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jakciehan
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/**
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* EnemyTank.js
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* Enemy tank with AI behavior: patrol, chase, and attack states.
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*/
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const Tank = require('./Tank');
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const {
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TANK_TYPE,
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TANK_CONFIG,
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DIRECTION,
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DIR_VECTORS,
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GRID_COLS,
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GRID_ROWS,
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TILE_SIZE,
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MAP_OFFSET_X,
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MAP_OFFSET_Y,
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} = require('../base/GameGlobal');
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/** AI States */
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const AI_STATE = {
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PATROL: 'patrol',
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CHASE: 'chase',
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ATTACK: 'attack',
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};
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class EnemyTank extends Tank {
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/**
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* @param {object} params
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* @param {string} params.type - TANK_TYPE enum value.
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* @param {number} params.col - Spawn grid column.
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* @param {number} params.row - Spawn grid row.
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* @param {number} [params.levelNum] - Current level number (affects AI).
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* @param {boolean} [params.hasPowerUp] - Whether destroying this tank drops a power-up.
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*/
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constructor(params) {
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const cfg = TANK_CONFIG[params.type];
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const spawnX = MAP_OFFSET_X + params.col * TILE_SIZE + TILE_SIZE / 2;
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const spawnY = MAP_OFFSET_Y + params.row * TILE_SIZE + TILE_SIZE / 2;
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const speedMul = params.speedMultiplier || 1;
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super({
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x: spawnX,
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y: spawnY,
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speed: cfg.speed * speedMul,
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hp: cfg.hp,
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color: cfg.color,
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size: cfg.size,
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direction: DIRECTION.DOWN,
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});
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this.type = params.type;
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this.score = cfg.score || 100;
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this.hasPowerUp = params.hasPowerUp || false;
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this.levelNum = params.levelNum || 1;
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// AI state
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this._aiState = AI_STATE.PATROL;
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this._moveTimer = 0;
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this._dirChangeInterval = 1.5 + Math.random() * 2; // seconds
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this._shootTimer = 0;
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this._shootInterval = 1 + Math.random() * 1.5; // seconds
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this._stuckTimer = 0;
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this._lastX = spawnX;
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this._lastY = spawnY;
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// Frozen state (from clock power-up)
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this.frozen = false;
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// Active bullets tracking
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this.activeBullets = 0;
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this._maxBullets = params.type === TANK_TYPE.ENEMY_BOSS ? 2 : 1;
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// HP indicator blink for armored tanks
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this._hitBlink = 0;
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}
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/**
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* Update enemy tank AI and state.
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* @param {number} dt - Delta time in seconds.
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* @param {MapManager} mapManager
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* @param {{x: number, y: number}} basePos - Base position for targeting.
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* @param {Function} onShoot - Callback to fire a bullet.
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*/
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update(dt, mapManager, basePos, onShoot) {
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if (!this.alive || this.frozen) return;
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// Hit blink effect
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if (this._hitBlink > 0) {
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this._hitBlink -= dt;
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}
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// Movement AI
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this._moveTimer += dt;
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this._shootTimer += dt;
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// Check if stuck
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const moved = Math.abs(this.x - this._lastX) + Math.abs(this.y - this._lastY);
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if (moved < 0.5) {
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this._stuckTimer += dt;
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} else {
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this._stuckTimer = 0;
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}
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this._lastX = this.x;
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this._lastY = this.y;
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// Determine AI behavior based on level
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if (this.levelNum >= 10 && this.type !== TANK_TYPE.ENEMY_NORMAL) {
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this._aiState = AI_STATE.CHASE;
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} else if (Math.random() < 0.3) {
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this._aiState = AI_STATE.CHASE;
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} else {
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this._aiState = AI_STATE.PATROL;
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}
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// Direction change
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if (this._moveTimer >= this._dirChangeInterval || this._stuckTimer > 0.5) {
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this._moveTimer = 0;
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this._stuckTimer = 0;
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this._chooseDirection(mapManager, basePos);
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}
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// Move
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this.move(this.direction, dt, mapManager);
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// Shoot
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if (this._shootTimer >= this._shootInterval) {
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this._shootTimer = 0;
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this._shootInterval = 0.8 + Math.random() * 1.5;
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if (this.activeBullets < this._maxBullets && onShoot) {
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onShoot(this);
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}
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}
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}
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/**
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* Choose a new direction based on AI state.
