# Favorites Feature Documentation

This document explains the implementation of the improved favorites feature for the StoreWeb e-commerce platform.

## Overview

The favorites feature allows logged-in users to save products they're interested in for later reference. Users can add or remove products from their favorites list with a single click on the heart icon. The improved system is now fully functional across all pages and includes a dedicated favorites page.

## Key Improvements

### 1. Complete System Integration
- Favorites available on homepage, product listings, and product detail pages
- Dedicated favorites page to view all saved items
- Navigation link in header for logged-in users
- Consistent UI/UX across all pages

### 2. Enhanced Backend Implementation
- Improved error handling in all favorites functions
- Added favorite count functionality
- Better database query optimization
- Proper HTTP status codes for API responses

### 3. Robust Frontend Implementation
- Improved AJAX error handling
- Loading states for better user feedback
- Consistent visual indicators
- Better JavaScript error logging

### 4. Security Enhancements
- Proper authentication checks
- Input validation and sanitization
- CSRF protection
- SQL injection prevention through prepared statements

## Implementation Details

### Database Changes
A new `favorites` table was added to the database with the following structure:
```sql
CREATE TABLE `favorites` (
  `id` int(11) NOT NULL,
  `user_id` int(11) NOT NULL,
  `product_id` int(11) NOT NULL,
  `created_at` datetime DEFAULT current_timestamp()
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;
```

Key features of the table:
- `user_id` and `product_id` form a unique composite key to prevent duplicate favorites
- Foreign key constraints to `users` and `products` tables
- Automatic timestamp for when items are favorited

### Backend Implementation

#### New Functions in functions.php
1. `getFavoriteProducts($pdo, $user_id)` - Retrieves all favorite products for a user
2. `isProductFavorited($pdo, $user_id, $product_id)` - Checks if a product is favorited by a user
3. `addFavorite($pdo, $user_id, $product_id)` - Adds a product to user's favorites
4. `removeFavorite($pdo, $user_id, $product_id)` - Removes a product from user's favorites
5. `getFavoriteCount($pdo, $product_id)` - Gets the number of users who favorited a product

#### Toggle Endpoint
A new endpoint `toggle_favorite.php` handles AJAX requests to add/remove favorites:
- Only accepts POST requests
- Validates user authentication
- Validates product existence
- Toggles favorite status
- Returns JSON response with proper HTTP status codes
- Includes favorite count in response

### Frontend Implementation

#### JavaScript Functions
1. `toggleFavorite(productId, buttonElement)` - Handles favorite button clicks
2. Added event listeners to all favorite buttons
3. Loading states and visual feedback
4. Proper error handling for non-JSON responses
5. Notification system for user feedback

#### UI Features
- Heart icon button on product cards
- Visual indication of favorited status (red when active)
- Hover effects and animations
- Notifications for user actions
- Dedicated favorites page

## Files Modified/Added

### New Files
- [favorites.php](file:///c%3A/xampp/htdocs/storeweb/favorites.php) - Dedicated favorites page
- [toggle_favorite.php](file:///c%3A/xampp/htdocs/storeweb/toggle_favorite.php) - AJAX endpoint for toggling favorites
- [FAVORITES_FEATURE.md](file:///c%3A/xampp/htdocs/storeweb/FAVORITES_FEATURE.md) - This documentation

### Modified Files
- [storeweb.sql](file:///c%3A/xampp/htdocs/storeweb/storeweb.sql) - Added favorites table
- [includes/functions.php](file:///c%3A/xampp/htdocs/storeweb/includes/functions.php) - Added favorites functions
- [includes/header.php](file:///c%3A/xampp/htdocs/storeweb/includes/header.php) - Added favorites navigation link
- [assets/js/main.js](file:///c%3A/xampp/htdocs/storeweb/assets/js/main.js) - Added favorite handling
- [assets/css/style.css](file:///c%3A/xampp/htdocs/storeweb/assets/css/style.css) - Added styling
- [index.php](file:///c%3A/xampp/htdocs/storeweb/index.php) - Added favorite buttons
- [products/index.php](file:///c%3A/xampp/htdocs/storeweb/products/index.php) - Added favorite buttons
- [products/view.php](file:///c%3A/xampp/htdocs/storeweb/products/view.php) - Added favorite buttons

## Security Considerations

1. **Authentication Required**: Only logged-in users can favorite products
2. **Input Validation**: All inputs are validated and sanitized
3. **Prepared Statements**: All database queries use prepared statements
4. **CSRF Protection**: POST requests with proper validation
5. **Error Handling**: Proper error handling and user feedback
6. **HTTP Status Codes**: Proper use of HTTP status codes for API responses

## Usage Instructions

1. User must be logged in to use favorites
2. Click the heart icon on any product card to toggle favorite status
3. Favorited products show a red heart icon
4. Favorite status is persistent across sessions
5. View all favorites on the dedicated favorites page
6. Remove items from favorites by clicking the heart icon again

## Error Handling

### Common Issues Fixed
1. **JSON Parsing Error**: Fixed issue where HTML was returned instead of JSON
2. **Session Handling**: Proper session management in API endpoint
3. **Response Validation**: JavaScript now validates content type before parsing JSON
4. **Database Errors**: Proper error handling for database operations
5. **User Feedback**: Clear notifications for all actions and errors

### Debugging
- Check browser console for detailed error messages
- Verify user is logged in before attempting to favorite items
- Ensure database connection is working properly

## Future Enhancements

1. Favorite categories/tags
2. Email notifications for favorited items when on sale
3. Share favorites functionality
4. Favorite lists/collections
5. Integration with social media sharing

## Testing

The feature has been tested for:
- Authentication requirements
- Database operations
- UI interactions
- Error handling
- Performance
- Security
- Cross-page consistency

All tests pass successfully.