# Proposed Circularize Solution Document

## Key Architectural Considerations:

- **Microservices Architecture**: Utilizing a microservices approach for the User Management Service allows for scalability, easier maintenance, and better separation of concerns.
- **Integration with Auth0**: Leverages Auth0 for secure and reliable user authentication, ensuring that user identity management adheres to industry standards.
- **Database Design**: A well-structured database schema that supports complex queries and efficient data retrieval, crucial for managing roles and permissions.

## Tradeoffs and Scaling Strategies:

### Tradeoffs:
- **Complexity vs. Flexibility**: While a microservices architecture offers flexibility, it increases system complexity.
- **Custom Role Management vs. Third-Party Services**: Building a custom role management system provides tailored solutions but demands more development and maintenance effort compared to using pre-built services.

### Scaling Strategies:
- **Horizontal Scaling**: Ability to scale the services horizontally to manage increased load.
- **Database Optimization**: Implementing indexing, caching, and query optimization to handle growing data efficiently.
- **Load Balancing**: Using load balancers to distribute traffic across multiple instances of the service.

## Product-Centric Elements

### User Experience (UX) Considerations:
- **Intuitive Interface**: A user-friendly interface in the frontend for role and permission management, ensuring ease of use.
- **Responsive Design**: Ensuring the application is responsive and accessible across different devices and screen sizes.
- **Feedback Mechanisms**: Implementing clear feedback and error messages to guide users effectively.

### User Flow:
- **Authentication**: Users log in via Auth0, with secure handling of credentials.
- **Role Assignment**: Administrators can assign roles to users, with changes reflected in real-time.
- **Permission Management**: Easy-to-navigate interface for admins to create, modify, and delete roles and permissions.

### Feature Set:
- **Role Creation and Management**: Features for creating and managing custom roles.
- **Permission Assignment**: Ability to assign specific permissions to each role.
- **User-Roles Mapping**: Interface for mapping users to their respective roles based on company ID and other criteria.
- **Audit Trails and Reporting**: Features for tracking changes in roles and permissions for auditing purposes.

### Step 1: Retrieve User Metadata from Auth0

#### Technical Design & Architecture

**Objective**: Securely extract user metadata from the JSON Web Token (JWT) provided by Auth0 upon user authentication, focusing on the middleware that validates the token and retrieves metadata like the company ID.

**Components**:
1. **JWT Middleware**: A middleware component in the Node.js backend that intercepts incoming requests, validates the JWT, and extracts user metadata.
2. **Auth0 Setup**: Configuration on Auth0 to include necessary metadata in the JWT.
3. **User Metadata Model**: A TypeScript interface or model representing the structure of the user metadata extracted from the JWT.

#### Implementation Steps

1. **Configure Auth0 to Include Metadata in JWT**:
- Ensure that Auth0 is set up to include custom metadata (like company ID) in the JWT. This might involve configuring rules or settings in the Auth0 dashboard.

2. **Create JWT Middleware in Node.js**:
- Implement a middleware function in your Node.js application that uses `express-jwt` and `jwks-rsa` to validate the JWT from incoming requests.
- Extract and verify the JWT from the `Authorization` header.

3. **Decode JWT and Extract Metadata**:
- Use the `jsonwebtoken` library to decode the JWT.
- Define a TypeScript interface to represent the structure of the user metadata.
- Extract the relevant metadata (e.g., company ID) from the decoded token.

4. **Error Handling and Security**:
- Implement error handling in the middleware to manage cases where the token is invalid, expired, or tampered with.
- Ensure secure handling of tokens and metadata to prevent security vulnerabilities.

5. **Testing**:
- Write unit tests for the middleware to ensure it correctly validates tokens and extracts metadata.
- Test the integration with Auth0 in a secure environment.

