Using the Workflow component for e-commerce

We got the task to make an order API, from open order, to delivered, with payments in between and after. So there are naturally a lot of states, and a lot of transitions where we needed to calculate the prices correctly and handle credit card transfers. Keeping track of all of this, and when we need to do what, ensuring that an order is always up to date, and that it has the data it needs, and that we send good error messages when a user can not do an action, was a challenge for us until we discovered the workflow component. This is a real happy use case story where I will show you how we did this, and how much more straightforward it was for us to build an otherwise complex system using the workflow component.

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1. @michellesanver #phpday Using the Workflow component for e-commerce
 #phpday | 10th of May 2019
2. @michellesanver #phpday “Learn the most by sharing your knowledge with others” - @coderabbi WIIIIE \o/
3. @michellesanver #phpday Using the Workflow component for e-commerce
4. @michellesanver #phpday Writing Good Code
5. @michellesanver #phpday This talk assumes little knowledge
6. @michellesanver #phpday This talk is… Open Source
8. @michellesanver #phpday Michelle Sanver Colour and code addict
9. @michellesanver #phpday Accent!?
10. @michellesanver #phpday
11. @michellesanver #phpday “It’s like Uber… 
 For shopping”
12. @michellesanver #phpday Order API Challenges
13. @michellesanver #phpday Keeping orders/prices up to date
14. @michellesanver #phpday Making our consumers love us
 (Good error messages and documentation)
15. @michellesanver #phpday Handling cancellation of an order
16. @michellesanver #phpday Handling a large amount of SMS and Push notifications
17. @michellesanver #phpday
18. @michellesanver #phpday State Machines
19. @michellesanver #phpday Why?
20. @michellesanver #phpday GREEN YELLOW RED
21. @michellesanver #phpday GREEN YELLOW RED
22. @michellesanver #phpday GREEN YELLOW RED
23. @michellesanver #phpday GREEN YELLOW RED
24. @michellesanver #phpday GREEN YELLOW RED Timer
25. @michellesanver #phpday GREEN YELLOW RED Timer T1
26. @michellesanver #phpday GREEN YELLOW RED Timer T1 T1
27. @michellesanver #phpday GREEN YELLOW RED Timer T1 T1 T1
28. @michellesanver #phpday GREEN YELLOW RED Timer T1 T1 T1 T0
29. @michellesanver #phpday GREEN YELLOW RED Timer T1 T1 T1 T0 T0 T0
30. @michellesanver #phpday GREEN RED ;) BLUE
31. @michellesanver #phpday GREEN YELLOW BLUE T1 T2 Workflow
32. @michellesanver #phpday GREEN YELLOW BLUE T1 T2 State Machine T3
33. @michellesanver #phpday We already think in states and workflows
34. @michellesanver #phpday The Order
 State Machine
35. @michellesanver #phpday Happy Workflow
36. @michellesanver #phpday 1. An order is created Open
37. @michellesanver #phpday 2. Items are updated Open
38. @michellesanver #phpday 3. User sets delivery address on order. Open
39. @michellesanver #phpday 4. User checks out Confirmed
40. @michellesanver #phpday 5. Pickers get notified Confirmed
41. @michellesanver #phpday 6. Picker accepts order Assigned To Picker
42. @michellesanver #phpday 7. Picker goes shopping Picked Up
43. @michellesanver #phpday 8. Picker delivers order Delivered
44. @michellesanver #phpday 9. Card gets charged for order, picker gets paid Delivered
45. @michellesanver #phpday Open Confirmed Assigned To Picker Picked Up Delivered Happy Workflow
46. @michellesanver #phpday Cancelled Aborted
47. @michellesanver #phpday Cancelled By System
48. @michellesanver #phpday Open Confirmed Assigned To Picker Picked Up Delivered Cancelled Aborted Cancelled By System
49. @michellesanver #phpday Open Confirmed Assigned To Picker Picked Up Delivered Cancelled Aborted Cancelled By System
50. @michellesanver #phpday Open Confirmed Assigned To Picker Picked Up Delivered Cancelled Aborted Cancelled By System Cancel Order For technical Reasons Cancel Abort Checkout Assign to picker Pick Up Deliver Cancel Cancel Cancel
51. @michellesanver #phpday Open Open UpdateItem
52. @michellesanver #phpday State machines make business logic explicit
53. @michellesanver #phpday Open Confirmed Assigned To Picker Picked Up Delivered Cancelled Aborted Cancelled By System Cancel Order For technical Reasons Cancel Abort Checkout Assign to picker Pick Up Deliver Cancel Cancel Cancel
54. @michellesanver #phpday A workflow does not contain all logic