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* @private
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*/
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_chooseDirection(mapManager, basePos) {
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if (this._aiState === AI_STATE.CHASE && basePos) {
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// Move towards base
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this._chaseTarget(basePos, mapManager);
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} else {
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// Random patrol
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this._randomDirection(mapManager);
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}
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}
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/**
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* Chase a target position (usually the base).
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* @private
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*/
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_chaseTarget(target, mapManager) {
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const dx = target.x - this.x;
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const dy = target.y - this.y;
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// Prefer the axis with greater distance
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const dirs = [];
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if (Math.abs(dy) > Math.abs(dx)) {
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dirs.push(dy > 0 ? DIRECTION.DOWN : DIRECTION.UP);
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dirs.push(dx > 0 ? DIRECTION.RIGHT : DIRECTION.LEFT);
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} else {
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dirs.push(dx > 0 ? DIRECTION.RIGHT : DIRECTION.LEFT);
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dirs.push(dy > 0 ? DIRECTION.DOWN : DIRECTION.UP);
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}
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// Add random alternatives for variety
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const allDirs = [DIRECTION.UP, DIRECTION.DOWN, DIRECTION.LEFT, DIRECTION.RIGHT];
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for (const d of allDirs) {
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if (!dirs.includes(d)) dirs.push(d);
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}
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// Try each direction, pick the first that isn't immediately blocked
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for (const dir of dirs) {
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const vec = DIR_VECTORS[dir];
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const testX = this.x + vec.dx * TILE_SIZE;
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const testY = this.y + vec.dy * TILE_SIZE;
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const left = testX - this.halfSize;
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const top = testY - this.halfSize;
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if (!mapManager.rectCollidesWithTerrain(left, top, this.size, this.size)) {
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this.direction = dir;
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return;
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}
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}
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// Fallback: random
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this.direction = allDirs[Math.floor(Math.random() * allDirs.length)];
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}
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/**
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* Choose a random direction.
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* @private
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*/
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_randomDirection(mapManager) {
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const dirs = [DIRECTION.UP, DIRECTION.DOWN, DIRECTION.LEFT, DIRECTION.RIGHT];
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// Bias towards down (towards base) 40% of the time
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if (Math.random() < 0.4) {
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this.direction = DIRECTION.DOWN;
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return;
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}
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this.direction = dirs[Math.floor(Math.random() * dirs.length)];
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}
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/**
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* Override takeDamage to add hit blink.
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*/
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takeDamage(amount = 1) {
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this._hitBlink = 0.15;
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return super.takeDamage(amount);
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}
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/**
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* Render with HP indicator for armored tanks.
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* @param {CanvasRenderingContext2D} ctx
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*/
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render(ctx) {
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if (!this.alive) return;
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// Hit blink effect
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if (this._hitBlink > 0) {
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ctx.save();
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ctx.globalAlpha = 0.5;
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super.render(ctx);
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ctx.restore();
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} else {
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super.render(ctx);
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}
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// Power-up indicator (flashing border)
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if (this.hasPowerUp) {
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ctx.save();
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ctx.strokeStyle = '#FF0000';
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ctx.lineWidth = 2;
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const blink = Math.sin(Date.now() / 150) > 0;
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if (blink) {
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ctx.strokeRect(
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this.x - this.halfSize - 2,
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this.y - this.halfSize - 2,
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this.size + 4,
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this.size + 4
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);
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}
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ctx.restore();
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}
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// HP bar for armored/boss tanks
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if (this.maxHp > 1) {
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const barW = this.size;
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const barH = 3;
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const barX = this.x - this.halfSize;
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const barY = this.y - this.halfSize - 6;
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ctx.fillStyle = '#333333';
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ctx.fillRect(barX, barY, barW, barH);
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ctx.fillStyle = this.hp > this.maxHp * 0.3 ? '#00FF00' : '#FF0000';
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ctx.fillRect(barX, barY, barW * (this.hp / this.maxHp), barH);
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}
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}
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/** Whether this enemy can fire. */
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canFire() {
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return this.alive && !this.frozen && this.activeBullets < this._maxBullets;
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}
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}
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module.exports = EnemyTank;
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