PKHeX/PKHeX.Core/Legality/Evolutions/EvolutionChain.cs

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using System;
using System.Collections.Generic;
using System.Linq;
using static PKHeX.Core.Legal;
namespace PKHeX.Core
{
public static class EvolutionChain
{
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private static readonly List<EvoCriteria> NONE = new(0);
internal static IReadOnlyList<EvoCriteria>[] GetEvolutionChainsAllGens(PKM pkm, IEncounterTemplate enc)
{
var chain = GetEvolutionChain(pkm, enc, pkm.Species, pkm.CurrentLevel);
if (enc is EncounterInvalid || pkm.IsEgg || chain.Count == 0)
return GetChainSingle(pkm, chain);
return GetChainAll(pkm, enc, chain);
}
private static List<EvoCriteria>[] GetChainBase(int maxgen)
{
var GensEvoChains = new List<EvoCriteria>[maxgen + 1];
for (int i = 0; i <= maxgen; i++)
GensEvoChains[i] = NONE; // default no-evolutions
return GensEvoChains;
}
private static List<EvoCriteria>[] GetChainSingle(PKM pkm, List<EvoCriteria> fullChain)
{
var chain = GetChainBase(Math.Max(2, pkm.Format));
chain[pkm.Format] = fullChain;
return chain;
}
private static List<EvoCriteria>[] GetChainAll(PKM pkm, IEncounterTemplate enc, IReadOnlyList<EvoCriteria> fullChain)
{
int maxgen = ParseSettings.AllowGen1Tradeback && pkm is PK1 ? 2 : pkm.Format;
var GensEvoChains = GetChainBase(maxgen);
var queue = new Queue<EvoCriteria>(fullChain);
var mostEvolved = queue.Dequeue();
int lvl = pkm.CurrentLevel;
int maxLevel = lvl;
int pkGen = enc.Generation;
// Iterate generations backwards
// Maximum level of an earlier generation (GenX) will never be greater than a later generation (GenX+Y).
int mingen = pkGen >= 3 ? pkGen : GBRestrictions.GetTradebackStatusInitial(pkm) == PotentialGBOrigin.Gen2Only ? 2 : 1;
bool noxfrDecremented = true;
for (int g = GensEvoChains.Length - 1; g >= mingen; g--)
{
if (pkGen <= 2 && g == 6)
g = 2;
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if (g <= 4 && pkm.Format > 2 && pkm.Format > g && !pkm.HasOriginalMetLocation && lvl > pkm.Met_Level)
{
// Met location was lost at this point but it also means the pokemon existed in generations 1 to 4 with maximum level equals to met level
lvl = pkm.Met_Level;
}
int maxspeciesgen = g == 2 && pkm.VC1 ? MaxSpeciesID_1 : GetMaxSpeciesOrigin(g);
// Remove future gen evolutions after a few special considerations:
// If the pokemon origin is illegal (e.g. Gen3 Infernape) the list will be emptied -- species lineage did not exist at any evolution stage.
while (mostEvolved.Species > maxspeciesgen)
{
if (queue.Count == 0)
{
if (g <= 2 && pkm.VC1)
GensEvoChains[pkm.Format] = NONE; // invalidate here since we haven't reached the regular invalidation
return GensEvoChains;
}
if (mostEvolved.RequiresLvlUp)
{
// This is a Gen3 pokemon in a Gen4 phase evolution that requires level up and then transferred to Gen5+
// We can deduce that it existed in Gen4 until met level,
// but if current level is met level we can also deduce it existed in Gen3 until maximum met level -1
if (g == 3 && pkm.Format > 4 && lvl == maxLevel)
lvl--;
// The same condition for Gen2 evolution of Gen1 pokemon, level of the pokemon in Gen1 games would be CurrentLevel -1 one level below Gen2 level
else if (g == 1 && pkm.Format == 2 && lvl == maxLevel)
lvl--;
}
mostEvolved = queue.Dequeue();
}
// Alolan form evolutions, remove from gens 1-6 chains
if (HasAlolanForm(mostEvolved.Species))
{
if (g < 7 && pkm.Format >= 7 && mostEvolved.Form > 0)
{
if (queue.Count == 0)
break;
mostEvolved = queue.Dequeue();
}
}
var genChain = GensEvoChains[g] = GetEvolutionChain(pkm, enc, mostEvolved.Species, lvl);
if (genChain.Count == 0)
continue;
if (g > 2 && !pkm.HasOriginalMetLocation && g >= pkGen && noxfrDecremented)
{
bool isTransferred = HasMetLocationUpdatedTransfer(pkGen, g);
if (!isTransferred)
continue;
noxfrDecremented = g > (pkGen != 3 ? 4 : 5);
// Remove previous evolutions below transfer level
// For example a gen3 Charizard in format 7 with current level 36 and met level 36, thus could never be Charmander / Charmeleon in Gen5+.
