PKHeX/PKHeX.Core/Legality/Encounters/EncounterStatic/EncounterStatic4.cs

namespace PKHeX.Core
{
    /// <summary>
    /// Generation 4 Static Encounter
    /// </summary>
    /// <inheritdoc cref="EncounterStatic"/>
    public class EncounterStatic4 : EncounterStatic
    {
        public sealed override int Generation => 4;

        protected sealed override bool IsMatchEggLocation(PKM pkm)
        {
            if (pkm.Egg_Location == EggLocation)
            {
                if (EggLocation == 0)
                    return true;

                // Check the inverse scenario for 4->5 eggs
                if (!Locations.IsPtHGSSLocationEgg(EggLocation))
                    return true;
                return pkm.Format == 4;
            }

            if (pkm.IsEgg) // unhatched
            {
                if (EggLocation != pkm.Met_Location)
                    return false;
                return pkm.Egg_Location == 0;
            }

            // Only way to mismatch is to be a Link Traded egg, or traded to Pt/HG/SS and hatched there.
            if (pkm.Egg_Location == Locations.LinkTrade4)
                return true;

            // check Pt/HGSS data
            if (pkm.Format == 4)
                return false;

            if (!Locations.IsPtHGSSLocationEgg(EggLocation)) // non-Pt/HG/SS egg gift
                return false;

            // transferring 4->5 clears Pt/HG/SS location value and keeps Faraway Place
            return pkm.Egg_Location == Locations.Faraway4;
        }

        protected override void ApplyDetails(ITrainerInfo sav, EncounterCriteria criteria, PKM pk)
        {
            base.ApplyDetails(sav, criteria, pk);
            SanityCheckVersion(pk);
        }

        private void SanityCheckVersion(PKM pk)
        {
            // Unavailable encounters in DP, morph them to Pt so they're legal.
            switch (Species)
            {
                case (int)Core.Species.Darkrai when Location == 079: // DP Darkrai
                case (int)Core.Species.Shaymin when Location == 063: // DP Shaymin
                    pk.Version = (int)GameVersion.Pt;
                    return;
            }
        }

        protected sealed override bool IsMatchLevel(PKM pkm, DexLevel evo)
        {
            if (pkm.Format != 4) // Met Level lost on PK3=>PK4
                return Level <= evo.Level;

            return pkm.Met_Level == (EggEncounter ? 0 : Level);
        }

        protected override bool IsMatchLocation(PKM pkm)
        {
            if (EggEncounter)
                return true;
            if (pkm.Format == 4)
                return Location == pkm.Met_Location;
            return true; // transfer location verified later
        }
    }
}