Port evolution, Rare Candy, evolution stones and vitamins

Pokémon that levelled up evolve after a won battle, following
EvolveAfterBattle's checks over the ROM's evolution bytes, with the
evolution screen that B can stop and move learning outside battle. The pack
uses Rare Candy, stones (with ABLE/NOT ABLE labels) and vitamins, and its
pocket tabs now sit in their own row.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/game/scripts/start-menu.ts

@@ -8,7 +8,8 @@ import {
   restoredPP,
 } from "../battle/battle";
 import { receiveItem, removeFromSlot, type ItemSlot } from "../party/bag";
-import { maxPP, type PartyMon } from "../party/pokemon";
+import { calcStats, maxPP, type PartyMon } from "../party/pokemon";
+import { PartyEvolution, evoStoneCompatible } from "./evolution";
 import {
   copyScriptState,
   type MartEntry,
@@ -86,6 +87,10 @@ export interface StartMenuHost {
   /** BikeFunction: the script that getting on or off the Bicycle queues
    * here, or undefined when .CheckEnvironment refuses it. */
   bicycleScript(state: ScriptState): number | undefined;
+  /** wTimeOfDay: morning 0, day 1, night 2. */
+  timeOfDay(): number;
+  /** GetWorldMapLocation for the current map (LevelUpHappinessMod). */
+  landmark(): number;
 }
 
 /** The overworld start menu (engine/menus/start_menu.asm) with its
@@ -269,7 +274,11 @@ export class StartMenuRun {
 
   /** The party menu with PlacePartyMenuText's prompt. Returns the party
    * index, or -1 when cancelled. `from` marks SwitchPartyMons' source. */
-  private *partyMenu(action: number, from?: number): Gen<number> {
+  private *partyMenu(
+    action: number,
+    from?: number,
+    item = 0,
+  ): Gen<number> {
     const r = this.reader,
       entry = MENU.PartyMenuStrings + action * 2;
     const prompt = this.string(r.near(entry, r.bank(entry)));
@@ -277,9 +286,17 @@ export class StartMenuRun {
     const choice = yield* this.menu(
       [prompt],
       party.map((mon, slot) => (slot === from ? `▷${mon.nickname}` : mon.nickname)),
-      party.map(
-        (mon) =>
-          `:L${mon.level} HP ${mon.hp}/${mon.stats[0]}${mon.hp ? statusName(mon.status) : " FNT"}`,
+      party.map((mon) =>
+        // PlacePartyMonEvoStoneCompatibility replaces the HP bar.
+        action === C.PARTYMENUACTION_EVO_STONE
+          ? mon.species === EGG
+            ? ""
+            : this.string(
+                evoStoneCompatible(r, mon.species, item)
+                  ? MENU["PlacePartyMonEvoStoneCompatibility.string_able"]
+                  : MENU["PlacePartyMonEvoStoneCompatibility.string_not_able"],
+              )
+          : `:L${mon.level} HP ${mon.hp}/${mon.stats[0]}${mon.hp ? statusName(mon.status) : " FNT"}`,
       ),
       // InitPartyMenuWithCancel: the last row chosen, if still listed.
       this.cursors.party >= 1 && this.cursors.party <= party.length
@@ -698,6 +715,12 @@ export class StartMenuRun {
       }
       case BATTLE.RestorePPEffect:
         return yield* this.restorePPEffect(use);
+      case MENU.RareCandyEffect:
+        return yield* this.rareCandyEffect(use);
+      case MENU.VitaminEffect:
+        return yield* this.vitaminEffect(use);
+      case MENU.EvoStoneEffect:
+        return yield* this.evoStoneEffect(use);
       case MENU.BicycleEffect: {
         const script = this.host.bicycleScript(this.state);
         if (script === undefined) return false;
@@ -712,8 +735,11 @@ export class StartMenuRun {
 
   /** UseItem_SelectMon: the party menu for an item. The party index, or
    * -1 when cancelled or an Egg was chosen. */
-  private *useItemSelectMon(): Gen<number> {
-    const slot = yield* this.partyMenu(PARTYMENUACTION_HEALING_ITEM);
+  private *useItemSelectMon(
+    action: number = PARTYMENUACTION_HEALING_ITEM,
+    item = 0,
+  ): Gen<number> {
+    const slot = yield* this.partyMenu(action, undefined, item);
     if (slot < 0) return -1;
     if (this.state.party[slot].species === EGG) {
       yield* this.print(BATTLE.ItemCantUseOnEggText);
@@ -825,6 +851,109 @@ export class StartMenuRun {
     return 0;
   }
 