55. @michellesanver #phpday The Workflow Component
56. @michellesanver #phpday composer require symfony/workflow
57. @michellesanver #phpday Our Workflow
58. @michellesanver #phpday Open Confirmed Assigned To Picker Picked Up Delivered Cancelled Aborted Cancelled By System Cancel Order For technical Reasons Cancel Abort Checkout Assign to picker Pick Up Deliver Cancel Cancel Cancel
59. @michellesanver #phpday framework: workflows: order: type: state_machine marking_store: type: 'single_state' arguments: - 'state' supports: - AppBundle\Entity\Order places: - open - confirmed - assigned-to-delivery-person - picked-up - delivered - aborted - cancelled transitions: updateItem: from: open to: open
60. @michellesanver #phpday framework: workflows: order: type: state_machine marking_store: type: 'single_state' arguments: - 'state' supports: - AppBundle\Entity\Order
61. @michellesanver #phpday framework: workflows: order: type: state_machine marking_store: type: 'single_state' arguments: - 'state' supports: - AppBundle\Entity\Order
62. @michellesanver #phpday framework: workflows: order: type: state_machine marking_store: type: 'single_state' arguments: - 'state' supports: - AppBundle\Entity\Order
63. @michellesanver #phpday framework: workflows: order: type: state_machine marking_store: type: 'single_state' arguments: - 'state' supports: - AppBundle\Entity\Order
64. @michellesanver #phpday framework: workflows: order: type: state_machine marking_store: type: 'single_state' arguments: - 'state' supports: - AppBundle\Entity\Order
65. @michellesanver #phpday places: - open - confirmed - assigned-to-picker - picked-up - delivered - aborted - cancelled - cancelled-by-system
66. @michellesanver #phpday transitions: updateItem: from: open to: open
67. @michellesanver #phpday The Model
68. @michellesanver #phpday public const STATE_OPEN = 'open'; public const STATE_CONFIRMED = 'confirmed'; public const STATE_ASSIGNED_TO_PICKER = 'assigned-to-picker'; public const STATE_PICKED_UP = 'picked-up'; public const STATE_DELIVERED = 'delivered'; public const STATE_ABORTED_BY_CUSTOMER = 'aborted'; public const STATE_CANCELLED_BY_SUPPORT = 'cancelled'; public const STATE_CANCELLED_BY_SYSTEM = 'cancelled-by-system';
69. @michellesanver #phpday public const STATES = [ self::STATE_OPEN, self::STATE_CONFIRMED, self::STATE_ASSIGNED_TO_PICKER, self::STATE_PICKED_UP, self::STATE_DELIVERED, self::STATE_ABORTED_BY_CUSTOMER, self::STATE_CANCELLED_BY_SUPPORT, self::STATE_CANCELLED_BY_SYSTEM, ];
70. @michellesanver #phpday public const TRANSITION_UPDATE_ITEM = 'updateItem';
71. @michellesanver #phpday /** * @var string */ private $state = self::STATE_OPEN;
72. @michellesanver #phpday
73. @michellesanver #phpday Events
74. @michellesanver #phpday Solves Tight Coupling
75. @michellesanver #phpday EventDispatcher
76. @michellesanver #phpday composer require symfony/event-dispatcher
77. @michellesanver #phpday The Listener
78. @michellesanver #phpday class OrderWorkflowListener implements EventSubscriberInterface {
 … }
79. @michellesanver #phpday /** * @return array Hashmap of Symfony events this handler cares about */ public static function getSubscribedEvents() { return [ // Guard events (Validate whether the transition is allowed at all) 'workflow.order.guard' => 'guardGeneralOrderWorkflow', sprintf('workflow.order.guard.%s', Order::TRANSITION_CHANGE_REGION) => 'guardChangeRegion', sprintf('workflow.order.guard.%s', Order::TRANSITION_CONFIRM_ORDER) => 'guardConfirmOrder', sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_PICKER) => 'guardAssignPicker', sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_CUSTOMER) => 'guardAssignCustomer', // Enter events (The object is about to enter a new place) sprintf('workflow.order.enter.%s', Order::STATE_CONFIRMED) => 'enterConfirmed', sprintf('workflow.order.enter.%s', Order::STATE_DELIVERED) => 'enterDelivered', // Entered events (The object entered a new place) sprintf('workflow.order.entered.%s', Order::STATE_PICKED_UP) => 'enteredPickedUp', // The object has completed this transition. 'workflow.order.completed' => 'onCompleted', ]; }
