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

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

/// <summary>
///     Comms-loss → recovery against the real pymodbus <c>standard</c> fixture, with a loopback
///     <see cref="TcpRelay"/> in front of it so the device can disappear and come back without touching the
///     shared container. Covers the review 07 High findings P3 (transport self-heal) and H2 (deadband
///     recovery publish).
/// </summary>
[Collection(ModbusSimulatorCollection.Name)]
[Trait("Category", "Integration")]
[Trait("Device", "Standard")]
public sealed class CommsRecoveryTests(ModbusSimulatorFixture sim)
{
    private const uint StatusGood = 0u;

    private void SkipUnlessStandardLive()
    {
        if (sim.SkipReason is not null) Assert.Skip(sim.SkipReason);
        var profile = Environment.GetEnvironmentVariable("MODBUS_SIM_PROFILE");
        if (profile is not null && !string.Equals(profile, "standard", StringComparison.OrdinalIgnoreCase))
            Assert.Skip($"MODBUS_SIM_PROFILE={profile} — these tests need the standard profile (HR[0..31] = address).");
    }

    private ModbusDriverOptions Options(TcpRelay relay, params ModbusTagDefinition[] tags) => new()
    {
        Host = "127.0.0.1",
        Port = relay.Port,
        UnitId = 1,
        Timeout = TimeSpan.FromSeconds(2),
        RawTags = ModbusRawTags.Entries(tags),
        Probe = new ModbusProbeOptions { Enabled = false },
    };

    private static async Task<T> WaitFor<T>(Func<Task<T>> probe, Func<T, bool> done, TimeSpan budget)
    {
        var sw = Stopwatch.StartNew();
        T last;
        do
        {
            last = await probe();
            if (done(last)) return last;
            await Task.Delay(200, TestContext.Current.CancellationToken);
        } while (sw.Elapsed < budget);
        return last;
    }

    /// <summary>
    ///     P3: after the device drops (two failed calls in a row, socket torn down, reconnect refused) the
    ///     transport must reconnect ON ITS OWN once the device is back — before this fix every later call
    ///     failed fast with "Transport not connected" until the 90 s comms-loss watchdog re-initialised the
    ///     driver.
    /// </summary>
    [Fact]
    public async Task Driver_reads_again_after_the_device_drops_and_returns_without_reinit()
    {
        SkipUnlessStandardLive();
        await using var relay = new TcpRelay(sim.Host, sim.Port);
        var tag = new ModbusTagDefinition("HR5", ModbusRegion.HoldingRegisters, 5, ModbusDataType.UInt16, Writable: false);
        await using var driver = new ModbusDriver(Options(relay, tag), "modbus-p3");
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        var good = await driver.ReadAsync(["HR5"], TestContext.Current.CancellationToken);
        good[0].StatusCode.ShouldBe(StatusGood);
        good[0].Value.ShouldBe((ushort)5);

        relay.Cut();
        for (var i = 0; i < 2; i++)
        {
            var bad = await driver.ReadAsync(["HR5"], TestContext.Current.CancellationToken);
            bad[0].StatusCode.ShouldNotBe(StatusGood);
        }
        driver.GetHealth().State.ShouldBe(DriverState.Degraded);

        relay.Restore();
        var recovered = await WaitFor(
            () => driver.ReadAsync(["HR5"], TestContext.Current.CancellationToken),
            r => r[0].StatusCode == StatusGood,
            TimeSpan.FromSeconds(20));
        recovered[0].StatusCode.ShouldBe(StatusGood, "the transport must reconnect by itself once the device is back");
        recovered[0].Value.ShouldBe((ushort)5);
        driver.GetHealth().State.ShouldBe(DriverState.Healthy);
    }
}