game-engine/modules/game-objects/camera.js

import { TILE_SIZE } from "../constants.js";
import { GameObject } from "./game-object.js";

export class Camera extends GameObject {
  constructor({ gameObjects = [], x = 0, y = 0, width = 160, height = 120 }) {
    super({ x, y });
    this.gameObjects = gameObjects;
    this.x = x;
    this.y = y;
    this.width = width;
    this.height = height;
    this.keys = [
      { key: "ArrowUp", pressed: false, value: [0, -1] },
      { key: "ArrowDown", pressed: false, value: [0, 1] },
      { key: "ArrowLeft", pressed: false, value: [-1, 0] },
      { key: "ArrowRight", pressed: false, value: [1, 0] },
    ];
    this.availableKeys = this.keys.reduce(
      (acc, item) => ({ ...acc, [item.key]: item }),
      {}
    );
  }

  update(delta) {
    this.keys.forEach((item) => {
      if (item.pressed) {
        this.moveCamera(...item.value, delta);
      }
    });
  }

  onKeyPressed(key) {
    if (!this.availableKeys[key]) return;
    this.availableKeys[key].pressed = true;
  }

  onKeyReleased(key) {
    if (!this.availableKeys[key]) return;
    this.availableKeys[key].pressed = false;
  }

  render(ctx) {
    this.gameObjects.forEach((item) =>
      item.render(ctx, this.x, this.y, this.width, this.height)
    );
  }

  moveCamera(dx, dy, delta) {
    const [item] = this.gameObjects;
    const { height, width } = item.selected ?? item;
    this.x = Math.min(
      Math.max(this.x + dx * Math.floor(delta * 100), 0),
      width * TILE_SIZE - this.width
    );
    this.y = Math.min(
      Math.max(this.y + dy * Math.floor(delta * 100), 0),
      height * TILE_SIZE - this.height
    );
  }
}