80. @michellesanver #phpday /** * @return array Hashmap of Symfony events this handler cares about */ public static function getSubscribedEvents() { return [ // Guard events (Validate whether the transition is allowed at all) 'workflow.order.guard' => 'guardGeneralOrderWorkflow', sprintf('workflow.order.guard.%s', Order::TRANSITION_CHANGE_REGION) => 'guardChangeRegion', sprintf('workflow.order.guard.%s', Order::TRANSITION_CONFIRM_ORDER) => 'guardConfirmOrder', sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_PICKER) => 'guardAssignPicker', sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_CUSTOMER) => 'guardAssignCustomer', // Enter events (The object is about to enter a new place) sprintf('workflow.order.enter.%s', Order::STATE_CONFIRMED) => 'enterConfirmed', sprintf('workflow.order.enter.%s', Order::STATE_DELIVERED) => 'enterDelivered', // Entered events (The object entered a new place) sprintf('workflow.order.entered.%s', Order::STATE_PICKED_UP) => 'enteredPickedUp', // The object has completed this transition. 'workflow.order.completed' => 'onCompleted', ]; }
81. @michellesanver #phpday /** * @return array Hashmap of Symfony events this handler cares about */ public static function getSubscribedEvents() { return [ // Guard events (Validate whether the transition is allowed at all) 'workflow.order.guard' => 'guardGeneralOrderWorkflow', sprintf('workflow.order.guard.%s', Order::TRANSITION_CHANGE_REGION) => 'guardChangeRegion', sprintf('workflow.order.guard.%s', Order::TRANSITION_CONFIRM_ORDER) => 'guardConfirmOrder', sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_PICKER) => 'guardAssignPicker', sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_CUSTOMER) => 'guardAssignCustomer', // Enter events (The object is about to enter a new place) sprintf('workflow.order.enter.%s', Order::STATE_CONFIRMED) => 'enterConfirmed', sprintf('workflow.order.enter.%s', Order::STATE_DELIVERED) => 'enterDelivered', // Entered events (The object entered a new place) sprintf('workflow.order.entered.%s', Order::STATE_PICKED_UP) => 'enteredPickedUp', // The object has completed this transition. 'workflow.order.completed' => 'onCompleted', ]; }
82. @michellesanver #phpday /** * @return array Hashmap of Symfony events this handler cares about */ public static function getSubscribedEvents() { return [ // Guard events (Validate whether the transition is allowed at all) 'workflow.order.guard' => 'guardGeneralOrderWorkflow', sprintf('workflow.order.guard.%s', Order::TRANSITION_CHANGE_REGION) => 'guardChangeRegion', sprintf('workflow.order.guard.%s', Order::TRANSITION_CONFIRM_ORDER) => 'guardConfirmOrder', sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_PICKER) => 'guardAssignPicker', sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_CUSTOMER) => 'guardAssignCustomer', // Enter events (The object is about to enter a new place) sprintf('workflow.order.enter.%s', Order::STATE_CONFIRMED) => 'enterConfirmed', sprintf('workflow.order.enter.%s', Order::STATE_DELIVERED) => 'enterDelivered', // Entered events (The object entered a new place) sprintf('workflow.order.entered.%s', Order::STATE_PICKED_UP) => 'enteredPickedUp', // The object has completed this transition. 'workflow.order.completed' => 'onCompleted', ]; }
83. @michellesanver #phpday /** * @return array Hashmap of Symfony events this handler cares about */ public static function getSubscribedEvents() { return [ // Guard events (Validate whether the transition is allowed at all) 'workflow.order.guard' => 'guardGeneralOrderWorkflow', sprintf('workflow.order.guard.%s', Order::TRANSITION_CHANGE_REGION) => 'guardChangeRegion', sprintf('workflow.order.guard.%s', Order::TRANSITION_CONFIRM_ORDER) => 'guardConfirmOrder', sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_PICKER) => 'guardAssignPicker', sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_CUSTOMER) => 'guardAssignCustomer', // Enter events (The object is about to enter a new place) sprintf('workflow.order.enter.%s', Order::STATE_CONFIRMED) => 'enterConfirmed', sprintf('workflow.order.enter.%s', Order::STATE_DELIVERED) => 'enterDelivered', // Entered events (The object entered a new place) sprintf('workflow.order.entered.%s', Order::STATE_PICKED_UP) => 'enteredPickedUp', // The object has completed this transition. 'workflow.order.completed' => 'onCompleted', ]; }
84. @michellesanver #phpday Workflow component does so much for us
85. @michellesanver #phpday Order API Challenges Solved
86. @michellesanver #phpday Keeping orders/prices up to date
