wc-composable-product/IMPLEMENTATION.md

# WooCommerce Composable Products - Implementation Summary

## Overview

This document provides a technical overview of the WooCommerce Composable Products plugin implementation.

**Version:** 1.0.0
**Created:** 2024-12-31
**AI-Generated:** 100% created with Claude.AI assistance

## Architecture

### Plugin Structure

```txt
wc-composable-product/
├── assets/                  # Frontend assets
│   ├── css/
│   │   ├── admin.css       # Admin styles
│   │   └── frontend.css    # Frontend styles
│   └── js/
│       ├── admin.js        # Admin JavaScript
│       └── frontend.js     # Frontend JavaScript
├── cache/                  # Twig template cache
├── includes/               # PHP classes
│   ├── Admin/
│   │   ├── Product_Data.php    # Product data tab
│   │   └── Settings.php        # Settings page
│   ├── Cart_Handler.php        # Cart integration
│   ├── Plugin.php              # Main plugin class
│   ├── Product_Selector.php    # Frontend selector
│   └── Product_Type.php        # Custom product type
├── languages/              # Translation files
│   └── wc-composable-product.pot
├── templates/              # Twig templates
│   └── product-selector.twig
└── wc-composable-product.php   # Main plugin file
```

## Core Components

### 1. Main Plugin Class (`Plugin.php`)

**Responsibilities:**

- Singleton pattern implementation
- Twig template engine initialization
- Hook registration
- Component initialization
- Asset enqueuing

**Key Methods:**

- `instance()`: Get singleton instance
- `init_twig()`: Initialize Twig with WordPress functions
- `render_template()`: Render Twig templates
- `add_product_type()`: Register composable product type

### 2. Product Type (`Product_Type.php`)

**Extends:** `WC_Product`

**Key Features:**

- Custom product type: `composable`
- Selection limit management (per-product or global)
- Pricing mode (fixed or sum)
- Product selection criteria (category/tag/SKU)
- Dynamic product availability
- Price calculation

**Key Methods:**

- `get_selection_limit()`: Get max selectable items
- `get_pricing_mode()`: Get pricing calculation mode
- `get_available_products()`: Query available products
- `calculate_composed_price()`: Calculate final price

### 3. Admin Settings (`Admin/Settings.php`)

**Extends:** `WC_Settings_Page`

**Global Settings:**

- Default selection limit
- Default pricing mode
- Display options (images, prices, total)

**Integration:** Adds tab to WooCommerce Settings

### 4. Product Data Tab (`Admin/Product_Data.php`)

**Responsibilities:**

- Add "Composable Options" tab to product edit page
- Render selection criteria fields
- Save product meta data
- Dynamic field visibility based on criteria type

**Saved Meta:**

- `_composable_selection_limit`: Item limit
- `_composable_pricing_mode`: Pricing calculation
- `_composable_criteria_type`: Selection method
- `_composable_categories`: Selected categories
- `_composable_tags`: Selected tags
- `_composable_skus`: SKU list

### 5. Product Selector (`Product_Selector.php`)

**Responsibilities:**

- Render frontend product selection interface
- Prepare data for Twig template
- Apply display settings

**Template Variables:**

- `products`: Available products array
- `selection_limit`: Max selections
- `pricing_mode`: Pricing calculation
- `show_images/prices/total`: Display flags

### 6. Cart Handler (`Cart_Handler.php`)

**Responsibilities:**

- Validate product selection
- Add selected products to cart data
- Calculate dynamic pricing
- Display selected products in cart

**Hooks:**

- `woocommerce_add_to_cart_validation`: Validate selections
- `woocommerce_add_cart_item_data`: Store selections
- `woocommerce_before_calculate_totals`: Update prices
- `woocommerce_get_item_data`: Display in cart

## Frontend Implementation

### Product Selector Template (`product-selector.twig`)

**Features:**

- Responsive grid layout
- Checkbox-based selection
- Product images and prices
- Real-time total calculation
- AJAX add-to-cart

**Data Attributes:**

- `data-product-id`: Composable product ID
- `data-selection-limit`: Max selections
- `data-pricing-mode`: Pricing mode
- `data-price`: Individual product prices

### JavaScript (`frontend.js`)

**Functionality:**

- Selection limit enforcement
- Visual feedback on selection
- Real-time price updates (sum mode)
- AJAX cart operations
- Error/success messages

**Key Functions:**

- `handleCheckboxChange()`: Selection logic
- `updateTotalPrice()`: Calculate total
- `addToCart()`: AJAX add-to-cart
- `showMessage()`: User feedback

### CSS Styling

**Approach:**

- Grid-based layout (responsive)
- Card-style product items
- Visual selection states
- Mobile-first design
- Breakpoints: 768px, 480px

## Data Flow

### Creating a Composable Product

1. Admin selects "Composable product" type
2. Configure selection limit and pricing mode
3. Choose selection criteria (category/tag/SKU)
4. Save product metadata
5. WooCommerce registers product with custom type

### Frontend Display

1. Customer visits product page
2. `Cart_Handler` renders `Product_Selector`
3. `Product_Type::get_available_products()` queries products
4. Twig template renders grid with products
5. JavaScript handles interactions

