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

import { COLS, ROWS, TILE_SIZE } from "../constants.js";
import { createCanvas } from "../utils.js";
import { GameObject } from "./game-object.js";

export class Map extends GameObject {
  constructor({ name, imageId, elementId, selected = false }) {
    super();
    this.name = name;
    this.imageId = imageId;
    this.image = document.getElementById(imageId);
    this.width = this.image.width;
    this.selected = selected;
    this.elementId = elementId;
  }

  async load() {
    const levelConfig = await fetch("/resources/" + this.name + ".json");
    this.levelConfig = await levelConfig.json();
  }

  get level() {
    if (this._level) {
      return this._level;
    }

    const { ctx, canvas } = createCanvas(COLS * TILE_SIZE, ROWS * TILE_SIZE);

    const image = this.image;
    const width = this.width;
    const level = this.levelConfig;
    const layer = level.layers[0];
    const data = layer.data;

    for (let row = 0; row < ROWS; row++) {
      for (let col = 0; col < COLS; col++) {
        const tile = data[row * COLS + col] - 1;
        ctx.drawImage(
          image,
          (tile * TILE_SIZE) % width,
          Math.floor((tile * TILE_SIZE) / width) * TILE_SIZE,
          TILE_SIZE,
          TILE_SIZE,
          col * TILE_SIZE,
          row * TILE_SIZE,
          TILE_SIZE,
          TILE_SIZE
        );
      }
    }
    return (this._level = canvas);
  }

  render(ctx) {
    if (!this.levelConfig || !this.selected) {
      return;
    }
    ctx.drawImage(this.level, 0, 0);
  }
}