Move sprite related files to separate folder

src/animation/anim.js

@@ -0,0 +1,92 @@
+import Frame from "./frame.js";
+import { BirdType } from "./sprites";
+
+class Anim {
+	/**
+	 * @param {Frame[]} frames
+	 * @param {number[]} durations
+	 * @param {boolean} loop
+	 */
+	constructor(frames, durations, loop = true) {
+		this.frames = frames;
+		this.durations = durations;
+		this.loop = loop;
+		this.lastFrameIndex = -1;
+		this.lastDirection = null;
+		this.lastTimeStart = null;
+	}
+
+	getAnimationDuration() {
+		return this.durations.reduce((a, b) => a + b, 0);
+	}
+
+	/**
+	 * Get the current frame index based on elapsed time
+	 * @param {number} time The elapsed time since animation start
+	 * @returns {number} The index of the current frame
+	 */
+	getCurrentFrameIndex(time) {
+		let totalDuration = 0;
+		for (let i = 0; i < this.durations.length; i++) {
+			totalDuration += this.durations[i];
+			if (time < totalDuration) {
+				return i;
+			}
+		}
+		return this.frames.length - 1;
+	}
+
+	/**
+	 * Clear the cached frame state
+	 */
+	#clearCache() {
+		this.lastFrameIndex = -1;
+		this.lastDirection = null;
+	}
+
+	/**
+	 * Check if the frame needs to be redrawn
+	 * @param {number} frameIndex The current frame index
+	 * @param {number} direction The current direction
+	 * @returns {boolean} Whether the frame needs to be redrawn
+	 */
+	#shouldRedraw(frameIndex, direction) {
+		return frameIndex !== this.lastFrameIndex || direction !== this.lastDirection;
+	}
+
+	/**
+	 * @param {CanvasRenderingContext2D} ctx
+	 * @param {number} direction
+	 * @param {number} timeStart The start time of the animation in milliseconds
+	 * @param {number} canvasPixelSize The size of a canvas pixel in pixels
+	 * @param {BirdType} [species] The species to use for the animation
+	 * @returns {boolean} Whether the animation is complete
+	 */
+	draw(ctx, direction, timeStart, canvasPixelSize, species) {
+		// Reset cache if animation was restarted
+		if (this.lastTimeStart !== timeStart) {
+			this.#clearCache();
+			this.lastTimeStart = timeStart;
+		}
+
+		let time = Date.now() - timeStart;
+		const duration = this.getAnimationDuration();
+		
+		if (this.loop) {
+			time %= duration;
+		}
+
+		const currentFrameIndex = this.getCurrentFrameIndex(time);
+		
+		if (this.#shouldRedraw(currentFrameIndex, direction)) {
+			this.frames[currentFrameIndex].draw(ctx, direction, canvasPixelSize, species);
+			this.lastFrameIndex = currentFrameIndex;
+			this.lastDirection = direction;
+		}
+		
+		// Return whether animation is complete (for non-looping animations)
+		return !this.loop && time >= duration;
+	}
+}
+
+export default Anim;