User Verification REST API

A simple Python REST API that verifies user existence by checking usernames from API headers against a local SQLite database.

Features

• ✅ User verification via API header
• ✅ Local SQLite database
• ✅ Pre-populated with sample users (including "toms")
• ✅ Returns 200 for existing users, 404 for non-existing users
• ✅ Additional endpoints to list and add users

Prerequisites

• Python 3.7 or higher
• pip (Python package manager)

Installation

1. Install required packages:

pip install -r requirements.txt

Running the API

1. Start the server:

python app.py

2. The API will start on http://127.0.0.1:5000

The database will be automatically initialized with sample users: toms, alice, bob, charlie

API Endpoints

1. Verify User (Main Endpoint)

Endpoint: GET /api/verify or POST /api/verify

Headers Required:

• X-Username: <username> or Username: <username>

Responses:

• 200 OK - User exists in database
• 404 Not Found - User does not exist
• 400 Bad Request - Username header missing

Example using curl:

# User exists (returns 200)
curl -H "X-Username: toms" http://127.0.0.1:5000/api/verify

# User doesn't exist (returns 404)
curl -H "X-Username: john" http://127.0.0.1:5000/api/verify

Example using PowerShell:

# User exists (returns 200)
Invoke-WebRequest -Uri "http://127.0.0.1:5000/api/verify" -Headers @{"X-Username"="toms"}

# User doesn't exist (returns 404)
Invoke-WebRequest -Uri "http://127.0.0.1:5000/api/verify" -Headers @{"X-Username"="john"}

Example using Python:

import requests

# User exists (returns 200)
response = requests.get('http://127.0.0.1:5000/api/verify', 
                       headers={'X-Username': 'toms'})
print(response.status_code)  # 200
print(response.json())

# User doesn't exist (returns 404)
response = requests.get('http://127.0.0.1:5000/api/verify', 
                       headers={'X-Username': 'john'})
print(response.status_code)  # 404

2. List All Users

Endpoint: GET /api/users

Response: 200 OK with list of all users

Example:

curl http://127.0.0.1:5000/api/users

3. Add New User

Endpoint: POST /api/users

Body: JSON with username

{
  "username": "newuser"
}

Responses:

• 201 Created - User added successfully
• 400 Bad Request - Username missing
• 409 Conflict - User already exists

Example:

curl -X POST -H "Content-Type: application/json" -d "{\"username\":\"newuser\"}" http://127.0.0.1:5000/api/users

4. Home/Help

Endpoint: GET /

Response: API information and available endpoints

Database

• Type: SQLite (file-based, no separate server needed)
• File: users.db (created automatically)
• Table: users with columns: id, username, created_at

Manual Database Initialization

If you need to reset or manually initialize the database:

python init_db.py

Testing the API

Once the server is running, test it using any of these methods:

1. Web Browser: Visit http://127.0.0.1:5000/ to see API info

2. PowerShell:

   Invoke-RestMethod -Uri "http://127.0.0.1:5000/api/verify" -Headers @{"X-Username"="toms"}

3. Postman:

   • Create a GET request to http://127.0.0.1:5000/api/verify
   • Add header: X-Username with value toms

Project Structure

restapi/
├── app.py              # Main Flask application
├── init_db.py          # Database initialization script
├── requirements.txt    # Python dependencies
├── README.md          # This file
└── users.db           # SQLite database (created automatically)

Status Codes

• 200 OK - User found in database
• 201 Created - User successfully added
• 400 Bad Request - Missing required header or body parameter
• 404 Not Found - User not found in database
• 409 Conflict - User already exists (when adding)

Stopping the Server

Press Ctrl+C in the terminal where the server is running.