PKHeX/PKHeX.Core/Legality/Verifiers/CXDVerifier.cs

using static PKHeX.Core.LegalityCheckStrings;

namespace PKHeX.Core;

/// <summary>
/// Verifies the specific origin data of <see cref="GameVersion.CXD"/> encounters.
/// </summary>
public sealed class CXDVerifier : Verifier
{
    protected override CheckIdentifier Identifier => CheckIdentifier.Misc;

    public override void Verify(LegalityAnalysis data)
    {
        var pk = data.Entity;
        if (data.EncounterMatch is EncounterStatic3 s3)
            VerifyCXDStarterCorrelation(data, s3);
        else if (pk.Egg_Location != 0 && pk is not PB8 {Egg_Location: Locations.Default8bNone}) // can't obtain eggs in CXD
            data.AddLine(GetInvalid(LEncInvalid, CheckIdentifier.Encounter)); // invalid encounter

        if (pk.OT_Gender == 1)
            data.AddLine(GetInvalid(LG3OTGender, CheckIdentifier.Trainer));
    }

    private static void VerifyCXDStarterCorrelation(LegalityAnalysis data, EncounterStatic3 enc)
    {
        var (type, seed) = data.Info.PIDIV;
        if (type is not (PIDType.CXD or PIDType.CXDAnti or PIDType.CXD_ColoStarter))
            return; // already flagged as invalid

        bool valid;
        if (enc.Species is (int)Species.Espeon or (int)Species.Umbreon)
        {
            valid = type == PIDType.CXD_ColoStarter;
        }
        else if (enc.Species == (int)Species.Eevee)
        {
            var pk = data.Entity;
            if (type == PIDType.CXD_ColoStarter && pk.Species == (int)Species.Umbreon)
            {
                // reset pidiv type to be CXD -- ColoStarter is same correlation as Eevee->Umbreon
                data.Info.PIDIV = new PIDIV(PIDType.CXD, seed);
                valid = true;
            }
            else
            {
                valid = LockFinder.IsXDStarterValid(seed, pk.TID, pk.SID);
                if (valid) // unroll seed to origin that generated TID/SID->pkm
                    data.Info.PIDIV = new PIDIV(PIDType.CXD, XDRNG.Prev4(seed));
            }
        }
        else
        {
            return;
        }

        if (!valid)
            data.AddLine(GetInvalid(LEncConditionBadRNGFrame, CheckIdentifier.PID));
    }
}