tankwar_proj/js/managers/BuffManager.js

/**
 * 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;