import { kachelCacheName } from "./cache-storage";

const SHELL_REPAIR_TRIED = "karte-shell-repaired";

export type BootRepairPorts = {
  registrations(): Promise<ReadonlyArray<{ unregister(): Promise<boolean> }>>;
  cacheNames(): Promise<string[]>;
  deleteCache(name: string): Promise<boolean>;
};

type FlagStore = {
  getItem(key: string): string | null;
  setItem(key: string, value: string): void;
  removeItem(key: string): void;
};

/** Drop the installed app shell. Kacheln stay in their own cache. */
export async function repairAppShell(ports: BootRepairPorts): Promise<void> {
  const registrations = await ports.registrations();
  await Promise.all(registrations.map((registration) => registration.unregister()));
  const names = await ports.cacheNames();
  await Promise.all(
    names
      .filter((name) => name !== kachelCacheName)
      .map((name) => ports.deleteCache(name)),
  );
}

/** Drop every stored Kachel. The heruntergeladen marks stay. */
export async function deleteKachelCache(ports: Pick<BootRepairPorts, "deleteCache">): Promise<void> {
  await ports.deleteCache(kachelCacheName);
}

export function bootFailureText(error: unknown): string {
  if (error instanceof Error && error.message.trim()) return error.message;
  return "Unbekannter Fehler";
}

export function createBrowserBootRepair(): BootRepairPorts {
  return {
    async registrations() {
      if (!navigator.serviceWorker) return [];
      return navigator.serviceWorker.getRegistrations();
    },
    cacheNames: () => caches.keys(),
    deleteCache: (name) => caches.delete(name),
  };
}

export function shellRepairWasTried(store: FlagStore | null = browserFlags()): boolean {
  try {
    return store?.getItem(SHELL_REPAIR_TRIED) === "1";
  } catch {
    return false;
  }
}

export function markShellRepairTried(store: FlagStore | null = browserFlags()): void {
  try {
    store?.setItem(SHELL_REPAIR_TRIED, "1");
  } catch {
    // sessionStorage can be blocked. The repair still runs.
  }
}

export function clearShellRepairTried(store: FlagStore | null = browserFlags()): void {
  try {
    store?.removeItem(SHELL_REPAIR_TRIED);
  } catch {
    // sessionStorage can be blocked.
  }
}

function browserFlags(): FlagStore | null {
  try {
    if (typeof sessionStorage === "undefined") return null;
    return sessionStorage;
  } catch {
    return null;
  }
}