using System;
using MongoDB.Bson;
using MongoDB.Bson.IO;
using MongoDB.Bson.Serialization.Conventions;

namespace LCU.API.Internal.DocumentLib.Containers;

public class DocumentAuditDiscriminatorConvention : IDiscriminatorConvention
{
    public static string Discriminator = StandardDiscriminatorConvention.Scalar.ElementName;
    public string ElementName => Discriminator;

    public Type GetActualType(IBsonReader bsonReader, Type nominalType)
    {
        var bookmark = bsonReader.GetBookmark();

        try
        {
            bsonReader.ReadStartDocument();

            if (!bsonReader.FindElement(ElementName)) return typeof(DocumentFieldAudit);

            return bsonReader.ReadString() switch
            {
                nameof(DocumentFieldAudit) => typeof(DocumentFieldAudit),
                nameof(DocumentActionAudit) => typeof(DocumentActionAudit),
                _ => throw new NotSupportedException()
            };
        }
        finally
        {
            bsonReader.ReturnToBookmark(bookmark);
        }
    }

    public BsonValue GetDiscriminator(Type nominalType, Type actualType)
    {
        return actualType.Name;
    }
}