gremlin-dotnet/src/Gremlin.Net/Structure/IO/GraphBinary/Types/TypeSerializer.cs

#region License

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

#endregion

using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using Gremlin.Net.Process.Traversal.Strategy;

namespace Gremlin.Net.Structure.IO.GraphBinary.Types
{
    /// <summary>
    /// A serializer for .NET types represented as Class in GraphBinary. Currently only
    /// <see cref="AbstractTraversalStrategy"/> types are supported.
    /// </summary>
    public class TypeSerializer : SimpleTypeSerializer<Type>
    {
        /// <summary>
        ///     Initializes a new instance of the <see cref="TypeSerializer" /> class.
        /// </summary>
        public TypeSerializer() : base(DataType.Class)
        {
        }

        /// <inheritdoc />
        protected override async Task WriteValueAsync(Type value, Stream stream, GraphBinaryWriter writer,
            CancellationToken cancellationToken = default)
        {
            if (typeof(AbstractTraversalStrategy).IsAssignableFrom(value))
            {
                var strategyInstance = (AbstractTraversalStrategy?)Activator.CreateInstance(value) ??
                                       throw new IOException(
                                           $"Cannot write the strategy {value} because an instance of that strategy could not be created");
                await writer.WriteNonNullableValueAsync(strategyInstance.Fqcn, stream, cancellationToken)
                    .ConfigureAwait(false);
            }
            else
            {
                throw new IOException("Currently, writing of Types is only supported for traversal strategies.");
            }
        }

        /// <summary>
        /// Currently not supported.
        /// </summary>
        protected override Task<Type> ReadValueAsync(Stream stream, GraphBinaryReader reader,
            CancellationToken cancellationToken = default)
        {
            throw new NotImplementedException("Reading a Type is not supported");
        }
    }
}