using System;
namespace PKHeX.Core;
///
/// Contains logic for the Generation 8b (BD/SP) wild and stationary spawns.
///
public static class Wild8bRNG
{
private const int UNSET = -1;
public static void ApplyDetails(PKM pk, EncounterCriteria criteria,
Shiny shiny = Shiny.FixedValue,
int flawless = -1,
AbilityPermission ability = AbilityPermission.Any12)
{
if (shiny == Shiny.FixedValue)
shiny = criteria.Shiny is Shiny.Random or Shiny.Never ? Shiny.Never : Shiny.Always;
if (flawless == -1)
flawless = 0;
int ctr = 0;
const int maxAttempts = 50_000;
var rnd = Util.Rand;
do
{
ulong s0 = rnd.Rand64();
ulong s1 = rnd.Rand64();
var xors = new XorShift128(s0, s1);
if (TryApplyFromSeed(pk, criteria, shiny, flawless, xors, ability))
return;
} while (++ctr != maxAttempts);
{
ulong s0 = rnd.Rand64();
ulong s1 = rnd.Rand64();
var xors = new XorShift128(s0, s1);
TryApplyFromSeed(pk, EncounterCriteria.Unrestricted, shiny, flawless, xors, ability);
}
}
public static bool TryApplyFromSeed(PKM pk, EncounterCriteria criteria, Shiny shiny, int flawless, XorShift128 xors, AbilityPermission ability)
{
// Encryption Constant
pk.EncryptionConstant = xors.NextUInt();
// PID
var fakeTID = xors.NextUInt(); // fakeTID
var pid = xors.NextUInt();
pid = GetRevisedPID(fakeTID, pid, pk);
if (shiny == Shiny.Never)
{
if (GetIsShiny(pk.TID, pk.SID, pid))
return false;
}
else if (shiny != Shiny.Random)
{
if (!GetIsShiny(pk.TID, pk.SID, pid))
return false;
if (shiny == Shiny.AlwaysSquare && pk.ShinyXor != 0)
return false;
if (shiny == Shiny.AlwaysStar && pk.ShinyXor == 0)
return false;
}
pk.PID = pid;
// Check IVs: Create flawless IVs at random indexes, then the random IVs for not flawless.
Span ivs = stackalloc[] { UNSET, UNSET, UNSET, UNSET, UNSET, UNSET };
const int MAX = 31;
var determined = 0;
while (determined < flawless)
{
var idx = (int)xors.NextUInt(6);
if (ivs[idx] != UNSET)
continue;
ivs[idx] = 31;
determined++;
}
for (var i = 0; i < ivs.Length; i++)
{
if (ivs[i] == UNSET)
ivs[i] = xors.NextInt(0, MAX + 1);
}
if (!criteria.IsIVsCompatible(ivs, 8))
return false;
pk.IV_HP = ivs[0];
pk.IV_ATK = ivs[1];
pk.IV_DEF = ivs[2];
pk.IV_SPA = ivs[3];
pk.IV_SPD = ivs[4];
pk.IV_SPE = ivs[5];
// Ability
var n = ability switch
{
AbilityPermission.Any12 => (int)xors.NextUInt(2),
AbilityPermission.Any12H => (int)xors.NextUInt(3),
_ => (int)ability >> 1,
};
pk.SetAbilityIndex(n);
// Gender (skip this if gender is fixed)
var genderRatio = PersonalTable.BDSP.GetFormEntry(pk.Species, pk.Form).Gender;
if (genderRatio == PersonalInfo.RatioMagicGenderless)
{
pk.Gender = 2;
}
else if (genderRatio == PersonalInfo.RatioMagicMale)
{
pk.Gender = 0;
}
else if (genderRatio == PersonalInfo.RatioMagicFemale)
{
pk.Gender = 1;
}
else
{
var next = (((int)xors.NextUInt(253) + 1 < genderRatio) ? 1 : 0);
if (criteria.Gender is 0 or 1 && next != criteria.Gender)
return false;
pk.Gender = next;
}
if (criteria.Nature is Nature.Random)
pk.Nature = (int)xors.NextUInt(25);
else // Skip nature, assuming Synchronize
pk.Nature = (int)criteria.Nature;
pk.StatNature = pk.Nature;
// Remainder
var scale = (IScaledSize)pk;
scale.HeightScalar = (byte)((int)xors.NextUInt(0x81) + (int)xors.NextUInt(0x80));
scale.WeightScalar = (byte)((int)xors.NextUInt(0x81) + (int)xors.NextUInt(0x80));
// Item, don't care
return true;
}
private static uint GetRevisedPID(uint fakeTID, uint pid, ITrainerID tr)
{
var xor = GetShinyXor(pid, fakeTID);
var newXor = GetShinyXor(pid, (uint)(tr.TID | (tr.SID << 16)));
var fakeRare = GetRareType(xor);
var newRare = GetRareType(newXor);
if (fakeRare == newRare)
return pid;
var isShiny = xor < 16;
if (isShiny)
return (((uint)(tr.TID ^ tr.SID) ^ (pid & 0xFFFF) ^ (xor == 0 ? 0u : 1u)) << 16) | (pid & 0xFFFF); // force same shiny star type
return pid ^ 0x1000_0000;
}
private static Shiny GetRareType(uint xor) => xor switch
{
0 => Shiny.AlwaysSquare,
< 16 => Shiny.AlwaysStar,
_ => Shiny.Never,
};
private static bool GetIsShiny(int tid, int sid, uint pid)
{
return GetIsShiny(pid, (uint)((sid << 16) | tid));
}
private static bool GetIsShiny(uint pid, uint oid) => GetShinyXor(pid, oid) < 16;
private static uint GetShinyXor(uint pid, uint oid)
{
var xor = pid ^ oid;
return (xor ^ (xor >> 16)) & 0xFFFF;
}
}