Refactor to production-ready architecture with security fixes

.env.example

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+# Database Configuration
+DB_HOST=127.0.0.1
+DB_PORT=3306
+DB_NAME=magento
+DB_USER=root
+DB_PASSWORD=
+
+# Server Configuration
+PORT=3000
+NODE_ENV=development
+
+# Magento Configuration
+MAGENTO_BASE_PATH=/var/www/html/magento/
+
+# Application Configuration
+CACHE_ENABLED=true
+LOG_LEVEL=info

.gitignore

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+# Dependencies
+node_modules/
+package-lock.json
+yarn.lock
+
+# Environment variables
+.env
+.env.local
+.env.*.local
+
+# Logs
+logs/
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Build artifacts
+dist/
+build/
+tmp/
+
+# Testing
+coverage/
+.nyc_output/
+
+# Misc
+*.bak
+*.tmp

ARCHITECTURE.md

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+# Architecture Improvements Documentation
+
+## Overview
+
+This document describes the architectural improvements made to the NodeJento project to enhance maintainability, scalability, and code quality.
+
+## What Was Improved
+
+### 1. Configuration Management
+
+**Before:**
+- Hardcoded credentials in `app.js`
+- No environment variable support
+- Connection strings embedded in code
+
+**After:**
+- Environment-based configuration using `dotenv`
+- Centralized configuration in `src/config/index.js`
+- `.env.example` file for easy setup
+- Support for different environments (development, production)
+
+**Usage:**
+```javascript
+const config = require('./src/config');
+const sequelize = new Sequelize(config.database);
+```
+
+### 2. Error Handling
+
+**Before:**
+- Only one catch block for database connection
+- No error handling in async routes
+- No error middleware
+- Silent failures
+
+**After:**
+- Comprehensive error handling middleware
+- `asyncHandler` wrapper for async routes
+- Custom `AppError` class
+- Proper error responses with status codes
+- Environment-specific error details
+
+**Usage:**
+```javascript
+const { asyncHandler, AppError } = require('./src/middleware/errorHandler');
+
+app.get('/product/:sku', asyncHandler(async (req, res) => {
+  // Your code here - errors are automatically caught
+}));
+```
+
+### 3. Service Layer Architecture
+
+**Before:**
+- All logic in route handlers
+- Data transformation mixed with routing
+- No separation of concerns
+
+**After:**
+- **EavService**: Manages EAV attribute loading and caching
+- **ProductService**: Handles business logic for products
+- **ProductTransformer**: Transforms raw data to API format
+- Clear separation between routes, services, and data access
+
+**Benefits:**
+- Easier to test
+- Reusable business logic
+- Better code organization
+- Single Responsibility Principle
+
+### 4. Caching Improvements
+
+**Before:**
+- Unbounded `requestCache` object (memory leak risk)
+- No cache expiration
+- No cache management
+
+**After:**
+- `Cache` utility class with TTL support
+- Maximum cache size limit (prevents memory leaks)
+- Cache statistics and monitoring
+- Cache management endpoints
+
+**Features:**
+```javascript
+const cache = new Cache({
+  maxSize: 100,
+  defaultTTL: 300000, // 5 minutes
+  enabled: true
+});
+
+cache.set('key', value, 60000); // Cache for 1 minute
+const data = cache.get('key');
+const stats = cache.getStats(); // Get cache statistics
+```
+
+### 5. Project Structure
+
+**Before:**
+```
+nodejento/
+├── Models/
+├── app.js
+├── config.js
+└── test.js
+```
+
+**After:**
+```
+nodejento/
+├── Models/                          (existing models)
+├── src/
+│   ├── config/
+│   │   └── index.js                (centralized configuration)
+│   ├── services/
+│   │   ├── EavService.js           (EAV data management)
+│   │   ├── ProductService.js       (business logic)
+│   │   └── ProductTransformer.js   (data transformation)
+│   ├── middleware/
+│   │   └── errorHandler.js         (error handling)
+│   └── utils/
+│       └── Cache.js                (caching utility)
+├── app.js                          (original, kept for compatibility)
+├── app-improved.js                 (new improved version)
