import { readFile, readdir } from 'node:fs/promises';
import { join, relative, resolve, sep } from 'node:path';
import { parseHTML } from 'linkedom';

async function listFiles(root, directory = root) {
  const entries = await readdir(directory, { withFileTypes: true });
  const files = [];
  for (const entry of entries) {
    const path = join(directory, entry.name);
    if (entry.isDirectory()) files.push(...await listFiles(root, path));
    else if (entry.isFile()) files.push(path);
  }
  return files.sort();
}

export async function checkRenderedOutput({ distRoot }) {
  const absoluteDistRoot = resolve(distRoot);
  const files = await listFiles(absoluteDistRoot);
  const relativeFiles = files.map((file) => relative(absoluteDistRoot, file).split(sep).join('/'));
  const htmlFiles = files.filter((file) => {
    const path = relative(absoluteDistRoot, file).split(sep).join('/');
    return path.endsWith('.html') && path !== '404.html';
  });
  const headingIssues = [];

  for (const file of htmlFiles) {
    const path = relative(absoluteDistRoot, file).split(sep).join('/');
    const { document } = parseHTML(await readFile(file, 'utf8'));
    if (document.querySelector('meta[http-equiv="refresh"]')) continue;
    const h1Count = document.querySelectorAll('h1').length;
    if (h1Count !== 1) headingIssues.push({ file: path, h1Count });
  }

  return {
    htmlFilesChecked: htmlFiles.length,
    headingIssues,
    unpublishedPaths: relativeFiles.filter((path) => path.split('/').includes('to-be-studied')),
  };
}