using System.Collections.Concurrent;
using Microsoft.Extensions.Logging;
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>
///     WP7 unit tests for <see cref="CalculationDriver"/>: dependency-ref extraction from the authored
///     tags, the change-gate (no publish until every declared dep has arrived), value dedup, the
///     Good→Bad transition + <c>ScriptLogEntry</c> emission + Good recovery, and timer-trigger recompute.
/// </summary>
public sealed class CalculationDriverTests
{
    private const uint StatusGood = 0u;
    private const uint StatusBadInternalError = 0x80020000u;
    private const uint StatusBadWaitingForInitialData = 0x80320000u;

    private static RawTagEntry CalcTag(string rawPath, string source, bool changeTriggered = true, int? timerMs = null)
    {
        var timer = timerMs is { } ms ? $",\"timerIntervalMs\":{ms}" : "";
        var json = $"{{\"scriptId\":\"s-{rawPath}\",\"changeTriggered\":{(changeTriggered ? "true" : "false")}{timer}," +
                   $"\"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>
    ///     Wait until the driver's evaluation pump has drained. A change-triggered evaluation is queued by
    ///     <c>OnDependencyValue</c> and run on the driver's own worker (Driver.Calculation-005), so a test
    ///     that used to assert on the very next line now settles first. Quiescence, not a sleep: the work
    ///     is enqueued synchronously inside the callback, so "idle" can never be observed before it lands.
    ///     The 30 s ceiling covers a cold Roslyn compile of the first evaluation on a loaded CI runner,
    ///     where 10 s ran out (#606); quiescence returns the instant the pump drains, so it costs nothing.
    /// </summary>
    private static async Task Settle(CalculationDriver driver)
    {
        var idle = await WaitUntil(() => driver.IsEvaluationIdle, TimeSpan.FromSeconds(30));
        idle.ShouldBeTrue("the calc driver's evaluation pump should have drained");
    }

    // ── dependency-ref extraction ─────────────────────────────────────────────────────────────

    [Fact]
    public void DependencyRefs_are_the_union_of_authored_tag_scripts()
    {
        var (driver, _, _) = Build(
            CalcTag("calc/e/x", "return (double)ctx.GetTag(\"src/a\").Value + (double)ctx.GetTag(\"src/b\").Value;"),
            CalcTag("calc/e/y", "return (double)ctx.GetTag(\"src/b\").Value + (double)ctx.GetTag(\"src/c\").Value;"));

        driver.DependencyRefs.OrderBy(r => r).ShouldBe(new[] { "src/a", "src/b", "src/c" });
    }

    // ── change-gate ───────────────────────────────────────────────────────────────────────────

    [Fact]
    public async Task No_publish_until_every_declared_dep_has_arrived()
    {
        var (driver, published, _) = Build(
            CalcTag("calc/e/sum", "return (double)ctx.GetTag(\"src/a\").Value + (double)ctx.GetTag(\"src/b\").Value;"));
        await driver.InitializeAsync("{}", default);

        // Only one of two deps arrived → the change-gate holds.
        driver.OnDependencyValue("src/a", 10.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        published.ShouldBeEmpty();

        // Second dep arrives → now it computes + publishes 30.
        driver.OnDependencyValue("src/b", 20.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        published.Count.ShouldBe(1);
        published.TryDequeue(out var e).ShouldBeTrue();
        e!.FullReference.ShouldBe("calc/e/sum");
        e.Snapshot.Value.ShouldBe(30.0);
        e.Snapshot.StatusCode.ShouldBe(StatusGood);
    }

    /// <summary>
    ///     The change-gate must hold BEFORE the script ever runs, not just before the publish. A
    ///     multi-dependency script that casts a missing dep's <c>.Value</c> to a non-nullable type (the
    ///     common idiom used throughout this file) throws when evaluated against a partial snapshot, so
    ///     evaluating anyway during ordinary warm-up produced a spurious "script threw" script-log Warning
    ///     on every partial dependency arrival — even though nothing is actually wrong with the script.
    /// </summary>
    [Fact]
    public async Task No_evaluation_or_script_log_while_a_declared_dep_is_still_missing()
    {
        var (driver, published, logs) = Build(
            CalcTag("calc/e/sum", "return (double)ctx.GetTag(\"src/a\").Value + (double)ctx.GetTag(\"src/b\").Value;"));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        driver.OnDependencyValue("src/a", 10.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);

        published.ShouldBeEmpty();
        logs.ShouldBeEmpty("a still-missing declared dependency must hold the gate BEFORE evaluation, " +
                            "not merely before the publish");
    }