+  /** Evolution and move learning on this menu's draft. */
+  private evolution() {
+    return new PartyEvolution(this.state, this.host);
+  }
+
+  /** RareCandyEffect: one level at the level's minimum experience, the
+   * stats (and HP, even of a fainted Pokémon) raised, the level-up
+   * happiness, new moves and a possible evolution. */
+  private *rareCandyEffect(use: FieldItemUse): Gen<boolean> {
+    const data = this.data;
+    const target = yield* this.useItemSelectMon();
+    if (target < 0) return false;
+    const mon = this.state.party[target];
+    this.strings[RAM.stringBuffer1] = mon.nickname;
+    if (mon.level >= C.MAX_LEVEL) {
+      yield* this.print(BATTLE.ItemWontHaveEffectText);
+      return false;
+    }
+    const level = ++mon.level;
+    mon.exp = data.expAtLevel(data.baseData(mon.species).growthRate, level);
+    const oldMax = mon.stats[0];
+    mon.stats = calcStats(data, mon.species, mon.dvs, level, mon.statExp);
+    mon.hp = (mon.hp + mon.stats[0] - oldMax) & 0xffff;
+    // LevelUpHappinessMod: more on the map where it was caught.
+    this.changeHappiness(
+      target,
+      (mon.caughtData & 0x7f) === this.host.landmark()
+        ? C.HAPPINESS_GAINLEVELATHOME
+        : C.HAPPINESS_GAINLEVEL,
+    );
+    this.numbers[RAM.curPartyLevel] = level;
+    yield* this.itemActionText(target, C.PARTYMENUTEXT_LEVEL_UP);
+    // PrintTempMonStats: Attack, Defense, Sp. Atk, Sp. Def and Speed.
+    const labels = readString(
+      this.reader,
+      BATTLE["PrintTempMonStats.StatNames"],
+      this.text(),
+      64,
+    )
+      .split("\n")
+      .filter(Boolean);
+    const values = [1, 2, 4, 5, 3].map((stat) => mon.stats[stat]);
+    yield {
+      kind: "text",
+      pages: [labels.map((label, i) => `${label} ${values[i]}`).join("\n")],
+    };
+    const evolution = this.evolution();
+    yield* evolution.learnLevelMoves(target, level);
+    // EvolvePokemon, not forced: a level or happiness evolution.
+    yield* evolution.evolveAfterBattle(1 << target, false, use.item);
+    this.useDisposableItem(use);
+    return true;
+  }
+
+  /** VitaminEffect: ten more in the high byte of a stat's experience, up
+   * to 100, then CalcMonStats (the current HP stays). */
+  private *vitaminEffect(use: FieldItemUse): Gen<boolean> {
+    const r = this.reader;
+    const target = yield* this.useItemSelectMon();
+    if (target < 0) return false;
+    const mon = this.state.party[target];
+    this.strings[RAM.stringBuffer1] = mon.nickname;
+    // GetStatExpRelativePointer: the stat experience word for the item.
+    let p = MENU.StatExpItemPointerOffsets;
+    while (r.byte(p) !== use.item) p += 2;
+    const offset = r.byte(p + 1),
+      stat = offset >> 1;
+    if (mon.statExp[stat] >> 8 >= 100) {
+      yield* this.print(BATTLE.ItemWontHaveEffectText);
+      return false;
+    }
+    mon.statExp[stat] += 10 << 8;
+    mon.stats = calcStats(this.data, mon.species, mon.dvs, mon.level, mon.statExp);
+    const entry = MENU.StatStrings + offset;
+    this.strings[RAM.stringBuffer2] = this.string(r.near(entry, r.bank(entry)));
+    yield* this.print(MENU.ItemStatRoseText);
+    this.changeHappiness(target, C.HAPPINESS_USEDITEM);
+    this.useDisposableItem(use);
+    return true;
+  }
+
+  /** EvoStoneEffect: a forced EvolvePokemon with the stone as wCurItem.
+   * An Everstone or no matching evolution has no effect. */
+  private *evoStoneEffect(use: FieldItemUse): Gen<boolean> {
+    const target = yield* this.useItemSelectMon(
+      C.PARTYMENUACTION_EVO_STONE,
+      use.item,
+    );
+    if (target < 0) return false;
+    if (this.state.party[target].item === C.EVERSTONE) {
+      yield* this.print(BATTLE.ItemWontHaveEffectText);
+      return false;
+    }
+    if (
+      !(yield* this.evolution().evolveAfterBattle(1 << target, true, use.item))
+    ) {
+      yield* this.print(BATTLE.ItemWontHaveEffectText);
+      return false;
+    }
+    this.useDisposableItem(use);
+    return true;
+  }
+
   /** RestorePPEffect for Ethers, Elixers, the MysteryBerry and PP Up. B on
    * the move list goes back to the party menu. */
   private *restorePPEffect(use: FieldItemUse): Gen<boolean> {