File: //home/shrsglobal/www/wp-content/plugins/woocommerce-paypal-payments/docs/plugin-architecture.md
# Plugin Architecture Documentation
This document provides a comprehensive overview of the WooCommerce PayPal Payments plugin architecture, explaining its modular design and how the various components work together.
## Overview
The WooCommerce PayPal Payments plugin is built using a modular architecture powered by the [Syde Modularity](https://github.com/inpsyde/modularity) framework. This design provides:
- **Modular Structure**: Each feature is contained within its own module with clear boundaries
- **Dependency Injection**: PSR-11 container for service management and dependency resolution
- **Feature Flags**: Dynamic module loading based on environment variables and filters
- **Extensibility**: Well-defined extension points for customization and enhancement
- **Maintainability**: Clear separation of concerns and consistent patterns
## Core Components
### Main Plugin File
The plugin initialization begins in `woocommerce-paypal-payments.php`, which:
- Loads the Composer autoloader if needed (e.g. may be already loaded in some tests)
- Contains plugin metadata and constants definitions
- It starts the bootstrap process, in `plugins_loaded` hook.
### Bootstrap System
The bootstrap process is handled by `bootstrap.php`, which:
```php
return function (
string $root_dir,
array $additional_containers = array(),
array $additional_modules = array()
): ContainerInterface {
// Load modules from modules.php
$modules = ( require "$root_dir/modules.php" )( $root_dir );
// Apply filters for customization
$modules = apply_filters( 'woocommerce_paypal_payments_modules', $modules );
// Initialize plugin with Syde Modularity
$properties = PluginProperties::new( "$root_dir/woocommerce-paypal-payments.php" );
$bootstrap = Package::new( $properties );
foreach ( $modules as $module ) {
$bootstrap->addModule( $module );
}
$bootstrap->boot();
return $bootstrap->container();
};
```
### PPCP Container
The global `PPCP` class (`src/PPCP.php`) provides access to the dependency injection container:
```php
class PPCP {
private static $container = null;
public static function container(): ContainerInterface {
if ( ! self::$container ) {
throw new LogicException( 'No PPCP container, probably called too early when the plugin is not initialized yet.' );
}
return self::$container;
}
}
```
This allows third-party access services easily, such as in `api/order-functions.php`.
## Module System
### Module Definition
Modules are defined in `modules.php` with both core and conditional modules:
```php
$modules = array(
new PluginModule(),
( require "$modules_dir/woocommerce-logging/module.php" )(),
( require "$modules_dir/ppcp-admin-notices/module.php" )(),
( require "$modules_dir/ppcp-api-client/module.php" )(),
// ... more core modules
);
```
### Feature-Flag Controlled Modules
Conditional modules are loaded based on environment variables and filters (`modules.php`):
```php
if ( apply_filters(
'woocommerce.feature-flags.woocommerce_paypal_payments.applepay_enabled',
getenv( 'PCP_APPLEPAY_ENABLED' ) !== '0'
) ) {
$modules[] = ( require "$modules_dir/ppcp-applepay/module.php" )();
}
```
This pattern allows for:
- **Environment-based control**: Use `PCP_*_ENABLED` environment variables
- **Runtime filtering**: Apply WordPress filters to override defaults
- **Graceful degradation**: Missing features don't break core functionality
### Module Structure
Each module follows a consistent directory structure:
```
modules/ppcp-example/
├── module.php # Module factory function
├── composer.json # PHP dependencies
├── package.json # JavaScript dependencies
├── webpack.config.js # Asset building configuration
├── services.php # Service definitions
├── extensions.php # Service extensions/modifications
├── src/ # PHP source code
│ └── ExampleModule.php
├── resources/ # Source assets
│ ├── js/
│ └── css/
└── assets/ # Built assets
├── js/
└── css/
```
### Module Interface Implementation
Most modules implement the Syde Modularity interfaces. For example in `modules/ppcp-api-client/src/ApiModule.php`:
```php
class ApiModule implements ServiceModule, FactoryModule, ExtendingModule, ExecutableModule {
use ModuleClassNameIdTrait;
public function services(): array {
return require __DIR__ . '/../services.php';
}
public function factories(): array {
return require __DIR__ . '/../factories.php';
}
public function extensions(): array {
return require __DIR__ . '/../extensions.php';
}
public function run( ContainerInterface $c ): bool {
// Module initialization logic
return true;
}
}
```
## Key Modules
### Core Infrastructure Modules
- **PluginModule** (`src/PluginModule.php`): Root module providing core services
- **woocommerce-logging**: Logging infrastructure integration
- **ppcp-api-client**: PayPal API integration, entities, and authentication
- **ppcp-session**: Session management for payment flows
- **ppcp-webhooks**: PayPal webhook handling
### Payment & Checkout Modules
- **ppcp-button**: PayPal Smart Payment Buttons and Advanced Credit and Debit Cards functionality
- **ppcp-blocks**: WooCommerce Blocks integration