+├── config.js                       (updated with env support)
+├── .env.example                    (environment template)
+└── .gitignore                      (proper ignore rules)
+```
+
+### 6. Dependencies
+
+**Before:**
+```json
+{
+  "mysql2": "^2.2.5",     // 2+ years outdated
+  "sequelize": "^6.6.5"   // 2+ years outdated
+}
+```
+
+**After:**
+```json
+{
+  "dependencies": {
+    "dotenv": "^16.3.1",
+    "express": "^4.18.2",
+    "mysql2": "^3.9.8",
+    "sequelize": "^6.35.2"
+  },
+  "devDependencies": {
+    "nodemon": "^3.0.2"
+  }
+}
+```
+
+### 7. Package Scripts
+
+**New scripts added:**
+```json
+{
+  "scripts": {
+    "start": "node app.js",
+    "dev": "nodemon app.js"
+  }
+}
+```
+
+## Migration Guide
+
+### For Existing Users
+
+1. **Install new dependencies:**
+   ```bash
+   npm install
+   ```
+
+2. **Create `.env` file from template:**
+   ```bash
+   cp .env.example .env
+   ```
+
+3. **Configure your environment:**
+   Edit `.env` and set your database credentials and other settings.
+
+4. **Use the improved app:**
+   ```bash
+   # Development mode with auto-reload
+   npm run dev
+
+   # Production mode
+   npm start
+   ```
+
+### Backward Compatibility
+
+- The original `app.js` is preserved for backward compatibility
+- Use `app-improved.js` for new projects or when ready to migrate
+- Can run both versions side by side on different ports
+
+## New API Endpoints
+
+### Product by SKU
+```
+GET /product/:sku?store_ids=0,1
+```
+
+Returns a single product by SKU with full EAV data.
+
+### Products by multiple SKUs
+```
+GET /nodejento?skus=24-MB01,24-MB04&store_ids=0,1
+```
+
+Returns multiple products with full EAV data.
+
+### Cache Statistics
+```
+GET /cache/stats
+```
+
+Returns cache performance metrics:
+```json
+{
+  "size": 45,
+  "maxSize": 100,
+  "hits": 150,
+  "misses": 50,
+  "hitRate": "75.00%",
+  "enabled": true
+}
+```
+
+### Clear Cache
+```
+POST /cache/clear
+```
+
+Clears all cached data.
+
+## Key Benefits
+
+### 1. Maintainability
+- Clear separation of concerns
+- Easier to understand and modify
+- Better organized code
+
+### 2. Testability
+- Services can be unit tested independently
+- Mock dependencies easily
+- Better test coverage potential
+
+### 3. Scalability
+- Services can be extracted to microservices
+- Caching prevents database overload
+- Better resource management
+
+### 4. Security
+- No hardcoded credentials
+- Environment-based configuration
+- Proper error handling (no stack traces in production)
+
+### 5. Performance
+- Improved caching strategy
+- Memory leak prevention
+- Better database connection pooling
+
+### 6. Developer Experience
+- Hot reload with nodemon
+- Clear error messages
+- Better documentation
+- Environment templates
+
+## Best Practices Implemented
+
+1. **Environment Variables**: All configuration through environment variables
+2. **Error Handling**: Comprehensive error handling at all levels
+3. **Separation of Concerns**: Clear boundaries between layers
+4. **Dependency Injection**: Services receive dependencies, not global state
+5. **Caching**: Proper cache management with TTL and size limits
+6. **Logging**: Structured logging with request IDs
+7. **Graceful Shutdown**: Proper cleanup on SIGTERM
+8. **API Design**: RESTful endpoints with proper HTTP status codes
+
+## Next Steps (Future Improvements)
+
+1. **Testing**: Add unit and integration tests with Jest or Mocha
+2. **Logging**: Implement structured logging (Winston, Pino)
+3. **Documentation**: Add OpenAPI/Swagger documentation
+4. **Monitoring**: Add APM integration (New Relic, DataDog)
+5. **Database**: Add connection retry logic and read replicas support
+6. **Rate Limiting**: Add rate limiting middleware for API protection
+7. **CORS**: Add CORS support for web clients
+8. **Authentication**: Add JWT-based authentication for secure endpoints
+
+## Support
+
+For questions or issues with the new architecture:
+- Create an issue on GitHub
+- Email: yegorshytikov@gmail.com
+
+## License
+
+Same as the main project (ISC)