using System.Collections.Concurrent;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
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>
///     Review 07 Calculation remediation: a compile failure is negative-cached by source hash and its
///     Warning/script-log fires on the Good→Bad transition only (P4); inputs are recorded before
///     <c>InitializeAsync</c> so a Restart computes from current inputs (H6); array results dedup
///     structurally (H8); <c>ShutdownAsync</c> drops the compiled scripts (L2).
/// </summary>
public sealed class CalculationDriverRemediationTests
{
    private const uint StatusGood = 0u;
    private const uint StatusBadInternalError = 0x80020000u;

    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, CapturingLogger HostLog)
        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 hostLog = new CapturingLogger();
        var driver = new CalculationDriver(new CalculationDriverOptions { RawTags = tags }, "calc-drv", scriptRoot, hostLog);
        var published = new ConcurrentQueue<DataChangeEventArgs>();
        driver.OnDataChange += (_, e) => published.Enqueue(e);
        return (driver, published, logs, hostLog);
    }

    private static async Task Settle(CalculationDriver driver)
    {
        var deadline = DateTime.UtcNow.AddSeconds(30);
        while (!driver.IsEvaluationIdle && DateTime.UtcNow < deadline) await Task.Delay(10);
        driver.IsEvaluationIdle.ShouldBeTrue("the calc driver's evaluation pump should have drained");
    }

    /// <summary>Fix round 1 minor: Dispose releases the evaluation gate and its cancellation source — even
    /// with a runaway run in flight (the guard lets the caller's cancel win, so the awaited run returns
    /// promptly) — and a trigger arriving after Dispose is harmless.</summary>
    [Fact]
    public async Task Dispose_with_a_run_in_flight_disposes_the_eval_gate_and_a_late_trigger_is_harmless()
    {
        var (driver, _, _, _) = Build(
            CalcTag("calc/e/spin", "var v = ctx.GetTag(\"src/a\").Value; var end = System.DateTime.UtcNow.AddSeconds(6); while (System.DateTime.UtcNow < end) { } return 1;"));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
        driver.OnDependencyValue("src/a", 1, StatusGood, DateTime.UtcNow);
        var deadline = DateTime.UtcNow.AddSeconds(10);
        while (driver.IsEvaluationIdle && DateTime.UtcNow < deadline) await Task.Delay(5);
        driver.IsEvaluationIdle.ShouldBeFalse("positive control: a run is in flight when Dispose lands");

        var sw = System.Diagnostics.Stopwatch.StartNew();
        driver.Dispose();
        sw.Elapsed.ShouldBeLessThan(TimeSpan.FromSeconds(5), "the caller's cancel releases the awaited run; Dispose is not held for the 6 s spin");
        driver.EvalResourcesDisposedForTest.ShouldBeTrue();

        Should.NotThrow(() => driver.OnDependencyValue("src/a", 2, StatusGood, DateTime.UtcNow));
        Should.NotThrow(() => driver.Dispose());
    }

    [Fact]
    public async Task A_compile_failure_is_remembered_and_logged_once_across_repeated_triggers()
    {
        var (driver, published, logs, hostLog) = Build(
            CalcTag("calc/e/broken", "var x = (double)ctx.GetTag(\"src/a\").Value; this is not valid C#;"));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        for (var i = 0; i < 5; i++)
        {
            driver.OnDependencyValue("src/a", i, StatusGood, DateTime.UtcNow);
            await Settle(driver);
        }

        published.Count.ShouldBe(1, "Bad is published once per transition");
        published.TryDequeue(out var bad).ShouldBeTrue();
        bad!.Snapshot.StatusCode.ShouldBe(StatusBadInternalError);
        logs.Count.ShouldBe(1, "the script-log entry fires on the Good→Bad transition only");
        hostLog.Entries.Count(e => e.Level == LogLevel.Warning && e.Message.Contains("compile failed")).ShouldBe(1,
            "Roslyn is consulted once per source; later triggers hit the negative cache");
        driver.CompileFailureCountForTest.ShouldBe(1);
    }

