Port the remaining battle items, the stats screen and hBattleTurn at the menu

- Run every non-ball item effect usable in battle from the ROM's
  ItemEffects: Full Restore, revives, bitter medicine, Bitter Berry, Ethers
  and Elixers, X items, X Accuracy, Guard Spec, Dire Hit and Poké Doll.
- Read happiness changes from HappinessChanges, including the larger
  level-up gain where a Pokémon was caught.
- Model hBattleTurn at the battle menu, including the trainer AI's writes,
  and drop the status-heal refusal.
- Port the stats screen for battles and Bill's PC.
- Compare the send-out and withdraw texts, RestoreHealth, RestorePP,
  ChangeHappiness and CalcPlayerStats with the original routines.

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

src/main.ts

@@ -10,7 +10,7 @@ import { drawTile } from "./game/rendering/pixels";
 import { PokemonData } from "./game/rom/pokemon";
 import type { Direction, Palette } from "./game/world/types";
 import type { Button } from "./input/types";
-import { NICKNAME_PATTERN } from "./game/party/pokemon";
+import { NICKNAME_PATTERN, maxPP } from "./game/party/pokemon";
 import { GameSession } from "./app/session";
 import { InputController } from "./input/controller";
 import { bindControls } from "./input/bindings";
@@ -47,6 +47,7 @@ function showWorld(world: GameWorld) {
   get("tiles-walked").textContent = `${world.tilesWalked} tiles walked`;
   get("game-notice").textContent = world.notice;
   showBattle(world);
+  showStatsScreen(world);
   showFieldMenu(world);
   get("town-map-view").hidden = !world.townMap;
   if (world.townMap)
@@ -59,7 +60,11 @@ function showWorld(world: GameWorld) {
   );
   const mart = dialogue?.choice && martChoice(dialogue.choice);
   get("native-dialogue").hidden =
-    !dialogue || pictureWait || Boolean(mart) || world.townMap;
+    !dialogue ||
+    pictureWait ||
+    Boolean(mart) ||
+    world.townMap ||
+    Boolean(world.statsScreen);
   get("pokepic-next").hidden = !pictureWait;
   get("dialogue-text").textContent = dialogue?.pages[dialogue.index] ?? "";
   get("dialogue-page").textContent =
@@ -384,6 +389,9 @@ let showPack = false;
 let packPocket: "item" | "ball" = "item";
 /** The party slot whose BattleMonMenu (SWITCH/STATS/CANCEL) is open. */
 let partyChoice: number | undefined;
+/** The stats screen and its page (pink, green, blue): opened from
+ * BattleMonMenu for a party slot, or by a script (Bill's PC) without one. */
+let statsView: { slot?: number; page: number } | undefined;
 let battleCursor = 0;
 let battleSelectionKey = "";
 
