using System.Collections.Concurrent;
using Serilog;
using Serilog.Events;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Logging;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Core.Scripting;

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

/// <summary>
///     Archreview <b>05/STAB-19</b> — what the Calculation driver does with a dependency's <b>quality</b>.
///
///     <para><b>The defect.</b> The driver stored dependency <i>values</i> only and ignored the status code
///     entirely, so a comms-lost input arrived as <em>arrived, Good, null</em>: the warm-up gate was
///     satisfied by a value that never came, <c>(double)ctx.GetTag("x").Value</c> threw on every trigger
///     (a "script threw" storm), and a null-tolerant script published a <b>Good</b> output computed from a
///     dead input — indefinitely.</para>
///
///     <para><b>The policy pinned here</b> matches <c>ScriptedAlarmEngine</c>'s, which is the in-tree
///     precedent: <b>hold on Bad, propagate the worst input's status; evaluate through Uncertain and stamp
///     the output with it.</b> Holding (rather than evaluating and degrading) is what removes the NRE
///     storm; a Bad sub-code (rather than Uncertain) is what tells the operator the value may be
///     arbitrarily old rather than merely imprecise.</para>
///
///     <para>⚠️ <b>Vacuity rule:</b> the recovery case re-publishes an <b>identical</b> computed value.
///     A recovery whose value differs passes against a value-only dedup and proves nothing — it is the
///     "Bad forever" trap the v3 Batch 4 live gate found.</para>
/// </summary>
public sealed class CalculationDriverInputQualityTests
{
    private const uint StatusGood = 0u;
    private const uint StatusUncertain = 0x40000000u;
    private const uint StatusBadNoCommunication = 0x80310000u;
    private const uint StatusBadInternalError = 0x80020000u;
    private const uint StatusBadWaitingForInitialData = 0x80320000u;

    private const string SumTag = "calc/e/sum";
    private const string SumScript = "return (double)ctx.GetTag(\"src/a\").Value + (double)ctx.GetTag(\"src/b\").Value;";

    private static RawTagEntry CalcTag(string rawPath, string source)
    {
        var json = $"{{\"scriptId\":\"s-{rawPath}\",\"changeTriggered\":true," +
                   $"\"scriptSource\":{System.Text.Json.JsonSerializer.Serialize(source)}}}";
        return new RawTagEntry(rawPath, json, WriteIdempotent: false);
    }

    private static (CalculationDriver Driver, ConcurrentQueue<DataChangeEventArgs> Published, List<ScriptLogEntry> Logs)
        Build(params RawTagEntry[] tags)
    {
        var logs = new List<ScriptLogEntry>();
        var sink = new ScriptLogTopicSink(new CapturingPublisher(logs), LogEventLevel.Information);
        var scriptRoot = new ScriptRootLogger(new LoggerConfiguration().WriteTo.Sink(sink).CreateLogger());
        var driver = new CalculationDriver(new CalculationDriverOptions { RawTags = tags }, "calc-drv", scriptRoot);
        var published = new ConcurrentQueue<DataChangeEventArgs>();
        driver.OnDataChange += (_, e) => published.Enqueue(e);
        return (driver, published, logs);
    }

    /// <summary>Local copy of the script-log capture sink (the sibling suite's is private to it).</summary>
    private sealed class CapturingPublisher(List<ScriptLogEntry> sink) : IScriptLogPublisher
    {
        private readonly object _lock = new();

        public void Publish(ScriptLogEntry entry)
        {
            lock (_lock) sink.Add(entry);
        }
    }

    private static async Task Settle(CalculationDriver driver)
    {
        var deadline = DateTime.UtcNow + TimeSpan.FromSeconds(10);
        while (DateTime.UtcNow < deadline)
        {
            if (driver.IsEvaluationIdle) return;
            await Task.Delay(10);
        }

        driver.IsEvaluationIdle.ShouldBeTrue("the calc driver's evaluation pump should have drained");
    }

    /// <summary>Drives both deps Good and drains the resulting publish, leaving a settled Good output.</summary>
    private static async Task<CalculationDriver> WarmedUpAsync(ConcurrentQueue<DataChangeEventArgs> published, CalculationDriver driver)
    {
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
        driver.OnDependencyValue("src/a", 10.0, StatusGood, DateTime.UtcNow);
        driver.OnDependencyValue("src/b", 20.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);

        published.Count.ShouldBe(1);
        published.TryDequeue(out var first).ShouldBeTrue();
        first!.Snapshot.Value.ShouldBe(30.0);
        first.Snapshot.StatusCode.ShouldBe(StatusGood);
        return driver;
    }

