using System.Text.Json;
using System.Text.Json.Serialization;

namespace JsonSerializationTests
{
    [Flags]
    public enum MyEnum1
    {
        UNKNOWN = 0,
        BIT0    = 1,
        BIT1    = 2,
        BIT2    = 4,
        BIT3    = 8,
        BITS01  = 3,
    }

    [Flags]
    public enum MyEnum2
    {
        UNKNOWN = 0,
        BIT0    = 1,
        // direct option for bit 1 missing
        BIT2    = 4,
        BIT3    = 8,
        BITS01  = 3,
    }

    [TestClass]
    public sealed class Test1
    {
        [TestMethod]
        public void FlagsEnumTest()
        {
            JsonSerializerOptions options = new()
            {
                WriteIndented = false,
                Converters    = { new JsonStringEnumConverter() }
            };

            var e1 = MyEnum1.BITS01 | MyEnum1.BIT3;
            string json1 = JsonSerializer.Serialize ( e1, options );
            // .NET8 => "BITS01, BIT3"
            // .NET9 => "BIT0, BIT1, BIT3" (which is not so bad, although different from .NET8)

            var e2 = MyEnum2.BITS01 | MyEnum2.BIT3;
            string json2 = JsonSerializer.Serialize ( e2, options );
            // .NET8 => "BITS01, BIT3"
            // .NET9 => "11"; // that's the problematic behaviour

            Assert.IsTrue ( json1.Contains("BITS01") && json1.Contains("BIT3"), "json 1 failed" );
            Assert.IsTrue ( json2.Contains("BITS01") && json2.Contains("BIT3"), "json 2 failed" );
        }
    }
}