Re-Add MovePriorityModifier

src/data/abilities/ability.ts

@@ -34,6 +34,7 @@ import { MoveCategory } from "#enums/move-category";
 import { MoveFlags } from "#enums/move-flags";
 import { MoveId } from "#enums/move-id";
 import { MovePhaseTimingModifier } from "#enums/move-phase-timing-modifier";
+import { MovePriorityModifier } from "#enums/move-priority-modifier";
 import { MoveResult } from "#enums/move-result";
 import { MoveTarget } from "#enums/move-target";
 import { MoveUseMode } from "#enums/move-use-mode";
@@ -4142,6 +4143,25 @@ export class ChangeMovePriorityAbAttr extends AbAttr {
   }
 }
 
+export class ChangeMovePriorityModifierAbAttr extends AbAttr {
+  private readonly newModifier: MovePriorityModifier;
+  private readonly moveFunc: (pokemon: Pokemon, move: Move) => boolean;
+
+  constructor(moveFunc: (pokemon: Pokemon, move: Move) => boolean, newModifier: MovePriorityModifier) {
+    super(false);
+    this.newModifier = newModifier;
+    this.moveFunc = moveFunc;
+  }
+
+  override canApply({ pokemon, move }: ChangeMovePriorityAbAttrParams): boolean {
+    return this.moveFunc(pokemon, move);
+  }
+
+  override apply({ priority }: ChangeMovePriorityAbAttrParams): void {
+    priority.value = this.newModifier;
+  }
+}
+
 export class IgnoreContactAbAttr extends AbAttr {
   private declare readonly _: never;
 }
@@ -6721,6 +6741,7 @@ const AbilityAttrs = Object.freeze({
   BlockStatusDamageAbAttr,
   BlockOneHitKOAbAttr,
   ChangeMovePriorityAbAttr,
+  ChangeMovePriorityModifierAbAttr,
   IgnoreContactAbAttr,
   PreWeatherEffectAbAttr,
   PreWeatherDamageAbAttr,
@@ -7238,7 +7259,7 @@ export function initAbilities() {
       .attr(DoubleBattleChanceAbAttr)
       .build(),
     new AbBuilder(AbilityId.STALL, 4)
-      .attr(ChangeMovePriorityAbAttr, (_pokemon, _move: Move) => true, -0.2)
+      .attr(ChangeMovePriorityModifierAbAttr, (_pokemon, _move: Move) => true, MovePriorityModifier.LAST_IN_BRACKET)
       .build(),
     new AbBuilder(AbilityId.TECHNICIAN, 4)
       .attr(MovePowerBoostAbAttr, (user, target, move) => {
@@ -8185,7 +8206,7 @@ export function initAbilities() {
       .ignorable()
       .build(),
     new AbBuilder(AbilityId.MYCELIUM_MIGHT, 9)
-      .attr(ChangeMovePriorityAbAttr, (_pokemon, move) => move.category === MoveCategory.STATUS, -0.2)
+      .attr(ChangeMovePriorityModifierAbAttr, (_pokemon, move) => move.category === MoveCategory.STATUS, MovePriorityModifier.LAST_IN_BRACKET)
       .attr(PreventBypassSpeedChanceAbAttr, (_pokemon, move) => move.category === MoveCategory.STATUS)
       .attr(MoveAbilityBypassAbAttr, (_pokemon, move: Move) => move.category === MoveCategory.STATUS)
       .build(),

src/data/moves/move.ts

@@ -101,6 +101,7 @@ import { MovePhaseTimingModifier } from "#enums/move-phase-timing-modifier";
 import { inSpeedOrder } from "#utils/speed-order-generator";
 import { canSpeciesTera, willTerastallize } from "#utils/pokemon-utils";
 import type { ReadonlyGenericUint8Array } from "#types/typed-arrays";
+import { MovePriorityModifier } from "#enums/move-priority-modifier";
 