### Adding to Cart

1. Customer selects products (JavaScript validation)
2. Click "Add to Cart" button
3. AJAX request with selected product IDs
4. `Cart_Handler::validate_add_to_cart()` validates
5. `Cart_Handler::add_cart_item_data()` stores selections
6. `Cart_Handler::calculate_cart_item_price()` updates price
7. Product added to cart with custom data

### Cart Display

1. WooCommerce loads cart
2. `Cart_Handler::get_cart_item_from_session()` restores data
3. `Cart_Handler::display_cart_item_data()` shows selections
4. Price calculated dynamically on each cart load

## Security Implementation

### Input Sanitization

- **Integers:** `absint()` for IDs and limits
- **Text:** `sanitize_text_field()` for modes and types
- **Textarea:** `sanitize_textarea_field()` for SKUs
- **Arrays:** `array_map()` with sanitization functions

### Output Escaping

- **HTML:** `esc_html()`, `esc_html_e()`
- **Attributes:** `esc_attr()`
- **URLs:** `esc_url()`
- **JavaScript:** Localized scripts with escaped data

### Validation

- Selection limit enforcement
- Product availability verification
- Cart data validation
- Nonce verification (via WooCommerce)

## Internationalization

### Text Domain

`wc-composable-product`

### Translation Functions

- `__()`: Return translated string
- `_e()`: Echo translated string
- `sprintf()` with `__()`: Variable substitution

### POT File

Generated template: `languages/wc-composable-product.pot`

**Supported Locales (per CLAUDE.md):**

- en_US (English)
- de_DE, de_DE_informal (German - Germany)
- de_CH, de_CH_informal (German - Switzerland)
- fr_CH (French - Switzerland)
- it_CH (Italian - Switzerland)

## Performance Considerations

### Caching

- Twig templates cached in `cache/` directory
- Auto-reload enabled in debug mode
- Optimized Composer autoloader

### Database Queries

- Efficient `WP_Query` for product selection
- Meta queries for SKU filtering
- Taxonomy queries for category/tag filtering

### Asset Loading

- Scripts only on relevant pages
- Minification ready (use build tools)
- Conditional enqueuing

## Extensibility

### Hooks & Filters

**Available Filters:**

- `wc_composable_settings`: Modify settings array
- `woocommerce_product_class`: Custom product class
- `product_type_selector`: Product type registration

**Customization Points:**

- Twig templates (override in theme)
- CSS styling (enqueue custom styles)
- JavaScript behavior (extend object)

### Developer API

```php
// Get composable product
$product = wc_get_product($product_id);

// Check if composable
if ($product->get_type() === 'composable') {
    // Get available products
    $products = $product->get_available_products();

    // Get selection limit
    $limit = $product->get_selection_limit();

    // Calculate price
    $price = $product->calculate_composed_price($selected_ids);
}
```

## Testing Checklist

### Admin Testing

- [ ] Product type appears in dropdown
- [ ] Composable Options tab displays
- [ ] Selection criteria toggle works
- [ ] Meta data saves correctly
- [ ] Settings page accessible
- [ ] Global defaults apply

### Frontend Testing

- [ ] Product selector renders
- [ ] Selection limit enforced
- [ ] Price calculation accurate (both modes)
- [ ] AJAX add-to-cart works
- [ ] Cart displays selections
- [ ] Checkout processes correctly

### Edge Cases

- [ ] Empty criteria (no products)
- [ ] Out of stock products excluded
- [ ] Invalid product selections rejected
- [ ] Multiple cart items unique
- [ ] Session persistence

## Known Limitations

1. **Variable Products:** Currently supports simple products in selection
2. **Grouped Products:** Cannot be used as selectable items
3. **Stock Management:** No automatic stock reduction for selected items
4. **Caching:** Template cache needs manual clearing after updates

## Future Enhancements

Potential features for future versions:

- Variable product support in selection
- Quantity selection per item (not just presence)
- Visual bundle previews
- Advanced pricing rules
- Stock management integration
- Product recommendations
- Selection templates/presets
- Multi-currency support enhancements

## Dependencies

### Runtime

- PHP 8.3+
- WordPress 6.0+
- WooCommerce 8.0+
- Twig 3.0 (via Composer)

### Development

- Composer for dependency management
- WP-CLI for i18n operations (optional)

## Deployment

### Production Checklist

1. Run `composer install --no-dev --optimize-autoloader`
2. Ensure `vendor/` directory is included
3. Ensure `cache/` directory is writable
4. Test on staging environment
5. Clear all caches after activation
6. Verify WooCommerce compatibility

### Release Package

Must include:

- All PHP files
- `vendor/` directory
- Assets (CSS, JS)
- Templates
- Language files
- Documentation

Must exclude:

- `.git/` directory
- `composer.lock`
- Development files
- `wp-core/`, `wp-plugins/` symlinks

## Support & Maintenance

### Code Standards

- WordPress Coding Standards
- WooCommerce best practices
- PSR-4 autoloading
- Inline documentation

### Version Control

- Semantic versioning (MAJOR.MINOR.PATCH)
- Changelog maintained
- Annotated git tags
- Development on `dev` branch

---

**Last Updated:** 2024-12-31
**Maintainer:** Marco Graetsch
**AI Assistant:** Claude.AI (Anthropic)