using Nonemm.Core;

namespace Nonemm.Network.Tests;

/// The checksum two stations compare during a resync. What matters is that the
/// same contacts hash the same whatever order they are handed over in, that a
/// change anywhere in a contact changes it, and that the columns each station
/// works out for itself do not.
public class LogChecksumTests
{
    private static readonly DateTime Start = new(2026, 5, 30, 12, 0, 0, DateTimeKind.Utc);

    [Fact]
    public void TheSameContactsHashTheSameInAnyOrder()
    {
        Qso one = Contact("G3XYZ", 0);
        Qso two = Contact("DL1ABC", 1);

        Assert.Equal(LogChecksum.Of([one, two]), LogChecksum.Of([two, one]));
    }

    /// Two contacts at the same second are ordered by callsign, the way N1MM
    /// reads them out of the database.
    [Fact]
    public void ContactsAtTheSameSecondAreOrderedByCall()
    {
        Qso one = Contact("G3XYZ", 0);
        Qso two = Contact("DL1ABC", 0);

        Assert.Equal(LogChecksum.Of([one, two]), LogChecksum.Of([two, one]));
    }

    [Fact]
    public void AChangedExchangeChangesTheChecksum()
    {
        Qso qso = Contact("G3XYZ", 0);

        Assert.NotEqual(
            LogChecksum.Of([qso]),
            LogChecksum.Of([qso with { ReceivedNumber = 42 }]));
    }

    /// Points and the multiplier flags are worked out from the rules at each
    /// station, and the two are allowed to disagree about them while holding
    /// the same contact.
    [Fact]
    public void ScoringDoesNotChangeTheChecksum()
    {
        Qso qso = Contact("G3XYZ", 0);

        Assert.Equal(
            LogChecksum.Of([qso]),
            LogChecksum.Of([qso with { Points = 3, IsMultiplier1 = true, IsMultiplier2 = true }]));
    }

    [Fact]
    public void AnEmptyBlockHashesToTheEmptyChecksum()
    {
        Assert.Equal(LogChecksum.Of([]), LogChecksum.Of([]));
    }

    /// A block is the contacts of one computer inside one stretch of time. The
    /// end of the block is not in it, so two blocks side by side neither share
    /// a contact nor drop one.
    [Fact]
    public void ABlockHoldsOneStationsContactsInsideTheHour()
    {
        List<Qso> log =
        [
            Contact("G3XYZ", 0) with { StationName = "RUN-PC" },
            Contact("DL1ABC", 30) with { StationName = "RUN-PC" },
            Contact("OK1AB", 45) with { StationName = "MULT-PC" },
            Contact("F5XY", 60) with { StationName = "RUN-PC" },
        ];

        IReadOnlyList<Qso> block = LogChecksum.Block(log, "run-pc", Start, TimeSpan.FromHours(1));

        Assert.Equal(["DL1ABC", "G3XYZ"], block.Select(q => q.Call.Text).Order());
    }

    private static Qso Contact(string call, int minutes) => new()
    {
        Id = $"{call}-{minutes}",
        TimestampUtc = Start.AddMinutes(minutes),
        Call = Callsign.Parse(call),
        Frequency = Frequency.FromKilohertz(14_025),
        Mode = Modes.Cw,
        ContestName = "CQWW",
        ContestNumber = 2,
        SentNumber = 41,
        StationName = "RUN-PC",
    };
}