    // ── the dependency callback must not execute scripts (Driver.Calculation-005) ─────────────

    /// <summary>
    ///     <c>OnDependencyValue</c> is called <b>directly and synchronously</b> from
    ///     <c>DependencyConsumerMuxAdapter.OnDependencyValueChanged</c> — i.e. on an Akka actor's own
    ///     dispatcher thread. Evaluating there means a script run (bounded only by <c>RunTimeout</c>,
    ///     default 2 s) occupies that thread, so the callback must queue the work and return instead.
    ///     <para>The publish is the observable: it can only happen after the script ran, so a publish that
    ///     lands on the caller's stack <em>between</em> entering and leaving the callback proves the script
    ///     ran inline. A thread-local flag set for exactly that window is the exact test — comparing thread
    ///     <i>ids</i> is not, because the pump is free to reuse the pooled thread the test released while
    ///     waiting, which makes an id match mean nothing. The value assertion is the positive control:
    ///     without it this would pass just as happily against a driver that evaluates nothing at all.</para>
    /// </summary>
    [Fact]
    public async Task A_dependency_arrival_does_not_run_the_script_on_the_callers_thread()
    {
        var (driver, published, _) = Build(
            CalcTag("calc/e/dbl", "return (double)ctx.GetTag(\"src/a\").Value * 2.0;"));
        using var insideCallback = new ThreadLocal<bool>();
        var publishedInline = false;
        driver.OnDataChange += (_, _) => { if (insideCallback.Value) publishedInline = true; };
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        insideCallback.Value = true;
        driver.OnDependencyValue("src/a", 5.0, StatusGood, DateTime.UtcNow);
        insideCallback.Value = false;

        (await WaitUntil(() => !published.IsEmpty, TimeSpan.FromSeconds(10)))
            .ShouldBeTrue("the queued evaluation must still compute and publish the value");
        published.TryDequeue(out var e).ShouldBeTrue();
        e!.Snapshot.Value.ShouldBe(10.0);

        publishedInline.ShouldBeFalse(
            "the calc script must run on the driver's own evaluation pump, never on the mux callback thread");
    }

    /// <summary>
    ///     The second half of Driver.Calculation-005: the evaluation also used to run <b>under the state
    ///     lock</b>, so a slow script froze every other lock-taking operation (here <c>ReadAsync</c>) for
    ///     its whole run as well as the callback itself. Both must now return while the script is still
    ///     executing; the trailing publish is the positive control that the script did run.
    /// </summary>
    [Fact]
    public async Task A_slow_script_blocks_neither_the_dependency_callback_nor_a_concurrent_read()
    {
        // A CPU-bound busy-wait: the sandbox forbids Thread/Task, and DateTime is explicitly allowed.
        const string slowScript =
            "var deadline = System.DateTime.UtcNow.AddMilliseconds(600); " +
            "while (System.DateTime.UtcNow < deadline) { } " +
            "return (double)ctx.GetTag(\"src/a\").Value;";
        var (driver, published, _) = Build(CalcTag("calc/e/slow", slowScript));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        var elapsed = System.Diagnostics.Stopwatch.StartNew();
        driver.OnDependencyValue("src/a", 7.0, StatusGood, DateTime.UtcNow);
        var callbackElapsed = elapsed.Elapsed;

