import { artManifest } from "./manifest";

/** Where `scripts/map-art.mjs` output is served from (`public/assets/map-gen`). */
export const ART_BASE_URL = "/assets/map-gen";
export const ART_BUNDLE = "map-art";

/** The generated files to load: 2x sprites on high-density screens (Step 10C.4). */
export function artBundle(devicePixelRatio: number): Record<string, string> {
  const density = devicePixelRatio >= 2 ? "2x" : "1x";
  const bundle: Record<string, string> = {};
  for (const [id, asset] of Object.entries(artManifest.assets)) {
    if (asset.file === null) continue;
    bundle[id] =
      asset.kind === "background"
        ? `${ART_BASE_URL}/${id}.webp`
        : `${ART_BASE_URL}/${id}@${density}.png`;
  }
  return bundle;
}

/** The part of PixiJS's `Assets` the loader uses (a fake in tests). */
export interface AssetLoader<T> {
  addBundle(name: string, assets: Record<string, string>): void;
  load(alias: string): Promise<T>;
}

/** Loaded textures by asset id. An id that is absent draws its placeholder (0.5.41). */
export type ArtTextures<T> = ReadonlyMap<string, T>;

let registered = false;

/**
 * Registers the map art as one bundle and loads each asset on its own, so one
 * failure only costs that asset: it is left out (placeholder) and one warning
 * names it. Never rejects.
 */
export async function loadArt<T>(
  loader: AssetLoader<T>,
  devicePixelRatio: number,
  warn: (message: string) => void = console.warn,
): Promise<ArtTextures<T>> {
  const bundle = artBundle(devicePixelRatio);
  if (!registered) {
    loader.addBundle(ART_BUNDLE, bundle);
    registered = true;
  }
  const ids = Object.keys(bundle);
  const results = await Promise.allSettled(ids.map((id) => loader.load(id)));
  const textures = new Map<string, T>();
  results.forEach((result, i) => {
    const id = ids[i]!;
    if (result.status === "fulfilled" && result.value) textures.set(id, result.value);
    else warn(`Map art "${id}" failed to load; drawing its placeholder.`);
  });
  return textures;
}

/** Test hook: forget that the bundle was registered. */
export function resetArtRegistration(): void {
  registered = false;
}