/**
 * Short link client — talks to the BFF /share endpoints.
 *
 * Used by the text-selection toolbar (`buildShortHighlightUrl`) and the
 * `/share/[code]` page (`resolveShortLink`).
 */

import { bff, bffPost } from "@/lib/bff";

// Module-scoped cache: a single user shouldn't generate a fresh code every
// time they re-click Share on the same selection. Keyed by the relative path
// (including ?hl=…), this returns the same promise for repeat calls.
const createCache = new Map<string, Promise<string | null>>();

type CreateResponse = { code: string };
type ResolveResponse = { url: string };

/**
 * Create a short code for a same-site relative path (`/books/bg/18/66?hl=…`).
 * Returns `null` on any failure — caller should fall back to the long URL.
 */
export function createShortLink(longPath: string): Promise<string | null> {
  const cached = createCache.get(longPath);
  if (cached) return cached;

  const promise = bffPost<CreateResponse>("/share", { url: longPath })
    .then((r) => r.code)
    .catch(() => null);

  createCache.set(longPath, promise);
  // If the request fails, evict so the next click can retry instead of
  // returning the cached null forever.
  promise.then((code) => {
    if (code === null) createCache.delete(longPath);
  });

  return promise;
}

/**
 * Resolve a short code to its full long path. Returns `null` when the code is
 * not found, expired, disabled, or the BFF is unreachable.
 */
export async function resolveShortLink(code: string): Promise<string | null> {
  try {
    const r = await bff<ResolveResponse>(`/share/${encodeURIComponent(code)}`, {
      revalidate: 0,
    });
    return r?.url ?? null;
  } catch {
    return null;
  }
}