        // ReadAsync takes the same state lock the inline evaluation used to hold for the whole run.
        var snapshot = await driver.ReadAsync(["calc/e/slow"], TestContext.Current.CancellationToken);
        var readElapsed = elapsed.Elapsed;

        callbackElapsed.ShouldBeLessThan(TimeSpan.FromMilliseconds(300),
            "the mux callback thread must not wait on the script run");
        readElapsed.ShouldBeLessThan(TimeSpan.FromMilliseconds(300),
            "the state lock must not be held across the script run");
        snapshot[0].StatusCode.ShouldBe(StatusBadWaitingForInitialData,
            "the read got through while the evaluation was still in flight");

        (await WaitUntil(() => !published.IsEmpty, TimeSpan.FromSeconds(10)))
            .ShouldBeTrue("the slow evaluation must still complete and publish");
        published.TryDequeue(out var e).ShouldBeTrue();
        e!.Snapshot.Value.ShouldBe(7.0);

        await driver.ShutdownAsync(TestContext.Current.CancellationToken);
    }

    // ── dedup + recompute ─────────────────────────────────────────────────────────────────────

    [Fact]
    public async Task Equal_result_is_deduped_and_a_changed_result_republishes()
    {
        var (driver, published, _) = Build(
            CalcTag("calc/e/dbl", "return (double)ctx.GetTag(\"src/a\").Value * 2.0;"));
        await driver.InitializeAsync("{}", default);

        // Each arrival is queued with the dependency snapshot that triggered it, so the three evaluations
        // see 5 / 5 / 7 in that order however far the pump lags behind them.
        driver.OnDependencyValue("src/a", 5.0, StatusGood, DateTime.UtcNow);   // → 10 (publish)
        driver.OnDependencyValue("src/a", 5.0, StatusGood, DateTime.UtcNow);   // → 10 (dedup, no publish)
        driver.OnDependencyValue("src/a", 7.0, StatusGood, DateTime.UtcNow);   // → 14 (publish)
        await Settle(driver);

        published.Select(p => p.Snapshot.Value).ShouldBe(new object?[] { 10.0, 14.0 });
    }

    // ── Bad transition + script-log + recovery ────────────────────────────────────────────────

    [Fact]
    public async Task Failure_publishes_Bad_once_per_transition_emits_script_log_and_recovers()
    {
        var (driver, published, logs) = Build(
            CalcTag("calc/e/div", "return 100 / (int)ctx.GetTag(\"src/a\").Value;"));
        await driver.InitializeAsync("{}", default);

        // a = 0 → DivideByZero → Failure → Bad (carrying last-known = null) + one script-log.
        driver.OnDependencyValue("src/a", 0, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        published.Count.ShouldBe(1);
        published.TryDequeue(out var bad).ShouldBeTrue();
        bad!.Snapshot.StatusCode.ShouldBe(StatusBadInternalError);
        logs.Count.ShouldBe(1);
        logs[0].Level.ShouldBe("Warning");
        logs[0].ScriptId.ShouldBe("s-calc/e/div");
        logs[0].VirtualTagId.ShouldBe("calc/e/div");

        // a = 0 again → still failing, but NOT a fresh transition → no second Bad publish (script-log still emits).
        driver.OnDependencyValue("src/a", 0, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        published.ShouldBeEmpty();
        logs.Count.ShouldBe(2);

        // a = 5 → 20 → Good recovery is force-published.
        driver.OnDependencyValue("src/a", 5, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        published.Count.ShouldBe(1);
        published.TryDequeue(out var good).ShouldBeTrue();
        good!.Snapshot.Value.ShouldBe(20);
        good.Snapshot.StatusCode.ShouldBe(StatusGood);
    }

    // ── timer trigger ─────────────────────────────────────────────────────────────────────────

    [Fact]
    public async Task Timer_only_tag_computes_on_its_interval()
    {
        // No dependencies (constant script) so only the timer can drive it.
        var (driver, published, _) = Build(
            CalcTag("calc/e/const", "return 42.0;", changeTriggered: false, timerMs: 50));
        await driver.InitializeAsync("{}", default);

        var fired = await WaitUntil(() => !published.IsEmpty, TimeSpan.FromSeconds(3));
        fired.ShouldBeTrue("the timer trigger should have computed the tag within 3s");
        published.TryDequeue(out var e).ShouldBeTrue();
        e!.FullReference.ShouldBe("calc/e/const");
        e.Snapshot.Value.ShouldBe(42.0);

        await driver.ShutdownAsync(default);
    }

    // ── IReadable ─────────────────────────────────────────────────────────────────────────────

