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using System;
using System.Text.Json;
using System.Threading.Tasks;
using NUnit.Framework;
using Opc.Ua;
using Opc.Ua.PubSub.Encoding;
using Opc.Ua.PubSub.MetaData;
using Opc.Ua.PubSub.Tests;

namespace OpcUaPubSubJsonTests
{
    /// <summary>
    /// Inverse of <c>JsonEncoderTests</c> — every mode and every
    /// DataSetMessage kind must round-trip cleanly when the metadata
    /// is registered.
    /// </summary>
    [TestFixture]
    [Category("PubSub")]
    [TestSpec("7.2.5.3")]
    [TestSpec("7.2.5.4")]
    public sealed class JsonDecoderTests
    {
        [TestCase(Opc.Ua.PubSub.Encoding.Json.JsonEncodingMode.Verbose,
            PubSubDataSetMessageType.KeyFrame)]
        [TestCase(Opc.Ua.PubSub.Encoding.Json.JsonEncodingMode.Verbose,
            PubSubDataSetMessageType.DeltaFrame)]
        [TestCase(Opc.Ua.PubSub.Encoding.Json.JsonEncodingMode.Verbose,
            PubSubDataSetMessageType.Event)]
        [TestCase(Opc.Ua.PubSub.Encoding.Json.JsonEncodingMode.Verbose,
            PubSubDataSetMessageType.KeepAlive)]
        [TestCase(Opc.Ua.PubSub.Encoding.Json.JsonEncodingMode.Compact,
            PubSubDataSetMessageType.KeyFrame)]
        [TestCase(Opc.Ua.PubSub.Encoding.Json.JsonEncodingMode.RawData,
            PubSubDataSetMessageType.KeyFrame)]
        public async Task RoundTripAsync(
            Opc.Ua.PubSub.Encoding.Json.JsonEncodingMode mode,
            PubSubDataSetMessageType type)
        {
            DataSetMetaDataType meta = JsonTestUtilities.CreateMetaData();
            var registry = new DataSetMetaDataRegistry();
            registry.Register(
                new DataSetMetaDataKey(PublisherId.FromUInt16(300), 0, 1, Uuid.Empty, 1),
                meta);
            PubSubNetworkMessageContext ctx = JsonTestUtilities.NewContext(registry);
            var dsm = new Opc.Ua.PubSub.Encoding.Json.JsonDataSetMessage
            {
                DataSetWriterId = 1,
                SequenceNumber = 99,
                MessageType = type,
                MetaDataVersion = meta.ConfigurationVersion,
                Fields = type == PubSubDataSetMessageType.KeepAlive
                    ? []
                    : JsonTestUtilities.CreateFields()
            };
            var message = new Opc.Ua.PubSub.Encoding.Json.JsonNetworkMessage
            {
                MessageId = "rt-1",
                PublisherId = PublisherId.FromUInt16(300),
                DataSetClassId = Uuid.Empty,
                DataSetMessages = [dsm]
            };
            var encoder = new Opc.Ua.PubSub.Encoding.Json.JsonEncoder(mode);
            ReadOnlyMemory<byte> bytes = await encoder
                .EncodeAsync(message, ctx).ConfigureAwait(false);
            var decoder = new Opc.Ua.PubSub.Encoding.Json.JsonDecoder();
            PubSubNetworkMessage? decoded = await decoder
                .TryDecodeAsync(bytes, ctx).ConfigureAwait(false);
            Assert.That(decoded, Is.Not.Null, $"Decoder returned null for mode={mode} type={type}");
            var data = decoded as Opc.Ua.PubSub.Encoding.Json.JsonNetworkMessage;
            Assert.That(data, Is.Not.Null);
            Assert.That(data!.MessageId, Is.EqualTo("rt-1"));
            Assert.That(data.PublisherId.IsNull, Is.False);
            Assert.That(((PubSubDataSetMessage[]?)data.DataSetMessages) ?? [], Has.Length.EqualTo(1),
                $"Expected exactly one decoded DataSetMessage for mode={mode} type={type}; got {data.DataSetMessages.Count}");
            var receivedDsm = data.DataSetMessages[0] as
                Opc.Ua.PubSub.Encoding.Json.JsonDataSetMessage;
            Assert.That(receivedDsm, Is.Not.Null);
            Assert.That(receivedDsm!.DataSetWriterId, Is.EqualTo(1));
            Assert.That(receivedDsm.SequenceNumber, Is.EqualTo(99));
            Assert.That(receivedDsm.MessageType, Is.EqualTo(type));
            if (type != PubSubDataSetMessageType.KeepAlive &&
                mode == Opc.Ua.PubSub.Encoding.Json.JsonEncodingMode.Verbose)
            {
                Assert.That(((DataSetField[]?)receivedDsm.Fields) ?? [], Has.Length.EqualTo(3));
            }
        }

