Port the fishing rods and wild Magikarp

The Old, Good and Super Rods run FishFunction facing water: the map's fish
group and Fish pick no fish, no bite, or a Pokémon from FishGroups and the
time of day's TimeFishGroups. The player casts and jiggles with the
fishing frames drawn from LoadFishingGFX's tiles, shows "!" on a bite, and
the hooked Pokémon attacks as BATTLETYPE_FISH. Facing pieces now use
signed offsets, which the rod above and left of the player needs.

Wild Magikarp no longer stop a battle: LoadEnemyMon redraws their DVs
through CalcMagikarpLength and its filters, as the original does. The
length routine matches the original in the reference emulator.

Part of #27

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

src/game/world/world.ts

@@ -61,6 +61,7 @@ import {
   type MenuFieldMove,
 } from "../scripts/start-menu";
 import { PartyEvolution } from "../scripts/evolution";
+import { fish } from "../scripts/fish";
 import type { MovementPose, MovementStep } from "../scripts/movement";
 import { emptyBag, validBag, type Bag, type ItemSlot } from "../party/bag";
 import {
@@ -211,6 +212,9 @@ interface Actor {
   hidden: boolean;
   fixedFacing: boolean;
   moved: boolean;
+  /** OBJECT_ACTION_FISHING, from fish_cast_rod or fish_got_bite until
+   * PutTheRodAway: the fishing frames replace the standing ones. */
+  fishing?: boolean;
   /** HandleNPCStep state for map objects: OBJECT_INIT_X/Y, the step type
    * and OBJECT_STEP_DURATION. "reset" runs the movement function next. */
   npc?: {
@@ -476,6 +480,8 @@ const forcedDirection = (tile: number): Direction | undefined => {
 const TURN_WAIT_TICKS = 3;
 /** STEP_BIKE: 4 ticks at 4 pixels per tick (bikes and ice). */
 const BIKE_TICKS = 4;
+/** The emote bubble's first tile (Emotes' vTiles0 tile $f8). */
+const EMOTE_BUBBLE_TILE = 0xf8;
 /** BGEVENT_ITEM: a hidden item's bg_event (constants/script_constants.asm). */
 const BGEVENT_ITEM = 7;
 /** An object's state as LoadMapObjects creates it from the map data. */
@@ -653,6 +659,9 @@ export class GameWorld {
   /** ShakeHeadbuttTree while it plays: the facing square and the frames
    * shown. */
   private shakingTree?: { x: number; y: number; frames: number };
+  /** The EMOTE_* whose graphics are in the emote bubble's tiles, which
+   * show_emote displays. */
+  private bubbleEmote = 0;
 
