/**
 * version-text — plain-text extraction from a version-snapshot block's
 * stored `content`, for the read-only compare/preview panel (T-150/T-151).
 *
 * Stored content is one of (see inline-editor `toHtml`, the canonical
 * renderer): a raw HTML string (legacy blocks), the API canonical
 * `{ text }` / `{ title }` shape, or a serialized Tiptap doc object. The
 * panel never renders HTML (a version snapshot is untrusted input) — it
 * extracts text only, which is all a block-level diff summary needs.
 */
export function blockText(content: unknown): string {
  if (content == null) return "";
  if (typeof content === "string") return stripHtml(content);
  if (typeof content === "object") {
    const c = content as { text?: unknown; title?: unknown };
    if (typeof c.text === "string") return c.text;
    if (typeof c.title === "string") return c.title;
    // Tiptap doc object: walk doc → content[] → text nodes (best effort —
    // the MVP stores `{ text }`/HTML, not full docs, so this is a fallback).
    const t = walkTiptapText(content);
    if (t) return t;
  }
  return "";
}

/** `stripHtml` for a string payload: DOMParser in the browser, tag-stripping
 * regex fallback elsewhere (tests). */
export function stripHtml(html: string): string {
  if (typeof DOMParser !== "undefined") {
    return new DOMParser().parseFromString(html, "text/html").body.textContent ?? "";
  }
  return html.replace(/<[^>]*>/g, "");
}

function walkTiptapText(node: unknown, depth = 0): string {
  if (!node || typeof node !== "object" || depth > 8) return "";
  const n = node as { type?: string; text?: unknown; content?: unknown };
  if (typeof n.text === "string") return n.text;
  if (Array.isArray(n.content)) return n.content.map((c) => walkTiptapText(c, depth + 1)).join("");
  return "";
}