# Payment Gateway Plugin Patterns Analysis

## Overview
Analysis of 4 Indonesian payment gateway plugins to identify common patterns and integration strategies for WooNooW.

---

## 1. TriPay Payment Gateway

### Architecture
- **Base Class:** `Tripay_Payment_Gateway extends WC_Payment_Gateway`
- **Pattern:** Abstract base class + Multiple child gateway classes
- **Registration:** Dynamic gateway loading via `glob()`

### Key Features
```php
// Base abstract class with shared functionality
abstract class Tripay_Payment_Gateway extends WC_Payment_Gateway {
    public $sub_id;           // Unique ID for each gateway
    public $payment_method;   // API payment method code
    public $apikey;
    public $merchantCode;
    public $privateKey;
    
    public function __construct() {
        $this->id = $this->sub_id;  // Set from child class
        $this->init_settings();
        // Shared configuration from global settings
        $this->apikey = get_option('tripay_api_key');
        $this->merchantCode = get_option('tripay_merchant_code');
    }
}
```

### Gateway Registration
```php
function add_tripay_gateway($methods) {
    foreach (TripayPayment::gateways() as $id => $property) {
        $methods[] = $property['class'];
    }
    return $methods;
}
add_filter('woocommerce_payment_gateways', 'add_tripay_gateway');

// Auto-load all gateway files
$filenames = glob(dirname(__FILE__).'/includes/gateways/*.php');
foreach ($filenames as $filename) {
    include_once $filename;
}
```

### Child Gateway Example (BNI VA)
```php
class WC_Gateway_Tripay_BNI_VA extends Tripay_Payment_Gateway {
    public $sub_id = 'tripay_bniva';  // Unique ID
    
    public function __construct() {
        parent::__construct();
        $this->method_title = 'TriPay - BNI VA';
        $this->method_description = 'Pembayaran melalui BNI Virtual Account';
        $this->payment_method = 'BNIVA';  // API code
        
        $this->init_form_fields();
        $this->init_settings();
    }
}
```

### Payment Processing
- Creates transaction via API
- Stores metadata: `_tripay_payment_type`, `_tripay_payment_expired_time`, `_tripay_payment_pay_code`
- Handles callbacks via `woocommerce_api_wc_gateway_tripay`

### Blocks Support
```php
add_action('woocommerce_blocks_loaded', 'woocommerce_tripay_gateway_woocommerce_block_support');
function woocommerce_tripay_gateway_woocommerce_block_support() {
    if (class_exists('Automattic\WooCommerce\Blocks\Payments\Integrations\AbstractPaymentMethodType')) {
        include_once dirname(__FILE__).'/includes/admin/class-wc-tripay-blocks.php';
        add_action('woocommerce_blocks_payment_method_type_registration',
            function ($payment_method_registry) {
                $payment_method_registry->register(new WC_Tripay_Blocks());
            }
        );
    }
}
```

---

## 2. Duitku Payment Gateway

### Architecture
- **Base Class:** `Duitku_Payment_gateway extends WC_Payment_Gateway`
- **Pattern:** Similar to TriPay - Abstract base + Multiple children
- **Registration:** Manual array of gateway class names

### Key Features
```php
class Duitku_Payment_gateway extends WC_Payment_Gateway {
    public $sub_id;           // Set by child
    public $payment_method;   // API method code
    public $apiKey;
    public $merchantCode;
    public $endpoint;
    
    public function __construct() {
        $this->id = $this->sub_id;
        $this->init_settings();
        
        // Global configuration
        $this->apiKey = get_option('duitku_api_key');
        $this->merchantCode = get_option('duitku_merchant_code');
        $this->endpoint = rtrim(get_option('duitku_endpoint'), '/');
    }
}
```

### Gateway Registration
```php
add_filter('woocommerce_payment_gateways', 'add_duitku_gateway');

function add_duitku_gateway($methods){
    $methods[] = 'WC_Gateway_Duitku_VA_Permata';
    $methods[] = 'WC_Gateway_Duitku_VA_BNI';
    $methods[] = 'WC_Gateway_Duitku_OVO';
    $methods[] = 'WC_Gateway_Duitku_CC';
    // ... 30+ gateways manually listed
    return $methods;
}

// Load all gateway files
foreach (glob(dirname(__FILE__) . '/includes/gateways/*.php') as $filename) {
    include_once $filename;
}
```

