using Microsoft.Extensions.Options;

namespace ZB.MOM.WW.ScadaBridge.HealthMonitoring.Tests;

/// <summary>
/// Regression tests: <see cref="HealthMonitoringOptions"/> intervals
/// are fed straight into <c>new PeriodicTimer(...)</c>, which throws
/// <see cref="ArgumentOutOfRangeException"/> for a zero/negative period. A
/// misconfigured <c>appsettings.json</c> must be rejected by an
/// <see cref="IValidateOptions{TOptions}"/> with a clear, key-naming message
/// rather than crashing the hosted service with an opaque exception.
/// </summary>
public class HealthMonitoringOptionsValidatorTests
{
    private static ValidateOptionsResult Validate(HealthMonitoringOptions options) =>
        new HealthMonitoringOptionsValidator().Validate(Options.DefaultName, options);

    /// <summary>Verifies that the default options pass validation.</summary>
    [Fact]
    public void DefaultOptions_AreValid()
    {
        var result = Validate(new HealthMonitoringOptions());
        Assert.True(result.Succeeded, result.FailureMessage);
    }

    /// <summary>Verifies that a zero report interval is rejected.</summary>
    [Fact]
    public void ZeroReportInterval_IsRejected()
    {
        var result = Validate(new HealthMonitoringOptions { ReportInterval = TimeSpan.Zero });

        Assert.True(result.Failed);
        Assert.Contains("ReportInterval", result.FailureMessage);
    }

    /// <summary>Verifies that a negative report interval is rejected.</summary>
    [Fact]
    public void NegativeReportInterval_IsRejected()
    {
        var result = Validate(new HealthMonitoringOptions { ReportInterval = TimeSpan.FromSeconds(-1) });

        Assert.True(result.Failed);
        Assert.Contains("ReportInterval", result.FailureMessage);
    }

    /// <summary>Verifies that a zero offline timeout is rejected.</summary>
    [Fact]
    public void ZeroOfflineTimeout_IsRejected()
    {
        var result = Validate(new HealthMonitoringOptions { OfflineTimeout = TimeSpan.Zero });

        Assert.True(result.Failed);
        Assert.Contains("OfflineTimeout", result.FailureMessage);
    }

    /// <summary>Verifies that a zero central offline timeout is rejected.</summary>
    [Fact]
    public void ZeroCentralOfflineTimeout_IsRejected()
    {
        var result = Validate(new HealthMonitoringOptions { CentralOfflineTimeout = TimeSpan.Zero });

        Assert.True(result.Failed);
        Assert.Contains("CentralOfflineTimeout", result.FailureMessage);
    }

    /// <summary>Verifies that a central offline timeout shorter than the offline timeout is rejected.</summary>
    [Fact]
    public void CentralOfflineTimeout_ShorterThanOfflineTimeout_IsRejected()
    {
        var result = Validate(new HealthMonitoringOptions
        {
            OfflineTimeout = TimeSpan.FromSeconds(60),
            CentralOfflineTimeout = TimeSpan.FromSeconds(30)
        });

        Assert.True(result.Failed);
        Assert.Contains("CentralOfflineTimeout", result.FailureMessage);
    }

    /// <summary>Verifies that a zero metrics stale timeout is rejected.</summary>
    [Fact]
    public void ZeroMetricsStaleTimeout_IsRejected()
    {
        var result = Validate(new HealthMonitoringOptions { MetricsStaleTimeout = TimeSpan.Zero });

        Assert.True(result.Failed);
        Assert.Contains("MetricsStaleTimeout", result.FailureMessage);
    }

    /// <summary>Verifies that a metrics stale timeout shorter than the report interval is rejected.</summary>
    [Fact]
    public void MetricsStaleTimeout_ShorterThanReportInterval_IsRejected()
    {
        // A stale window shorter than one report interval flags every site.
        var result = Validate(new HealthMonitoringOptions
        {
            ReportInterval = TimeSpan.FromSeconds(30),
            MetricsStaleTimeout = TimeSpan.FromSeconds(10)
        });

        Assert.True(result.Failed);
        Assert.Contains("MetricsStaleTimeout", result.FailureMessage);
    }

    // ------------------------------------------------------------------
    // LocalDb sustained-backlog badge (register row 33)
    // ------------------------------------------------------------------

    /// <summary>Verifies that a non-positive LocalDb backlog threshold is rejected.</summary>
    /// <param name="threshold">The invalid backlog threshold under test.</param>
    [Theory]
    [InlineData(0)]
    [InlineData(-1)]
    public void NonPositiveLocalDbBacklogThreshold_IsRejected(long threshold)
    {
        // An idle backlog of 0 already sits at or above a zero/negative threshold, so this
        // would badge every replicated site permanently.
        var result = Validate(new HealthMonitoringOptions { LocalDbBacklogThreshold = threshold });

        Assert.True(result.Failed);
        Assert.Contains("LocalDbBacklogThreshold", result.FailureMessage);
    }

    /// <summary>Verifies that a zero LocalDb backlog sustained-for window is rejected.</summary>
    [Fact]
    public void ZeroLocalDbBacklogSustainedFor_IsRejected()
    {
        var result = Validate(new HealthMonitoringOptions
        {
            LocalDbBacklogSustainedFor = TimeSpan.Zero,
        });

        Assert.True(result.Failed);
        Assert.Contains("LocalDbBacklogSustainedFor", result.FailureMessage);
    }

    /// <summary>Verifies that a LocalDb backlog sustained-for window shorter than the report interval is rejected.</summary>
    [Fact]
    public void LocalDbBacklogSustainedFor_ShorterThanReportInterval_IsRejected()
    {
        // A dwell shorter than one report interval can be satisfied by a single sample, which
        // collapses the sustained check back into the bare threshold it replaced — and that
        // fires on every daily purge burst.
        var result = Validate(new HealthMonitoringOptions
        {
            ReportInterval = TimeSpan.FromSeconds(30),
            LocalDbBacklogSustainedFor = TimeSpan.FromSeconds(10),
        });

        Assert.True(result.Failed);
        Assert.Contains("LocalDbBacklogSustainedFor", result.FailureMessage);
    }

    /// <summary>Verifies that the default sustained window comfortably outlasts a purge drain.</summary>
    [Fact]
    public void DefaultSustainedWindow_ComfortablyOutlastsAPurgeDrain()
    {
        // Guards the intent of the default rather than its digits: the dwell must be long
        // enough that an expected purge spike drains inside it, or the badge becomes daily
        // noise and gets ignored.
        var options = new HealthMonitoringOptions();

        Assert.True(options.LocalDbBacklogSustainedFor >= TimeSpan.FromMinutes(5));
        Assert.True(options.LocalDbBacklogSustainedFor >= options.ReportInterval);
    }
}