/**
 * Group-sync Lambda entrypoint — runs every 5 minutes (EventBridge).
 *
 * Mirrors Google Group membership into the matching Cognito groups and, on full
 * success, writes the freshness marker the pre-token Lambda fails closed on. Any
 * error propagates so the CloudWatch alarm fires and the marker stays stale.
 *
 * Reads the Google service-account credentials from Secrets Manager on cold
 * start (never an env var — secrets-and-config handbook rule).
 */

import { SecretsManagerClient, GetSecretValueCommand } from '@aws-sdk/client-secrets-manager';

import { GoogleDirectoryReader, type GoogleServiceAccount } from './clients.js';
import { CognitoGroupSync, DynamoSyncStateWriter } from './aws.js';
import { runSync } from './sync.js';
import { DEFAULT_DOMAIN } from './groups.js';

let cachedSa: GoogleServiceAccount | undefined;

async function loadServiceAccount(secretArn: string): Promise<GoogleServiceAccount> {
  if (cachedSa) return cachedSa;
  const sm = new SecretsManagerClient({});
  const res = await sm.send(new GetSecretValueCommand({ SecretId: secretArn }));
  if (!res.SecretString) throw new Error('Google SA secret has no SecretString');
  cachedSa = JSON.parse(res.SecretString) as GoogleServiceAccount;
  return cachedSa;
}

function requireEnv(name: string): string {
  const v = process.env[name];
  if (!v) throw new Error(`Missing required env var ${name}`);
  return v;
}

export async function handler(): Promise<{ ok: true; results: unknown }> {
  const userPoolId = requireEnv('USER_POOL_ID');
  const syncStateTable = requireEnv('SYNC_STATE_TABLE');
  const saSecretArn = requireEnv('GOOGLE_SA_SECRET_ARN');
  const domain = process.env['WORKSPACE_DOMAIN'] ?? DEFAULT_DOMAIN;

  const sa = await loadServiceAccount(saSecretArn);
  const results = await runSync({
    directory: new GoogleDirectoryReader(sa),
    cognito: new CognitoGroupSync(userPoolId),
    syncState: new DynamoSyncStateWriter(syncStateTable),
    domain,
  });
  console.log(JSON.stringify({ event: 'group_sync_ok', results }));
  return { ok: true, results };
}