using SQLInsight.Core.Data;

namespace SQLInsight.Core.Tests;

public class BaselineTests
{
    [Theory]
    [InlineData("2026-09-28T00:30:00Z", 0)]     // Monday
    [InlineData("2026-09-29T13:10:00Z", 37)]    // Tuesday 13
    [InlineData("2026-10-04T23:59:00Z", 167)]   // Sunday 23
    public void Hour_of_week_starts_monday(string utc, int expected)
    {
        Assert.Equal(expected, BaselineCalculator.HourOfWeek(DateTime.Parse(utc, System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.AdjustToUniversal)));
    }

    [Fact]
    public void Uses_the_same_hour_and_its_neighbours_in_earlier_weeks()
    {
        var now = new DateTimeOffset(2026, 9, 29, 13, 20, 0, TimeSpan.Zero); // Tuesday 13
        var history = new List<HourlyValue>();
        for (var week = 1; week <= 3; week++)
        {
            var sameHour = new DateTime(2026, 9, 29, 13, 0, 0, DateTimeKind.Utc).AddDays(-7 * week);
            history.Add(new HourlyValue("cpu", sameHour.AddHours(-1), 20));
            history.Add(new HourlyValue("cpu", sameHour, 30));
            history.Add(new HourlyValue("cpu", sameHour.AddHours(1), 40));
            history.Add(new HourlyValue("cpu", sameHour.AddHours(5), 99)); // other hour: ignored
        }

        history.Add(new HourlyValue("cpu", new DateTime(2026, 9, 29, 12, 0, 0, DateTimeKind.Utc), 99)); // today, too recent

        var baseline = BaselineCalculator.Calculate(history, now);

        var cpu = baseline.Metrics["cpu"];
        Assert.Equal(37, baseline.HourOfWeek);
        Assert.Equal(9, cpu.Samples);
        Assert.Equal(30, cpu.Mean, 6);
        Assert.Equal(Math.Sqrt(75), cpu.StandardDeviation, 6); // (3×100 + 3×0 + 3×100) / 8
    }

    [Fact]
    public void Neighbour_hours_wrap_around_the_week()
    {
        var now = new DateTimeOffset(2026, 9, 28, 0, 30, 0, TimeSpan.Zero); // Monday 00
        var sundayLate = new DateTime(2026, 9, 20, 23, 0, 0, DateTimeKind.Utc);

        var baseline = BaselineCalculator.Calculate([new HourlyValue("cpu", sundayLate, 10)], now);

        Assert.Equal(1, baseline.Metrics["cpu"].Samples);
    }
}