsync();
	}