import { createHash } from 'node:crypto';
import { readdir, readFile, stat } from 'node:fs/promises';
import { resolve } from 'node:path';

async function hasFiles(directory) {
  const entries = await readdir(directory, { withFileTypes: true }).catch(() => []);
  for (const entry of entries) {
    if (entry.isFile()) return true;
    if (entry.isDirectory() && await hasFiles(resolve(directory, entry.name))) return true;
  }
  return false;
}

export async function validateLearningPlayerArtifact(directory) {
  const root = resolve(directory);
  const [artifactText, html] = await Promise.all([
    readFile(resolve(root, 'artifact.json'), 'utf8'),
    readFile(resolve(root, 'index.html')),
  ]).catch((error) => {
    throw new Error(`Invalid learning player artifact at ${root}: ${error.message}`);
  });
  const artifact = JSON.parse(artifactText);
  if (artifact.schemaVersion !== 1
    || artifact.entrypoint !== 'index.html'
    || typeof artifact.htmlSha256 !== 'string'
    || !/^[0-9a-f]{64}$/.test(artifact.htmlSha256)) {
    throw new Error(`Invalid learning player artifact manifest at ${root}`);
  }
  const htmlSha256 = createHash('sha256').update(html).digest('hex');
  if (htmlSha256 !== artifact.htmlSha256) {
    throw new Error(`Learning player index hash mismatch at ${root}`);
  }
  if (!(await stat(resolve(root, '_next', 'static')).then((entry) => entry.isDirectory()).catch(() => false))
    || !await hasFiles(resolve(root, '_next', 'static'))) {
    throw new Error(`Learning player static assets are missing at ${root}`);
  }
  if (!(await stat(resolve(root, 'avatars')).then((entry) => entry.isDirectory()).catch(() => false))
    || !await hasFiles(resolve(root, 'avatars'))) {
    throw new Error(`Learning player avatars are missing at ${root}`);
  }
  if (!(await stat(resolve(root, 'public')).then((entry) => entry.isDirectory()).catch(() => false))
    || !await hasFiles(resolve(root, 'public'))) {
    throw new Error(`Learning player public assets are missing at ${root}`);
  }
  return { root, artifact, htmlSha256 };
}