import fs from "node:fs/promises";
import path from "node:path";
import catalog from "../../../../content/catalog.json";

const directory = path.resolve(process.cwd(), "../../content/docs");
const validSlug = /^[a-z0-9]+(?:-[a-z0-9]+)*(?:\/[a-z0-9]+(?:-[a-z0-9]+)*)*$/;
type Metadata = { slug?: string; category?: string; collection?: string; group?: string; description?: string; draft?: boolean; featured?: boolean };
export type DocLink = {
  slug: string; sourceSlug: string; category: string; title: string; searchText?: string;
  group: string; collection: string; description: string; draft: boolean; featured: boolean;
};
export type Doc = DocLink & { content: string };

export async function readDoc(slug: string): Promise<Doc> {
  if (!validSlug.test(slug)) throw new Error("Invalid document slug");
  const sourceSlug = Object.entries(catalog.documents).find(([, metadata]) => metadata.slug === slug)?.[0] ?? slug;
  const content = await fs.readFile(path.join(directory, `${sourceSlug}.md`), "utf8");
  const title = content.match(/^# (.+)$/m)?.[1]?.trim() ?? slug;
  const collection = catalog.collections.find((c) => !c.path || sourceSlug.startsWith(`${c.path}/`))!;
  const metadata: Metadata = (catalog.documents as Record<string, Metadata>)[sourceSlug] ?? {};
  if (!metadata.slug || !metadata.category || !validSlug.test(metadata.slug) || metadata.slug.split("/").some((part) => /^\d+-/.test(part))) {
    throw new Error(`Register a semantic slug and category in content/catalog.json: ${sourceSlug}`);
  }
  return { slug: metadata.slug, sourceSlug, category: metadata.category, title, content, searchText: content,
    group: metadata.group ?? collection.title, collection: metadata.collection ?? collection.title,
    description: metadata.description ?? collection.description,
    draft: metadata.draft ?? false, featured: metadata.featured ?? false,
  };
}

export async function listDocs(): Promise<DocLink[]> {
  async function walk(folder: string): Promise<string[]> {
    const entries = await fs.readdir(path.join(directory, folder), { withFileTypes: true });
    const files = await Promise.all(entries.map(async (entry) => {
      const relative = folder ? `${folder}/${entry.name}` : entry.name;
      if (entry.isDirectory()) return walk(relative);
      if (entry.isFile() && relative.endsWith(".md") && validSlug.test(relative.slice(0, -3)))
        return [relative.slice(0, -3)];
      return [];
    }));
    return files.flat();
  }
  const docs = await Promise.all((await walk("")).sort().map(async (slug) => {
    const { content: _, searchText: __, ...doc } = await readDoc(slug);
    void _; void __;
    return doc;
  }));
  if (new Set(docs.map((doc) => doc.slug)).size !== docs.length) throw new Error("Duplicate public document slug");
  return docs;
}