[Ability] Implementing Friend Guard (#4718)

* implementing friend guard ability

* Update src/data/ability.ts

Co-authored-by: NightKev <34855794+DayKev@users.noreply.github.com>

* Update src/data/ability.ts

Co-authored-by: NightKev <34855794+DayKev@users.noreply.github.com>

* Update src/data/ability.ts

Co-authored-by: NightKev <34855794+DayKev@users.noreply.github.com>

* Update src/test/abilities/friend_guard.test.ts

Co-authored-by: NightKev <34855794+DayKev@users.noreply.github.com>

* Update src/field/pokemon.ts

Co-authored-by: innerthunder <168692175+innerthunder@users.noreply.github.com>

* more tests and fixing other issues

* more tests and fixing other issues

* Update Friend Guard test with damage mocks

---------

Co-authored-by: NightKev <34855794+DayKev@users.noreply.github.com>
Co-authored-by: innerthunder <168692175+innerthunder@users.noreply.github.com>
Co-authored-by: innerthunder <brandonerickson98@gmail.com>

src/data/ability.ts

@@ -330,6 +330,30 @@ export class ReceivedMoveDamageMultiplierAbAttr extends PreDefendAbAttr {
   }
 }
 
+/**
+ * Reduces the damage dealt to an allied Pokemon. Used by Friend Guard.
+ * @see {@linkcode applyPreDefend}
+ */
+export class AlliedFieldDamageReductionAbAttr extends PreDefendAbAttr {
+  private damageMultiplier: number;
+
+  constructor(damageMultiplier: number) {
+    super();
+    this.damageMultiplier = damageMultiplier;
+  }
+
+  /**
+   * Handles the damage reduction
+   * @param args
+   * - `[0]` {@linkcode Utils.NumberHolder} - The damage being dealt
+   */
+  override applyPreDefend(_pokemon: Pokemon, _passive: boolean, _simulated: boolean, _attacker: Pokemon, _move: Move, _cancelled: Utils.BooleanHolder, args: any[]): boolean {
+    const damage = args[0] as Utils.NumberHolder;
+    damage.value = Utils.toDmgValue(damage.value * this.damageMultiplier);
+    return true;
+  }
+}
+
 export class ReceivedTypeDamageMultiplierAbAttr extends ReceivedMoveDamageMultiplierAbAttr {
   constructor(moveType: Type, damageMultiplier: number) {
     super((target, user, move) => user.getMoveType(move) === moveType, damageMultiplier);
@@ -5310,8 +5334,8 @@ export function initAbilities() {
     new Ability(Abilities.HEALER, 5)
       .conditionalAttr(pokemon => pokemon.getAlly() && Utils.randSeedInt(10) < 3, PostTurnResetStatusAbAttr, true),
     new Ability(Abilities.FRIEND_GUARD, 5)
-      .ignorable()
+      .attr(AlliedFieldDamageReductionAbAttr, 0.75)
-      .unimplemented(),
+      .ignorable(),
     new Ability(Abilities.WEAK_ARMOR, 5)
       .attr(PostDefendStatStageChangeAbAttr, (target, user, move) => move.category === MoveCategory.PHYSICAL, Stat.DEF, -1)
       .attr(PostDefendStatStageChangeAbAttr, (target, user, move) => move.category === MoveCategory.PHYSICAL, Stat.SPD, 2),

