basic mimicry implementation

src/data/ability.ts

@@ -4679,6 +4679,47 @@ export class PreventBypassSpeedChanceAbAttr extends AbAttr {
   }
 }
 
+export class TerrainEventTypeChangeAbAttr extends PostSummonAbAttr {
+  constructor() {
+    super(true);
+  }
+
+  /**
+   * This applies a terrain-based type change to the Pokemon.
+   */
+  apply(pokemon: Pokemon, passive: boolean, simulated: boolean, cancelled: Utils.BooleanHolder, args: any[]): boolean {
+    if (pokemon.isTerastallized()) {
+      return false;
+    }
+    const currentTerrain = pokemon.scene.arena.getTerrainType();
+    const typeChange: Type[] = [];
+    if (currentTerrain !== TerrainType.NONE) {
+      switch (currentTerrain) {
+      case TerrainType.ELECTRIC:
+        typeChange.push(Type.ELECTRIC);
+        break;
+      case TerrainType.MISTY:
+        typeChange.push(Type.FAIRY);
+        break;
+      case TerrainType.GRASSY:
+        typeChange.push(Type.GRASS);
+        break;
+      case TerrainType.PSYCHIC:
+        typeChange.push(Type.PSYCHIC);
+        break;
+      default:
+        pokemon.getTypes(false, false, true).forEach(t => {
+          typeChange.push(t);
+        });
+        break;
+      }
+    }
+    pokemon.summonData.types = typeChange;
+    pokemon.updateInfo();
+    return true;
+  }
+}
+
 async function applyAbAttrsInternal<TAttr extends AbAttr>(
   attrType: Constructor<TAttr>,
   pokemon: Pokemon | null,
@@ -5743,6 +5784,7 @@ export function initAbilities() {
     new Ability(Abilities.POWER_SPOT, 8)
       .attr(AllyMoveCategoryPowerBoostAbAttr, [ MoveCategory.SPECIAL, MoveCategory.PHYSICAL ], 1.3),
     new Ability(Abilities.MIMICRY, 8)
+      .attr(TerrainEventTypeChangeAbAttr)
       .unimplemented(),
     new Ability(Abilities.SCREEN_CLEANER, 8)
       .attr(PostSummonRemoveArenaTagAbAttr, [ ArenaTagType.AURORA_VEIL, ArenaTagType.LIGHT_SCREEN, ArenaTagType.REFLECT ]),

src/field/arena.ts

@@ -10,7 +10,7 @@ import Move from "#app/data/move";
 import { ArenaTag, ArenaTagSide, ArenaTrapTag, getArenaTag } from "#app/data/arena-tag";
 import { BattlerIndex } from "#app/battle";
 import { Terrain, TerrainType } from "#app/data/terrain";
-import { applyPostTerrainChangeAbAttrs, applyPostWeatherChangeAbAttrs, PostTerrainChangeAbAttr, PostWeatherChangeAbAttr } from "#app/data/ability";
+import { applyAbAttrs, applyPostTerrainChangeAbAttrs, applyPostWeatherChangeAbAttrs, PostTerrainChangeAbAttr, PostWeatherChangeAbAttr, TerrainEventTypeChangeAbAttr } from "#app/data/ability";
 import Pokemon from "#app/field/pokemon";
 import Overrides from "#app/overrides";
 import { TagAddedEvent, TagRemovedEvent, TerrainChangedEvent, WeatherChangedEvent } from "#app/events/arena";
@@ -387,6 +387,7 @@ export class Arena {
     this.scene.getField(true).filter(p => p.isOnField()).map(pokemon => {
       pokemon.findAndRemoveTags(t => "terrainTypes" in t && !(t.terrainTypes as TerrainType[]).find(t => t === terrain));
       applyPostTerrainChangeAbAttrs(PostTerrainChangeAbAttr, pokemon, terrain);
+      applyAbAttrs(TerrainEventTypeChangeAbAttr, pokemon, null, false);
     });
 
     return true;