import { Node } from 'prosemirror-model';

import { slugify } from '../ponds';

export interface OutlineEntry {
  id: string;
  level: number;
  text: string;
}

/**
 * Heading tree for TOC plugins (data-model.md `page_content_cache`). Ids
 * are stable across re-derivation: same heading text + position in the
 * duplicate sequence always yields the same id (deterministic suffixes,
 * mirroring the pond-slug convention in `../ponds`).
 */
export function extractOutline(doc: Node): OutlineEntry[] {
  const entries: OutlineEntry[] = [];
  const seen = new Map<string, number>();
  doc.descendants((node) => {
    if (node.type.name !== 'heading') return true;
    const text = node.textContent.trim();
    const base = slugify(text) || 'section';
    const count = seen.get(base) ?? 0;
    seen.set(base, count + 1);
    const id = count === 0 ? base : `${base}-${count + 1}`;
    entries.push({ id, level: node.attrs.level as number, text });
    return false;
  });
  return entries;
}