/**
 * Link completion source — extracts markdown headings from all .md files.
 *
 * Produces two entries per heading section, plus one for the file itself.
 * Uses github-slugger to match marked-gfm-heading-id's generated IDs.
 */

import Slugger from "github-slugger";
import type { CompletionSource, LinkCompletion } from "../types.js";

export const linksSource: CompletionSource = {
  key: "links",

  scan(index) {
    const items: LinkCompletion[] = [];

    for (const [filePath, content] of Object.entries(index)) {
      if (!filePath.endsWith(".md")) continue;

      // Strip .md extension for the router-friendly path
      const basePath = filePath.replace(/\.md$/, "");
      const fileName = fileNameFromPath(basePath);
      const slugger = new Slugger();

      // Add the file itself as a link (whole article)
      items.push({
        path: basePath,
        label: fileName,
        section: null,
      });

      // Parse headings for section-scoped links
      const headingRegex = /^(#{1,6})\s+(.+)$/gm;
      let match: RegExpExecArray | null;

      while ((match = headingRegex.exec(content)) !== null) {
        const title = match[2].trim();
        const id = slugger.slug(title.toLowerCase());

        items.push({
          path: basePath,
          label: `${fileName} § ${title}`,
          section: id,
        });
      }
    }

    return items;
  },
};

function fileNameFromPath(path: string): string {
  const parts = path.split("/").filter(Boolean);
  return parts[parts.length - 1] || path;
}