Add state module with combat init, draw, play, end turn

src/effects.js

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+export function resolveEffects(state) {
+  return state;
+}

src/enemies.js

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+import enemyDb from "../data/enemies.json";
+
+export function getEnemy(id) {
+  return enemyDb[id];
+}

src/state.js

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+import { getCard, getStarterDeck } from "./cards.js";
+import { resolveEffects } from "./effects.js";
+import { getEnemy } from "./enemies.js";
+
+export function createCombatState(character, enemyId) {
+  const enemy = getEnemy(enemyId);
+  return {
+    player: {
+      hp: 11,
+      maxHp: 11,
+      energy: 3,
+      maxEnergy: 3,
+      block: 0,
+      strength: 0,
+      vulnerable: 0,
+      weak: 0,
+      drawPile: shuffle([...getStarterDeck(character)]),
+      hand: [],
+      discardPile: [],
+      exhaustPile: [],
+      powers: [],
+    },
+    enemy: {
+      id: enemy.id,
+      name: enemy.name,
+      hp: enemy.hp,
+      maxHp: enemy.hp,
+      block: 0,
+      strength: 0,
+      vulnerable: 0,
+      weak: 0,
+      actionType: enemy.actionType,
+      actions: enemy.actions,
+      actionTrack: enemy.actionTrack || null,
+      trackPosition: 0,
+    },
+    combat: {
+      turn: 1,
+      phase: "player_turn",
+      dieResult: null,
+      selectedCard: null,
+      log: [],
+    },
+  };
+}
+
+export function drawCards(state, count) {
+  let drawPile = [...state.player.drawPile];
+  let discardPile = [...state.player.discardPile];
+  const hand = [...state.player.hand];
+
+  for (let i = 0; i < count; i++) {
+    if (drawPile.length === 0) {
+      drawPile = shuffle(discardPile);
+      discardPile = [];
+    }
+    if (drawPile.length > 0) {
+      hand.push(drawPile.pop());
+    }
+  }
+
+  return {
+    ...state,
+    player: { ...state.player, drawPile, hand, discardPile },
+  };
+}
+
+export function playCard(state, handIndex) {
+  const cardId = state.player.hand[handIndex];
+  const card = getCard(cardId);
+  if (state.player.energy < card.cost) return null;
+
+  const hand = [...state.player.hand];
+  hand.splice(handIndex, 1);
+  const discardPile = [...state.player.discardPile, cardId];
+  const energy = state.player.energy - card.cost;
+
+  let next = {
+    ...state,
+    player: { ...state.player, hand, discardPile, energy },
+  };
+
+  next = resolveEffects(next, card.effects, "player", "enemy");
+  return next;
+}
+
+export function endTurn(state) {
+  return {
+    ...state,
+    player: {
+      ...state.player,
+      hand: [],
+      discardPile: [...state.player.discardPile, ...state.player.hand],
+    },
+    combat: { ...state.combat, phase: "enemy_turn" },
+  };
+}
+
+function shuffle(arr) {
+  const a = [...arr];
+  for (let i = a.length - 1; i > 0; i--) {
+    const j = Math.floor(Math.random() * (i + 1));
+    [a[i], a[j]] = [a[j], a[i]];
+  }
+  return a;
+}

src/state.test.js

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+import { describe, expect, test } from "bun:test";
+import { createCombatState, drawCards, endTurn, playCard } from "./state.js";
+
+describe("createCombatState", () => {
+  test("creates initial state with shuffled deck and correct values", () => {
+    const state = createCombatState("ironclad", "jaw_worm");
+    expect(state.player.hp).toBe(11);
+    expect(state.player.maxHp).toBe(11);
+    expect(state.player.energy).toBe(3);
+    expect(state.player.block).toBe(0);
+    expect(state.player.strength).toBe(0);
+    expect(state.player.hand).toHaveLength(0);
+    expect(state.player.drawPile).toHaveLength(10);
+    expect(state.enemy.name).toBe("Jaw Worm");
+    expect(state.enemy.hp).toBeGreaterThan(0);
+    expect(state.combat.turn).toBe(1);
+    expect(state.combat.phase).toBe("player_turn");
+  });
+});
+
+describe("drawCards", () => {
+  test("moves cards from draw pile to hand", () => {
+    const state = createCombatState("ironclad", "jaw_worm");
+    const next = drawCards(state, 5);
+    expect(next.player.hand).toHaveLength(5);
+    expect(next.player.drawPile).toHaveLength(5);
+  });
+
+  test("shuffles discard into draw when draw pile runs out", () => {
+    let state = createCombatState("ironclad", "jaw_worm");
+    state = {
+      ...state,
+      player: {
+        ...state.player,
+        drawPile: state.player.drawPile.slice(0, 2),
+        discardPile: state.player.drawPile.slice(2),
+      },
+    };
+    const next = drawCards(state, 5);
+    expect(next.player.hand).toHaveLength(5);
+    expect(next.player.discardPile).toHaveLength(0);
+  });
+});
+
+describe("playCard", () => {
+  test("deducts energy and moves card to discard", () => {
+    let state = createCombatState("ironclad", "jaw_worm");
+    state = drawCards(state, 5);
+    const cardIndex = state.player.hand.indexOf("strike_r");
+    const next = playCard(state, cardIndex);
+    expect(next.player.energy).toBe(2);
+    expect(next.player.hand).toHaveLength(4);
+  });
+
+  test("returns null if not enough energy", () => {
+    let state = createCombatState("ironclad", "jaw_worm");
+    state = drawCards(state, 5);
+    state = { ...state, player: { ...state.player, energy: 0 } };
+    const cardIndex = state.player.hand.indexOf("strike_r");
+    const result = playCard(state, cardIndex);
+    expect(result).toBeNull();
+  });
+});
+
+describe("endTurn", () => {
+  test("discards hand and switches to enemy phase", () => {
+    let state = createCombatState("ironclad", "jaw_worm");
+    state = drawCards(state, 5);
+    const next = endTurn(state);
+    expect(next.player.hand).toHaveLength(0);
+    expect(next.player.discardPile.length).toBeGreaterThan(0);
+    expect(next.combat.phase).toBe("enemy_turn");
+  });
+});