        [Test]
        [TestSpec("7.2.5.3")]
        [TestSpec("7.2.5.4.1")]
        public async Task NumericPublisherIdStringResolvesNumericMetadataAsync()
        {
            DataSetMetaDataType meta = JsonTestUtilities.CreateMetaData();
            var registry = new DataSetMetaDataRegistry();
            registry.Register(
                new DataSetMetaDataKey(PublisherId.FromUInt16(5), 0, 1, Uuid.Empty, 1),
                meta);
            PubSubNetworkMessageContext ctx = JsonTestUtilities.NewContext(registry);
            var dsm = new Opc.Ua.PubSub.Encoding.Json.JsonDataSetMessage
            {
                DataSetWriterId = 1,
                MessageType = PubSubDataSetMessageType.KeyFrame,
                MetaDataVersion = meta.ConfigurationVersion,
                Fields = JsonTestUtilities.CreateFields()
            };
            var message = new Opc.Ua.PubSub.Encoding.Json.JsonNetworkMessage
            {
                MessageId = "numeric-publisher",
                PublisherId = PublisherId.FromUInt16(5),
                DataSetMessages = [dsm]
            };
            var encoder = new Opc.Ua.PubSub.Encoding.Json.JsonEncoder(
                Opc.Ua.PubSub.Encoding.Json.JsonEncodingMode.Compact);
            ReadOnlyMemory<byte> bytes = await encoder
                .EncodeAsync(message, ctx).ConfigureAwait(false);
            using (var document = JsonDocument.Parse(bytes))
            {
                Assert.That(document.RootElement.GetProperty("PublisherId").GetString(), Is.EqualTo("5"));
            }

            var decoder = new Opc.Ua.PubSub.Encoding.Json.JsonDecoder();
            PubSubNetworkMessage? decoded = await decoder
                .TryDecodeAsync(bytes, ctx).ConfigureAwait(false);

            var decodedNetwork = decoded as Opc.Ua.PubSub.Encoding.Json.JsonNetworkMessage;
            Assert.That(decodedNetwork, Is.Not.Null);
            Assert.That(decodedNetwork!.DataSetMessages, Has.Count.EqualTo(1));
            var decodedMessage = decodedNetwork.DataSetMessages[0] as
                Opc.Ua.PubSub.Encoding.Json.JsonDataSetMessage;
            Assert.That(decodedMessage, Is.Not.Null);
            Assert.That(decodedMessage!.Fields, Has.Count.EqualTo(3),
                "Part 14 Tables 184 and 185 encode UInteger PublisherId as a JSON string without changing identity.");
        }

        [Test]
        public void Decoder_Defaults_ExposeJsonProfile()
        {
            var decoder = new Opc.Ua.PubSub.Encoding.Json.JsonDecoder();
            Assert.That(decoder.TransportProfileUri,
                Is.EqualTo(Profiles.PubSubMqttJsonTransport));
        }

        [Test]
        public async Task TryDecodeAsync_NullContext_ThrowsAsync()
        {
            var decoder = new Opc.Ua.PubSub.Encoding.Json.JsonDecoder();
            Assert.ThrowsAsync<ArgumentNullException>(async () =>
                await decoder.TryDecodeAsync(
                    new ReadOnlyMemory<byte>([1, 2, 3]),
                    null!).ConfigureAwait(false));
            await Task.CompletedTask.ConfigureAwait(false);
        }
    }
}