    [Fact]
    public async Task A_changed_failure_reason_is_logged_even_while_already_Bad()
    {
        // Throws with a different message depending on the input, so the failure REASON changes while the
        // published status stays Bad — the operator must see the new reason.
        var (driver, published, logs, _) = Build(
            CalcTag("calc/e/thrower", "throw new System.InvalidOperationException(\"boom \" + (int)ctx.GetTag(\"src/a\").Value);"));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        driver.OnDependencyValue("src/a", 1, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        driver.OnDependencyValue("src/a", 1, StatusGood, DateTime.UtcNow); // same reason → no new log
        await Settle(driver);
        driver.OnDependencyValue("src/a", 2, StatusGood, DateTime.UtcNow); // new reason → logged
        await Settle(driver);

        published.Count.ShouldBe(1);
        logs.Count.ShouldBe(2);
        logs[0].Message.ShouldContain("boom 1");
        logs[1].Message.ShouldContain("boom 2");
    }

    [Fact]
    public async Task Inputs_delivered_before_InitializeAsync_are_kept_so_the_first_trigger_computes()
    {
        // H6: a Restart is a new driver whose adapter registers interest at construction; the mux's
        // retained-value replay therefore lands BEFORE InitializeAsync. It used to be dropped.
        var (driver, published, _, _) = Build(
            CalcTag("calc/e/sum", "return (double)ctx.GetTag(\"src/a\").Value + (double)ctx.GetTag(\"src/b\").Value;"));

        driver.OnDependencyValue("src/a", 10.0, StatusGood, DateTime.UtcNow); // replayed, pre-init
        driver.OnDependencyValue("src/b", 20.0, StatusGood, DateTime.UtcNow);
        published.ShouldBeEmpty("evaluation is gated on running");

        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
        driver.OnDependencyValue("src/a", 12.0, StatusGood, DateTime.UtcNow); // only ONE input moves after init
        await Settle(driver);

        published.Count.ShouldBe(1, "src/b's pre-init value satisfied the change-gate");
        published.TryDequeue(out var e).ShouldBeTrue();
        e!.Snapshot.Value.ShouldBe(32.0);
    }

    [Fact]
    public async Task An_equal_array_result_is_deduped_structurally()
    {
        var (driver, published, _, _) = Build(
            CalcTag("calc/e/arr", "var v = (double)ctx.GetTag(\"src/a\").Value; return new double[] { v, v * 2 };"));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);

        driver.OnDependencyValue("src/a", 1.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        driver.OnDependencyValue("src/a", 1.0, StatusGood, DateTime.UtcNow); // same array contents
        await Settle(driver);
        published.Count.ShouldBe(1, "a structurally equal array is not a change");

        driver.OnDependencyValue("src/a", 2.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        published.Count.ShouldBe(2, "a different array still publishes");
        published.Last().Snapshot.Value.ShouldBe(new double[] { 2.0, 4.0 });
    }

    [Fact]
    public async Task ShutdownAsync_drops_the_compiled_scripts()
    {
        var (driver, published, _, _) = Build(CalcTag("calc/e/x", "return (double)ctx.GetTag(\"src/a\").Value * 2.0;"));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
        driver.OnDependencyValue("src/a", 1.0, StatusGood, DateTime.UtcNow);
        await Settle(driver);
        published.Count.ShouldBe(1);
        driver.CompiledScriptCountForTest.ShouldBe(1);

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

        driver.CompiledScriptCountForTest.ShouldBe(0, "the collectible ALCs must not survive the generation");
    }

    private sealed class CapturingPublisher(List<ScriptLogEntry> entries) : IScriptLogPublisher
    {
        public void Publish(ScriptLogEntry entry) { lock (entries) entries.Add(entry); }
    }

    internal sealed class CapturingLogger : ILogger<CalculationDriver>
    {
        public ConcurrentBag<(LogLevel Level, string Message)> Entries { get; } = new();
        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)));
    }
}