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js/managers/BuffManager.js

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+/**
+ * BuffManager.js
+ * Manages pre-game buff purchases and activation.
+ * Buffs are one-time per round: Shield (100g) and Double Fire (150g).
+ */
+
+/** Buff type definitions. */
+const BUFF_TYPE = {
+  SHIELD: 'SHIELD',
+  DOUBLE_FIRE: 'DOUBLE_FIRE',
+};
+
+/** Buff cost in gold. */
+const BUFF_COST = {
+  [BUFF_TYPE.SHIELD]: 100,
+  [BUFF_TYPE.DOUBLE_FIRE]: 150,
+};
+
+/** Double fire duration in seconds. */
+const DOUBLE_FIRE_DURATION = 10;
+
+class BuffManager {
+  constructor() {
+    /** @type {Set<string>} Active buffs for the current round. */
+    this._activeBuffs = new Set();
+
+    /** @type {number} Remaining double fire time in seconds. */
+    this._doubleFireTimer = 0;
+
+    /** @type {boolean} Whether shield is currently active. */
+    this._shieldActive = false;
+  }
+
+  // ============================================================
+  // Purchase
+  // ============================================================
+
+  /**
+   * Purchase a buff for the upcoming round.
+   * Deducts gold via CurrencyManager.
+   * @param {string} buffType - One of BUFF_TYPE values.
+   * @returns {{ success: boolean, error?: string }}
+   */
+  purchaseBuff(buffType) {
+    const cost = BUFF_COST[buffType];
+    if (cost === undefined) {
+      return { success: false, error: 'Invalid buff type' };
+    }
+
+    if (this._activeBuffs.has(buffType)) {
+      return { success: false, error: 'Already purchased' };
+    }
+
+    const cm = GameGlobal.currencyManager;
+    if (!cm || !cm.hasGold(cost)) {
+      return { success: false, error: 'Insufficient gold' };
+    }
+
+    const spent = cm.spendGold(cost);
+    if (!spent) {
+      return { success: false, error: 'Insufficient gold' };
+    }
+
+    this._activeBuffs.add(buffType);
+    console.log(`[BuffManager] Purchased buff: ${buffType} for ${cost} gold`);
+
+    // Emit event
+    try {
+      if (GameGlobal.eventBus) {
+        GameGlobal.eventBus.emit('buff:purchased', { type: buffType, cost });
+      }
+    } catch (e) {}
+
+    return { success: true };
+  }
+
+  // ============================================================
+  // Activation & Game Logic
+  // ============================================================
+
+  /**
+   * Check if a buff was purchased for this round.
+   * @param {string} buffType
+   * @returns {boolean}
+   */
+  hasBuff(buffType) {
+    return this._activeBuffs.has(buffType);
+  }
+
+  /**
+   * Get all active buffs for this round.
+   * @returns {string[]}
+   */
+  getActiveBuffs() {
+    return Array.from(this._activeBuffs);
+  }
+
+  /**
+   * Activate buffs at the start of a round.
+   * Should be called when the game scene initializes.
+   * @param {object} playerTank - The player tank instance.
+   */
+  activateBuffs(playerTank) {
+    if (!playerTank) return;
+
+    // Shield buff: add a shield layer to the player tank
+    if (this._activeBuffs.has(BUFF_TYPE.SHIELD)) {
+      this._shieldActive = true;
+      playerTank._buffShield = true;
+      console.log('[BuffManager] Shield buff activated');
+    }
+
+    // Double fire buff: start the timer
+    if (this._activeBuffs.has(BUFF_TYPE.DOUBLE_FIRE)) {
+      this._doubleFireTimer = DOUBLE_FIRE_DURATION;
+      playerTank._buffDoubleFire = true;
+      console.log('[BuffManager] Double fire buff activated');
+    }
+  }
+
+  /**
+   * Update buff timers. Called every frame from GameScene.
+   * @param {number} dt - Delta time in seconds.
+   * @param {object} playerTank - The player tank instance.
+   */
+  update(dt, playerTank) {
+    if (!playerTank) return;
+
+    // Double fire timer countdown
+    if (this._doubleFireTimer > 0) {
+      this._doubleFireTimer -= dt;
+      if (this._doubleFireTimer <= 0) {
+        this._doubleFireTimer = 0;
+        playerTank._buffDoubleFire = false;
+        console.log('[BuffManager] Double fire buff expired');
+      }
+    }
+  }
+
+  /**
+   * Consume the shield buff (called when player takes damage).
+   * @param {object} playerTank - The player tank instance.
+   * @returns {boolean} True if shield was consumed (damage absorbed).
+   */
+  consumeShield(playerTank) {
+    if (this._shieldActive && playerTank && playerTank._buffShield) {
+      this._shieldActive = false;
+      playerTank._buffShield = false;
+      console.log('[BuffManager] Shield buff consumed');
+
+      // Emit event for visual feedback
+      try {
+        if (GameGlobal.eventBus) {
+          GameGlobal.eventBus.emit('buff:shield:consumed');
+        }
+      } catch (e) {}
+
+      return true;
+    }
+    return false;
+  }
+
+  /**
+   * Check if double fire is currently active.
+   * @returns {boolean}
+   */
+  isDoubleFireActive() {
+    return this._doubleFireTimer > 0;
+  }
+
+  /**
+   * Get remaining double fire time in seconds.
+   * @returns {number}
+   */
+  getDoubleFireRemaining() {
+    return Math.max(0, this._doubleFireTimer);
+  }
+
+  /**
+   * Check if shield buff is still active (not yet consumed).
+   * @returns {boolean}
+   */
+  isShieldActive() {
+    return this._shieldActive;
+  }
+
+  // ============================================================
+  // Round Lifecycle
+  // ============================================================
+
+  /**
+   * Clear all buffs at the end of a round.
+   * Must be called when the game ends (win or lose).
+   */
+  clearBuffs() {
+    this._activeBuffs.clear();
+    this._doubleFireTimer = 0;
+    this._shieldActive = false;
+    console.log('[BuffManager] All buffs cleared');
+  }
+
+  /**
+   * Get buff cost.
+   * @param {string} buffType
+   * @returns {number}
+   */
+  getBuffCost(buffType) {
+    return BUFF_COST[buffType] || 0;
+  }
+}
+
+// Export constants
+BuffManager.BUFF_TYPE = BUFF_TYPE;
+BuffManager.BUFF_COST = BUFF_COST;
+BuffManager.DOUBLE_FIRE_DURATION = DOUBLE_FIRE_DURATION;
+
+module.exports = BuffManager;