using Serilog;
using Serilog.Core;
using Serilog.Events;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Logging;

namespace ZB.MOM.WW.OtOpcUa.Core.Scripting.Tests;

/// <summary>
///     Per-source rate limit on the script-log fan-out (review R05:9 / R02:P6): a script that logs — or
///     fails — on every evaluation of a 1 Hz input used to put one entry per second per script onto the
///     cluster bus and the main log. The limiter admits the first 20 entries per source per minute, drops
///     the rest, and surfaces one summary line (with the dropped count) when the next entry arrives after
///     the window rolled — so nothing is silently lost, and a chatty script cannot shed everyone else's
///     entries out of the bounded telemetry channels.
/// </summary>
[Trait("Category", "Unit")]
public sealed class ScriptLogRateLimiterTests
{
    private sealed class Clock
    {
        public DateTime Now = new(2026, 1, 1, 12, 0, 0, DateTimeKind.Utc);
        public void Advance(TimeSpan by) => Now += by;
    }

    [Fact]
    public void Admits_the_first_N_per_window_then_suppresses_and_summarises_once_the_window_rolls()
    {
        var clock = new Clock();
        var limiter = new ScriptLogRateLimiter(limitPerWindow: 3, window: TimeSpan.FromMinutes(1), clock: () => clock.Now);

        limiter.Admit("s1").Admitted.ShouldBeTrue();
        limiter.Admit("s1").Admitted.ShouldBeTrue();
        limiter.Admit("s1").Admitted.ShouldBeTrue();
        limiter.Admit("s1").Admitted.ShouldBeFalse();
        limiter.Admit("s1").Admitted.ShouldBeFalse();
        limiter.Admit("s1").SuppressedInPreviousWindow.ShouldBe(0, "no summary until the window rolls");

        clock.Advance(TimeSpan.FromMinutes(1));
        var first = limiter.Admit("s1");
        first.Admitted.ShouldBeTrue("a fresh window admits again");
        first.SuppressedInPreviousWindow.ShouldBe(3, "the caller emits one summary for the three dropped entries");
        limiter.Admit("s1").SuppressedInPreviousWindow.ShouldBe(0, "the summary is reported exactly once");
    }

    [Fact]
    public void Sources_are_independent()
    {
        var limiter = new ScriptLogRateLimiter(limitPerWindow: 1);
        limiter.Admit("a").Admitted.ShouldBeTrue();
        limiter.Admit("a").Admitted.ShouldBeFalse();
        limiter.Admit("b").Admitted.ShouldBeTrue("a chatty source must not shed another source's entries");
    }

    [Fact]
    public void Defaults_are_20_per_minute()
    {
        ScriptLogRateLimiter.DefaultLimitPerWindow.ShouldBe(20);
        ScriptLogRateLimiter.DefaultWindow.ShouldBe(TimeSpan.FromMinutes(1));
        var limiter = new ScriptLogRateLimiter();
        limiter.LimitPerWindow.ShouldBe(20);
        new ScriptLogRateLimiter(limitPerWindow: 3).LimitPerWindow.ShouldBe(3);
        new ScriptLogRateLimiter(limitPerWindow: 0).LimitPerWindow.ShouldBe(1, "values below 1 are treated as 1");
        for (var i = 0; i < 20; i++) limiter.Admit("s").Admitted.ShouldBeTrue();
        limiter.Admit("s").Admitted.ShouldBeFalse();
    }

    // ── the two sinks ────────────────────────────────────────────────────────────────────────

    private sealed class FakePublisher : IScriptLogPublisher
    {
        public List<ScriptLogEntry> Published { get; } = [];
        public void Publish(ScriptLogEntry entry) => Published.Add(entry);
    }

    private static LogEvent Evt(LogEventLevel level, string template, params (string Key, string Val)[] props)
    {
        var tmpl = new Serilog.Parsing.MessageTemplateParser().Parse(template);
        var logProps = props.Select(p => new LogEventProperty(p.Key, new ScalarValue(p.Val)));
        return new LogEvent(DateTimeOffset.UtcNow, level, exception: null, tmpl, logProps);
    }

    [Fact]
    public void Topic_sink_rate_limits_per_source_and_publishes_a_summary_entry()
    {
        var clock = new Clock();
        var publisher = new FakePublisher();
        var sink = new ScriptLogTopicSink(publisher, LogEventLevel.Information,
            new ScriptLogRateLimiter(limitPerWindow: 2, clock: () => clock.Now));

        for (var i = 0; i < 5; i++)
            sink.Emit(Evt(LogEventLevel.Warning, "chatty", (ScriptLoggerFactory.ScriptIdProperty, "S1"), (ScriptLoggerFactory.VirtualTagIdProperty, "V1")));
        sink.Emit(Evt(LogEventLevel.Warning, "other", (ScriptLoggerFactory.ScriptIdProperty, "S2")));

        publisher.Published.Count(e => e.ScriptId == "S1").ShouldBe(2, "the limit is per source");
        publisher.Published.Count(e => e.ScriptId == "S2").ShouldBe(1, "another source is unaffected");

        clock.Advance(TimeSpan.FromMinutes(1));
        sink.Emit(Evt(LogEventLevel.Warning, "chatty again", (ScriptLoggerFactory.ScriptIdProperty, "S1"), (ScriptLoggerFactory.VirtualTagIdProperty, "V1")));

        var s1 = publisher.Published.Where(e => e.ScriptId == "S1").ToList();
        s1.Count.ShouldBe(4, "2 admitted + 1 summary + 1 admitted in the new window");
        var summary = s1[2];
        summary.Message.ShouldContain("3");
        summary.Message.ShouldContain("suppressed");
        summary.Message.ShouldContain("limit 2/window", Case.Sensitive, "the summary names the CONFIGURED limit, not the default");
        summary.VirtualTagId.ShouldBe("V1", "the summary carries the source's identity so the page attributes it");
        summary.Level.ShouldBe("Warning");
        s1[3].Message.ShouldBe("chatty again");
    }

    private sealed class CapturingSink : ILogEventSink
    {
        public List<LogEvent> Events { get; } = [];
        public void Emit(LogEvent logEvent) => Events.Add(logEvent);
    }

    [Fact]
    public void Companion_sink_rate_limits_per_script_and_mirrors_a_summary_line()
    {
        var clock = new Clock();
        var main = new CapturingSink();
        var mainLogger = new LoggerConfiguration().MinimumLevel.Verbose().WriteTo.Sink(main).CreateLogger();
        var sink = new ScriptLogCompanionSink(mainLogger, LogEventLevel.Error,
            new ScriptLogRateLimiter(limitPerWindow: 2, clock: () => clock.Now));

        for (var i = 0; i < 5; i++)
            sink.Emit(Evt(LogEventLevel.Error, "boom", (ScriptLoggerFactory.ScriptNameProperty, "HighTemp")));
        main.Events.Count.ShouldBe(2);

        clock.Advance(TimeSpan.FromMinutes(1));
        sink.Emit(Evt(LogEventLevel.Error, "boom", (ScriptLoggerFactory.ScriptNameProperty, "HighTemp")));

        main.Events.Count.ShouldBe(4);
        var summary = main.Events[2].RenderMessage();
        summary.ShouldContain("HighTemp");
        summary.ShouldContain("3");
        summary.ShouldContain("suppressed");
    }
}