    [Fact]
    public async Task Read_returns_BadWaitingForInitialData_before_first_eval_then_the_computed_value()
    {
        var (driver, _, _) = Build(CalcTag("calc/e/x", "return (double)ctx.GetTag(\"src/a\").Value * 2.0;"));
        await driver.InitializeAsync("{}", default);

        var before = await driver.ReadAsync(new[] { "calc/e/x" }, default);
        before[0].StatusCode.ShouldBe(StatusBadWaitingForInitialData);

        driver.OnDependencyValue("src/a", 3.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        var after = await driver.ReadAsync(new[] { "calc/e/x" }, default);
        after[0].StatusCode.ShouldBe(StatusGood);
        after[0].Value.ShouldBe(6.0);
    }

    // REMOVED (Gitea #517): `Health_is_always_Connected` asserted that a driver which had never been
    // initialized still reported Healthy — a characterization test of the defect, not of a requirement.
    // Its valid half (a running Calculation driver has no transport to be Degraded about, so it is simply
    // Healthy) is covered by GetHealth_tracks_the_lifecycle_rather_than_reporting_a_constant below.

    private static async Task<bool> WaitUntil(Func<bool> predicate, TimeSpan timeout)
    {
        var deadline = DateTime.UtcNow + timeout;
        while (DateTime.UtcNow < deadline)
        {
            if (predicate()) return true;
            await Task.Delay(20);
        }
        return predicate();
    }

    // ── health lifecycle (Gitea #517) ─────────────────────────────────────────────────────────

    /// <summary>
    ///     Gitea #517 — <c>GetHealth()</c> must not report Healthy for a driver that is not running.
    ///     <para>This driver returned a hard-coded <see cref="DriverState.Healthy"/> that consulted
    ///     nothing, which made it the fleet's only driver reporting Healthy with its timers stopped —
    ///     deterministically, not as a race window. Every other driver reads a <c>_health</c> field that
    ///     shutdown lands on <see cref="DriverState.Unknown"/>.</para>
    ///     <para>The pre-initialize leg is what makes this falsifiable against the old code: a test that
    ///     only checked post-shutdown could be satisfied by a driver that happened to write Unknown once,
    ///     whereas asserting BOTH ends pins the value to the lifecycle flag.</para>
    /// </summary>
    [Fact]
    public async Task GetHealth_tracks_the_lifecycle_rather_than_reporting_a_constant()
    {
        var (driver, _, _) = Build(CalcTag("calc/e/x", "return 1.0;"));

        // Constructed but never initialized — nothing is computing, so Healthy would be a lie.
        driver.GetHealth().State.ShouldBe(DriverState.Unknown);

        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
        driver.GetHealth().State.ShouldBe(DriverState.Healthy);

        await driver.ShutdownAsync(TestContext.Current.CancellationToken);
        driver.GetHealth().State.ShouldBe(DriverState.Unknown,
            "timers are stopped and _running is false — the driver computes nothing");

        // Re-initialize brings it back, so the flag is genuinely read each call rather than latched once.
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
        driver.GetHealth().State.ShouldBe(DriverState.Healthy);

        driver.Dispose();
        driver.GetHealth().State.ShouldBe(DriverState.Unknown);
    }

    // ── evaluator diagnostics reach the driver's own logger ──────────────────────────────────────

