import { Client } from 'pg';

/** Arbitrary keys, one per shared resource a suite needs to own alone. */
export const EXCLUSIVE_KEYS = {
  /** Open drafts are unique per kind: only one suite may create/clear them. */
  authorityNotices: 72707371,
} as const;

/**
 * Holds a Postgres session advisory lock for the lifetime of a suite, so
 * suites that clear or count a table whose rows are global (e.g. the open
 * draft per notice kind) never run at the same time, even in parallel jest
 * workers. Blocks until the previous owner released it; the lock disappears
 * with the connection if a worker dies. Call release() in afterAll.
 */
export async function acquireExclusive(
  key: number,
): Promise<() => Promise<void>> {
  const url = process.env.DATABASE_URL;
  if (!url) {
    throw new Error('DATABASE_URL is not set');
  }
  const connection = new URL(url);
  connection.searchParams.delete('schema');
  const client = new Client({ connectionString: connection.toString() });
  await client.connect();
  await client.query('SELECT pg_advisory_lock($1)', [key]);
  return async () => {
    await client.end();
  };
}