@@ -458,6 +466,18 @@ function highlightBattleChoice() {
 function handleBattleInput(button: Button): boolean {
   if (handleFieldInput(button)) return true;
   const world = runtime.world;
+  if (statsView && world) {
+    // StatsScreen_JoypadAction: left and right turn pages, B leaves.
+    // BattleMenuPKMN_ReturnFromStats reopens the party menu itself.
+    if (button === "b" && statsView.slot === undefined) world.advanceDialogue();
+    else if (button === "b") statsView = partyChoice = undefined;
+    else if (button === "left" || button === "up")
+      statsView.page = (statsView.page + 2) % 3;
+    else if (button === "right" || button === "down" || button === "a")
+      statsView.page = (statsView.page + 1) % 3;
+    showWorld(world);
+    return true;
+  }
   if (!world?.battle) return false;
   if (button === "b" && (showMoves || showPack)) {
     showMoves = showPack = false;
@@ -540,11 +560,14 @@ function showBattle(world: GameWorld) {
   get("battle-text").textContent =
     prompt?.kind === "name"
       ? prompt.title
-      : prompt?.kind === "party"
+      : prompt?.kind === "party" || prompt?.kind === "move"
         ? prompt.text
         : (view.message?.text ?? "");
   if (prompt?.kind !== "action") showMoves = showPack = false;
-  if (prompt?.kind !== "party") partyChoice = undefined;
+  if (prompt?.kind !== "party") {
+    partyChoice = undefined;
+    if (statsView?.slot !== undefined) statsView = undefined;
+  }
   const selectionKey = `${prompt?.kind ?? "text"}:${showMoves}:${showPack}:${partyChoice}`;
   if (selectionKey !== battleSelectionKey) {
     battleCursor = 0;
@@ -706,8 +729,9 @@ function showBattle(world: GameWorld) {
         partyChoice = undefined;
         runtime.battleChoose(slot);
       }),
-      button("STATS", () => {}, {
-        disabled: "The stats screen is not ported yet.",
+      button("STATS", () => {
+        statsView = { slot, page: 0 };
+        showWorld(world);
       }),
       button("CANCEL", () => {
         partyChoice = undefined;
@@ -737,6 +761,18 @@ function showBattle(world: GameWorld) {
       buttons.push(
         button("CANCEL", () => runtime.battleChoose(-1), { wide: true }),
       );
+  } else if (prompt?.kind === "move") {
+    prompt.moves.forEach((move, index) => {
+      if (!move) return;
+      buttons.push(
+        button(data.moveName(move), () => runtime.battleChoose(index), {
+          detail: `PP ${prompt.pp[index] & 63}`,
+        }),
+      );
+    });
+    buttons.push(
+      button("CANCEL", () => runtime.battleChoose(-1), { wide: true }),
+    );
   } else if (prompt?.kind === "forget") {
     prompt.moves.forEach((move, index) =>
       buttons.push(
@@ -774,6 +810,143 @@ function showBattle(world: GameWorld) {
   );
   highlightBattleChoice();
 }
+/** The stats screen's pages (engine/pokemon/stats_screen.asm), with its
+ * strings, type names and stat labels read from the ROM. */
+function showStatsScreen(world: GameWorld) {
+  const panel = get("stats-screen");
+  const view = world.battle;
+  // A script's stats screen opens on the first page and closes with it.
+  if (world.statsScreen && !statsView) statsView = { page: 0 };
+  if (!world.statsScreen && statsView?.slot === undefined) statsView = undefined;
+  const slot = statsView?.slot;
+  const own = view?.engine.player.mon;
+  const stored =
+    slot === undefined ? world.statsScreen : world.liveState.party[slot];
+  panel.hidden = !statsView || !stored;
+  if (!statsView || !stored) return;
+  const data = world.assets.pokemon;
+  const mon =
+    view && slot === view.engine.curBattleMon && own
+      ? { ...stored, hp: own.hp, status: own.status }
+      : stored;
+  const shiny = PokemonData.shiny(mon.dvs);
+  const text = (label: Parameters<PokemonData["statsString"]>[0]) =>
+    data.statsString(label);
+  drawPic(
+    get("stats-pic"),
+    data.frontPic(mon.species),
+    7,
+    data.palette(mon.species, shiny),
+  );
+  get("stats-pic").setAttribute("aria-label", data.speciesName(mon.species));
+  const gender = data.gender(mon.species, mon.dvs);
+  const line = (...parts: (string | Node)[]) => {
