tankwar_proj/js/entities/Bullet.js

/**
 * Bullet.js
 * Bullet entity that travels in a straight line and interacts with terrain/tanks.
 */

const {
  BULLET_SPEED,
  BULLET_SIZE,
  DIRECTION,
  DIR_VECTORS,
  MAP_OFFSET_X,
  MAP_OFFSET_Y,
  MAP_WIDTH,
  MAP_HEIGHT,
} = require('../base/GameGlobal');

class Bullet {
  constructor() {
    this.x = 0;
    this.y = 0;
    this.direction = DIRECTION.UP;
    this.speed = BULLET_SPEED;
    this.size = BULLET_SIZE;
    this.halfSize = BULLET_SIZE / 2;
    this.alive = false;
    this.canBreakSteel = false;

    /** @type {'player'|'enemy'} */
    this.owner = 'player';
    /** @type {object|null} Reference to the tank that fired this bullet */
    this.ownerTank = null;
  }

  /**
   * Initialize/reset the bullet for reuse from object pool.
   * @param {object} config
   * @param {number} config.x
   * @param {number} config.y
   * @param {number} config.direction
   * @param {string} config.owner - 'player' or 'enemy'
   * @param {boolean} [config.canBreakSteel]
   * @param {object} [config.ownerTank]
   */
  init(config) {
    this.x = config.x;
    this.y = config.y;
    this.direction = config.direction;
    this.owner = config.owner || 'player';
    this.canBreakSteel = config.canBreakSteel || false;
    this.ownerTank = config.ownerTank || null;
    this.alive = true;
  }

  /**
   * Update bullet position.
   * @param {number} dt - Delta time in seconds.
   */
  update(dt) {
    if (!this.alive) return;

    const vec = DIR_VECTORS[this.direction];
    const moveAmount = this.speed * dt * 60;

    this.x += vec.dx * moveAmount;
    this.y += vec.dy * moveAmount;

    // Check map boundaries
    if (
      this.x < MAP_OFFSET_X ||
      this.y < MAP_OFFSET_Y ||
      this.x > MAP_OFFSET_X + MAP_WIDTH ||
      this.y > MAP_OFFSET_Y + MAP_HEIGHT
    ) {
      this.destroy();
    }
  }

  /**
   * Render the bullet.
   * In team battle mode, bullet color is determined by the _isAlly flag
   * set by the scene: ally = bright yellow, enemy = red.
   * In single-player / PVE mode, owner-based colors are used.
   * @param {CanvasRenderingContext2D} ctx
   */
  render(ctx) {
    if (!this.alive) return;

    let fillColor;
    if (this._isAlly !== undefined) {
      // Team mode: use team-aware coloring
      fillColor = this._isAlly ? '#FFFF00' : '#FF4444';
    } else {
      // Single-player / PVE fallback
      fillColor = this.owner === 'player' ? '#FFFF00' : '#FF6600';
    }

    ctx.fillStyle = fillColor;
    ctx.fillRect(
      this.x - this.halfSize,
      this.y - this.halfSize,
      this.size,
      this.size
    );
  }

  /**
   * Get bounding box.
   * @returns {{x: number, y: number, w: number, h: number}}
   */
  getBounds() {
    return {
      x: this.x - this.halfSize,
      y: this.y - this.halfSize,
      w: this.size,
      h: this.size,
    };
  }

  /**
   * Destroy the bullet (mark for recycling).
   */
  destroy() {
    this.alive = false;
    // Decrement owner's active bullet count
    if (this.ownerTank && typeof this.ownerTank.activeBullets === 'number') {
      this.ownerTank.activeBullets = Math.max(0, this.ownerTank.activeBullets - 1);
    }
  }
}

module.exports = Bullet;