Manage Order state

[making]

https://github.com/kbastani/spring-cloud-event-sourcing-example/blob/master/order-service/src/main/java/demo/order/Order.java#L86-L144

    /**
     * The incorporate method uses a simple state machine for an order's status to generate
     * the current state of an order using event sourcing and aggregation.
     * <p>
     * The event diagram below represents how events are incorporated into generating the
     * order status. The event log for the order status can be used to rollback the state
     * of the order in the case of a failed distributed transaction.
     * <p>
     * Events:   +<--PURCHASED+  +<--CREATED+  +<---ORDERED+  +<----SHIPPED+
     * *         |            |  |          |  |           |  |            |
     * Status    +PURCHASED---+PENDING------+CONFIRMED-----+SHIPPED--------+DELIVERED
     * *         |            |  |          |  |           |  |            |
     * Events:   +CREATED---->+  +ORDERED-->+  +SHIPPED--->+  +DELIVERED-->+
     *
     * @param orderEvent is the event to incorporate into the state machine
     * @return the aggregate {@link Order} with the aggregated order status
     */
    public Order incorporate(OrderEvent orderEvent) {

        if (orderStatus == null)
            orderStatus = OrderStatus.PURCHASED;

        switch (orderStatus) {
            case PURCHASED:
                if (orderEvent.getType() == OrderEventType.CREATED)
                    orderStatus = OrderStatus.PENDING;
                break;
            case PENDING:
                if (orderEvent.getType() == OrderEventType.ORDERED) {
                    orderStatus = OrderStatus.CONFIRMED;
                } else if (orderEvent.getType() == OrderEventType.PURCHASED) {
                    orderStatus = OrderStatus.PURCHASED;
                }
                break;
            case CONFIRMED:
                if (orderEvent.getType() == OrderEventType.SHIPPED) {
                    orderStatus = OrderStatus.SHIPPED;
                } else if (orderEvent.getType() == OrderEventType.CREATED) {
                    orderStatus = OrderStatus.PENDING;
                }
                break;
            case SHIPPED:
                if (orderEvent.getType() == OrderEventType.DELIVERED) {
                    orderStatus = OrderStatus.DELIVERED;
                } else if (orderEvent.getType() == OrderEventType.ORDERED) {
                    orderStatus = OrderStatus.CONFIRMED;
                }
                break;
            case DELIVERED:
                if (orderEvent.getType() == OrderEventType.SHIPPED)
                    orderStatus = OrderStatus.SHIPPED;
                break;
            default:
                // Invalid event type with regards to the order status
                break;
        }

        return this;
    }

[making]

https://docs.spring.io/spring-statemachine/docs/3.0.0-SNAPSHOT/reference/#statemachine-examples-ordershipping

https://github.com/spring-projects/spring-statemachine/tree/master/spring-statemachine-samples/ordershipping