using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Driver.Mqtt.Browser;
using SparkplugDataType = Org.Eclipse.Tahu.Protobuf.DataType;

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

/// <summary>
///     <b>R06:M-4.</b> <c>sparkplug.birthObservationWindowSeconds</c> was authored, range-checked and
///     persisted by the AdminUI and consumed by nothing. It now bounds how long the Sparkplug browse surface
///     collects NBIRTH/DBIRTH traffic before calling the observed set stable: the open budget grows by it,
///     the open lingers while births are still arriving, and an operator rebirth request waits (bounded) for
///     the births it asked for, so the tree the picker re-renders already carries them.
/// </summary>
public sealed class MqttBirthObservationWindowTests
{
    private static MqttDriverOptions Sparkplug(int windowSeconds, int connectTimeoutSeconds = 10) => new()
    {
        Mode = MqttMode.SparkplugB,
        ConnectTimeoutSeconds = connectTimeoutSeconds,
        Sparkplug = new MqttSparkplugOptions { GroupId = "Plant1", BirthObservationWindowSeconds = windowSeconds },
    };

    [Fact]
    public void OpenBudget_Sparkplug_AddsTheBirthObservationWindow()
    {
        MqttDriverBrowser.OpenBudget(Sparkplug(windowSeconds: 15)).ShouldBe(TimeSpan.FromSeconds(10 + 15));
        MqttDriverBrowser.OpenBudget(Sparkplug(windowSeconds: 40)).ShouldBe(TimeSpan.FromSeconds(10 + 40));
    }

    [Fact]
    public void OpenBudget_Plain_IgnoresTheSparkplugWindow()
    {
        var plain = Sparkplug(windowSeconds: 40) with { Mode = MqttMode.Plain };
        MqttDriverBrowser.OpenBudget(plain).ShouldBe(TimeSpan.FromSeconds(10));
    }

    [Theory]
    [InlineData(0, 1)]
    [InlineData(-5, 1)]
    [InlineData(15, 15)]
    [InlineData(100_000, 120)]
    public void BirthWindow_IsClamped(int configured, int expectedSeconds)
        => MqttDriverBrowser.BirthWindow(Sparkplug(configured)).ShouldBe(TimeSpan.FromSeconds(expectedSeconds));

    /// <summary>
    ///     Review minor 4: the rebirth wait is capped below the AdminUI's 20 s per-call timeout, so a long
    ///     configured window cannot hold the button past it (and a short one still governs).
    /// </summary>
    [Theory]
    [InlineData(120, 15)]
    [InlineData(15, 15)]
    [InlineData(5, 5)]
    public async Task RebirthWait_IsTheWindowCappedAt15Seconds(int windowSeconds, int expectedSeconds)
    {
        await using var s = new MqttBrowseSession(
            MqttMode.SparkplugB, client: null, logger: null, birthWindow: TimeSpan.FromSeconds(windowSeconds));
        s.RebirthWait.ShouldBe(TimeSpan.FromSeconds(expectedSeconds));
    }

    /// <summary>An idle plant costs one quiet interval, not the whole window.</summary>
    [Fact]
    public async Task Settle_WithNoBirths_ReturnsAfterOneQuietInterval()
    {
        var reads = 0;
        await MqttBrowseSession.SettleBirthsAsync(
                () => { reads++; return 0; },
                baseline: 0,
                awaitFirstBirth: false,
                quiet: TimeSpan.FromMilliseconds(20),
                window: TimeSpan.FromMinutes(5),
                TestContext.Current.CancellationToken)
            .WaitAsync(TimeSpan.FromSeconds(10), TestContext.Current.CancellationToken);

        reads.ShouldBe(1);
    }

    /// <summary>
    ///     While births keep arriving the settle keeps collecting; it returns on the first quiet interval
    ///     after the last one. Counted in reads, not wall-clock, so it cannot flake.
    /// </summary>
    [Fact]
    public async Task Settle_KeepsCollectingWhileBirthsArrive_ThenReturnsOnQuiet()
    {
        var reads = 0;
        long births = 0;
        await MqttBrowseSession.SettleBirthsAsync(
                () =>
                {
                    reads++;
                    if (reads <= 5) births++;   // five intervals with fresh births, then silence
                    return births;
                },
                baseline: 0,
                awaitFirstBirth: false,
                quiet: TimeSpan.FromMilliseconds(20),
                window: TimeSpan.FromMinutes(5),
                TestContext.Current.CancellationToken)
            .WaitAsync(TimeSpan.FromSeconds(10), TestContext.Current.CancellationToken);

        reads.ShouldBe(6);
    }

    /// <summary>The window is a hard ceiling: a birth flood that never goes quiet still ends.</summary>
    [Trait("Category", "SlowUnit")]
    [Fact]
    public async Task Settle_NeverQuiet_EndsAtTheWindow()
    {
        long births = 0;
        await MqttBrowseSession.SettleBirthsAsync(
                () => ++births,
                baseline: 0,
                awaitFirstBirth: false,
                quiet: TimeSpan.FromMilliseconds(20),
                window: TimeSpan.FromSeconds(1),
                TestContext.Current.CancellationToken)
            .WaitAsync(TimeSpan.FromSeconds(10), TestContext.Current.CancellationToken);

        births.ShouldBeGreaterThan(1);
    }

    /// <summary>
    ///     A rebirth request waits for the birth it asked for. The fixed version cannot complete
    ///     synchronously (it awaits the settle), the unfixed one completes before the call returns — so the
    ///     <c>IsCompleted</c> check is deterministic, not a timing race. The birth then releases it.
    /// </summary>
    [Fact]
    public async Task RequestRebirth_WaitsForTheRequestedBirths_ThenReturns()
    {
        await using var s = new MqttBrowseSession(
            MqttMode.SparkplugB, client: null, logger: null, birthWindow: TimeSpan.FromMinutes(5));

        var request = s.RequestRebirthAsync("Plant1/EdgeA", TestContext.Current.CancellationToken);
        request.IsCompleted.ShouldBeFalse("the request must wait for the births it asked for");

        s.ObserveBirthForTest("Plant1", "EdgeA", null, "Uptime", SparkplugDataType.Int64);

        (await request.WaitAsync(TimeSpan.FromSeconds(10), TestContext.Current.CancellationToken)).ShouldBe(1);
        s.PublishCountForTest.ShouldBe(1);
    }

    /// <summary>
    ///     The wait is a courtesy, never a failure: the NCMD was already published, so a caller deadline
    ///     during the settle returns the published count instead of reporting an error for a request that
    ///     succeeded.
    /// </summary>
    [Fact]
    public async Task RequestRebirth_CallerCancelsDuringTheSettle_StillReportsThePublish()
    {
        await using var s = new MqttBrowseSession(
            MqttMode.SparkplugB, client: null, logger: null, birthWindow: TimeSpan.FromMinutes(5));
        using var cts = CancellationTokenSource.CreateLinkedTokenSource(TestContext.Current.CancellationToken);

        var request = s.RequestRebirthAsync("Plant1/EdgeA", cts.Token);
        request.IsCompleted.ShouldBeFalse();
        await cts.CancelAsync();

        (await request.WaitAsync(TimeSpan.FromSeconds(10), TestContext.Current.CancellationToken)).ShouldBe(1);
    }
}