func GenerateOrders()

in db/generate_orders.go [17:85]
60 lines of code
13 McCabe index (conditional complexity)

func GenerateOrders(db *sqlx.DB, driver string, n int, rng *rand.Rand) error {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	productIDs, err := getIDs(ctx, db, "products")
	if err != nil {
		return err
	}

	customerIDs, err := getIDs(ctx, db, "customers")
	if err != nil {
		return err
	}

	tx, err := db.BeginTx(ctx, nil)
	if err != nil {
		return err
	}

	returningID := "RETURNING id"
	if driver == "sqlite3" {
		returningID = ""
	}

	insertOrderStmt, err := tx.PrepareContext(ctx, db.Rebind(
		"INSERT INTO orders (customer_id) VALUES (?) "+returningID,
	))
	if err != nil {
		return errors.Wrap(err, "failed to prepare insert orders statement")
	}
	defer insertOrderStmt.Close()

	insertOrderLineStmt, err := tx.PrepareContext(ctx, db.Rebind(
		"INSERT INTO order_lines (order_id, product_id, amount) VALUES(?, ?, ?)",
	))
	if err != nil {
		return errors.Wrap(err, "failed to prepare insert order lines statement")
	}
	defer insertOrderLineStmt.Close()

	for i := 0; i < n; i++ {
		productID := productIDs[rng.Intn(len(productIDs))]
		customerID := customerIDs[rng.Intn(len(customerIDs))]
		var orderID int64
		if driver == "sqlite3" {
			result, err := insertOrderStmt.ExecContext(ctx, customerID)
			if err != nil {
				return err
			}
			rowID, err := result.LastInsertId()
			if err != nil {
				return err
			}
			orderID = rowID
		} else {
			err := insertOrderStmt.QueryRowContext(ctx, customerID).Scan(&orderID)
			if err != nil {
				return err
			}
		}

		amount := rng.Intn(maxOrderAmount + 1)
		if _, err := insertOrderLineStmt.ExecContext(ctx, orderID, productID, amount); err != nil {
			return err
		}
	}

	return tx.Commit()
}