Troubleshooting

Relevant source files

The following files were used as context for generating this wiki page:

• server.js
• APP/config/db.config.js
• APP/models/model.model.js
• public/index.html
• seed.js
• package.json
• model_database.py

This document provides guidance for diagnosing and resolving common issues within the LostData application. It covers problems related to server startup, database connectivity, API errors, and frontend behavior. The application consists of a Node.js/Express backend, a MongoDB database, and a vanilla JavaScript frontend.

Troubleshooting generally involves checking server console logs for startup messages and runtime errors, inspecting browser developer tools for network request failures and client-side errors, and verifying database state and configuration.

Server Startup and Connectivity

Issues in this area typically prevent the application from running or connecting to its database.

Server Won't Start

If the Node.js server fails to start, check the following:

1. Dependencies: Ensure all required npm packages are installed by running npm install. The necessary dependencies are listed in package.json.
   Sources: package.json
2. Environment Variables: The server requires a MONGODB_URI environment variable to connect to the database. If this is not set, it falls back to a default local URI. The server port can be set via the PORT environment variable, defaulting to 3000.
   Sources: server.js:2, server.js:143, APP/config/db.config.js:2
3. Console Logs: Check the console for error messages. A successful startup will log "DB connected" followed by "Server on [PORT]".
   Sources: server.js:26, server.js:144

The diagram below illustrates the server startup sequence.

Database Connection Failure

A failure to connect to MongoDB is a common startup issue.

• Connection String: The connection URI is defined by process.env.MONGODB_URI or defaults to mongodb://127.0.0.1:27017/model_db. Verify that the MongoDB instance is running and accessible at this address.
  Sources: APP/config/db.config.js:2, server.js:25
• Error Logging: Any connection error is caught and logged to the console. This log will contain details about the connection failure.
  Sources: server.js:25

API Endpoint Errors

The backend exposes a REST API for managing models. Errors can occur due to invalid requests, lack of permissions, or server-side problems. All API routes are defined in server.js.

Authentication and Authorization

Most write operations (create, update, delete) and data management features (import/export) are protected and require admin privileges.

• Admin Role: A user is considered an 'admin' if their login email ends with @admin.com. Otherwise, they are a 'chatter'.
  Sources: server.js:30
• Admin Middleware: The isAdmin middleware checks if req.session.user.role is 'admin'. If not, it returns a 403 Forbidden status with the message 'Admin required'.
  Sources: server.js:40-43

The following sequence diagram shows a failed request to an admin-only endpoint by a non-admin user.

API Endpoint Error Summary

All API endpoints include try...catch blocks that respond with a 500 Internal Server Error if an unhandled exception occurs on the server.

Endpoint	Method	Admin	Description	Common Errors
/api/login	POST	No	Logs a user in and sets their role in the session.	N/A (creates session)
/api/logout	POST	No	Destroys the user session.	N/A (destroys session)
/api/models	GET	No	Fetches all models.	500 on database query failure.
/api/models/:id	GET	No	Fetches a single model by ID.	500 on database query failure.
/api/models	POST	Yes	Creates a new model.	403 if not admin. 500 on database save error (e.g., validation).
/api/models/:id	PUT	Yes	Updates an existing model.	403 if not admin. 500 on database save error.
/api/models/:id	DELETE	Yes	Deletes a model.	403 if not admin. 500 if model not found or DB error.
/api/export/json	GET	Yes	Exports all models as JSON.	403 if not admin. 500 on database query failure.
/api/export/csv	GET	Yes	Exports all models as CSV.	403 if not admin. 500 on database query failure.
/api/import/csv	POST	Yes	Imports models from a CSV file.	403 if not admin. 500 if file parsing or insertMany fails.

Sources: server.js:28-132

Database and Data Integrity

Issues can arise from incorrect data schemas, failed data seeding, or validation errors during create/update operations.

Model Schema

The Model schema is defined using Mongoose. All data operations must conform to this schema.

This ER diagram shows the structure of the Model collection.

Key fields and constraints are listed below:

Field	Type	Constraints	Description
id	String	required, unique	A unique identifier for the model.
name	String	required	The name of the model.
profile	String	required	The model's profile description.
pricing	String	required	Pricing information.
dosAndDonts	String	required	List of allowed and disallowed activities.
history	Array	default: []	An array tracking changes to the record.

Sources: APP/models/model.model.js:2-15

A common issue is a 500 error on POST /api/models if required fields are missing from the request body or if the id is not unique.

Data Seeding

The project includes a seed.js script to populate the MongoDB database with initial data. If the application shows no models, it may be because the database is empty.

• Running the Seeder: Execute node seed.js to populate the database.
• Seeder Logic: The script connects to the MongoDB instance defined in db.config.js, then uses Model.insertMany() to add a predefined list of models.
• Error Handling: Any errors during connection or insertion are logged to the console.

Sources: seed.js

Note: The repository also contains a Python script, model_database.py, which manages a local models.json file. This is a separate utility and does not interact with the MongoDB database used by the main Node.js application.
Sources: model_database.py

Frontend Issues

Client-side problems usually manifest as missing data, non-functional buttons, or incorrect UI states. Use the browser's developer tools (Console and Network tabs) for diagnosis.

Login and UI State

The user's role (admin or chatter) is stored in localStorage after a successful login. This role determines the visibility of admin-only UI elements like the "Add Model", "Edit", and "Delete" buttons.

• Symptom: Admin buttons are not visible after logging in with an admin email.
• Cause: The localStorage.setItem('role', data.role) call may have failed, or the role was not correctly determined by the backend.
• Troubleshooting:
  1. Check localStorage in the browser's developer tools to see if the role key is set to admin.
  2. Inspect the response from POST /api/login in the Network tab to ensure it returns { "role": "admin" }.

The following diagram shows the client-side login and data fetching flow.

Data Display and Search

• Symptom: The model grid shows "Loading..." indefinitely or is empty.
• Cause: The fetch('/api/models') call might be failing, or it's returning an empty array.
• Troubleshooting:
  1. Check the browser's Network tab for the GET /api/models request. Verify its status code (should be 200 OK) and response payload.
  2. Check the browser's Console for any JavaScript errors occurring within the fetchModels or renderModels functions.
• Symptom: Search functionality is not working correctly.
• Cause: The search filter logic is case-sensitive or the search term doesn't match the name or profile fields. The filtering is performed client-side on the already-fetched data.
  Sources: public/index.html:128-135