[Move] Improved damage forecasting for Shell Side Arm (#4310)

src/data/move.ts

@@ -3974,18 +3974,17 @@ export class StatusCategoryOnAllyAttr extends VariableMoveCategoryAttr {
 export class ShellSideArmCategoryAttr extends VariableMoveCategoryAttr {
   apply(user: Pokemon, target: Pokemon, move: Move, args: any[]): boolean {
     const category = (args[0] as Utils.NumberHolder);
-    const atkRatio = user.getEffectiveStat(Stat.ATK, target, move) / target.getEffectiveStat(Stat.DEF, user, move);
-    const specialRatio = user.getEffectiveStat(Stat.SPATK, target, move) / target.getEffectiveStat(Stat.SPDEF, user, move);
 
-    // Shell Side Arm is much more complicated than it looks, this is a partial implementation to try to achieve something similar to the games
-    if (atkRatio > specialRatio) {
+    const predictedPhysDmg = target.getBaseDamage(user, move, MoveCategory.PHYSICAL, true, true);
+    const predictedSpecDmg = target.getBaseDamage(user, move, MoveCategory.SPECIAL, true, true);
+
+    if (predictedPhysDmg > predictedSpecDmg) {
       category.value = MoveCategory.PHYSICAL;
       return true;
-    } else if (atkRatio === specialRatio && user.randSeedInt(2) === 0) {
+    } else if (predictedPhysDmg === predictedSpecDmg && user.randSeedInt(2) === 0) {
       category.value = MoveCategory.PHYSICAL;
       return true;
     }
-
     return false;
   }
 }
@@ -9106,7 +9105,7 @@ export function initMoves() {
     new AttackMove(Moves.SHELL_SIDE_ARM, Type.POISON, MoveCategory.SPECIAL, 90, 100, 10, 20, 0, 8)
       .attr(ShellSideArmCategoryAttr)
       .attr(StatusEffectAttr, StatusEffect.POISON)
-      .partial(),
+      .partial(), // Physical version of the move does not make contact
     new AttackMove(Moves.MISTY_EXPLOSION, Type.FAIRY, MoveCategory.SPECIAL, 100, 100, 5, -1, 0, 8)
       .attr(SacrificialAttr)
       .target(MoveTarget.ALL_NEAR_OTHERS)

src/field/pokemon.ts

@@ -2322,11 +2322,61 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
     return accuracyMultiplier.value / evasionMultiplier.value;
   }
 
+  /**
+   * Calculates the base damage of the given move against this Pokemon when attacked by the given source.
+   * Used during damage calculation and for Shell Side Arm's forecasting effect.
+   * @param source the attacking {@linkcode Pokemon}.
+   * @param move the {@linkcode Move} used in the attack.
+   * @param moveCategory the move's {@linkcode MoveCategory} after variable-category effects are applied.
+   * @param ignoreAbility if `true`, ignores this Pokemon's defensive ability effects (defaults to `false`).
+   * @param ignoreSourceAbility if `true`, ignore's the attacking Pokemon's ability effects (defaults to `false`).
+   * @param isCritical if `true`, calculates effective stats as if the hit were critical (defaults to `false`).
+   * @param simulated if `true`, suppresses changes to game state during calculation (defaults to `true`).
+   * @returns The move's base damage against this Pokemon when used by the source Pokemon.
+   */
+  getBaseDamage(source: Pokemon, move: Move, moveCategory: MoveCategory, ignoreAbility: boolean = false, ignoreSourceAbility: boolean = false, isCritical: boolean = false, simulated: boolean = true): number {
+    const isPhysical = moveCategory === MoveCategory.PHYSICAL;
+
+    /** A base damage multiplier based on the source's level */
+    const levelMultiplier = (2 * source.level / 5 + 2);
+
+    /** The power of the move after power boosts from abilities, etc. have applied */
+    const power = move.calculateBattlePower(source, this, simulated);
+
+    /**
+     * The attacker's offensive stat for the given move's category.
+     * Critical hits cause negative stat stages to be ignored.
+     */
+    const sourceAtk = new Utils.NumberHolder(source.getEffectiveStat(isPhysical ? Stat.ATK : Stat.SPATK, this, undefined, ignoreSourceAbility, ignoreAbility, isCritical, simulated));
+    applyMoveAttrs(VariableAtkAttr, source, this, move, sourceAtk);
+
+    /**
+     * This Pokemon's defensive stat for the given move's category.
+     * Critical hits cause positive stat stages to be ignored.
+     */
+    const targetDef = new Utils.NumberHolder(this.getEffectiveStat(isPhysical ? Stat.DEF : Stat.SPDEF, source, move, ignoreAbility, ignoreSourceAbility, isCritical, simulated));
+    applyMoveAttrs(VariableDefAttr, source, this, move, targetDef);
+
+    /**
+     * The attack's base damage, as determined by the source's level, move power
+     * and Attack stat as well as this Pokemon's Defense stat
+     */
+    const baseDamage = ((levelMultiplier * power * sourceAtk.value / targetDef.value) / 50) + 2;
+
+    /** Debug message for non-simulated calls (i.e. when damage is actually dealt) */
+    if (!simulated) {
+      console.log("base damage", baseDamage, move.name, power, sourceAtk.value, targetDef.value);
+    }
+
+    return baseDamage;
+  }
+
   /**
    * Calculates the damage of an attack made by another Pokemon against this Pokemon
    * @param source {@linkcode Pokemon} the attacking Pokemon
    * @param move {@linkcode Pokemon} the move used in the attack
    * @param ignoreAbility If `true`, ignores this Pokemon's defensive ability effects
+   * @param ignoreSourceAbility If `true`, ignores the attacking Pokemon's ability effects
    * @param isCritical If `true`, calculates damage for a critical hit.
    * @param simulated If `true`, suppresses changes to game state during the calculation.
    * @returns a {@linkcode DamageCalculationResult} object with three fields:
@@ -2395,35 +2445,11 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
       };
     }
 