 /**
  * A function used to conditionally determine execution of a given {@linkcode MoveAttr}.
@@ -1060,17 +1061,19 @@ export abstract class Move implements Localizable {
 
   getPriority(user: Pokemon, simulated: boolean = true) {
     const priority = new NumberHolder(this.priority);
-
     applyMoveAttrs("IncrementMovePriorityAttr", user, null, this, priority);
     applyAbAttrs("ChangeMovePriorityAbAttr", {pokemon: user, simulated, move: this, priority});
 
-    if (user.getTag(BattlerTagType.BYPASS_SPEED)) {
-      priority.value += 0.2;
-    }
-
     return priority.value;
   }
 
+  public getPriorityModifier(user: Pokemon, simulated = true) {
+    const modifierHolder = new NumberHolder(MovePriorityModifier.NORMAL);
+    applyAbAttrs("ChangeMovePriorityModifierAbAttr", {pokemon: user, simulated: simulated, move: this, priority: modifierHolder});
+    modifierHolder.value = user.getTag(BattlerTagType.BYPASS_SPEED) ? MovePriorityModifier.FIRST_IN_BRACKET : modifierHolder.value;
+    return modifierHolder.value;
+  }
+
   /**
    * Calculate the [Expected Power](https://en.wikipedia.org/wiki/Expected_value) per turn
    * of this move, taking into account multi hit moves, accuracy, and the number of turns it

src/data/terrain.ts

@@ -67,7 +67,7 @@ export class Terrain {
         return (
           !isFieldTargeted(move)
           && !isSpreadMove(move)
-          && move.getPriority(user) > 0.2 // fractional priority is used by quick claw etc and is not blocked by terrain
+          && move.getPriority(user) > 0
           && user.getOpponents(true).some(o => targets.includes(o.getBattlerIndex()) && o.isGrounded())
         );
     }

src/enums/move-priority-modifier.ts

@@ -0,0 +1,13 @@
+import type { ObjectValues } from "#types/type-helpers";
+
+/**
+ * Enum representing modifiers for Move priorities.
+ */
+export const MovePriorityModifier = Object.freeze({
+  /** Used when moves go last in their priority bracket, but before moves of lower priority. */
+  LAST_IN_BRACKET: 0,
+  NORMAL: 1,
+  /** Used when moves go first in their priority bracket, but before moves of lower priority. */
+  FIRST_IN_BRACKET: 2,
+});
+export type MovePriorityModifier = ObjectValues<typeof MovePriorityModifier>;

src/queues/move-phase-priority-queue.ts

@@ -92,11 +92,18 @@ export class MovePhasePriorityQueue extends PokemonPhasePriorityQueue<MovePhase>
       });
 
       const timingModifiers = [a, b].map(movePhase => movePhase.timingModifier);
+      const priorityModifiers = [a, b].map(movePhase =>
+        movePhase.move.getMove().getPriorityModifier(movePhase.pokemon),
+      );
 
       if (timingModifiers[0] !== timingModifiers[1]) {
         return timingModifiers[1] - timingModifiers[0];
       }
 
+      if (priority[0] === priority[1] && priorityModifiers[0] !== priorityModifiers[1]) {
+        return priorityModifiers[1] - priorityModifiers[0];
+      }
+
       return priority[1] - priority[0];
     });
   }

test/arena/psychic-terrain.test.ts

@@ -72,7 +72,7 @@ describe("Arena - Psychic Terrain", () => {
     await game.phaseInterceptor.to("MovePhase", false);
 
     const feebas = game.field.getPlayerPokemon();
-    expect(allMoves[MoveId.POUND].getPriority(feebas)).toBe(0.2);
+    expect(allMoves[MoveId.POUND].getPriority(feebas)).toBe(0);
 
     await game.toEndOfTurn();
 
@@ -93,7 +93,7 @@ describe("Arena - Psychic Terrain", () => {
     await game.phaseInterceptor.to("MovePhase", false);
 
     const feebas = game.field.getPlayerPokemon();
-    expect(allMoves[MoveId.QUICK_ATTACK].getPriority(feebas)).toBe(1.2);
+    expect(allMoves[MoveId.QUICK_ATTACK].getPriority(feebas)).toBe(1);
 
     await game.toEndOfTurn();