   constructor(
     readonly assets: CrystalAssets,
@@ -877,7 +886,9 @@ export class GameWorld {
         : {};
       const posed = actor.pose && this.posePresentation(actor.pose);
       const poseFacing =
-        actor.pose?.pose === "fish-bite" || actor.pose?.pose === "fish-cast"
+        actor.pose?.pose === "fish-bite" ||
+        actor.pose?.pose === "fish-cast" ||
+        (!actor.pose && actor.fishing)
           ? 0x10 + DIRECTION_ORDER.indexOf(actor.direction)
           : actor.pose?.pose === "tree"
             ? FACING_WEIRD_TREE_0 + ((actor.stepFrame >> 2) & 3)
@@ -1977,6 +1988,34 @@ export class GameWorld {
       facingObject: () => this.facingObject(),
     };
   }
+  /** FishFunction with rod 0-2 (Old, Good, Super): never while surfing,
+   * and only facing water (the facing tile may hold an object, as in the
+   * original). The map's fish group decides the script: nothing at all,
+   * no bite, or a bite with the hooked Pokémon. A failure (.FailFish)
+   * prints nothing before Oak's warning. */
+  private fishFunction(state: ScriptState, rod: number): MenuFieldMove {
+    const surfing =
+      state.playerState === OW.PLAYER_SURF ||
+      state.playerState === OW.PLAYER_SURF_PIKA;
+    const [dx, dy] = VECTORS[this.player.direction];
+    const tile =
+      this.assets.collision(this.map, this.player.x + dx, this.player.y + dy) ?? 0;
+    if (surfing || this.assets.permission(tile) !== OW.WATER_TILE)
+      return { texts: [] };
+    const fieldMove = { mon: 0 },
+      group = this.map.fishGroup;
+    if (!group) return { script: OVERWORLD.Script_NotEvenANibble2, fieldMove };
+    const hooked = fish(
+      this.assets.reader,
+      group,
+      rod,
+      this.clockTimeOfDay,
+      () => this.random() & 0xff,
+    );
+    return hooked
+      ? { script: OVERWORLD.Script_GotABite, fieldMove, wild: hooked, fish: true }
+      : { script: OVERWORLD.Script_NotEvenANibble, fieldMove };
+  }
   /** GetFacingObject: the visible object on the tile the player faces. */
   private facingObject() {
     const [dx, dy] = VECTORS[this.player.direction];
@@ -2021,8 +2060,11 @@ export class GameWorld {
       callerScript,
       fieldMove,
       usedItem,
+      fish,
     }: {
       usedItem?: number;
+      /** BATTLETYPE_FISH, set by FishFunction for a hooked Pokémon. */
+      fish?: boolean;
       fieldMove?: FieldMoveContext;
       committedPosition?: { x: number; y: number };
       scene?: boolean;
@@ -2055,6 +2097,7 @@ export class GameWorld {
           callerScript,
           fieldMove,
           usedItem,
+          fish,
         },
       ),
       committed,
@@ -2126,6 +2169,7 @@ export class GameWorld {
           landmarkOf: (mapId) => this.assets.map(mapId).landmark,
           gameTime: () => this.gameTime,
           hiddenItemOnScreen: (state) => this.hiddenItemOnScreen(state),
+          fish: (state, rod) => this.fishFunction(state, rod),
         },
         this.menuCursors,
         select,
@@ -2321,6 +2365,7 @@ export class GameWorld {
       case "emote":
         // ShowEmoteScript: show (1 tick), pause N ticks, hide (1 tick).
         this.emote = { object: effect.object, emote: effect.emote };
+        this.bubbleEmote = effect.emote;
         script.waitTicks = effect.ticks + 2;
         return true;
       case "pause":
@@ -2376,6 +2421,8 @@ export class GameWorld {
           trainer,
           canLose: effect.canLose,
           tree: effect.tree,
+          fish: effect.fish,
+          mapId: this.mapId,
           text: () => this.host(PLAYER).text(),
           bag: draft.bag,
           storage: draft.storage,
@@ -2419,6 +2466,15 @@ export class GameWorld {
         this.flight = { ...effect, frames: 0 };
         script.waitTicks = effect.landing ? 33 : 65;
         return true;
+      case "loademote":
+        // Emotes bound for the bubble's tiles ($f8) replace its graphics;
+        // the others (the rod, the shadow, dust) go elsewhere.
+        if (this.assets.emoteTile(effect.emote) === EMOTE_BUBBLE_TILE)
+          this.bubbleEmote = effect.emote;
+        return false;
+      case "putrodaway":
+        this.player.fishing = false;
+        return false;
       case "headbutt": {
         const [dx, dy] = VECTORS[this.player.direction];
         this.shakingTree = {
@@ -2663,6 +2719,8 @@ export class GameWorld {
         return true;
       case "pose":
         actor.pose = this.startPose(actor, step.pose);
+        if (step.pose === "fish-cast" || step.pose === "fish-bite")
+          actor.fishing = true;
         if (step.pose === "tree") actor.stepFrame = (actor.stepFrame + 1) & 15;
         movement.wait = step.ticks;
         return true;
@@ -2680,7 +2738,7 @@ export class GameWorld {
         return false;
       case "emote":
         this.emote = step.shown
-          ? { object: id, emote: this.emote?.emote ?? 0 }
+          ? { object: id, emote: this.bubbleEmote }
           : undefined;
         return false;
       case "shake":
@@ -2945,6 +3003,7 @@ export class GameWorld {
               usedItem: script.run.deferredItem,
               fieldMove: script.run.deferredMove?.fieldMove,
               wild: script.run.deferredMove?.wild,
+              fish: script.run.deferredMove?.fish,
             }
           : {},
       );