import type { DrawCall } from "../DrawCall.ts";

interface SortableDrawList {
	calls: DrawCall[];
}

function compareBackToFront(a: DrawCall, b: DrawCall): number {
	return b._tileDistance - a._tileDistance;
}

/** Sorts draw calls by tile distance from camera. */
export class TileDistanceSorter {
	/** Sorts draw calls back-to-front by Manhattan tile distance from camera. */
	sort(
		drawList: SortableDrawList,
		cameraPosition: { x: number; y: number },
	): void {
		const calls = drawList.calls;
		const n = calls.length;

		const cx = cameraPosition.x;
		const cy = cameraPosition.y;
		for (let i = 0; i < n; i++) {
			const call = calls[i];
			const c = call.centroid;
			call._tileDistance = Math.abs(c.x - cx) + Math.abs(c.y - cy);
		}

		calls.sort(compareBackToFront);
	}
}