Fix Knock Off damage in Klutz/Magic Room (#651)

A `Pokemon#disabledItem` field is used to check Knock Off damage
during Klutz/Magic Room.

calc/src/mechanics/gen56.ts

@@ -620,18 +620,20 @@ export function calculateBPModsBWXY(
 ) {
   const bpMods = [];
 
+  const defenderItem = (defender.item && defender.item !== '')
+    ? defender.item : defender.disabledItem;
   let resistedKnockOffDamage =
-    !defender.item ||
-    (defender.named('Giratina-Origin') && defender.hasItem('Griseous Orb')) ||
-    (defender.name.includes('Arceus') && defender.item.includes('Plate')) ||
-    (defender.name.includes('Genesect') && defender.item.includes('Drive')) ||
-    (defender.named('Groudon', 'Groudon-Primal') && defender.hasItem('Red Orb')) ||
-    (defender.named('Kyogre', 'Kyogre-Primal') && defender.hasItem('Blue Orb'));
+    !defenderItem ||
+    (defender.named('Giratina-Origin') && defenderItem === 'Griseous Orb') ||
+    (defender.name.includes('Arceus') && defenderItem.includes('Plate')) ||
+    (defender.name.includes('Genesect') && defenderItem.includes('Drive')) ||
+    (defender.named('Groudon', 'Groudon-Primal') && defenderItem === 'Red Orb') ||
+    (defender.named('Kyogre', 'Kyogre-Primal') && defenderItem === 'Blue Orb');
 
   // The last case only applies when the Pokemon is holding the Mega Stone that matches its species
   // (or when it's already a Mega-Evolution)
-  if (!resistedKnockOffDamage && defender.item) {
-    const item = gen.items.get(toID(defender.item))!;
+  if (!resistedKnockOffDamage && defenderItem) {
+    const item = gen.items.get(toID(defenderItem))!;
     resistedKnockOffDamage = !!(item.megaEvolves && defender.name.includes(item.megaEvolves));
   }
 

calc/src/mechanics/gen789.ts

@@ -1028,30 +1028,31 @@ export function calculateBPModsSMSSSV(
   const bpMods = [];
 
   // Move effects
-
+  const defenderItem = (defender.item && defender.item !== '')
+    ? defender.item : defender.disabledItem;
   let resistedKnockOffDamage =
-    (!defender.item || isQPActive(defender, field)) ||
-    (defender.named('Dialga-Origin') && defender.hasItem('Adamant Crystal')) ||
-    (defender.named('Palkia-Origin') && defender.hasItem('Lustrous Globe')) ||
+    (!defenderItem || isQPActive(defender, field)) ||
+    (defender.named('Dialga-Origin') && defenderItem === 'Adamant Crystal') ||
+    (defender.named('Palkia-Origin') && defenderItem === 'Lustrous Globe') ||
     // Griseous Core for gen 9, Griseous Orb otherwise
-    (defender.name.includes('Giratina-Origin') && defender.item.includes('Griseous')) ||
-    (defender.name.includes('Arceus') && defender.item.includes('Plate')) ||
-    (defender.name.includes('Genesect') && defender.item.includes('Drive')) ||
-    (defender.named('Groudon', 'Groudon-Primal') && defender.hasItem('Red Orb')) ||
-    (defender.named('Kyogre', 'Kyogre-Primal') && defender.hasItem('Blue Orb')) ||
-    (defender.name.includes('Silvally') && defender.item.includes('Memory')) ||
-    defender.item.includes(' Z') ||
-    (defender.named('Zacian') && defender.hasItem('Rusted Sword')) ||
-    (defender.named('Zamazenta') && defender.hasItem('Rusted Shield')) ||
-    (defender.name.includes('Ogerpon-Cornerstone') && defender.hasItem('Cornerstone Mask')) ||
-    (defender.name.includes('Ogerpon-Hearthflame') && defender.hasItem('Hearthflame Mask')) ||
-    (defender.name.includes('Ogerpon-Wellspring') && defender.hasItem('Wellspring Mask')) ||
-    (defender.named('Venomicon-Epilogue') && defender.hasItem('Vile Vial'));
+    (defender.name.includes('Giratina-Origin') && defenderItem.includes('Griseous')) ||
+    (defender.name.includes('Arceus') && defenderItem.includes('Plate')) ||
+    (defender.name.includes('Genesect') && defenderItem.includes('Drive')) ||
+    (defender.named('Groudon', 'Groudon-Primal') && defenderItem === 'Red Orb') ||
+    (defender.named('Kyogre', 'Kyogre-Primal') && defenderItem === 'Blue Orb') ||
+    (defender.name.includes('Silvally') && defenderItem.includes('Memory')) ||
+    defenderItem.includes(' Z') ||
+    (defender.named('Zacian') && defenderItem === 'Rusted Sword') ||
+    (defender.named('Zamazenta') && defenderItem === 'Rusted Shield') ||
+    (defender.name.includes('Ogerpon-Cornerstone') && defenderItem === 'Cornerstone Mask') ||
+    (defender.name.includes('Ogerpon-Hearthflame') && defenderItem === 'Hearthflame Mask') ||
+    (defender.name.includes('Ogerpon-Wellspring') && defenderItem === 'Wellspring Mask') ||
+    (defender.named('Venomicon-Epilogue') && defenderItem === 'Vile Vial');
 
