Update 4. Demonstrate ability to customize shipping and pa yment methods.md

Author: unicoder88

8. Customizing the Checkout Process/4. Demonstrate ability to customize shipping and pa yment methods.md

@@ -216,3 +216,79 @@ But this doesn't seem to be used.
 - void() - `can_void`, `void` command
 - acceptPayment() - `can_accept_payment`, `accept_payment` command
 - denyPayment() - `can_deny_payment`, `deny_payment` command
+
+
+Two more special commands: `vault_authorize`, `vault_sale`, `vault_capture`
+
+
+braintree - BraintreeFacade = Model\Method\Adapter:
+- BraintreeValueHandlerPool: default, can_void, can_cancel
+- BraintreeCommandPool: authorize, sale, capture, settlement, vault_authorize, vault_sale, vault_capture, void, refund, cancel, deny_payment
+- BraintreeValidatorPool: country
+
+braintree_cc_vault - BraintreeCreditCardVaultFacade = Magento\Vault\Model\Method\Vault:
+- `vaultProvider` = BraintreeFacade. very important, all methods proxy to this
+- BraintreeVaultPaymentValueHandlerPool: default
+
+Magento\Vault\Model\Method\Vault:
+- pure class, no parent, interface \Magento\Vault\Model\VaultPaymentInterface
+- proxies almost all methods: is`*`, can`*`, validate
+- not implemented, throws error: initialize(), order(), refund(), cancel(), void(), acceptPayment(), denyPayment()
+- assignData:
+  * event `payment_method_assign_data_vault`
+  * event `payment_method_assign_data_vault_{$code}`
+  * original payment `method.assignData`
+- authorize:
+  * attach token extension attribute:
+    + `customer_id` from payment.additional_information
+    + `publish_hash` from payment.additional_information
+    + order payment.extension attributes[`vault_payment_token`] =
+    \Magento\Vault\Api\PaymentTokenManagementInterface::getByPublicHash(`publish_hash`, `customer_id`)
+    + select from `vault_payment_token` where publish_hash = ? and customer_id = ?/NULL
+  * commandManagerPool[`method.code`].executeBycode(`vault_authorize`)
+- capture:
+  * ONLY for `order`=`sale` payment action? Authorization transaction must not exist
+  * attach token extension attribute
+  * commandManagerPool[`method.code`].executeBycode(`vault_sale`)
+
+### Payment Tips
+
+Sometimes capture should do one of 3 things - sale, capture or vault_capture.
+Braintree makes CaptureStrategyCommand command that checks payment and
+calls needed capture type command.
+
+Virtual types can extend and augment each other pretty heavily, for example
+BraintreePayPalSaleCommand is based on BraintreePayPalAuthorizeCommand
+and changes only request builder.
+
+To make Vault work, after you receive normal payment, you save token by customer. Braintree
+does this in AuthorizationCommand handler chain in one of handlers. Token
+is simply read from response and put to order payment.extension_attributes[`vault_payment_token`].
+
+Vault on frontend:
+- in checkout config provider, finds all payment methods implementing Vault interface and returns codes for JS
+- in checkout payment methods, adds `vault` payment method group
+- get component providers \Magento\Vault\Model\Ui\TokenUiComponentProviderInterface - return params for JS component
+  * Braintree registers component in DI \Magento\Vault\Model\Ui\TokensConfigProvider
+- tokens = select from `vault_payment_token` where customer_id = ? and is_visible = 1 and is_active = 1 and expires_at > time
+- for each token, run component providers[method.code].getComponentForToken
+- window.checkoutConfig.payment.vault = [
+    `{$code}_{$i}` = componentConfig,
+    braintree_cc_vault_0 = {...},
+    braintree_cc_vault_1 = {...},
+  ]
+
+
+## What types of payment methods exist?
+- offline
+- online
+- gateway
+- vault - works over gateway, but executes different commands for authorize and capture. Always work in terms of previously saved token for customer.
+
+## What are the different payment flows?
+- isInitializationNeeded = true
+
+  Manually do the job in `initialize` and return custom order status and state.
+
+- authorize, capture
+- order = authorize + capture