/**
 * Builds the shareable text for a post — the caption, its source reference,
 * and a link.
 *
 * Extracted so the native share sheet and "send to a chat" quote a post
 * identically. They differ only in where the text ends up, and two copies of
 * this would drift the moment either format changed.
 */

import { createShortLink } from "@/lib/share";
import { structuredReferenceForPost } from "@/lib/source-reference";
import type { Post } from "@/lib/social";

export type PostShareText = {
  /** Short link when the shortener answered, canonical URL otherwise. */
  url: string;
  /** Source reference on one line, for a native share sheet's title slot. */
  title: string;
  /** Caption, source reference and link — the body of the share. */
  text: string;
};

/**
 * `viewerHandle` covers the case where the BFF's create response omits
 * author_handle: the poster IS the signed-in user right after posting.
 * Returns null when neither yields a handle, since there is no post URL
 * without one.
 */
export async function buildPostShareText(
  post: Post,
  viewerHandle: string | undefined,
): Promise<PostShareText | null> {
  const handle = post.author_handle ?? viewerHandle ?? "";
  if (!handle) return null;

  const longPath = `/u/${encodeURIComponent(handle)}/posts#post-${post.id}`;
  const code = await createShortLink(longPath);
  const origin = window.location.origin;
  const url = code
    ? new URL(`/share/${code}`, origin).toString()
    : new URL(longPath, origin).toString();

  const ref = structuredReferenceForPost(post.source_url, post.source_title);
  const lines = [`“${post.caption}”`, "", "Source:", ref.title];
  if (ref.detail) lines.push(ref.detail);
  lines.push(url);

  return {
    url,
    title: ref.detail ? `${ref.title} — ${ref.detail}` : ref.title,
    text: lines.join("\n"),
  };
}