/// Batch order processing with concurrent per-order validation and stock deduction.
///
/// Fetches all pending orders for a customer, then fans out across every order in parallel.
/// Within each iteration, stock deduction is gated on successful validation. Final results
/// are collected by a summary node after all iterations complete.
///
/// Key DSL concepts demonstrated:
///   foreach (parallel)  — default mode; each (order, idx) pair is processed concurrently
///   depends_on          — deductStock waits for validate to complete within the same iteration
///
/// Context variables:
///   ctx.customerId — identifies the customer whose pending orders are fetched and processed
graph batchOrderParallel {

  /// Fetches pending orders for the given customer
  node fetchOrders : OrderFetcherOperator {
    input {
      customerId = ctx.customerId
    }
  }

  /// foreach parallel mode (default): process each order concurrently
  /// order — variable referencing the current order
  /// idx — variable referencing the 0-based index
  foreach processOrders : (order, idx) in fetchOrders.output.orders {
    node validate : OrderValidatorOperator {
      input {
        order = order
        index = idx
      }
    }
    node deductStock : StockDeductionOperator {
      depends_on = [validate]
      input {
        orderId = order.orderId
        quantity = order.quantity
        validated = validate.output.valid
      }
    }
  }

  /// Summarizes all processed order results from the foreach output
  node summarize : BatchSummaryOperator {
    depends_on = [processOrders]
    input {
      results = processOrders.output
    }
  }
}