/**
 * Transaction-based test isolation helper
 *
 * Wraps test code in a transaction that auto-rollbacks, providing
 * fast test isolation without truncating tables between tests.
 */

import type { Database } from "@reviq/db-schema";
import type { Kysely } from "kysely";

/**
 * Signal used to trigger transaction rollback after test completes
 */
class RollbackSignal extends Error {
  constructor() {
    super("RollbackSignal");
    this.name = "RollbackSignal";
  }
}

/**
 * Runs a test function inside a transaction that auto-rollbacks.
 *
 * The transaction implements the same interface as Kysely<Database>,
 * so it can be passed to context builders and used for all queries.
 * After the test completes, the transaction is rolled back, providing
 * instant cleanup without truncating tables.
 *
 * @example
 * ```typescript
 * test("creates user", async () => {
 *   await withTestTransaction(getSharedDb(), async (db) => {
 *     const user = await createTestUser(db, { email: "test@example.com" });
 *     const ctx = createAPIContext({ db });
 *     // ... test code
 *   }); // Auto-rollback here
 * });
 * ```
 */
export async function withTestTransaction<T>(
  db: Kysely<Database>,
  testFn: (trx: Kysely<Database>) => Promise<T>,
): Promise<T | undefined> {
  let result: T | undefined;

  try {
    await db.transaction().execute(async (trx) => {
      result = await testFn(trx);
      // Force rollback by throwing after test completes successfully
      throw new RollbackSignal();
    });
  } catch (e) {
    // Swallow the rollback signal - this is expected behavior
    if (!(e instanceof RollbackSignal)) {
      throw e;
    }
  }

  return result;
}