   // The last case only applies when the Pokemon has the Mega Stone that matches its species
   // (or when it's already a Mega-Evolution)
-  if (!resistedKnockOffDamage && defender.item) {
-    const item = gen.items.get(toID(defender.item))!;
+  if (!resistedKnockOffDamage && defenderItem) {
+    const item = gen.items.get(toID(defenderItem))!;
     resistedKnockOffDamage = !!item.megaEvolves && defender.name.includes(item.megaEvolves);
   }
 

calc/src/mechanics/util.ts

@@ -200,6 +200,7 @@ export function checkItem(pokemon: Pokemon, magicRoomActive?: boolean) {
     pokemon.hasAbility('Klutz') && !EV_ITEMS.includes(pokemon.item!) ||
     magicRoomActive
   ) {
+    pokemon.disabledItem = pokemon.item;
     pokemon.item = '' as ItemName;
   }
 }

calc/src/pokemon.ts

@@ -25,6 +25,7 @@ export class Pokemon implements State.Pokemon {
   alliesFainted?: number;
   boostedStat?: I.StatIDExceptHP | 'auto';
   item?: I.ItemName;
+  disabledItem?: I.ItemName;
   teraType?: I.TypeName;
 
   nature: I.NatureName;

calc/src/test/calc.test.ts

@@ -479,6 +479,23 @@ describe('calc', () => {
       });
     });
 
+    inGens(6, 9, ({gen, calculate, Pokemon, Move}) => {
+      test('Knock Off vs. Klutz', () => {
+        const weavile = Pokemon('Weavile');
+        const audino = Pokemon('Audino', {ability: 'Klutz', item: 'Leftovers'});
+        const audinoMega = Pokemon('Audino', {ability: 'Klutz', item: 'Audinite'});
+        const knockoff = Move('Knock Off');
+        const result = calculate(weavile, audino, knockoff);
+        expect(result.desc()).toBe(
+          '0 Atk Weavile Knock Off (97.5 BP) vs. 0 HP / 0 Def Audino: 139-165 (40 - 47.5%) -- guaranteed 3HKO'
+        );
+        const result2 = calculate(weavile, audinoMega, knockoff);
+        expect(result2.desc()).toBe(
+          '0 Atk Weavile Knock Off vs. 0 HP / 0 Def Audino: 93-111 (26.8 - 31.9%) -- guaranteed 4HKO'
+        );
+      });
+    });
+
     inGens(5, 9, ({gen, calculate, Pokemon, Move}) => {
       test(`Multi-hit interaction with Multiscale (gen ${gen})`, () => {
         const result = calculate(