src/field/pokemon.ts

@@ -22,7 +22,7 @@ import { reverseCompatibleTms, tmSpecies, tmPoolTiers } from "#app/data/balance/
 import { BattlerTag, BattlerTagLapseType, EncoreTag, GroundedTag, HighestStatBoostTag, SubstituteTag, TypeImmuneTag, getBattlerTag, SemiInvulnerableTag, TypeBoostTag, MoveRestrictionBattlerTag, ExposedTag, DragonCheerTag, CritBoostTag, TrappedTag, TarShotTag, AutotomizedTag, PowerTrickTag } from "../data/battler-tags";
 import { WeatherType } from "#app/data/weather";
 import { ArenaTagSide, NoCritTag, WeakenMoveScreenTag } from "#app/data/arena-tag";
-import { Ability, AbAttr, StatMultiplierAbAttr, BlockCritAbAttr, BonusCritAbAttr, BypassBurnDamageReductionAbAttr, FieldPriorityMoveImmunityAbAttr, IgnoreOpponentStatStagesAbAttr, MoveImmunityAbAttr, PreDefendFullHpEndureAbAttr, ReceivedMoveDamageMultiplierAbAttr, StabBoostAbAttr, StatusEffectImmunityAbAttr, TypeImmunityAbAttr, WeightMultiplierAbAttr, allAbilities, applyAbAttrs, applyStatMultiplierAbAttrs, applyPreApplyBattlerTagAbAttrs, applyPreAttackAbAttrs, applyPreDefendAbAttrs, applyPreSetStatusAbAttrs, UnsuppressableAbilityAbAttr, SuppressFieldAbilitiesAbAttr, NoFusionAbilityAbAttr, MultCritAbAttr, IgnoreTypeImmunityAbAttr, DamageBoostAbAttr, IgnoreTypeStatusEffectImmunityAbAttr, ConditionalCritAbAttr, applyFieldStatMultiplierAbAttrs, FieldMultiplyStatAbAttr, AddSecondStrikeAbAttr, UserFieldStatusEffectImmunityAbAttr, UserFieldBattlerTagImmunityAbAttr, BattlerTagImmunityAbAttr, MoveTypeChangeAbAttr, FullHpResistTypeAbAttr, applyCheckTrappedAbAttrs, CheckTrappedAbAttr, PostSetStatusAbAttr, applyPostSetStatusAbAttrs, InfiltratorAbAttr } from "#app/data/ability";
+import { Ability, AbAttr, StatMultiplierAbAttr, BlockCritAbAttr, BonusCritAbAttr, BypassBurnDamageReductionAbAttr, FieldPriorityMoveImmunityAbAttr, IgnoreOpponentStatStagesAbAttr, MoveImmunityAbAttr, PreDefendFullHpEndureAbAttr, ReceivedMoveDamageMultiplierAbAttr, StabBoostAbAttr, StatusEffectImmunityAbAttr, TypeImmunityAbAttr, WeightMultiplierAbAttr, allAbilities, applyAbAttrs, applyStatMultiplierAbAttrs, applyPreApplyBattlerTagAbAttrs, applyPreAttackAbAttrs, applyPreDefendAbAttrs, applyPreSetStatusAbAttrs, UnsuppressableAbilityAbAttr, SuppressFieldAbilitiesAbAttr, NoFusionAbilityAbAttr, MultCritAbAttr, IgnoreTypeImmunityAbAttr, DamageBoostAbAttr, IgnoreTypeStatusEffectImmunityAbAttr, ConditionalCritAbAttr, applyFieldStatMultiplierAbAttrs, FieldMultiplyStatAbAttr, AddSecondStrikeAbAttr, UserFieldStatusEffectImmunityAbAttr, UserFieldBattlerTagImmunityAbAttr, BattlerTagImmunityAbAttr, MoveTypeChangeAbAttr, FullHpResistTypeAbAttr, applyCheckTrappedAbAttrs, CheckTrappedAbAttr, PostSetStatusAbAttr, applyPostSetStatusAbAttrs, InfiltratorAbAttr, AlliedFieldDamageReductionAbAttr } from "#app/data/ability";
 import PokemonData from "#app/system/pokemon-data";
 import { BattlerIndex } from "#app/battle";
 import { Mode } from "#app/ui/ui";
@@ -2667,9 +2667,15 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
       this.scene.applyModifiers(EnemyDamageReducerModifier, false, damage);
     }
 
+
     /** Apply this Pokemon's post-calc defensive modifiers (e.g. Fur Coat) */
     if (!ignoreAbility) {
       applyPreDefendAbAttrs(ReceivedMoveDamageMultiplierAbAttr, this, source, move, cancelled, simulated, damage);
+
+      /** Additionally apply friend guard damage reduction if ally has it. */
+      if (this.scene.currentBattle.double && this.getAlly()?.isActive(true)) {
+        applyPreDefendAbAttrs(AlliedFieldDamageReductionAbAttr, this.getAlly(), source, move, cancelled, simulated, damage);
+      }
     }
 
     // This attribute may modify damage arbitrarily, so be careful about changing its order of application.