    /// <summary>
    ///     A Bad input holds the script and publishes the input's own sub-code, once, carrying the last
    ///     known value. Three things are asserted together because each is a separate way the old
    ///     behaviour was wrong: no evaluation (no NRE storm), the sub-code propagated (not a generic
    ///     <c>BadInternalError</c>, which would blame the script), and no script-log entry (an input
    ///     dying is not a script fault).
    /// </summary>
    [Fact]
    public async Task A_bad_input_holds_evaluation_and_publishes_the_inputs_own_sub_code_once()
    {
        var (driver, published, logs) = Build(CalcTag(SumTag, SumScript));
        await WarmedUpAsync(published, driver);

        driver.OnDependencyValue("src/a", null, StatusBadNoCommunication, DateTime.UtcNow);
        await Settle(driver);

        published.Count.ShouldBe(1);
        published.TryDequeue(out var bad).ShouldBeTrue();
        bad!.Snapshot.StatusCode.ShouldBe(StatusBadNoCommunication);
        bad.Snapshot.StatusCode.ShouldNotBe(StatusBadInternalError, "the script did not fail — its input did");
        bad.Snapshot.Value.ShouldBe(30.0, "the last known value rides out with the Bad status");
        logs.ShouldBeEmpty("a dead input is not a script fault; the script log stays the per-failure diagnostic");

        // Transition-once: a second Bad push of the same code changes nothing observable.
        driver.OnDependencyValue("src/a", null, StatusBadNoCommunication, DateTime.UtcNow);
        await Settle(driver);
        published.ShouldBeEmpty();
    }

    /// <summary>
    ///     A different Bad sub-code IS republished: the sub-code is the diagnostic, and masking
    ///     <c>BadNoCommunication</c> behind an earlier <c>BadWaitingForInitialData</c> (or vice versa)
    ///     hides which input died and why.
    /// </summary>
    [Fact]
    public async Task A_different_bad_sub_code_is_republished()
    {
        var (driver, published, _) = Build(CalcTag(SumTag, SumScript));
        await WarmedUpAsync(published, driver);

        driver.OnDependencyValue("src/a", null, StatusBadNoCommunication, DateTime.UtcNow);
        await Settle(driver);
        published.TryDequeue(out _).ShouldBeTrue();

        driver.OnDependencyValue("src/a", null, StatusBadInternalError, DateTime.UtcNow);
        await Settle(driver);

        published.Count.ShouldBe(1);
        published.TryDequeue(out var second).ShouldBeTrue();
        second!.Snapshot.StatusCode.ShouldBe(StatusBadInternalError);
    }

    /// <summary>
    ///     <b>The vacuity-sensitive assertion.</b> The input recovers with the value it had before the
    ///     outage, so the computed output is <b>identical</b> to the pre-outage one — and it must still be
    ///     republished Good, because the node is currently Bad and only a publish can clear it. A
    ///     value-only dedup swallows exactly this case, which is why a recovery test with a changed value
    ///     is not the guard.
    /// </summary>
    [Fact]
    public async Task An_identical_value_is_republished_when_recovering_from_a_bad_input()
    {
        var (driver, published, _) = Build(CalcTag(SumTag, SumScript));
        await WarmedUpAsync(published, driver);

        driver.OnDependencyValue("src/a", null, StatusBadNoCommunication, DateTime.UtcNow);
        await Settle(driver);
        published.TryDequeue(out _).ShouldBeTrue();

        // The device comes back holding the same reading it had before.
        driver.OnDependencyValue("src/a", 10.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);

        published.Count.ShouldBe(1);
        published.TryDequeue(out var recovered).ShouldBeTrue();
        recovered!.Snapshot.Value.ShouldBe(30.0, "the same value as before the outage — that is the point");
        recovered.Snapshot.StatusCode.ShouldBe(StatusGood);
    }

    /// <summary>
    ///     An Uncertain input is still computable, so the script runs and the output inherits the
    ///     Uncertain code — the alarm engine's rule (Uncertain is "ready"). Holding here would take a
    ///     perfectly good arithmetic result hostage.
    /// </summary>
    [Fact]
    public async Task An_uncertain_input_is_evaluated_and_stamps_the_output_uncertain()
    {
        var (driver, published, _) = Build(CalcTag(SumTag, SumScript));
        await WarmedUpAsync(published, driver);

        driver.OnDependencyValue("src/a", 11.0, StatusUncertain, DateTime.UtcNow);
        await Settle(driver);

        published.Count.ShouldBe(1);
        published.TryDequeue(out var uncertain).ShouldBeTrue();
        uncertain!.Snapshot.Value.ShouldBe(31.0, "the script DID run — Uncertain is usable");
        uncertain.Snapshot.StatusCode.ShouldBe(StatusUncertain);

        // …and returning to Good republishes, even though the computed value changes back to a value the
        // tag has held before.
        driver.OnDependencyValue("src/a", 10.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        published.TryDequeue(out var good).ShouldBeTrue();
        good!.Snapshot.StatusCode.ShouldBe(StatusGood);
        good.Snapshot.Value.ShouldBe(30.0);
    }

