Deserializers.cs

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using Fauna.Exceptions;
using Fauna.Mapping;
using Fauna.Serialization;
 
namespace Fauna.Linq;
 
internal class MappedDeserializer<I, O> : BaseSerializer<O>
{
    private ISerializer<I> _inner;
    private Func<I, O> _mapper;
 
    public MappedDeserializer(ISerializer<I> inner, Func<I, O> mapper)
    {
        _inner = inner;
        _mapper = mapper;
    }
 
    public override List<FaunaType> GetSupportedTypes() => _inner.GetSupportedTypes();
 
    public override O Deserialize(MappingContext ctx, ref Utf8FaunaReader reader) =>
        _mapper(_inner.Deserialize(ctx, ref reader));
 
    public override void Serialize(MappingContext context, Utf8FaunaWriter writer, object? o)
    {
        throw new NotImplementedException();
    }
}
 
internal class ProjectionDeserializer : BaseSerializer<object?[]>
{
    private ISerializer[] _fields;
 
    public ProjectionDeserializer(IEnumerable<ISerializer> fields)
    {
        _fields = fields.ToArray();
    }
 
    public override List<FaunaType> GetSupportedTypes() => _fields.SelectMany(x => x.GetSupportedTypes()).Distinct().ToList();
 
    public override object?[] Deserialize(MappingContext ctx, ref Utf8FaunaReader reader)
    {
        if (reader.CurrentTokenType != TokenType.StartArray)
            throw UnexpectedToken(reader.CurrentTokenType);
 
        var values = new object?[_fields.Length];
 
        for (var i = 0; i < _fields.Length; i++)
        {
            if (!reader.Read()) throw new SerializationException("Unexpected end of stream");
            if (reader.CurrentTokenType == TokenType.EndArray) throw UnexpectedToken(reader.CurrentTokenType);
 
            values[i] = _fields[i].Deserialize(ctx, ref reader);
        }
 
        if (!reader.Read()) throw new SerializationException("Unexpected end of stream");
        if (reader.CurrentTokenType != TokenType.EndArray) throw UnexpectedToken(reader.CurrentTokenType);
 
        return values;
    }
 
    public override void Serialize(MappingContext context, Utf8FaunaWriter writer, object? o)
    {
        throw new NotImplementedException();
    }
 
    private new static SerializationException UnexpectedToken(TokenType tokenType) =>
        new($"Unexpected token while deserializing LINQ element: {tokenType}");
}