- **ppcp-wc-gateway**: WooCommerce gateway integration
- **ppcp-axo**: PayPal Fastlane (Accelerated Checkout) implementation
### Feature Modules
- **ppcp-settings**: New React-based admin settings interface
- **ppcp-vaulting**: Saved payment methods functionality
- **ppcp-onboarding**: Merchant onboarding flow
### Alternative Payment Methods
- **ppcp-applepay/ppcp-googlepay**: Digital wallet integrations
- **ppcp-local-alternative-payment-methods**: Regional payment options
## Dependency Injection & Services
### Service Definition
Services are defined in each module's `services.php` file using factory functions:
```php
return array(
'example.service' => static function ( ContainerInterface $container ): ExampleService {
return new ExampleService(
$container->get( 'dependency.service' )
);
},
'example.config' => static function (): array {
return array(
'setting' => 'value',
);
},
);
```
### Service Extensions
The `extensions.php` files allow modules to modify or extend existing services:
```php
return array(
'existing.service' => static function ( ContainerInterface $container, ExistingService $service ): ExistingService {
// Modify or wrap the existing service
return new EnhancedService( $service );
},
);
```
### Container Access Patterns
Services can be accessed in multiple ways:
```php
// In our modules/services/extensions (also often passed to hook handlers via `use`)
$service = $container->get( 'service.id' );
// In third-party plugins etc. (if not adding a custom module via the `woocommerce_paypal_payments_modules` filter)
$service = PPCP::container()->get( 'service.id' );
// Check for service availability
if ( $container->has( 'optional.service' ) ) {
$service = $container->get( 'optional.service' );
}
```
### Plugin Feature Definition
The plugin has different features that can be enabled or disabled depending on assertions such as:
```php
// WooCommerce country location.
$container->get( 'api.shop.country' );
// PayPal merchant country location (notice this will fallback to WooCommerce country location if the user is not onboarded.
$container->get( 'api.merchant.country' );
// Currency
$currency = $container->get( 'api.shop.currency.getter' );
$currency->get(); // USD
// PayPal API Feature flags
$product_status = $container->get( 'applepay.apple-product-status' );
assert( $product_status instanceof AppleProductStatus );
$apple_pay_enabled = $product_status->is_active();
// Any other feature dependency. For instance, checking if own_brand_only is no enabled.
$is_enabled => $feature_is_enabled && ! $general_settings->own_brand_only(),
```
The `FeaturesDefinition.php` file is used to define these features so they can be used in other services.
For instance, they are used in places as:
- Endpoint serving the UI to know which features to show under the Features section under the Overview tab
- Define the TODO list in the UI Overview tab
The features should be defined as public constants for easy access an prefixed as `FEATURE_`
```php
// Defining Pay with Crypto feature
public const FEATURE_PAY_WITH_CRYPTO = 'pwc';
```
The features have different fields and a status field (enabled/disabled)
```php
self::FEATURE_PAY_WITH_CRYPTO => array(
'title' => __( 'Pay with Crypto', 'woocommerce-paypal-payments' ),
'description' => __( 'Enable customers to pay with cryptocurrency, and receive payments in USD in your PayPal balance.', 'woocommerce-paypal-payments' ),
'enabled' => $this->merchant_capabilities[ self::FEATURE_PAY_WITH_CRYPTO ],
'buttons' => array(
array(
'type' => 'secondary',
'text' => __( 'Configure', 'woocommerce-paypal-payments' ),
'action' => array(
'type' => 'tab',
'tab' => 'payment_methods',
'section' => 'ppcp-pay-with-crypto',
),
'showWhen' => 'enabled',
'class' => 'small-button',
),
array(
'type' => 'secondary',
'text' => __( 'Sign up', 'woocommerce-paypal-payments' ),
'urls' => array(
'sandbox' => 'https://www.sandbox.paypal.com/bizsignup/add-product?product=CRYPTO_PYMTS',
'live' => 'https://www.paypal.com/bizsignup/add-product?product=CRYPTO_PYMTS',
),
'showWhen' => 'disabled',
'class' => 'small-button',
),
array(
'type' => 'tertiary',
'text' => __( 'Learn more', 'woocommerce-paypal-payments' ),
'url' => 'https://www.paypal.com/us/digital-wallet/manage-money/crypto',
'class' => 'small-button',
),
),
),
```
There is a hook named `woocommerce_paypal_payments_rest_common_merchant_features`
allowing to define which features are enabled or disabled:
```php
// Enable Google Pay Feature
add_filter(
'woocommerce_paypal_payments_rest_common_merchant_features',
function ( array $features ) use ( $container ): array {
$product_status = $container->get( 'googlepay.helpers.apm-product-status' );
assert( $product_status instanceof ApmProductStatus );
$google_pay_enabled = $product_status->is_active();
$features[ FeaturesDefinition::FEATURE_GOOGLE_PAY ] = array(
'enabled' => $google_pay_enabled,
);
return $features;
}
);
```
The FeaturesDefinition class is initialized in ```settings.data.definition.features```
Another important part of the Features is the `FeaturesEligibilityService.php`
This service defines different callbacks to check if a feature is eligible for the merchant
in runtime.
