dev-plan 26-12.md

��# Backend Implementation 1. Initialize Node.js project - npm init - Install dependencies: express, pg/mysql, dotenv 2. Set up Express server - Initialize Express app - Define middleware (e.g., body-parser for JSON) 3. Connect to SQL database - Use pg/mysql to connect to the database - Configure connection with environment variables 4. Define database schema - Write SQL for creating `categories` table - Write SQL for creating `expenses` table 5. API Endpoints - POST /categories to add a new category - Validate input - Insert into `categories` table - GET /categories to get all categories - Select from `categories` table - POST /expenses to log a new expense - Validate input - Insert into `expenses` table - GET /expenses to get expenses (with optional category filter) - Select from `expenses` table, possibly with JOIN to `categories` - PUT /categories/:id and /expenses/:id to update records - Validate input and ID - Update the respective table - DELETE /categories/:id and /expenses/:id to delete records - Delete from the respective table 6. Error Handling - Catch database errors and respond with appropriate status codes - Validate incoming data to prevent SQL injection 7. Testing - Write tests for each endpoint using a testing framework