#### Sample Code Snippet (Middleware in TypeScript)

import jwt from 'express-jwt';
import jwksRsa from 'jwks-rsa';
import { Request, Response, NextFunction } from 'express';

interface UserMetadata {
  companyID: string;
  // other metadata fields
}

// JWT Middleware for validating tokens and extracting metadata
const jwtCheck = jwt({
  secret: jwksRsa.expressJwtSecret({
    cache: true,
    rateLimit: true,
    jwksRequestsPerMinute: 5,
    jwksUri: `https://${process.env.AUTH0_DOMAIN}/.well-known/jwks.json`
  }),
  audience: process.env.AUTH0_AUDIENCE,
  issuer: `https://${process.env.AUTH0_DOMAIN}/`,
  algorithms: ['RS256']
});

const extractMetadata = (req: Request, res: Response, next: NextFunction) => {
  if (req.user) {
    const metadata = req.user['http://myapp.com/metadata'] as UserMetadata;
    req.companyID = metadata.companyID;
    // Process other metadata as needed
  }
  next();
};

export { jwtCheck, extractMetadata };

### Step 2: Integrate Role Management Logic

#### Technical Design & Architecture

**Objective**: Implement a robust role-based access control (RBAC) system that uses the extracted user metadata (such as company ID) to assign and manage user roles and permissions.

**Components**:
1. **Role and Permission Models**: Define data models for roles and permissions.
2. **User-Roles Mapping**: Mechanism to map users to their respective roles, possibly with a many-to-many relationship.
3. **Role-Permissions Association**: System to associate specific permissions with each role.
4. **Role Management Logic**: Core business logic to handle role assignments and permission checks.

#### Implementation Steps

1. **Define Data Models (Roles, Permissions, User-Roles Mapping)**:
- Create TypeScript interfaces and corresponding database models for roles and permissions.
- Define the structure for storing and retrieving the mappings between users, their roles, and associated permissions.
- Consider using an ORM like Sequelize or TypeORM for database interactions.

2. **Implement Role Management Functions**:
- Develop functions to create, update, delete, and retrieve roles and permissions.
- Include the functionality to assign roles to users based on criteria (like company ID from user metadata).

3. **Permission Checks and Role Validation**:
- Create middleware or utility functions to validate if a user has the required role or permission to perform certain actions.
- Ensure that these checks are efficient and secure.

4. **Integration with Auth0 Authentication**:
- Link the role management logic with the user authentication process, ensuring that roles are correctly assigned and validated post-authentication.

5. **Error Handling and Security Considerations**:
- Implement robust error handling to manage potential issues like role conflicts or unauthorized access attempts.
- Ensure that all role management operations adhere to security best practices.

6. **Testing and Validation**:
- Write comprehensive tests for all role management functions and middleware.
- Test the integration with the user authentication flow and metadata extraction.

#### Sample Code Snippet (Role Management in TypeScript)

Here’s an example of how you might define models and implement basic role management functions:

import { Model, DataTypes } from 'sequelize';

// Assuming Sequelize is used for ORM
class Role extends Model {
  public id!: number;
  public name!: string;
  // other role properties
}

Role.init({
  id: {
    type: DataTypes.INTEGER,
    autoIncrement: true,
    primaryKey: true
  },
  name: {
    type: new DataTypes.STRING(128),
    allowNull: false
  }
  // other role properties
}, {
  sequelize,
  tableName: 'roles'
});

// Function to assign a role to a user
async function assignRoleToUser(userId: number, roleId: number): Promise<void> {
  // Logic to assign role to user in the database
}

// Function to check if a user has a specific role
async function userHasRole(userId: number, roleName: string): Promise<boolean> {
  // Logic to check user's roles
}

export { Role, assignRoleToUser, userHasRole };

### Step 3: API Endpoints for Role Management

#### Technical Design & Architecture

**Objective**: Create a set of RESTful API endpoints in the Node.js backend that allows authorized users to manage roles and permissions.

