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

import { 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 levelConfig = this.levelConfig;
    const layer = levelConfig.layers[0];
    const { data, height, width } = layer;
    const { ctx, canvas } = createCanvas(width * TILE_SIZE, height * TILE_SIZE);

    for (let row = 0; row < height; row++) {
      for (let col = 0; col < width; col++) {
        if (row < 0 || col < 0 || row >= height || col >= width) continue;

        const tile = data[row * width + col] - 1;
        ctx.drawImage(
          this.image,
          (tile * TILE_SIZE) % this.width,
          Math.floor((tile * TILE_SIZE) / this.width) * TILE_SIZE,
          TILE_SIZE,
          TILE_SIZE,
          col * TILE_SIZE,
          row * TILE_SIZE,
          TILE_SIZE,
          TILE_SIZE
        );
      }
    }

    return (this._level = canvas);
  }

  render(ctx, sourceX, sourceY, width, height) {
    if (!this.levelConfig || !this.selected) {
      return;
    }

    ctx.drawImage(
      this.level,
      sourceX,
      sourceY,
      width,
      height,
      0,
      0,
      width,
      height
    );
  }
}