Use rollup and split up files

src/Frame.js

@@ -0,0 +1,74 @@
+// @ts-check
+import { TRANSPARENT, Directions } from './constants.js';
+import Layer from './Layer.js';
+import BirdType from './birdType.js';
+
+class Frame {
+
+	/** @type {{ [tag: string]: string[][] }} */
+	#pixelsByTag = {};
+
+	/**
+	 * @param {Layer[]} layers
+	 */
+	constructor(layers) {
+		/** @type {Set<string>} */
+		let tags = new Set();
+		for (let layer of layers) {
+			tags.add(layer.tag);
+		}
+		tags.add("default");
+		for (let tag of tags) {
+			let maxHeight = layers.reduce((max, layer) => Math.max(max, layer.pixels.length), 0);
+			if (layers[0].tag !== "default") {
+				throw new Error("First layer must have the 'default' tag");
+			}
+			this.pixels = layers[0].pixels.map(row => row.slice());
+			// Pad from top with transparent pixels
+			while (this.pixels.length < maxHeight) {
+				this.pixels.unshift(new Array(this.pixels[0].length).fill(TRANSPARENT));
+			}
+			// Combine layers
+			for (let i = 1; i < layers.length; i++) {
+				if (layers[i].tag === "default" || layers[i].tag === tag) {
+					let layerPixels = layers[i].pixels;
+					let topMargin = maxHeight - layerPixels.length;
+					for (let y = 0; y < layerPixels.length; y++) {
+						for (let x = 0; x < layerPixels[y].length; x++) {
+							this.pixels[y + topMargin][x] = layerPixels[y][x] !== TRANSPARENT ? layerPixels[y][x] : this.pixels[y + topMargin][x];
+						}
+					}
+				}
+			}
+			this.#pixelsByTag[tag] = this.pixels.map(row => row.slice());
+		}
+	}
+
+	/**
+	 * @param {string} [tag]
+	 * @returns {string[][]}
+	 */
+	getPixels(tag = "default") {
+		return this.#pixelsByTag[tag] ?? this.#pixelsByTag["default"];
+	}
+
+	/**
+	 * @param {CanvasRenderingContext2D} ctx
+	 * @param {BirdType} [species]
+	* @param {number} direction
+	 * @param {number} canvasPixelSize
+	 */
+	draw(ctx, direction, canvasPixelSize, species) {
+		const pixels = this.getPixels(species?.tags[0]);
+		for (let y = 0; y < pixels.length; y++) {
+			const row = pixels[y];
+			for (let x = 0; x < pixels[y].length; x++) {
+				const cell = direction === Directions.LEFT ? row[x] : row[pixels[y].length - x - 1];
+				ctx.fillStyle = species?.colors[cell] ?? cell;
+				ctx.fillRect(x * canvasPixelSize, y * canvasPixelSize, canvasPixelSize, canvasPixelSize);
+			};
+		};
+	}
+}
+
+export default Frame;