WordPress Plugin Integration

# KeyKit WordPress Plugin License Validation Integration

## Context
KeyKit is a Stripe-connected license key management service. When customers buy your WordPress plugin on Stripe, KeyKit automatically creates license keys and emails them to customers. 

**Your WordPress plugin only needs to check if a key is valid - KeyKit handles all the complex license management, renewal, and status tracking.**

## Setup Requirements
- Customer must have a Stripe account
- Products must be marked with "keykit_eligible=true" in Stripe product description
- KeyKit webhook must be configured in Stripe Dashboard
- WordPress plugin with admin settings capability

## Integration Steps

### 1. License Validation Function
Create a simple function to check if a license key is valid:

**NO pre-validation needed - just send the key to KeyKit and trust the response**

```php
function check_license($license_key, $site_url) {
    $response = wp_remote_post('https://keykit.app/api/validate', [
        'headers' => [
            'Content-Type' => 'application/json'
        ],
        'body' => json_encode([
            'token' => $license_key,
            'siteId' => $site_url
        ])
    ]);
    
    if (is_wp_error($response)) {
        return false;
    }
    
    $body = wp_remote_retrieve_body($response);
    $data = json_decode($body, true);
    
    return $data['valid'] ?? false;
}
```

> **Keep it simple**: Just return true/false. KeyKit handles all the complex license management!
> **NO pre-validation needed**: Don't check format, length, or anything else - just send to KeyKit

### 2. License Check on Plugin Load
Add license validation when your plugin initializes:

```php
// Check license when plugin loads
add_action('init', function() {
    $license_key = get_option('my_plugin_license_key');
    $site_url = home_url();
    
    if (!check_license($license_key, $site_url)) {
        // Show license error or disable features
        add_action('admin_notices', function() {
            echo '<div class="notice notice-error"><p>Invalid license key. Please check your license.</p></div>';
        });
        
        // Optionally disable premium features
        add_filter('my_plugin_premium_features', '__return_false');
    }
});
```

### 3. License Settings Page
Add a settings page for customers to enter their license key:

```php
// Add license field to settings page
add_action('admin_menu', function() {
    add_options_page(
        'Plugin License',
        'Plugin License',
        'manage_options',
        'plugin-license',
        function() {
            if (isset($_POST['license_key'])) {
                $license_key = sanitize_text_field($_POST['license_key']);
                $site_url = home_url();
                
                if (check_license($license_key, $site_url)) {
                    update_option('my_plugin_license_key', $license_key);
                    echo '<div class="notice notice-success"><p>License key saved and validated!</p></div>';
                } else {
                    echo '<div class="notice notice-error"><p>Invalid license key. Please check and try again.</p></div>';
                }
            }
            
            $current_key = get_option('my_plugin_license_key', '');
            echo '<form method="post">';
            echo '<table class="form-table">';
            echo '<tr><th>License Key</th><td><input type="text" name="license_key" value="' . esc_attr($current_key) . '" class="regular-text" placeholder="Enter your license key" /></td></tr>';
            echo '</table>';
            echo '<input type="submit" class="button-primary" value="Save License" />';
            echo '</form>';
        }
    );
});
```

### 4. Premium Feature Protection
Protect premium features with license validation:

```php
// Example: Protect a premium feature
function my_premium_feature() {
    $license_key = get_option('my_plugin_license_key');
    $site_url = home_url();
    
    if (!check_license($license_key, $site_url)) {
        wp_die('This feature requires a valid license key. Please enter your license key in the settings.');
    }
    
    // Your premium feature code here
    echo "Premium feature content";
}

// Only show premium features if license is valid
add_action('wp_ajax_my_premium_action', function() {
    my_premium_feature();
});
```

### 5. License Status Display
Show license status in admin dashboard:

```php
// Add license status to admin dashboard
add_action('wp_dashboard_setup', function() {
    wp_add_dashboard_widget(
        'my_plugin_license_status',
        'Plugin License Status',
        function() {
            $license_key = get_option('my_plugin_license_key');
            $site_url = home_url();
            
            if (empty($license_key)) {
                echo '<p>No license key entered. <a href="' . admin_url('options-general.php?page=plugin-license') . '">Enter license key</a></p>';
            } elseif (check_license($license_key, $site_url)) {
                echo '<p style="color: green;">✓ License is valid and active</p>';
            } else {
                echo '<p style="color: red;">✗ License is invalid. <a href="' . admin_url('options-general.php?page=plugin-license') . '">Update license key</a></p>';
            }
        }
    );
});
```

## Customer Experience
- Customers receive license keys via email immediately after purchase
- License keys are formatted as: `lk_1234567890abcdef1234567890abcdef`
- Keys are safe to share with customers and work immediately
- Customers enter the key in your WordPress plugin settings to activate their license

## Important Notes
- **Keep it simple**: Just check if the key is valid (true/false)
- **KeyKit handles everything else**: License creation, renewal, status tracking, etc.
- **NO pre-validation needed**: Don't check format, length, or anything else - just send to KeyKit
- **Trust KeyKit's response**: If KeyKit says it's valid, it's valid
- Validate on the server (WordPress/PHP) when possible
- Handle network errors gracefully to avoid app crashes
- License keys are automatically created and emailed when customers buy on Stripe
- License status syncs automatically with Stripe subscription status
- Use WordPress sanitization functions for all user inputs

## Error Handling
- Network errors: Handle gracefully, don't crash the app
- Invalid keys: Show clear error message and upgrade prompt
- Consider caching to reduce API calls
- WordPress errors: Use wp_die() for fatal errors, admin_notices for warnings

## Security
- Always validate on server-side for production plugins
- Use HTTPS for all API calls
- Sanitize all user inputs with WordPress functions
- Use nonces for form submissions
- Implement proper capability checks for admin functions

## WordPress Best Practices
- Use WordPress hooks and filters appropriately
- Follow WordPress coding standards
- Use WordPress database functions (get_option, update_option)
- Implement proper activation/deactivation hooks
- Use WordPress internationalization functions
- Follow WordPress security guidelines