src/test/abilities/friend_guard.test.ts

@@ -0,0 +1,120 @@
+import { Moves } from "#enums/moves";
+import { Species } from "#enums/species";
+import { Abilities } from "#enums/abilities";
+import GameManager from "#test/utils/gameManager";
+import Phaser from "phaser";
+import { afterEach, beforeAll, beforeEach, describe, expect, it, vi } from "vitest";
+import { BattlerIndex } from "#app/battle";
+import { allAbilities } from "#app/data/ability";
+import { allMoves, MoveCategory } from "#app/data/move";
+
+describe("Moves - Friend Guard", () => {
+  let phaserGame: Phaser.Game;
+  let game: GameManager;
+
+  beforeAll(() => {
+    phaserGame = new Phaser.Game({
+      type: Phaser.HEADLESS,
+    });
+  });
+
+  afterEach(() => {
+    game.phaseInterceptor.restoreOg();
+  });
+
+  beforeEach(() => {
+    game = new GameManager(phaserGame);
+    game.override
+      .battleType("double")
+      .enemyAbility(Abilities.BALL_FETCH)
+      .enemyMoveset([ Moves.TACKLE, Moves.SPLASH, Moves.DRAGON_RAGE ])
+      .enemySpecies(Species.SHUCKLE)
+      .moveset([ Moves.SPLASH ])
+      .startingLevel(100);
+  });
+
+  it("should reduce damage that other allied Pokémon receive from attacks (from any Pokémon) by 25%", async () => {
+    await game.classicMode.startBattle([ Species.BULBASAUR, Species.CHARMANDER ]);
+    const [ player1, player2 ] = game.scene.getPlayerField();
+    const spy = vi.spyOn(player1, "getAttackDamage");
+
+    const enemy1 = game.scene.getEnemyField()[0];
+
+    game.move.select(Moves.SPLASH);
+    game.move.select(Moves.SPLASH, 1);
+    await game.forceEnemyMove(Moves.TACKLE, BattlerIndex.PLAYER);
+    await game.forceEnemyMove(Moves.SPLASH);
+    await game.toNextTurn();
+
+    // Get the last return value from `getAttackDamage`
+    const turn1Damage = spy.mock.results[spy.mock.results.length - 1].value.damage;
+    // Making sure the test is controlled; turn 1 damage is equal to base damage (after rounding)
+    expect(turn1Damage).toBe(Math.floor(player1.getBaseDamage(enemy1, allMoves[Moves.TACKLE], MoveCategory.PHYSICAL)));
+
+    vi.spyOn(player2, "getAbility").mockReturnValue(allAbilities[Abilities.FRIEND_GUARD]);
+
+    game.move.select(Moves.SPLASH);
+    game.move.select(Moves.SPLASH, 1);
+    await game.forceEnemyMove(Moves.TACKLE, BattlerIndex.PLAYER);
+    await game.forceEnemyMove(Moves.SPLASH);
+    await game.toNextTurn();
+
+    // Get the last return value from `getAttackDamage`
+    const turn2Damage = spy.mock.results[spy.mock.results.length - 1].value.damage;
+    // With the ally's Friend Guard, damage should have been reduced from base damage by 25%
+    expect(turn2Damage).toBe(Math.floor(player1.getBaseDamage(enemy1, allMoves[Moves.TACKLE], MoveCategory.PHYSICAL) * 0.75));
+  });
+
+  it("should NOT reduce damage to pokemon with friend guard", async () => {
+    await game.classicMode.startBattle([ Species.BULBASAUR, Species.CHARMANDER ]);
+
+    const player2  = game.scene.getPlayerField()[1];
+    const spy = vi.spyOn(player2, "getAttackDamage");
+
+    game.move.select(Moves.SPLASH);
+    game.move.select(Moves.SPLASH, 1);
+    await game.forceEnemyMove(Moves.TACKLE, BattlerIndex.PLAYER_2);
+    await game.forceEnemyMove(Moves.SPLASH);
+    await game.toNextTurn();
+
+    const turn1Damage = spy.mock.results[spy.mock.results.length - 1].value.damage;
+
+    vi.spyOn(player2, "getAbility").mockReturnValue(allAbilities[Abilities.FRIEND_GUARD]);
+
+    game.move.select(Moves.SPLASH);
+    game.move.select(Moves.SPLASH, 1);
+    await game.forceEnemyMove(Moves.TACKLE, BattlerIndex.PLAYER_2);
+    await game.forceEnemyMove(Moves.SPLASH);
+    await game.toNextTurn();
+
+    const turn2Damage = spy.mock.results[spy.mock.results.length - 1].value.damage;
+    expect(turn2Damage).toBe(turn1Damage);
+  });
+
+  it("should NOT reduce damage from fixed damage attacks", async () => {
+    await game.classicMode.startBattle([ Species.BULBASAUR, Species.CHARMANDER ]);
+
+    const [ player1, player2 ] = game.scene.getPlayerField();
+    const spy = vi.spyOn(player1, "getAttackDamage");
+
+    game.move.select(Moves.SPLASH);
+    game.move.select(Moves.SPLASH, 1);
+    await game.forceEnemyMove(Moves.DRAGON_RAGE, BattlerIndex.PLAYER);
+    await game.forceEnemyMove(Moves.SPLASH);
+    await game.toNextTurn();
+
+    const turn1Damage = spy.mock.results[spy.mock.results.length - 1].value.damage;
+    expect(turn1Damage).toBe(40);
+
+    vi.spyOn(player2, "getAbility").mockReturnValue(allAbilities[Abilities.FRIEND_GUARD]);
+
+    game.move.select(Moves.SPLASH);
+    game.move.select(Moves.SPLASH, 1);
+    await game.forceEnemyMove(Moves.DRAGON_RAGE, BattlerIndex.PLAYER);
+    await game.forceEnemyMove(Moves.SPLASH);
+    await game.toNextTurn();
+
+    const turn2Damage = spy.mock.results[spy.mock.results.length - 1].value.damage;
+    expect(turn2Damage).toBe(40);
+  });
+});