### Payment Processing
- API endpoint: `/api/merchant/v2/inquiry`
- Stores order items as array
- Handles fees and surcharges
- Callback via `woocommerce_api_wc_gateway_{$this->id}`

---

## 3. Xendit Payment

### Architecture
- **Base Class:** `WC_Xendit_Invoice extends WC_Payment_Gateway`
- **Pattern:** Singleton + Conditional loading
- **Registration:** Simple array, conditional CC gateway

### Key Features
```php
class WC_Xendit_PG {
    private static $instance;
    
    public static function get_instance() {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }
    
    public function add_xendit_payment_gateway($methods) {
        $methods[] = 'WC_Xendit_Invoice';
        
        // For admin
        if (is_admin()) {
            return $this->xendit_payment_gateway_settings($methods);
        }
        
        // Conditional CC gateway (with/without addons)
        $cc_methods = 'WC_Xendit_CC';
        if ($this->should_load_addons()) {
            $cc_methods = 'WC_Xendit_CC_Addons';
        }
        
        $methods[] = $cc_methods;
        return $methods;
    }
    
    public function should_load_addons() {
        if (class_exists('WC_Subscriptions_Order') && function_exists('wcs_create_renewal_order')) {
            return true;
        }
        if (class_exists('WC_Pre_Orders_Order')) {
            return true;
        }
        return false;
    }
}
```

### Gateway Registration
```php
add_filter('woocommerce_payment_gateways', array($this, 'add_xendit_payment_gateway'));
```

### Unique Features
- **Singleton pattern** for main plugin class
- **Conditional gateway loading** based on installed plugins
- **Addon support** for subscriptions and pre-orders
- **Helper classes** for logging, phone formatting, webhooks

---

## 4. WooCommerce PayPal Payments

### Architecture
- **Pattern:** Enterprise-level with dependency injection
- **Structure:** Modular with services, modules, and extensions
- **Registration:** Complex with feature detection

### Key Features
```php
// Modern PHP with namespaces and DI
namespace WooCommerce\PayPalCommerce;

class PPCP {
    private $container;
    
    public function __construct() {
        $this->container = new Container();
        $this->load_modules();
    }
}
```

### Gateway Registration
- Uses WooCommerce Blocks API
- Feature flags and capability detection
- Multiple payment methods (PayPal, Venmo, Cards, etc.)
- Advanced settings and onboarding flow

---

## Common Patterns Identified

### 1. **Base Class Pattern** ✅
All plugins use abstract/base class extending `WC_Payment_Gateway`:
```php
abstract class Base_Gateway extends WC_Payment_Gateway {
    public $sub_id;           // Unique gateway ID
    public $payment_method;   // API method code
    
    public function __construct() {
        $this->id = $this->sub_id;
        $this->init_settings();
        $this->load_global_config();
    }
}
```

### 2. **Global Configuration** ✅
Shared API credentials stored in WordPress options:
```php
$this->apiKey = get_option('provider_api_key');
$this->merchantCode = get_option('provider_merchant_code');
$this->endpoint = get_option('provider_endpoint');
```

### 3. **Multiple Gateway Classes** ✅
One class per payment method:
- `WC_Gateway_Provider_BNI_VA`
- `WC_Gateway_Provider_BCA_VA`
- `WC_Gateway_Provider_OVO`
- etc.

### 4. **Dynamic Registration** ✅
Two approaches:
```php
// Approach A: Loop through array
function add_gateways($methods) {
    $methods[] = 'Gateway_Class_1';
    $methods[] = 'Gateway_Class_2';
    return $methods;
}

// Approach B: Auto-discover
foreach (glob(__DIR__ . '/gateways/*.php') as $file) {
    include_once $file;
}
```

### 5. **Metadata Storage** ✅
Order metadata for tracking:
```php
$order->update_meta_data('_provider_transaction_id', $transaction_id);
$order->update_meta_data('_provider_payment_type', $payment_type);
$order->update_meta_data('_provider_expired_time', $expired_time);
```

### 6. **Callback Handling** ✅
WooCommerce API endpoints:
```php
add_action('woocommerce_api_wc_gateway_' . $this->id, [$this, 'handle_callback']);
```

### 7. **Blocks Support** ✅
WooCommerce Blocks integration:
```php
add_action('woocommerce_blocks_loaded', 'register_blocks_support');
add_action('woocommerce_blocks_payment_method_type_registration', 
    function($registry) {
        $registry->register(new Gateway_Blocks());
    }
);
```

