import { System } from '../ecs/System.js';
import { Score } from '../components/Score.js';
import { Health } from '../components/Health.js';
import { SoundEvent } from '../components/SoundEvent.js';
import { Collidable } from '../components/Collidable.js';
import { GameConfig } from '../game/GameConfig.js';

/**
 * GameStateSystem - manages game state (score, combo, health regen, difficulty)
 * Operates on a singleton Score component
 */
export class GameStateSystem extends System {
  constructor(entityFactory) {
    super();
    
    /** @type {import('../game/EntityFactory.js').EntityFactory} */
    this.entityFactory = entityFactory;
    
    /** @type {import('../ecs/World.js').EntityId|null} Reference to player entity */
    this.playerEntity = null;
    
    /** @type {number} Last time obstacle was added */
    this.lastDifficultyTime = 0;
  }

  /**
   * Set player entity reference
   * @param {import('../ecs/World.js').EntityId} entityId
   */
  setPlayerEntity(entityId) {
    this.playerEntity = entityId;
  }

  /**
   * Initialize - create score entity and load high score
   */
  init() {
    const scoreEntity = this.world.createEntity();
    const score = new Score();
    score.highScore = this.loadHighScore();
    this.world.addComponent(scoreEntity, score);
  }

  /**
   * Update - manages combo timer, health regen, difficulty scaling
   * @param {number} deltaTime
   */
  update(deltaTime) {
    const scoreEntity = this.getScoreEntity();
    const score = this.getComponent(scoreEntity, Score);
    if (!score) return;

    // Update combo timer
    score.comboTimer = Math.max(0, score.comboTimer - deltaTime);
    if (score.comboTimer <= 0 && score.comboMultiplier > 1) {
      score.comboMultiplier = 1;
    }

    // Update health regeneration
    // Health regen is handled here but could be a separate component
    // For simplicity, we'll check player health directly
    if (this.playerEntity) {
      const health = this.getComponent(this.playerEntity, Health);
      if (health && health.currentHealth < health.maxHealth) {
        // Simple approach: heal every interval
        // In a more complex system, this would be a HealthRegen component
        const currentTime = performance.now() / 1000;
        if (!this.lastHealthRegenTime) {
          this.lastHealthRegenTime = currentTime;
        }
        
        if (currentTime - this.lastHealthRegenTime >= GameConfig.HEALTH_REGEN_INTERVAL) {
          health.heal(GameConfig.HEALTH_REGEN_AMOUNT);
          const healthRegenEntity = this.world.createEntity();
          this.world.addComponent(healthRegenEntity, new SoundEvent('health'));
          this.lastHealthRegenTime = currentTime;
        }
      }
    }

    // Update difficulty scaling
    const currentTime = performance.now() / 1000;
    
    // Check score-based difficulty
    const obstacles = this.getEntities(Collidable).filter(id => {
      const collidable = this.getComponent(id, Collidable);
      return collidable && collidable.layer === 'obstacle';
    });
    
    if (score.score - (score.lastDifficultyScore || 0) >= GameConfig.DIFFICULTY_SCORE_INTERVAL &&
        obstacles.length < GameConfig.MAX_OBSTACLES) {
      this.entityFactory.createObstacle();
      score.lastDifficultyScore = score.score;
    }

    // Check time-based difficulty
    if (currentTime - this.lastDifficultyTime >= GameConfig.DIFFICULTY_TIME_INTERVAL) {
      if (obstacles.length < GameConfig.MAX_OBSTACLES) {
        this.entityFactory.createObstacle();
        this.lastDifficultyTime = currentTime;
      }
    }
  }

  /**
   * Reset game state
   */
  reset() {
    const scoreEntity = this.getScoreEntity();
    const score = this.getComponent(scoreEntity, Score);
    if (score) {
      score.score = 0;
      score.comboMultiplier = 1;
      score.comboTimer = 0;
      score.lastCoinTime = 0;
      score.lastDifficultyScore = 0;
    }
    this.lastDifficultyTime = 0;
    this.lastHealthRegenTime = 0;
  }

  /**
   * Get score entity (singleton)
   * @private
   */
  getScoreEntity() {
    const scoreEntities = this.getEntities(Score);
    if (scoreEntities.length > 0) {
      return scoreEntities[0];
    }
    // Create if doesn't exist
    const entity = this.world.createEntity();
    this.world.addComponent(entity, new Score());
    return entity;
  }

  /**
   * Load high score from localStorage
   * @private
   */
  loadHighScore() {
    try {
      const saved = localStorage.getItem(GameConfig.STORAGE_HIGH_SCORE);
      return saved ? parseInt(saved, 10) : 0;
    } catch (error) {
      console.debug('Failed to load high score:', error);
      return 0;
    }
  }
}