-    // ----- BEGIN BASE DAMAGE MULTIPLIERS -----
-
-    /** A base damage multiplier based on the source's level */
-    const levelMultiplier = (2 * source.level / 5 + 2);
-
-    /** The power of the move after power boosts from abilities, etc. have applied */
-    const power = move.calculateBattlePower(source, this, simulated);
-
-    /**
-     * The attacker's offensive stat for the given move's category.
-     * Critical hits ignore negative stat stages.
-     */
-    const sourceAtk = new Utils.NumberHolder(source.getEffectiveStat(isPhysical ? Stat.ATK : Stat.SPATK, this, undefined, ignoreSourceAbility, ignoreAbility, isCritical, simulated));
-    applyMoveAttrs(VariableAtkAttr, source, this, move, sourceAtk);
-
-    /**
-     * This Pokemon's defensive stat for the given move's category.
-     * Critical hits ignore positive stat stages.
-     */
-    const targetDef = new Utils.NumberHolder(this.getEffectiveStat(isPhysical ? Stat.DEF : Stat.SPDEF, source, move, ignoreAbility, ignoreSourceAbility, isCritical, simulated));
-    applyMoveAttrs(VariableDefAttr, source, this, move, targetDef);
-
     /**
      * The attack's base damage, as determined by the source's level, move power
      * and Attack stat as well as this Pokemon's Defense stat
      */
-    const baseDamage = ((levelMultiplier * power * sourceAtk.value / targetDef.value) / 50) + 2;
-
-    // ------ END BASE DAMAGE MULTIPLIERS ------
+    const baseDamage = this.getBaseDamage(source, move, moveCategory, ignoreAbility, ignoreSourceAbility, isCritical, simulated);
 
     /** 25% damage debuff on moves hitting more than one non-fainted target (regardless of immunities) */
     const { targets, multiple } = getMoveTargets(source, move.id);
@@ -2549,7 +2575,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
 
     // debug message for when damage is applied (i.e. not simulated)
     if (!simulated) {
-      console.log("damage", damage.value, move.name, power, sourceAtk, targetDef);
+      console.log("damage", damage.value, move.name);
     }
 
     let hitResult: HitResult;

src/test/moves/shell_side_arm.test.ts

@@ -0,0 +1,87 @@
+import { BattlerIndex } from "#app/battle";
+import { allMoves, ShellSideArmCategoryAttr } from "#app/data/move";
+import { Abilities } from "#enums/abilities";
+import { Moves } from "#enums/moves";
+import { Species } from "#enums/species";
+import GameManager from "#test/utils/gameManager";
+import Phaser from "phaser";
+import { afterEach, beforeAll, beforeEach, describe, it, expect, vi } from "vitest";
+
+describe("Moves - Shell Side Arm", () => {
+  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.SHELL_SIDE_ARM])
+      .battleType("single")
+      .startingLevel(100)
+      .enemyLevel(100)
+      .enemyAbility(Abilities.BALL_FETCH)
+      .enemyMoveset(Moves.SPLASH);
+  });
+
+  it("becomes a physical attack if forecasted to deal more damage as physical", async () => {
+    game.override.enemySpecies(Species.SNORLAX);
+
+    await game.classicMode.startBattle([Species.MANAPHY]);
+
+    const shellSideArm = allMoves[Moves.SHELL_SIDE_ARM];
+    const shellSideArmAttr = shellSideArm.getAttrs(ShellSideArmCategoryAttr)[0];
+    vi.spyOn(shellSideArmAttr, "apply");
+
+    game.move.select(Moves.SHELL_SIDE_ARM);
+
+    await game.phaseInterceptor.to("MoveEffectPhase");
+
+    expect(shellSideArmAttr.apply).toHaveLastReturnedWith(true);
+  }, TIMEOUT);
+
+  it("remains a special attack if forecasted to deal more damage as special", async () => {
+    game.override.enemySpecies(Species.SLOWBRO);
+
+    await game.classicMode.startBattle([Species.MANAPHY]);
+
+    const shellSideArm = allMoves[Moves.SHELL_SIDE_ARM];
+    const shellSideArmAttr = shellSideArm.getAttrs(ShellSideArmCategoryAttr)[0];
+    vi.spyOn(shellSideArmAttr, "apply");
+
+    game.move.select(Moves.SHELL_SIDE_ARM);
+
+    await game.phaseInterceptor.to("MoveEffectPhase");
+
+    expect(shellSideArmAttr.apply).toHaveLastReturnedWith(false);
+  }, TIMEOUT);
+
+  it("respects stat stage changes when forecasting base damage", async () => {
+    game.override
+      .enemySpecies(Species.SNORLAX)
+      .enemyMoveset(Moves.COTTON_GUARD);
+
+    await game.classicMode.startBattle([Species.MANAPHY]);
+
+    const shellSideArm = allMoves[Moves.SHELL_SIDE_ARM];
+    const shellSideArmAttr = shellSideArm.getAttrs(ShellSideArmCategoryAttr)[0];
+    vi.spyOn(shellSideArmAttr, "apply");
+
+    game.move.select(Moves.SHELL_SIDE_ARM);
+
+    await game.setTurnOrder([BattlerIndex.ENEMY, BattlerIndex.PLAYER]);
+
+    await game.phaseInterceptor.to("BerryPhase", false);
+
+    expect(shellSideArmAttr.apply).toHaveLastReturnedWith(false);
+  }, TIMEOUT);
+});