using SQLInsight.Core.Data;
using SQLInsight.Core.Findings;
using SQLInsight.Rules.Engine;
using SQLInsight.Rules.Performance;
using static SQLInsight.Rules.Tests.TestInstances;

namespace SQLInsight.Rules.Tests;

public class AnomalyRuleTests
{
    private static RuleResult Run(RuleContext context) => Assert.Single(new RuleEngine([new AnomalyRule()]).Evaluate(context));

    private static BaselineSnapshot Baseline(params (string Metric, double Mean, double Stdev, int Samples)[] metrics) => new()
    {
        CapturedAt = Now,
        HourOfWeek = 37,
        Metrics = metrics.ToDictionary(m => m.Metric, m => new MetricBaseline(m.Mean, m.Stdev, m.Samples)),
    };

    private static CpuUtilization Cpu(int percent) => new()
    {
        CapturedAt = Now,
        Samples = Enumerable.Range(0, 15).Select(i => new CpuSample(Now.AddMinutes(i - 15), percent, 100 - percent)).ToList(),
    };

    private static CumulativeSample<PerformanceCounterSnapshot, PerformanceCounterRates> Counters(double batches, long ple) => new(
        new PerformanceCounterSnapshot { CapturedAt = Now, SqlServerStartTime = Now.UtcDateTime.AddDays(-1), PageLifeExpectancySeconds = ple },
        new PerformanceCounterRates { From = Now.AddMinutes(-5), To = Now, BatchRequestsPerSecond = batches });

    [Fact]
    public void Too_little_history_is_not_measurable()
    {
        var result = Run(With(Baseline((AnomalyRule.CpuMetric, 20, 5, 3)), Cpu(90)));

        Assert.Equal(RuleOutcome.NotMeasurable, result.Outcome);
        Assert.Contains("uger", result.Reason, StringComparison.Ordinal);
    }

    [Fact]
    public void Cpu_far_above_normal_for_this_hour()
    {
        var finding = Assert.Single(Run(With(Baseline((AnomalyRule.CpuMetric, 20, 5, 9)), Cpu(75))).Findings);

        Assert.Equal("anomaly: cpu", finding.Subject);
        Assert.Contains("tirsdag kl. 13–14 UTC", finding.Evidence[1].Value, StringComparison.Ordinal);
    }

    [Fact]
    public void High_cpu_that_is_normal_for_this_hour_passes()
    {
        Assert.Equal(RuleOutcome.Passed, Run(With(Baseline((AnomalyRule.CpuMetric, 80, 8, 9)), Cpu(88))).Outcome);
    }

    [Fact]
    public void Traffic_drop_suggests_an_application_is_down()
    {
        var finding = Assert.Single(Run(With(Baseline((AnomalyRule.BatchMetric, 800, 100, 9)), Counters(batches: 40, ple: 5000))).Findings);

        Assert.Equal(Severity.Medium, finding.Severity);
        Assert.Contains("færre", finding.Explanation, StringComparison.Ordinal);
    }

    [Fact]
    public void Ple_collapse()
    {
        var finding = Assert.Single(Run(With(Baseline((AnomalyRule.PleMetric, 4000, 500, 9)), Counters(batches: 0, ple: 300))).Findings);

        Assert.Equal("anomaly: ple", finding.Subject);
    }
}