87. @michellesanver #phpday public function onCompleted(Event $event): void { $transition = $event->getTransition(); $fromState = $transition->getFroms()[0]; /** @var Order $order */ $order = $event->getSubject(); // If an order is already in delivered state, all calculations are done, and should stay as they are. if (Order::STATE_DELIVERED !== $fromState) { $this->orderModifier->updateTotals($order); } $this->orderStateHistoryRepository->storeOrderStateTransition($order, $transition); $this->orderEventService->eventHappened($transition->getName(), $order->getId(), $fromState); }
88. @michellesanver #phpday public function onCompleted(Event $event): void { $transition = $event->getTransition(); $fromState = $transition->getFroms()[0]; /** @var Order $order */ $order = $event->getSubject(); // If an order is already in delivered state, all calculations are done, and should stay as they are. if (Order::STATE_DELIVERED !== $fromState) { $this->orderModifier->updateTotals($order); } $this->orderStateHistoryRepository->storeOrderStateTransition($order, $transition); $this->orderEventService->eventHappened($transition->getName(), $order->getId(), $fromState); }
89. @michellesanver #phpday if (Order::STATE_DELIVERED !== $fromState) { $this->orderModifier->updateTotals($order); }
90. @michellesanver #phpday Making our consumers love us
 (Good error messages and documentation)
91. @michellesanver #phpday Handling cancellation of an order
92. @michellesanver #phpday Handling a large amount of SMS and Push notifications
93. @michellesanver #phpday public function onCompleted(Event $event): void { $transition = $event->getTransition(); $fromState = $transition->getFroms()[0]; /** @var Order $order */ $order = $event->getSubject(); // If an order is already in delivered state, all calculations are done, and should stay as they are. if (Order::STATE_DELIVERED !== $fromState) { $this->orderModifier->updateTotals($order); } $this->orderStateHistoryRepository->storeOrderStateTransition($order, $transition); $this->orderEventService->eventHappened($transition->getName(), $order->getId(), $fromState); }
94. @michellesanver #phpday public function onCompleted(Event $event): void { $transition = $event->getTransition(); $fromState = $transition->getFroms()[0]; /** @var Order $order */ $order = $event->getSubject(); // If an order is already in delivered state, all calculations are done, and should stay as they are. if (Order::STATE_DELIVERED !== $fromState) { $this->orderModifier->updateTotals($order); } $this->orderStateHistoryRepository->storeOrderStateTransition($order, $transition); $this->orderEventService->eventHappened($transition->getName(), $order->getId(), $fromState); }
95. @michellesanver #phpday $this->orderEventService->eventHappened($transition->getName(), $order->getId(), $fromState);
96. @michellesanver #phpday public function eventHappened(string $type, string $orderId, ?string $previousState) { foreach ($this->handlers as $handler) { if ($handler->canHandle($type)) { $this->orderEventProducer->publish( $type, $orderId, $previousState, $handler->getPriority() ); return; } } }
97. @michellesanver #phpday public function eventHappened(string $type, string $orderId, ?string $previousState) { foreach ($this->handlers as $handler) { if ($handler->canHandle($type)) { $this->orderEventProducer->publish( $type, $orderId, $previousState, $handler->getPriority() ); return; } } }
98. @michellesanver #phpday class SmsNotificationHandler implements OrderEventHandler { private const TRANSITION_STATE_MAP = [ Order::TRANSITION_ASSIGN_PICKER => Order::STATE_ASSIGNED_TO_PICKER, Order::TRANSITION_TIMEOUT_FINDING_PICKER => Order::STATE_ABORTED_BY_CUSTOMER, Order::TRANSITION_PICKER_CONFIRMS_PURCHASE => Order::STATE_PICKED_UP, Order::TRANSITION_CONFIRM_DELIVERY => Order::STATE_DELIVERED, Order::TRANSITION_REFERRAL_PICKER_RECEIVES_REWARD => Order::STATE_DELIVERED, Order::TRANSITION_SEND_ORDER_AVAILABLE_REMINDER => Order::STATE_CONFIRMED, ];
99. @michellesanver #phpday public function canHandle(string $type): bool { return array_key_exists($type, self::TRANSITION_STATE_MAP); }
100. @michellesanver #phpday Conclusion
101. @michellesanver #phpday We already think in states and workflows
102. @michellesanver #phpday State machines make business logic explicit
103. @michellesanver #phpday Workflow component does so much for us!
104. @michellesanver #phpday Writing Good Code
105. @michellesanver #phpday This talk is for you Questions? Contributions?
106. @michellesanver #phpday Thank You #phpday! https://joind.in/talk/caf64