import {
  contentPackIsUsable,
  getContentManagerSnapshot,
  installContentPack,
  removeContentPack,
  resolveContentUrl,
  subscribeContentManager,
} from "../content/contentManager";

export const COMBAT_MEDIA_MANIFEST_URL = "/assets/game/combat-effects/manifest.json";
export const COMBAT_MEDIA_CONTENT_PACK_ID = "core:combat-media";

export interface CombatMediaDownloadProgress {
  readonly completed: number;
  readonly total: number;
}

export interface CombatMediaDownloadResult {
  readonly fileCount: number;
}

type ProgressListener = (progress: CombatMediaDownloadProgress) => void;
let installRequest: Promise<void> | null = null;

function isCombatMediaUrl(value: unknown): value is string {
  return typeof value === "string" && value.startsWith("/assets/game/combat-effects/");
}

/** Fetch original media after the enabled pack is ready. */
export async function fetchCombatMediaAsset(url: string): Promise<Response> {
  if (!isCombatMediaUrl(url)) throw new Error(`Unsupported combat media URL: ${url}`);
  return fetchOptionalMediaAsset(url);
}

/** Fetch source media only after its shared optional pack has been enabled. */
export async function fetchOptionalMediaAsset(url: string): Promise<Response> {
  if (!combatMediaPackReady()) throw new Error("Original spell media is not installed.");
  return fetch(resolveContentUrl(url), { cache: "no-store" });
}

/** Download and verify every file owned by the original combat-media pack. */
export async function downloadCombatMediaPack(
  onProgress?: ProgressListener,
): Promise<CombatMediaDownloadResult> {
  const publishProgress = () => {
    const state = getContentManagerSnapshot();
    onProgress?.({
      completed: state.downloadedBytes,
      total: Math.max(1, state.totalBytes),
    });
  };
  const unsubscribe = subscribeContentManager(publishProgress);
  try {
    installRequest ??= installContentPack(COMBAT_MEDIA_CONTENT_PACK_ID)
      .finally(() => { installRequest = null; });
    await installRequest;
    publishProgress();
    const pack = getContentManagerSnapshot().manifest?.packs.find((candidate) => (
      candidate.id === COMBAT_MEDIA_CONTENT_PACK_ID
    ));
    return { fileCount: pack?.fileCount ?? 0 };
  } finally {
    unsubscribe();
  }
}

/** Prepare the default media without blocking gameplay when it is unavailable. */
export async function ensureCombatMediaPack(): Promise<boolean> {
  if (combatMediaPackReady()) return true;
  try {
    await downloadCombatMediaPack();
    return combatMediaPackReady();
  } catch {
    return false;
  }
}

export async function removeCombatMediaPack(): Promise<void> {
  await removeContentPack(COMBAT_MEDIA_CONTENT_PACK_ID);
}

export function combatMediaPackReady(): boolean {
  // Vite serves the complete source media tree, just as it does dungeon assets.
  // Shipped builds still require the verified optional content pack.
  return import.meta.env.DEV || contentPackIsUsable(COMBAT_MEDIA_CONTENT_PACK_ID);
}