Jason
172 lines
4.4 KiB
Markdown
172 lines
4.4 KiB
Markdown
# Data Access Layer (DAL) - SQLite and JSON Toggle
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The application now supports switching between **SQLite** and **JSON** data storage through a simple configuration toggle.
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## Configuration
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Open `app/config.py` and set:
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```python
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# Set to True for SQLite, False for JSON files
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USE_DATABASE = True # or False
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```
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## Architecture
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### Modules
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1. **config.py** - Application configuration
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- `USE_DATABASE` - Toggle between SQLite and JSON
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- Database URI and other settings
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2. **data_access_sqlite.py** - SQLite implementation
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- Uses SQLAlchemy models
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- Supports transactions and rollback
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3. **data_access_json.py** - JSON file implementation
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- Thread-safe file operations
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- Immediate writes (no transactions)
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4. **data_access.py** - Universal wrapper
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- Automatically imports correct module based on config
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- Provides unified interface to all blueprints
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### Standardized Functions
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Both modules implement the same functions:
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**User Operations:**
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- `get_user_by_username(username)`
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- `get_user_by_id(user_id)`
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- `get_all_users()`
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- `create_user(user_data)`
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- `update_user(user_id, user_data)`
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- `delete_user(user_id)`
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- `toggle_user_active(user_id, active)`
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- `change_user_password(user_id, new_password)`
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**Product Operations:**
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- `get_all_products(location=None)`
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- `get_product_by_code(product_code)`
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- `create_product(product_data)`
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- `update_product(product_code, product_data)`
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- `delete_product(product_code)`
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**Location Operations:**
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- `get_all_locations()`
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- `get_location_by_code(code)`
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**Product Attributes:**
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- `get_product_attributes()`
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- `update_product_attributes(attributes_data)`
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**Utilities:**
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- `commit()` - Commit transaction (no-op for JSON)
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- `rollback()` - Rollback transaction (no-op for JSON)
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## Usage in Blueprints
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All blueprints now import from the data access layer:
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```python
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import data_access as da
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# Get user
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user = da.get_user_by_username('Master')
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# Get products
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products = da.get_all_products(location='IOLA')
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# Create product
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product = da.create_product(product_data)
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```
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## Switching Between Modes
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### To Use SQLite:
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1. Set `USE_DATABASE = True` in `config.py`
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2. Run migration: `python migrate_to_sqlite.py`
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3. Start app: `python app.py`
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### To Use JSON:
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1. Set `USE_DATABASE = False` in `config.py`
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2. Ensure JSON files exist in `data/` folder
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3. Start app: `python app.py`
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## Key Differences
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| Feature | SQLite | JSON |
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|---------|--------|------|
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| **Transactions** | Yes | No (immediate writes) |
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| **Concurrency** | Better | File locks |
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| **Performance** | Faster for large datasets | Faster for small datasets |
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| **Backup** | Single .db file | Multiple .json files |
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| **Queries** | Complex SQL queries | Load entire file |
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| **User IDs** | Database auto-increment | Array index |
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## Important Notes
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### User IDs
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- **SQLite**: Uses database-generated IDs
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- **JSON**: Uses array index (changes if users deleted)
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### Session Management
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- Both modes use username-based sessions (not user_id)
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- Session keys: `username`, `currentLocation`, `accessibleLocations`
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### Data Consistency
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- **SQLite**: ACID compliant with rollback support
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- **JSON**: No rollback - writes are immediate and final
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### File Serving
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- The `/quiz/data/<filename>` route still serves static JSON files
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- When using SQLite, these JSON files may become stale
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- Consider using API endpoints instead for dynamic data
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## Migration
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To migrate existing JSON data to SQLite:
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```bash
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cd app
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python migrate_to_sqlite.py
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```
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This will:
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- Create `data/products.db`
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- Backup JSON files to `data/json_backup/`
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- Migrate users, products, locations, and attributes
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- Skip duplicates on subsequent runs
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## Testing
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Test both modes:
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```bash
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# Test with SQLite
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# Set USE_DATABASE = True in config.py
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python app.py
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# Test with JSON
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# Set USE_DATABASE = False in config.py
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python app.py
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```
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## Troubleshooting
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**"Import 'flask' could not be resolved"**
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- This is just an editor warning, not a runtime error
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- Install dependencies: `pip install -r requirements.txt`
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**Data not updating**
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- Check `USE_DATABASE` setting in config.py
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- Verify correct data files exist (`.db` or `.json`)
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- Check terminal for data access layer mode message
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**User not found after switching modes**
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- User IDs differ between SQLite and JSON
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- Clear browser cookies/session
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- Re-login to create new session
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