    /// <summary>
    ///     Cold start is unchanged: with one dep never pushed, a Bad arrival on the other publishes
    ///     nothing at all (the node stays at the materialiser's <c>BadWaitingForInitialData</c>). Only once
    ///     every dep has arrived does a Bad among them become reportable.
    /// </summary>
    [Fact]
    public async Task Nothing_is_published_while_a_dep_has_never_arrived()
    {
        var (driver, published, _) = Build(CalcTag(SumTag, SumScript));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        driver.OnDependencyValue("src/a", null, StatusBadNoCommunication, DateTime.UtcNow);
        await Settle(driver);
        published.ShouldBeEmpty("src/b has never arrived — this is warm-up, not a fault");

        driver.OnDependencyValue("src/b", 20.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);

        published.Count.ShouldBe(1);
        published.TryDequeue(out var bad).ShouldBeTrue();
        bad!.Snapshot.StatusCode.ShouldBe(StatusBadNoCommunication);
    }

    /// <summary>
    ///     A passthrough script over a Bad input must not publish <c>Ok(null)</c> Good — the worst case of
    ///     the laundering, since the passthrough fast path bypasses the read cache entirely.
    /// </summary>
    [Fact]
    public async Task A_passthrough_over_a_bad_input_is_bad_not_good_null()
    {
        var (driver, published, _) = Build(CalcTag("calc/e/pass", "return ctx.GetTag(\"src/a\").Value;"));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        driver.OnDependencyValue("src/a", 42.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        published.TryDequeue(out var good).ShouldBeTrue();
        good!.Snapshot.Value.ShouldBe(42.0);

        driver.OnDependencyValue("src/a", null, StatusBadNoCommunication, DateTime.UtcNow);
        await Settle(driver);

        published.Count.ShouldBe(1);
        published.TryDequeue(out var bad).ShouldBeTrue();
        bad!.Snapshot.StatusCode.ShouldBe(StatusBadNoCommunication);
        bad.Snapshot.StatusCode.ShouldNotBe(StatusGood);
    }

    /// <summary>
    ///     <c>ReadAsync</c> reports what the subscriber was told. A read that answered Good while the
    ///     subscription carried Bad would leave two clients of the same node disagreeing about it.
    /// </summary>
    [Fact]
    public async Task ReadAsync_reports_the_same_status_the_subscriber_saw()
    {
        var (driver, published, _) = Build(CalcTag(SumTag, SumScript));
        await WarmedUpAsync(published, driver);

        driver.OnDependencyValue("src/a", null, StatusBadNoCommunication, DateTime.UtcNow);
        await Settle(driver);
        published.TryDequeue(out var bad).ShouldBeTrue();

        var read = await driver.ReadAsync([SumTag], TestContext.Current.CancellationToken);

        read[0].StatusCode.ShouldBe(bad!.Snapshot.StatusCode);
        read[0].Value.ShouldBe(bad.Snapshot.Value);
    }

    /// <summary>
    ///     A tag whose ONLY publish was inputs-Bad — it never produced a value — must read back that Bad
    ///     status, not <c>BadWaitingForInitialData</c>. Guarding the read on "has a value" rather than
    ///     "has published" made a polled read say "never polled" while the subscriber on the same node had
    ///     been told <c>BadNoCommunication</c>: the two clients disagree, and the read is the one that
    ///     lies (something HAS been observed about this tag — that its input is dead).
    /// </summary>
    [Fact]
    public async Task ReadAsync_after_an_inputs_Bad_with_no_prior_value_reports_the_bad_status()
    {
        var (driver, published, _) = Build(CalcTag(SumTag, SumScript));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        // The first thing that ever happens to this tag is a dead input — no successful evaluation, so
        // there is no last value to carry.
        driver.OnDependencyValue("src/a", null, StatusBadNoCommunication, DateTime.UtcNow);
        driver.OnDependencyValue("src/b", 20.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);

        published.Count.ShouldBe(1);
        published.TryDequeue(out var bad).ShouldBeTrue();
        bad!.Snapshot.StatusCode.ShouldBe(StatusBadNoCommunication);
        bad.Snapshot.Value.ShouldBeNull();

        var read = await driver.ReadAsync([SumTag], TestContext.Current.CancellationToken);

        read[0].StatusCode.ShouldBe(StatusBadNoCommunication);
        read[0].StatusCode.ShouldNotBe(StatusBadWaitingForInitialData,
            "something HAS been observed about this tag — that its input is dead");
        read[0].Value.ShouldBeNull();
    }

    /// <summary>A never-evaluated tag still reads BadWaitingForInitialData (regression).</summary>
    [Fact]
    public async Task An_unevaluated_tag_still_reads_BadWaitingForInitialData()
    {
        var (driver, _, _) = Build(CalcTag(SumTag, SumScript));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        var read = await driver.ReadAsync([SumTag], TestContext.Current.CancellationToken);

        read[0].StatusCode.ShouldBe(StatusBadWaitingForInitialData);
    }
}