### 8. **HPOS Compatibility** ✅
Declare HPOS support:
```php
add_action('before_woocommerce_init', function () {
    if (class_exists(\Automattic\WooCommerce\Utilities\FeaturesUtil::class)) {
        \Automattic\WooCommerce\Utilities\FeaturesUtil::declare_compatibility(
            'custom_order_tables', 
            __FILE__, 
            true
        );
    }
});
```

---

## WooNooW Integration Strategy

### Current Implementation ✅
We already have a good foundation:
1. **Payment channels filter** - `woonoow/payment_gateway_channels`
2. **Channel-based payment IDs** - `bacs_account-name_0`
3. **Dynamic gateway detection** - `payment_gateways()` vs `get_available_payment_gateways()`

### Recommended Enhancements

#### 1. **Gateway Metadata API** 🆕
Provide a filter for gateways to register their metadata:
```php
// In PaymentChannels.php or new PaymentGatewayMeta.php
add_filter('woonoow/payment_gateway_meta', function($meta, $gateway_id, $gateway) {
    // Allow gateways to provide additional metadata
    return $meta;
}, 10, 3);
```

#### 2. **Order Metadata Display** 🆕
Show payment-specific metadata in Order Detail:
```php
// In OrdersController.php show() method
$payment_meta = [];
$meta_keys = apply_filters('woonoow/payment_meta_keys', [
    '_tripay_payment_pay_code' => 'Payment Code',
    '_tripay_payment_expired_time' => 'Expires At',
    '_duitku_reference' => 'Reference',
    '_xendit_invoice_id' => 'Invoice ID',
], $order);

foreach ($meta_keys as $key => $label) {
    $value = $order->get_meta($key);
    if (!empty($value)) {
        $payment_meta[$key] = [
            'label' => $label,
            'value' => $value,
        ];
    }
}
```

#### 3. **Gateway Instructions Display** 🆕
Show payment instructions in Order Detail:
```php
// Allow gateways to provide custom instructions
$instructions = apply_filters('woonoow/payment_instructions', '', $order, $gateway_id);
```

#### 4. **Webhook/Callback Logging** 🆕
Log payment callbacks for debugging:
```php
// In a new WebhookLogger.php
add_action('woocommerce_api_*', function() {
    // Log all API callbacks
    error_log('[WooNooW] Payment callback: ' . $_SERVER['REQUEST_URI']);
}, 1);
```

#### 5. **Payment Status Sync** 🆕
Provide a unified way to sync payment status:
```php
do_action('woonoow/payment_status_changed', $order, $old_status, $new_status, $gateway_id);
```

---

## Implementation Priority

### Phase 1: Essential (Current) ✅
- [x] Payment channels filter
- [x] Gateway title retrieval
- [x] Channel-based IDs

### Phase 2: Enhanced Display 🎯
- [ ] Payment metadata display in Order Detail
- [ ] Payment instructions card
- [ ] Gateway-specific order notes

### Phase 3: Developer Experience 🎯
- [ ] Gateway metadata API
- [ ] Webhook logging
- [ ] Payment status hooks

### Phase 4: Advanced 🔮
- [ ] Payment retry mechanism
- [ ] Refund integration
- [ ] Multi-currency support

---

## Key Takeaways

### What Works Well ✅
1. **Base class pattern** - Easy to extend
2. **Global configuration** - Centralized API credentials
3. **Metadata storage** - Flexible tracking
4. **WooCommerce hooks** - Standard integration points

### What Could Be Better ⚠️
1. **Manual gateway registration** - Error-prone, hard to maintain
2. **Hardcoded metadata keys** - Not discoverable
3. **No standard for instructions** - Each gateway implements differently
4. **Limited admin UI** - Payment details not easily visible

### WooNooW Advantages 🎉
1. **REST API first** - Modern architecture
2. **React SPA** - Better UX for payment details
3. **HPOS native** - Future-proof
4. **Centralized channels** - Unified payment method handling

---

## Conclusion

All payment gateways follow similar patterns:
- Extend `WC_Payment_Gateway`
- Use global configuration
- Store order metadata
- Handle callbacks via WooCommerce API
- Support WooCommerce Blocks

**WooNooW is already well-positioned** to handle these gateways. The main enhancements needed are:
1. Better display of payment metadata in Order Detail
2. Unified API for gateways to provide instructions
3. Developer-friendly hooks for payment events

These can be implemented incrementally without breaking existing functionality.