using System.Diagnostics;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.TwinCAT;

namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.IntegrationTests;

/// <summary>
///     PR 2.1 perf gate — verifies the bulk Sum-read path is materially faster than the
///     equivalent serial per-tag <see cref="TwinCAT.Ads.AdsClient.ReadValueAsync(string, Type, System.Threading.CancellationToken)"/>
///     loop on a real XAR runtime. The driver's <see cref="TwinCATDriver.ReadAsync"/>
///     already routes through the bulk path; the baseline calls through a hand-rolled
///     loop so we're comparing apples to apples on the same wire.
/// </summary>
/// <remarks>
///     Requires the perf fixture: <c>GVL_Perf.aTags : ARRAY[1..1000] OF DINT</c> per
///     <c>TwinCatProject/README.md §Performance scenarios</c>. Skipped unless
///     <c>TWINCAT_PERF=1</c> is set.
/// </remarks>
[Collection("TwinCATXar")]
[Trait("Category", "Performance")]
[Trait("Simulator", "TwinCAT-XAR")]
public sealed class TwinCATSumCommandPerfTests(TwinCATXarFixture sim)
{
    private const int TagCount = 1000;

    [TwinCATPerfFact]
    public async Task Driver_sum_read_1000_tags_beats_loop_baseline_by_5x()
    {
        if (sim.SkipReason is not null) Assert.Skip(sim.SkipReason);

        var deviceAddress = $"ads://{sim.TargetNetId}:{sim.AmsPort}";
        var tags = new TwinCATTagDefinition[TagCount];
        var refs = new string[TagCount];
        for (var i = 0; i < TagCount; i++)
        {
            // GVL_Perf.aTags is 1-based per IEC 61131-3 ARRAY declaration.
            var name = $"Perf{i + 1}";
            refs[i] = name;
            tags[i] = new TwinCATTagDefinition(
                Name: name,
                DeviceHostAddress: deviceAddress,
                SymbolPath: $"GVL_Perf.aTags[{i + 1}]",
                DataType: TwinCATDataType.DInt);
        }

        var options = new TwinCATDriverOptions
        {
            Devices = [new TwinCATDeviceOptions(deviceAddress, "XAR-VM")],
            Tags = tags,
            UseNativeNotifications = false,
            Timeout = TimeSpan.FromSeconds(15),
            Probe = new TwinCATProbeOptions { Enabled = false },
        };

        // ---- Bulk (PR 2.1) measurement ----
        await using var bulkDrv = new TwinCATDriver(options, "tc3-perf-bulk");
        await bulkDrv.InitializeAsync("{}", TestContext.Current.CancellationToken);

        // Warm-up: prime symbol-handle caches in the XAR runtime so the timed run
        // measures sum-read steady state, not first-touch handle resolution.
        await bulkDrv.ReadAsync(refs, TestContext.Current.CancellationToken);

        var bulkSw = Stopwatch.StartNew();
        var bulkResults = await bulkDrv.ReadAsync(refs, TestContext.Current.CancellationToken);
        bulkSw.Stop();

        // ---- Loop baseline measurement ----
        // Use a fresh driver instance so the cache state matches the bulk run on first
        // call. Single-tag-per-call across the full set is what PR 2.1 replaces.
        await using var loopDrv = new TwinCATDriver(options, "tc3-perf-loop");
        await loopDrv.InitializeAsync("{}", TestContext.Current.CancellationToken);
        // Warm-up against the same refs.
        for (var i = 0; i < TagCount; i++)
            _ = await loopDrv.ReadAsync([refs[i]], TestContext.Current.CancellationToken);

        var loopSw = Stopwatch.StartNew();
        for (var i = 0; i < TagCount; i++)
            _ = await loopDrv.ReadAsync([refs[i]], TestContext.Current.CancellationToken);
        loopSw.Stop();

        // Sanity: bulk path must produce TagCount snapshots all Good.
        bulkResults.Count.ShouldBe(TagCount);
        bulkResults.ShouldAllBe(s => s.StatusCode == TwinCATStatusMapper.Good);

        // Conservative ratio — on the dev box bulk is ~10-20× the loop, target is 5×.
        // Lower bound exists so the test is robust to noisy CI / VM scheduling.
        var ratio = (double)loopSw.ElapsedMilliseconds / Math.Max(1, bulkSw.ElapsedMilliseconds);
        ratio.ShouldBeGreaterThan(5.0,
            $"Bulk Sum-read should be >5x faster than per-tag loop; got bulk={bulkSw.ElapsedMilliseconds}ms, loop={loopSw.ElapsedMilliseconds}ms (ratio={ratio:F2})");
    }
}