+    const p = document.createElement("p");
+    p.append(...parts);
+    return p;
+  };
+  const name = document.createElement("strong");
+  name.textContent = `${mon.nickname}${gender === "male" ? "♂" : gender === "female" ? "♀" : ""}`;
+  get("stats-header").replaceChildren(
+    line(
+      `№.${String(mon.species).padStart(3, "0")}  :L${mon.level}${shiny ? "  ★" : ""}`,
+    ),
+    line(name),
+    line(`/${data.speciesName(mon.species)}`),
+  );
+  const list = (rows: [string, string][], wide = false) => {
+    const dl = document.createElement("dl");
+    if (wide) dl.classList.add("wide");
+    for (const [term, value] of rows) {
+      const dt = document.createElement("dt"),
+        dd = document.createElement("dd");
+      dt.textContent = term;
+      dd.textContent = value;
+      dl.append(dt, dd);
+    }
+    return dl;
+  };
+  const growth = data.baseData(mon.species).growthRate;
+  const page: Node[] = [];
+  if (statsView.page === 0) {
+    const [statusLabel, typeLabel] = text("LoadPinkPage.Status_Type").split(
+      "\n",
+    );
+    const types = [...new Set(data.baseData(mon.species).types)].map((type) =>
+      data.typeName(type),
+    );
+    const next = Math.min(mon.level + 1, 100);
+    page.push(
+      list([
+        ["HP", `${mon.hp}/ ${mon.stats[0]}`],
+        [
+          statusLabel,
+          mon.pokerus & 0x0f
+            ? text("LoadPinkPage.PkrsStr")
+            : !mon.hp
+              ? "FNT"
+              : statusName(mon.status) || text("LoadPinkPage.OK_str").trim(),
+        ],
+        [typeLabel, types.join(" / ")],
+      ]),
+      list([
+        [text("LoadPinkPage.ExpPointStr"), String(mon.exp)],
+        [
+          text("LoadPinkPage.LevelUpStr"),
+          String(
+            mon.level >= 100 ? 0 : data.expAtLevel(growth, next) - mon.exp,
+          ),
+        ],
+        [text("LoadPinkPage.ToStr"), `:L${next}`],
+      ]),
+    );
+  } else if (statsView.page === 1) {
+    page.push(
+      list(
+        [
+          [
+            text("LoadGreenPage.Item"),
+            mon.item
+              ? data.itemName(mon.item)
+              : text("LoadGreenPage.ThreeDashes"),
+          ],
+          ...mon.moves.flatMap((move, index): [string, string][] =>
+            move
+              ? [
+                  [
+                    index ? "" : text("LoadGreenPage.Move"),
+                    `${data.moveName(move)}  PP ${mon.pp[index] & 63}/${maxPP(data, move, mon.pp[index] >> 6) & 63}`,
+                  ],
+                ]
+              : [],
+          ),
+        ],
+        true,
+      ),
+    );
+  } else {
+    // The OT's gender comes from the caught data unless it is unset.
+    const caught = mon.caughtData & 0xff;
+    const otGender =
+      !caught || caught === 0x7f ? "" : caught & 0x80 ? "♀" : "♂";
+    const labels = data.statNames();
+    page.push(
+      list([
+        [text("IDNoString"), String(mon.otId).padStart(5, "0")],
+        [text("OTString"), `${mon.ot}${otGender}`],
+      ]),
+      list(
+        labels.map((label, index): [string, string] => [
+          label,
+          String(mon.stats[[1, 2, 4, 5, 3][index]]),
+        ]),
+      ),
+    );
+  }
+  get("stats-page").replaceChildren(...page);
+  panel.dataset.page = String(statsView.page);
+  get("stats-page-number").textContent = `${statsView.page + 1} / 3`;
+}
 function setHp(bar: HTMLElement, hp: number, max: number) {
   const fraction = max ? hp / max : 0;
   bar.style.width = `${Math.round(fraction * 100)}%`;
@@ -1067,3 +1240,17 @@ get("town-map-close").onclick = () => {
   runtime.advanceDialogue();
   canvas.focus({ preventScroll: true });
 };
+for (const [id, turn] of [
+  ["stats-prev", 2],
+  ["stats-next", 1],
+  ["stats-close", 0],
+] as const)
+  get(id).onclick = () => {
+    const world = runtime.world;
+    if (session.state !== "playing" || !statsView || !world) return;
+    if (turn) statsView.page = (statsView.page + turn) % 3;
+    else if (statsView.slot === undefined) runtime.advanceDialogue();
+    else statsView = partyChoice = undefined;
+    showWorld(world);
+    canvas.focus({ preventScroll: true });
+  };