When using `FeaturesDefinition::get()` the plugin will run the registered eligibility callbacks
checks for each Feature. The plugin will unset those Features without check or returning false in the eligibility check.
### Payment Method Definition
Besides PayPal itself, we have different Payment methods such as Apple Pay, Pay with Crypto...etc.
These methods are defined in `PaymentMethodsDefinition.php` and they are divided in several groups:
**PayPal methods**
- PayPal
- Venmo
- PayPal PayLater.
- CardButtonGateway. Only in Own Brand Mode. It allows the user to pay with card even if the customer doesn't have a PayPal account.
Filterable via `woocommerce_paypal_payments_gateway_group_paypal` hook.
**Card Methods**
- Advanced Credit and Debit Card Payments
- Fastlane by PayPal
- Apple Pay
- Google Pay
Filterable via `woocommerce_paypal_payments_gateway_group_cards` hook.
**Alternative Payment Methods**
- Pay with Crypto
- Bancontact
- Blik
- EPS
- iDeal
- MyBank
- Przelewy24
- Trustly
- Multibanco
- Pay upon Invoice
- OXXO
Filterable via `woocommerce_paypal_payments_gateway_group_apm` hook.
As in FeaturesDefinition, Payment Methods has also an eligibility service.
This service is defined in `PaymentMethodsEligibilityService.php`
It creates different callbacks that unset the Payment methods based on the eligibility checks:
```php
public function get_eligibility_checks(): array {
return array(
BancontactGateway::ID => fn() => ! $this->is_mexico_merchant() && $this->is_apm_eligible,
BlikGateway::ID => fn() => ! $this->is_mexico_merchant() && $this->is_apm_eligible,
EPSGateway::ID => fn() => ! $this->is_mexico_merchant() && $this->is_apm_eligible,
IDealGateway::ID => fn() => ! $this->is_mexico_merchant() && $this->is_apm_eligible,
MyBankGateway::ID => fn() => ! $this->is_mexico_merchant() && $this->is_apm_eligible,
P24Gateway::ID => fn() => ! $this->is_mexico_merchant() && $this->is_apm_eligible,
TrustlyGateway::ID => fn() => ! $this->is_mexico_merchant() && $this->is_apm_eligible,
MultibancoGateway::ID => fn() => ! $this->is_mexico_merchant() && $this->is_apm_eligible,
OXXO::ID => fn() => $this->is_mexico_merchant() && $this->is_apm_eligible,
PWCGateway::ID => fn() => $this->has_pwc_capability() && $this->is_apm_eligible,
PayUponInvoiceGateway::ID => fn() => $this->merchant_country === 'DE',
CreditCardGateway::ID => fn() => $this->is_mexico_merchant() || $this->is_card_fields_supported(),
CardButtonGateway::ID => fn() => $this->is_mexico_merchant() || ! $this->is_card_fields_supported(),
GooglePayGateway::ID => fn() => $this->google_pay_available,
ApplePayGateway::ID => fn() => $this->apple_pay_available,
AxoGateway::ID => fn() => $this->dcc_product_status->is_active() && call_user_func( $this->axo_eligible ),
'venmo' => fn() => $this->merchant_country === 'US',
);
}
```
## Asset Management
### Webpack Configuration
Each module with JavaScript assets includes a `webpack.config.js`:
```javascript
const path = require('path');
const defaultConfig = require('@wordpress/scripts/config/webpack.config');
module.exports = {
...defaultConfig,
entry: {
'boot': path.resolve(process.cwd(), 'resources/js', 'boot.js'),
},
output: {
path: path.resolve(process.cwd(), 'assets/js'),
filename: '[name].js',
},
};
```
### Build Process
Assets are built using the shared configuration:
- **Individual builds**: `npm run build:modules:ppcp-{module-name}`
- **Watch mode**: `npm run watch:modules:ppcp-{module-name}` or `npm run watch:modules` (all modules)
- **All modules**: `npm run build:modules` (parallel builds)
### Asset Registration
Built assets are registered through module services and enqueued conditionally:
```php
'asset.example-script' => static function( ContainerInterface $container ): Asset {
return new Asset(
'example-script',
plugin_dir_url( __DIR__ ) . 'assets/js/example.js',
array( 'wp-element' ), // dependencies
'1.0.0'
);
},
```
## Extension Points
### WordPress Hooks
The plugin provides numerous action and filter hooks:
```php
// Allow modification of order request data
apply_filters( 'ppcp_create_order_request_body_data', $data );
// PayPal order creation notification
do_action( 'woocommerce_paypal_payments_paypal_order_created', $order );
// API cache clearing
do_action( 'woocommerce_paypal_payments_flush_api_cache' );
```
### Module Filters
Modules can be modified via filters:
```php
// Add or remove modules
$modules = apply_filters( 'woocommerce_paypal_payments_modules', $modules );
// Feature flag overrides
apply_filters( 'woocommerce.feature-flags.woocommerce_paypal_payments.applepay_enabled', $default );
```