    /// <summary>
    ///     The <see cref="CalculationEvaluator"/> the driver constructs internally must log its host-side
    ///     diagnostics (compile errors, sandbox violations, execution throws) through the SAME
    ///     <c>ILogger&lt;CalculationDriver&gt;</c> the driver itself was given — not silently into a
    ///     no-op logger. A timer-triggered tag with a deliberately broken script is the vehicle: it
    ///     evaluates on its own cadence with no dependency needed to arrive first.
    /// </summary>
    [Fact]
    public async Task Evaluator_compile_diagnostics_flow_through_to_the_drivers_own_logger()
    {
        var logger = new CapturingLogger();
        var scriptRoot = new ScriptRootLogger(new LoggerConfiguration().CreateLogger());
        var driver = new CalculationDriver(
            new CalculationDriverOptions
            {
                RawTags = [CalcTag("calc/e/bad", "this is not valid C#;", changeTriggered: false, timerMs: 50)],
            },
            "calc-drv", scriptRoot, logger);
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        var fired = await WaitUntil(
            () => logger.Entries.Any(e => e.Level == LogLevel.Warning && e.Message.Contains("Roslyn compile failed")),
            TimeSpan.FromSeconds(3));

        fired.ShouldBeTrue("the evaluator's compile-failure diagnostic should reach the driver-supplied logger");

        await driver.ShutdownAsync(TestContext.Current.CancellationToken);
    }

    // ── skipped-tag reporting (Gitea #541) ────────────────────────────────────────────────────────

    [Fact]
    public async Task GetSkippedTags_reports_a_raw_tag_with_no_scriptId_alongside_the_authored_total()
    {
        var noScriptId = new RawTagEntry("calc/e/nogood", "{\"foo\":\"bar\"}", WriteIdempotent: false);
        var good = CalcTag("calc/e/good", "return 1.0;", changeTriggered: false);
        var (driver, _, _) = Build(noScriptId, good);
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        var report = driver.GetSkippedTags();

        report.ShouldNotBeNull();
        report!.AuthoredCount.ShouldBe(2);
        report.SkippedCount.ShouldBe(1);
        report.Sample.ShouldContain(s => s.RawPath == "calc/e/nogood");
    }

    [Fact]
    public async Task GetSkippedTags_has_no_skips_when_every_authored_tag_maps()
    {
        var (driver, _, _) = Build(CalcTag("calc/e/good", "return 1.0;", changeTriggered: false));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        var report = driver.GetSkippedTags();

        report.ShouldNotBeNull();
        report!.AuthoredCount.ShouldBe(1);
        report.SkippedCount.ShouldBe(0);
        report.HasSkips.ShouldBeFalse();
    }

    /// <summary>The skip ledger must be REBUILT on ReinitializeAsync, not just at construction — an
    /// ApplyDelta that drops a tag's scriptId (or adds a new tag with none) must be reflected immediately,
    /// since RebuildTagTable is the one routine both the ctor and reinit share.</summary>
    [Fact]
    public async Task GetSkippedTags_updates_after_reinitialize()
    {
        var (driver, _, _) = Build(CalcTag("calc/e/x", "return 1.0;", changeTriggered: false));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
        driver.GetSkippedTags()!.SkippedCount.ShouldBe(0);

        const string reinitJson = """{"rawTags":[{"rawPath":"calc/e/x","tagConfig":"{}","writeIdempotent":false}]}""";
        await driver.ReinitializeAsync(reinitJson, TestContext.Current.CancellationToken);

        var report = driver.GetSkippedTags();
        report!.AuthoredCount.ShouldBe(1);
        report.SkippedCount.ShouldBe(1, "the reinit payload's tag has no scriptId, so it is no longer a calc tag");
    }

    /// <summary>Minimal capturing <see cref="ILogger{T}"/> so a test can assert on what the driver's own
    /// logger received (mirrors the equivalent helper in CalculationEvaluatorTests).</summary>
    private sealed class CapturingLogger : ILogger<CalculationDriver>
    {
        public List<(LogLevel Level, string Message)> Entries { get; } = [];

        public IDisposable? BeginScope<TState>(TState state) where TState : notnull => null;

        public bool IsEnabled(LogLevel logLevel) => true;

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception,
            Func<TState, Exception?, string> formatter) =>
            Entries.Add((logLevel, formatter(state, exception)));
    }

    private sealed class CapturingPublisher(List<ScriptLogEntry> sink) : IScriptLogPublisher
    {
        private readonly object _lock = new();
        public void Publish(ScriptLogEntry entry)
        {
            lock (_lock) sink.Add(entry);
        }
    }
}