using Moq;
using Opc.Ua;
using Opc.Ua.Client;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;

/// <summary>#275 — the driver splits Read / Write calls to the server's declared OperationLimits.</summary>
[Trait("Category", "Unit")]
public sealed class OpcUaClientOperationLimitsTests
{
    [Theory]
    [InlineData(0, 0u, new int[0])]                  // nothing to send => no call
    [InlineData(5, 0u, new[] { 5 })]                 // 0 = unlimited
    [InlineData(5, 5u, new[] { 5 })]                 // exactly fits
    [InlineData(5, 100u, new[] { 5 })]               // limit larger than the batch
    [InlineData(10, 4u, new[] { 4, 4, 2 })]          // remainder chunk
    [InlineData(9, 3u, new[] { 3, 3, 3 })]
    [InlineData(3, 1u, new[] { 1, 1, 1 })]
    public void Chunk_splits_to_the_limit(int total, uint limit, int[] expectedSizes)
    {
        var chunks = OpcUaClientOperationLimits.Chunk(total, limit).ToList();

        chunks.Select(c => c.Count).ToArray().ShouldBe(expectedSizes);
        // Contiguous cover of [0, total): every item exactly once, in order.
        var next = 0;
        foreach (var (start, count) in chunks) { start.ShouldBe(next); next += count; }
        next.ShouldBe(total);
    }

    [Fact]
    public void FromValues_reads_good_uints_and_treats_bad_or_missing_as_unlimited()
    {
        var values = new List<DataValue>
        {
            new(new Variant(100u)),
            new(new Variant(50u)),
            new(StatusCodes.BadNodeIdUnknown),     // server doesn't publish MaxNodesPerBrowse
            new(new Variant(7u)),
        };

        var limits = OpcUaClientOperationLimits.FromValues(values);

        limits.MaxNodesPerRead.ShouldBe(100u);
        limits.MaxNodesPerWrite.ShouldBe(50u);
        limits.MaxNodesPerBrowse.ShouldBe(0u);
        limits.MaxMonitoredItemsPerCall.ShouldBe(7u);
        limits.MaxNodesPerHistoryReadData.ShouldBe(0u);   // short list => 0
        limits.MaxNodesPerHistoryReadEvents.ShouldBe(0u);
    }

    private static (OpcUaClientDriver Drv, Mock<ISession> Session, List<int> ReadSizes, List<int> WriteSizes) Rig(
        uint readLimit, uint writeLimit, int tagCount)
    {
        var tags = Enumerable.Range(0, tagCount)
            .Select(i => new RawTagEntry($"raw/t{i}", $$"""{"nodeId":"ns=2;s=T{{i}}"}""", WriteIdempotent: false))
            .ToList();
        var options = new OpcUaClientDriverOptions { RawTags = tags };
        var drv = new OpcUaClientDriver(options, "opcua-limits");
        drv.SetNamespaceMapForTest(ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.NamespaceMap.FromTable(new NamespaceTable(), tags));
        drv.SetOperationLimitsForTest(OpcUaClientOperationLimits.None with
        {
            MaxNodesPerRead = readLimit, MaxNodesPerWrite = writeLimit,
        });

        var readSizes = new List<int>();
        var writeSizes = new List<int>();
        var mock = new Mock<ISession>(MockBehavior.Loose);
        mock.SetupGet(s => s.MessageContext)
            .Returns(new ServiceMessageContext(SdkTelemetry.Context));
        mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
        mock.Setup(s => s.ReadAsync(It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, CancellationToken _) =>
            {
                readSizes.Add(nodes.Count);
                // Echo each node's identifier number back as the value so ordering across chunks is checkable.
                var results = new DataValueCollection();
                foreach (var n in nodes) results.Add(new DataValue(new Variant((string)n.NodeId.Identifier)));
                return new ReadResponse { ResponseHeader = new ResponseHeader(), Results = results };
            });
        mock.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<WriteValueCollection>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync((RequestHeader _, WriteValueCollection nodes, CancellationToken _) =>
            {
                writeSizes.Add(nodes.Count);
                var codes = new StatusCodeCollection();
                foreach (var _ in nodes) codes.Add(StatusCodes.Good);
                return new WriteResponse { ResponseHeader = new ResponseHeader(), Results = codes };
            });
        drv.SetSessionForTest(mock.Object);
        return (drv, mock, readSizes, writeSizes);
    }

    [Fact]
    public async Task ReadAsync_splits_to_MaxNodesPerRead_and_keeps_result_order()
    {
        var (drv, _, readSizes, _) = Rig(readLimit: 4, writeLimit: 0, tagCount: 10);
        using var _ = drv;

        var refs = Enumerable.Range(0, 10).Select(i => $"raw/t{i}").ToList();
        var res = await drv.ReadAsync(refs, TestContext.Current.CancellationToken);

        readSizes.ShouldBe([4, 4, 2]);
        res.Count.ShouldBe(10);
        for (var i = 0; i < 10; i++) res[i].Value.ShouldBe($"T{i}");   // positional mapping survives chunking
        drv.GetHealth().State.ShouldBe(DriverState.Healthy);
        drv.GetHealth().Diagnostics!["ChunkedRequestCount"].ShouldBe(1);
    }

    [Fact]
    public async Task ReadAsync_with_no_declared_limit_sends_one_request()
    {
        var (drv, _, readSizes, _) = Rig(readLimit: 0, writeLimit: 0, tagCount: 10);
        using var _ = drv;

        await drv.ReadAsync(Enumerable.Range(0, 10).Select(i => $"raw/t{i}").ToList(), TestContext.Current.CancellationToken);

        readSizes.ShouldBe([10]);
    }

    [Fact]
    public async Task ReadAsync_a_failing_chunk_only_fails_its_own_tags()
    {
        var (drv, session, _, _) = Rig(readLimit: 2, writeLimit: 0, tagCount: 4);
        using var _ = drv;
        var call = 0;
        session.Setup(s => s.ReadAsync(It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
            .Returns((RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, CancellationToken _) =>
            {
                if (Interlocked.Increment(ref call) == 2) throw new ServiceResultException(StatusCodes.BadConnectionClosed);
                var results = new DataValueCollection();
                foreach (var n in nodes) results.Add(new DataValue(new Variant((string)n.NodeId.Identifier)));
                return Task.FromResult(new ReadResponse { ResponseHeader = new ResponseHeader(), Results = results });
            });

        var res = await drv.ReadAsync(["raw/t0", "raw/t1", "raw/t2", "raw/t3"], TestContext.Current.CancellationToken);

        res[0].Value.ShouldBe("T0");
        res[1].Value.ShouldBe("T1");
        res[2].StatusCode.ShouldBe(0x80050000u);   // BadCommunicationError, chunk 2 only
        res[3].StatusCode.ShouldBe(0x80050000u);
        drv.GetHealth().State.ShouldBe(DriverState.Degraded);
        drv.GetHealth().Diagnostics!["ReadFailureCount"].ShouldBe(1);
    }

    [Fact]
    public async Task WriteAsync_splits_to_MaxNodesPerWrite()
    {
        var (drv, _, _, writeSizes) = Rig(readLimit: 0, writeLimit: 3, tagCount: 7);
        using var _ = drv;

        var res = await drv.WriteAsync(
            Enumerable.Range(0, 7).Select(i => new Core.Abstractions.WriteRequest($"raw/t{i}", i)).ToList(),
            TestContext.Current.CancellationToken);

        writeSizes.ShouldBe([3, 3, 1]);
        res.Count.ShouldBe(7);
        res.ShouldAllBe(r => r.StatusCode == 0u);
    }
}