slime/src/systems/InputSystem.ts

import { System } from '../core/System.ts';
import { SystemName } from '../core/Constants.ts';
import type { Engine } from '../core/Engine.ts';
import type { Entity } from '../core/Entity.ts';

interface MouseState {
  x: number;
  y: number;
  buttons: Record<number, boolean>;
  buttonsPrevious: Record<number, boolean>;
}

/**
 * System responsible for capturing and managing keyboard and mouse input.
 */
export class InputSystem extends System {
  keys: Record<string, boolean>;
  keysPrevious: Record<string, boolean>;
  mouse: MouseState;

  constructor() {
    super(SystemName.INPUT);
    this.requiredComponents = [];
    this.priority = 0;

    this.keys = {};
    this.keysPrevious = {};
    this.mouse = {
      x: 0,
      y: 0,
      buttons: {},
      buttonsPrevious: {},
    };
  }

  /**
   * Initialize the system and set up event listeners.
   * @param engine - The game engine instance
   */
  init(engine: Engine): void {
    super.init(engine);
    this.setupEventListeners();
  }

  /**
   * Set up browser event listeners for keyboard and mouse.
   */
  setupEventListeners(): void {
    window.addEventListener('keydown', (e) => {
      const key = e.key.toLowerCase();
      const code = e.code.toLowerCase();

      this.keys[key] = true;
      this.keys[code] = true;

      if (key === ' ') {
        this.keys['space'] = true;
      }
      if (code === 'space') {
        this.keys['space'] = true;
      }

      if (code === 'arrowup') this.keys['arrowup'] = true;
      if (code === 'arrowdown') this.keys['arrowdown'] = true;
      if (code === 'arrowleft') this.keys['arrowleft'] = true;
      if (code === 'arrowright') this.keys['arrowright'] = true;

      if ([' ', 'w', 'a', 's', 'd', '1', '2', '3', '4', '5', '6', '7', '8', '9'].includes(key)) {
        e.preventDefault();
      }
    });

    window.addEventListener('keyup', (e) => {
      const key = e.key.toLowerCase();
      const code = e.code.toLowerCase();

      this.keys[key] = false;
      this.keys[code] = false;

      if (key === ' ') {
        this.keys['space'] = false;
      }
      if (code === 'space') {
        this.keys['space'] = false;
      }

      if (code === 'arrowup') this.keys['arrowup'] = false;
      if (code === 'arrowdown') this.keys['arrowdown'] = false;
      if (code === 'arrowleft') this.keys['arrowleft'] = false;
      if (code === 'arrowright') this.keys['arrowright'] = false;
    });

    window.addEventListener('mousemove', (e) => {
      if (this.engine && this.engine.canvas) {
        const canvas = this.engine.canvas;
        const rect = canvas.getBoundingClientRect();
        const scaleX = canvas.width / rect.width;
        const scaleY = canvas.height / rect.height;

        this.mouse.x = (e.clientX - rect.left) * scaleX;
        this.mouse.y = (e.clientY - rect.top) * scaleY;
      }
    });

    window.addEventListener('mousedown', (e) => {
      this.mouse.buttons[e.button] = true;
    });

    window.addEventListener('mouseup', (e) => {
      this.mouse.buttons[e.button] = false;
    });
  }

  /**
   * Process input state (placeholder as processing happens via events).
   * @param _deltaTime - Time elapsed
   * @param _entities - Matching entities
   */
  process(_deltaTime: number, _entities: Entity[]): void {}

  /**
   * Update previous frame states. Should be called at the end of each frame.
   */
  updatePreviousStates(): void {
    this.keysPrevious = {};
    for (const key in this.keys) {
      this.keysPrevious[key] = this.keys[key];
    }
    this.mouse.buttonsPrevious = {};
    for (const button in this.mouse.buttons) {
      this.mouse.buttonsPrevious[button] = this.mouse.buttons[button];
    }
  }

  /**
   * Check if a key is currently being held down.
   * @param key - The key name or code
   * @returns True if the key is pressed
   */
  isKeyPressed(key: string): boolean {
    return this.keys[key.toLowerCase()] === true;
  }

  /**
   * Check if a key was pressed in the current frame.
   * @param key - The key name or code
   * @returns True if the key was just pressed
   */
  isKeyJustPressed(key: string): boolean {
    const keyLower = key.toLowerCase();
    const isPressed = this.keys[keyLower] === true;
    const wasPressed = this.keysPrevious[keyLower] === true;
    return isPressed && !wasPressed;
  }

  /**
   * Get the current mouse position in world coordinates.
   * @returns The mouse coordinates
   */
  getMousePosition(): { x: number; y: number } {
    return { x: this.mouse.x, y: this.mouse.y };
  }

  /**
   * Check if a mouse button is currently being held down.
   * @param button - The button index (0=left, 1=middle, 2=right)
   * @returns True if the button is pressed
   */
  isMouseButtonPressed(button = 0): boolean {
    return this.mouse.buttons[button] === true;
  }

  /**
   * Check if a mouse button was pressed in the current frame.
   * @param button - The button index
   * @returns True if the button was just pressed
   */
  isMouseButtonJustPressed(button = 0): boolean {
    const isPressed = this.mouse.buttons[button] === true;
    const wasPressed = this.mouse.buttonsPrevious[button] === true;
    return isPressed && !wasPressed;
  }
}