function issue(code, message, details = {}) {
  return { code, message, ...details };
}

function isReadableUrl(value) {
  const text = String(value ?? '').trim();
  return (
    text.startsWith('http://') ||
    text.startsWith('https://') ||
    text.startsWith('/api/') ||
    text.startsWith('/MindSpace/')
  );
}

function normalizeStorageKey(value) {
  return String(value ?? '').trim().replace(/^\/+/, '');
}

export async function verifyConversationPackageManifest(manifest, options = {}) {
  const issues = [];
  const statObject = typeof options.statObject === 'function' ? options.statObject : null;
  const packageId = String(manifest?.packageId ?? '').trim();
  const storagePrefix = normalizeStorageKey(manifest?.storagePrefix);
  const artifacts = Array.isArray(manifest?.artifacts) ? manifest.artifacts : null;

  if (!packageId) issues.push(issue('missing_package_id', 'manifest.packageId is required'));
  if (!String(manifest?.userId ?? '').trim()) issues.push(issue('missing_user_id', 'manifest.userId is required'));
  if (!String(manifest?.sessionId ?? '').trim()) {
    issues.push(issue('missing_session_id', 'manifest.sessionId is required'));
  }
  if (!storagePrefix) issues.push(issue('missing_storage_prefix', 'manifest.storagePrefix is required'));
  if (!artifacts) issues.push(issue('invalid_artifacts', 'manifest.artifacts must be an array'));

  const seenArtifactIds = new Set();
  for (const artifact of artifacts ?? []) {
    const artifactId = String(artifact?.artifactId ?? '').trim();
    if (!artifactId) {
      issues.push(issue('missing_artifact_id', 'artifact.artifactId is required'));
      continue;
    }
    if (seenArtifactIds.has(artifactId)) {
      issues.push(issue('duplicate_artifact_id', `duplicate artifact id: ${artifactId}`, { artifactId }));
    }
    seenArtifactIds.add(artifactId);

    const canonicalUrl = String(artifact?.canonicalUrl ?? '').trim();
    const storageKey = normalizeStorageKey(artifact?.storageKey);
    if (!canonicalUrl && !storageKey) {
      issues.push(
        issue('artifact_without_backing_reference', 'artifact must have canonicalUrl or storageKey', { artifactId }),
      );
    }
    if (canonicalUrl && !isReadableUrl(canonicalUrl)) {
      issues.push(issue('invalid_canonical_url', `artifact canonicalUrl is not readable: ${canonicalUrl}`, {
        artifactId,
        canonicalUrl,
      }));
    }
    if (storageKey && storagePrefix && !storageKey.startsWith(`${storagePrefix}/`)) {
      issues.push(issue('storage_key_outside_package', 'artifact storageKey is outside manifest.storagePrefix', {
        artifactId,
        storageKey,
        storagePrefix,
      }));
    }
    if (storageKey && statObject) {
      const stat = await statObject(storageKey);
      if (!stat?.exists) {
        issues.push(issue('missing_backing_object', `artifact backing object is missing: ${storageKey}`, {
          artifactId,
          storageKey,
        }));
      }
    }
  }

  return { ok: issues.length === 0, issues };
}

export const conversationPackageVerifyInternals = {
  isReadableUrl,
  normalizeStorageKey,
};