Chat Application API Documentation

Overview

A RESTful chat application backend built with PHP, Slim Framework, SQLite, and Redis. The application allows users to create chat groups, join them, and exchange messages.

Technology Stack

• PHP 8.0+
• Slim Framework 4.0
• SQLite Database
• Redis (for caching and rate limiting)
• PHPUnit for testing

Setup Instructions

Prerequisites

• PHP 8.0 or higher
• Composer
• SQLite
• Redis server

Installation

1. Clone the repository
2. Run composer install
3. Configure environment variables in .envor use default values:
4. Initialize database: php src/Database/setup.php
5. Make sure redis server is running otherwise send message endpoint will not work: redis-server
6. Start server: php server.php

API Endpoints

Users

Create User

• POST /users
• Body: {"username": "john_doe"}
• Response: 201 Created

  {
    "id": 1,
    "username": "john_doe",
    "created_at": "2024-01-29 15:00:00"
  }

Get User

• GET /users/{id}
• Response: 200 OK

  {
    "id": 1,
    "username": "john_doe",
    "created_at": "2024-01-29 15:00:00"
  }

Groups

Create Group

• POST /groups
• Body: {"name": "General Chat"}
• Response: 201 Created

  {
    "id": 1,
    "name": "General Chat",
    "created_at": "2024-01-29 15:00:00"
  }

Join Group

• POST /groups/{group_id}/join
• Body: {"user_id": 1}
• Response: 200 OK

  {
    "message": "Successfully joined group"
  }

Get Group Members

• GET /groups/{group_id}/members
• Response: 200 OK

  [
    {
      "id": 1,
      "username": "john_doe",
      "joined_at": "2024-01-29 15:00:00"
    }
  ]

Messages

Send Message

• POST /groups/{group_id}/messages
• Body: {"user_id": 1, "content": "Hello, everyone!"}
• Response: 201 Created
• Rate Limit: 60 messages per minute per user enforced by redis

  {
    "id": 1,
    "group_id": 1,
    "user_id": 1,
    "content": "Hello, everyone!",
    "created_at": "2024-01-29 15:00:00"
  }

Get Group Messages

• GET /groups/{group_id}/messages?user_id=1
• Response: 200 OK

  [
    {
      "id": 1,
      "content": "Hello, everyone!",
      "created_at": "2024-01-29 15:00:00",
      "user_id": 1,
      "username": "john_doe"
    }
  ]

Get New Messages

• GET /groups/{group_id}/messages/since/{timestamp}?user_id=1
• Response: 200 OK

  [
    {
      "id": 2,
      "content": "New message",
      "created_at": "2024-01-29 15:10:00",
      "user_id": 1,
      "username": "john_doe"
    }
  ]

Error Responses

• 400 Bad Request: Invalid input
• 401 Unauthorized: Authentication required
• 403 Forbidden: Not a group member
• 404 Not Found: Resource doesn't exist
• 409 Conflict: Resource already exists
• 429 Too Many Requests: Rate limit exceeded
• 500 Internal Server Error: Server error

Caching

• Message lists are cached in Redis for 5 minutes
• Cache is automatically invalidated when new messages are posted
• Rate limiting uses Redis for tracking message counts

Testing

1. Install dependencies: composer install
2. Run tests: ./vendor/bin/phpunit

Test Suites

• Unit Tests: ./vendor/bin/phpunit --testsuite Unit
• Integration Tests: ./vendor/bin/phpunit --testsuite Integration
• API Tests: ./vendor/bin/phpunit --testsuite API

Database Schema

users

• id (INTEGER PRIMARY KEY)
• username (TEXT UNIQUE)
• created_at (DATETIME)

groups

• id (INTEGER PRIMARY KEY)
• name (TEXT)
• created_at (DATETIME)

group_members

• group_id (INTEGER)
• user_id (INTEGER)
• joined_at (DATETIME)
• PRIMARY KEY (group_id, user_id)
• FOREIGN KEY references to groups and users

messages

• id (INTEGER PRIMARY KEY)
• group_id (INTEGER)
• user_id (INTEGER)
• content (TEXT)
• created_at (DATETIME)
• FOREIGN KEY references to groups and users

Postman Collection

A Postman collection is available in docs/postman/Chat_API.postman_collection.json for testing all endpoints.

Running Tests

Setup Test Environment

1. Make sure Redis server is running
2. No need for SQLite file as tests use in-memory database

Running All Tests

./vendor/bin/phpunit

Running Specific Test Suites

# Run only unit tests
./vendor/bin/phpunit --testsuite Unit

# Run only integration tests
./vendor/bin/phpunit --testsuite Integration

# Run only API tests
./vendor/bin/phpunit --testsuite API

Running Individual Test Files

# Run specific test file
./vendor/bin/phpunit tests/Unit/Models/UserTest.php

# Run specific test method
./vendor/bin/phpunit --filter testCreateUser tests/Unit/Models/UserTest.php

Test Coverage

• Unit Tests: Model methods and basic functionality
• Integration Tests: Cross-component interactions
• API Tests: HTTP endpoints and responses

Common Test Cases

• Creating/retrieving users
• Creating/joining groups
• Sending/retrieving messages
• Rate limiting
• Cache invalidation
• Error handling