// chain level for Charmander is 35, is below met level.
int minlvl = GetMinLevelGeneration(pkm, g);
genChain.RemoveAll(e => e.Level < minlvl);
}
else if (g == 1)
{
var g1 = GensEvoChains[1];
// Remove Gen2 post-evolutions (Scizor, Blissey...)
if (g1[0].Species > MaxSpeciesID_1)
g1.RemoveAt(0);
// Remove Gen2 pre-evolutions (Pichu, Cleffa...)
int lastIndex = g1.Count - 1;
if (lastIndex >= 0 && g1[lastIndex].Species > MaxSpeciesID_1)
g1.RemoveAt(lastIndex);
// Remove Gen7 pre-evolutions and chain break scenarios
if (pkm.VC1)
TrimVC1Transfer(pkm, GensEvoChains);
// Update min level for the encounter to prevent certain level up moves.
if (g1.Count != 0)
g1[^1].MinLevel = enc.LevelMin;
}
}
return GensEvoChains;
}
private static bool HasMetLocationUpdatedTransfer(int originalGeneration, int currentGeneration) => originalGeneration switch
{
< 3 => currentGeneration >= 3,
<= 4 => currentGeneration != originalGeneration,
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_ => false,
};
private static void TrimVC1Transfer(PKM pkm, IList<List<EvoCriteria>> allChains)
{
if (allChains[7].All(z => z.Species > MaxSpeciesID_1))
allChains[pkm.Format] = NONE; // needed a Gen1 species present; invalidate the chain.
}
internal static int GetEvoChainSpeciesIndex(IReadOnlyList<EvoCriteria> chain, int species)
{
for (int i = 0; i < chain.Count; i++)
{
if (chain[i].Species == species)
return i;
}
return -1;
}
private static List<EvoCriteria> GetEvolutionChain(PKM pkm, IEncounterTemplate enc, int mostEvolvedSpecies, int maxlevel)
{
var min = enc.LevelMin;
if (pkm.HasOriginalMetLocation && pkm.Met_Level != 0)
min = pkm.Met_Level;
var chain = GetValidPreEvolutions(pkm, minLevel: min);
if (enc.Species == mostEvolvedSpecies)
{
if (chain.Count != 1)
chain.RemoveAll(z => z.Species != enc.Species);
return chain;
}
// Evolution chain is in reverse order (devolution)
// Find the index of the minimum species to determine the end of the chain
int minIndex = GetEvoChainSpeciesIndex(chain, enc.Species);
bool last = minIndex < 0 || minIndex == chain.Count - 1;
// If we remove a pre-evolution, update the chain if appropriate.
if (!last)
{
// Remove chain species after the encounter
int count = chain.Count;
for (int i = minIndex + 1; i < count; i++)
chain.RemoveAt(i);
if (chain.Count == 0)
return chain; // no species left in chain
CheckLastEncounterRemoval(enc, chain);
}
// maxspec is used to remove future geneneration evolutions, to gather evolution chain of a pokemon in previous generations
int skip = Math.Max(0, GetEvoChainSpeciesIndex(chain, mostEvolvedSpecies));
for (int i = 0; i < skip; i++)
chain.RemoveAt(0);
// Gen3->4 and Gen4->5 transfer sets the Met Level property to the Pokémon's current level.
// Removes evolutions impossible before the transfer level.
// For example a FireRed Charizard with a current level (in XY) is 50 but Met Level is 20; it couldn't be a Charizard in Gen3 and Gen4 games
chain.RemoveAll(e => e.MinLevel > maxlevel);
// Reduce the evolution chain levels to max level to limit any later analysis/results.
foreach (var d in chain)
d.Level = Math.Min(d.Level, maxlevel);
return chain;
}
private static void CheckLastEncounterRemoval(IEncounterTemplate enc, IReadOnlyList<EvoCriteria> chain)
{
// Last entry from chain is removed, turn next entry into the encountered Pokémon
var last = chain[^1];
last.MinLevel = enc.LevelMin;
last.RequiresLvlUp = false;
var first = chain[0];
if (first.RequiresLvlUp)
return;
if (first.MinLevel == 2)
{
// Example: Raichu in Gen2 or later
// Because Pichu requires a level up, the minimum level of the resulting Raichu must be be >2
// But after removing Pichu (because the origin species is Pikachu), the Raichu minimum level should be 1.
first.MinLevel = 1;
first.RequiresLvlUp = false;
}
else // in-game trade or evolution stone can evolve immediately
{
first.MinLevel = last.MinLevel;
}
}
internal static List<EvoCriteria> GetValidPreEvolutions(PKM pkm, int maxspeciesorigin = -1, int maxLevel = -1, int minLevel = 1, bool skipChecks = false)
{
if (maxLevel < 0)
maxLevel = pkm.CurrentLevel;
if (maxspeciesorigin == -1 && pkm.InhabitedGeneration(2) && pkm.Format <= 2 && pkm.Generation == 1)
maxspeciesorigin = MaxSpeciesID_2;
int tree = Math.Max(2, pkm.Format);
var et = EvolutionTree.GetEvolutionTree(pkm, tree);
return et.GetValidPreEvolutions(pkm, maxLevel: maxLevel, maxSpeciesOrigin: maxspeciesorigin, skipChecks: skipChecks, minLevel: minLevel);
}
private static int GetMinLevelGeneration(PKM pkm, int generation)
{
if (!pkm.InhabitedGeneration(generation))
return 0;
if (pkm.Format <= 2)
return 2;
var origin = pkm.Generation;
if (!pkm.HasOriginalMetLocation && generation != origin)
return pkm.Met_Level;
// gen 3 and prior can't obtain anything at level 1
if (origin <= 3)
return 2;
return 1;
}
}
}