[Move] Implement Power Shift (#4083)

* fully implement power shift

* cleanup

src/data/move.ts

@@ -5987,9 +5987,8 @@ export class SwapStatAttr extends MoveEffectAttr {
   }
 
   /**
-   * Takes the average of the user's and target's corresponding current
-   * {@linkcode stat} values and sets that stat to the average for both
-   * temporarily.
+   * Swaps the user's and target's corresponding current
+   * {@linkcode EffectiveStat | stat} values
    * @param user the {@linkcode Pokemon} that used the move
    * @param target the {@linkcode Pokemon} that the move was used on
    * @param move N/A
@@ -6013,6 +6012,62 @@ export class SwapStatAttr extends MoveEffectAttr {
   }
 }
 
+/**
+ * Attribute used to switch the user's own stats.
+ * Used by Power Shift.
+ * @extends MoveEffectAttr
+ */
+export class ShiftStatAttr extends MoveEffectAttr {
+  private statToSwitch: EffectiveStat;
+  private statToSwitchWith: EffectiveStat;
+
+  constructor(statToSwitch: EffectiveStat, statToSwitchWith: EffectiveStat) {
+    super();
+
+    this.statToSwitch = statToSwitch;
+    this.statToSwitchWith = statToSwitchWith;
+  }
+
+  /**
+   * Switches the user's stats based on the {@linkcode statToSwitch} and {@linkcode statToSwitchWith} attributes.
+   * @param {Pokemon} user the {@linkcode Pokemon} that used the move
+   * @param target n/a
+   * @param move n/a
+   * @param args n/a
+   * @returns whether the effect was applied
+   */
+  override apply(user: Pokemon, target: Pokemon, move: Move, args: any[]): boolean {
+    if (!super.apply(user, target, move, args)) {
+      return false;
+    }
+
+    const firstStat = user.getStat(this.statToSwitch, false);
+    const secondStat = user.getStat(this.statToSwitchWith, false);
+
+    user.setStat(this.statToSwitch, secondStat, false);
+    user.setStat(this.statToSwitchWith, firstStat, false);
+
+    user.scene.queueMessage(i18next.t("moveTriggers:shiftedStats", {
+      pokemonName: getPokemonNameWithAffix(user),
+      statToSwitch: i18next.t(getStatKey(this.statToSwitch)),
+      statToSwitchWith: i18next.t(getStatKey(this.statToSwitchWith))
+    }));
+
+    return true;
+  }
+
+  /**
+   * Encourages the user to use the move if the stat to switch with is greater than the stat to switch.
+   * @param {Pokemon} user the {@linkcode Pokemon} that used the move
+   * @param target n/a
+   * @param move n/a
+   * @returns number of points to add to the user's benefit score
+   */
+  override getUserBenefitScore(user: Pokemon, target: Pokemon, move: Move): integer {
+    return user.getStat(this.statToSwitchWith, false) > user.getStat(this.statToSwitch, false) ? 10 : 0;
+  }
+}
+
 /**
  * Attribute used for status moves, namely Power Split and Guard Split,
  * that take the average of a user's and target's corresponding
@@ -8894,7 +8949,8 @@ export function initMoves() {
     new AttackMove(Moves.PSYSHIELD_BASH, Type.PSYCHIC, MoveCategory.PHYSICAL, 70, 90, 10, 100, 0, 8)
       .attr(StatStageChangeAttr, [ Stat.DEF ], 1, true),
     new SelfStatusMove(Moves.POWER_SHIFT, Type.NORMAL, -1, 10, -1, 0, 8)
-      .unimplemented(),
+      .target(MoveTarget.USER)
+      .attr(ShiftStatAttr, Stat.ATK, Stat.DEF),
     new AttackMove(Moves.STONE_AXE, Type.ROCK, MoveCategory.PHYSICAL, 65, 90, 15, 100, 0, 8)
       .attr(AddArenaTrapTagHitAttr, ArenaTagType.STEALTH_ROCK)
       .slicingMove(),

src/locales/en/move-trigger.json

@@ -7,6 +7,7 @@
   "switchedStat": "{{pokemonName}} switched {{stat}} with its target!",
   "sharedGuard": "{{pokemonName}} shared its guard with the target!",
   "sharedPower": "{{pokemonName}} shared its power with the target!",
+  "shiftedStats": "{{pokemonName}} switched its {{statToSwitch}} and {{statToSwitchWith}}!",
   "goingAllOutForAttack": "{{pokemonName}} is going all out for this attack!",
   "regainedHealth": "{{pokemonName}} regained\nhealth!",
   "keptGoingAndCrashed": "{{pokemonName}} kept going\nand crashed!",

src/test/moves/power_shift.test.ts

@@ -0,0 +1,64 @@
+import { Moves } from "#app/enums/moves";
+import { Species } from "#app/enums/species";
+import { Stat } from "#app/enums/stat";
+import { Abilities } from "#enums/abilities";
+import GameManager from "#test/utils/gameManager";
+import { SPLASH_ONLY } from "#test/utils/testUtils";
+import Phaser from "phaser";
+import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+
+describe("Moves - Power Shift", () => {
+  let phaserGame: Phaser.Game;
+  let game: GameManager;
+  const TIMEOUT = 20 * 1000;
+
+  beforeAll(() => {
+    phaserGame = new Phaser.Game({
+      type: Phaser.HEADLESS,
+    });
+  });
+
+  afterEach(() => {
+    game.phaseInterceptor.restoreOg();
+  });
+
+  beforeEach(() => {
+    game = new GameManager(phaserGame);
+    game.override
+      .moveset([Moves.POWER_SHIFT, Moves.BULK_UP])
+      .battleType("single")
+      .ability(Abilities.BALL_FETCH)
+      .enemyAbility(Abilities.BALL_FETCH)
+      .enemyMoveset(SPLASH_ONLY);
+  });
+
+  it("switches the user's raw Attack stat with its raw Defense stat", async () => {
+    await game.classicMode.startBattle([Species.MAGIKARP]);
+
+    const playerPokemon = game.scene.getPlayerPokemon()!;
+
+    playerPokemon.setStat(Stat.ATK, 10, false);
+    playerPokemon.setStat(Stat.DEF, 20, false);
+
+    game.move.select(Moves.BULK_UP);
+
+    await game.phaseInterceptor.to("TurnEndPhase");
+
+    // Stat stages are increased by 1
+    expect(playerPokemon.getStatStageMultiplier(Stat.ATK)).toBe(1.5);
+    expect(playerPokemon.getStatStageMultiplier(Stat.DEF)).toBe(1.5);
+
+    await game.toNextTurn();
+
+    game.move.select(Moves.POWER_SHIFT);
+
+    await game.phaseInterceptor.to("TurnEndPhase");
+
+    // Effective stats are calculated correctly
+    expect(playerPokemon.getEffectiveStat(Stat.ATK)).toBe(30);
+    expect(playerPokemon.getEffectiveStat(Stat.DEF)).toBe(15);
+    // Raw stats are swapped
+    expect(playerPokemon.getStat(Stat.ATK, false)).toBe(20);
+    expect(playerPokemon.getStat(Stat.DEF, false)).toBe(10);
+  }, TIMEOUT);
+});