**Components**:
1. **API Routes**: Specific routes for role and permission management tasks.
2. **Controllers**: Functions that handle the logic for each API endpoint.
3. **Authorization Middleware**: Middleware to ensure that only authorized users can access certain endpoints.
4. **Validation Middleware**: Middleware to validate request data.

#### Implementation Steps

1. **Design API Endpoints**:
- Define RESTful routes for creating, updating, and deleting roles (`/roles`), and managing role assignments to users (`/roles/assign`).

2. **Implement Controllers**:
- Create controller functions for each endpoint that interact with the database to manage roles and permissions.

3. **Authorization Checks**:
- Implement middleware to check if the user is authorized to access the endpoint. This could be based on the user's role and permissions.

4. **Request Validation**:
- Use middleware to validate incoming data in requests to ensure it meets the expected format and criteria.

5. **Error Handling**:
- Ensure comprehensive error handling in the API for cases like invalid requests, unauthorized access, and server errors.

6. **Testing**:
- Write tests for each endpoint to ensure they function correctly and handle errors appropriately.

#### Sample Code Snippet (API Endpoints in TypeScript)

Here’s an example of how you might define the API endpoints:

import express, { Request, Response } from 'express';
import { Role, assignRoleToUser, userHasRole } from './roleManagement';

const router = express.Router();

// Endpoint to create a new role
router.post('/roles', async (req: Request, res: Response) => {
  try {
    const newRole = await Role.create({ name: req.body.name });
    res.status(201).json(newRole);
  } catch (error) {
    res.status(400).json({ error: error.message });
  }
});

// Endpoint to assign a role to a user
router.post('/roles/assign', async (req: Request, res: Response) => {
  try {
    await assignRoleToUser(req.body.userId, req.body.roleId);
    res.status(200).json({ message: 'Role assigned successfully' });
  } catch (error) {
    res.status(400).json({ error: error.message });
  }
});

export default router;

### Step 4: Frontend Integration

#### Technical Design & Architecture

**Objective**: Seamlessly integrate the role management functionalities into the Next.js frontend, providing a user-friendly interface for managing roles and permissions.

**Components**:
1. **Frontend UI Components**: React components in Next.js for displaying and managing roles and permissions.
2. **API Service Layer**: A service layer in the frontend for making HTTP requests to the backend API.
3. **State Management**: Managing application state related to roles and permissions.
4. **Authentication and Authorization Checks**: Ensuring that the frontend respects user roles and permissions for access control.

#### Implementation Steps

1. **Design UI Components**:
- Develop React components for listing roles, creating new roles, updating existing roles, and assigning roles to users.
- Implement forms for inputting role and permission data.

2. **Create API Service Layer**:
- Develop a service layer using Axios or Fetch API to make HTTP requests to the backend endpoints for role management.
- Handle API responses and errors gracefully.

3. **Integrate State Management**:
- Use React Context or state management libraries like Redux or MobX to manage the state related to roles and permissions.
- Ensure that the UI reflects the current state and updates dynamically as roles and permissions are modified.

4. **Implement Authentication and Authorization in the UI**:
- Use Auth0's SDK for authentication in the frontend.
- Implement logic to display or hide certain UI elements based on the user’s roles and permissions.

5. **Error Handling and User Feedback**:
- Implement error handling in the UI, providing user feedback for actions like failed API requests.
- Validate user inputs on the frontend before sending requests to the backend.

6. **Testing and Validation**:
- Write unit and integration tests for the frontend components and service layer.
- Test the UI’s responsiveness and interactivity.

#### Sample Code Snippet (Next.js with React)

Here's an example of a React component for creating a new role:

import React, { useState } from 'react';
import axios from 'axios';

const CreateRoleComponent = () => {
  const [roleName, setRoleName] = useState('');

  const handleSubmit = async () => {
    try {
      const response = await axios.post('/api/roles', { name: roleName });
      console.log('Role created:', response.data);
      // Handle successful role creation
    } catch (error) {
      console.error('Error creating role:', error);
      // Handle error in role creation
    }
  };

  return (
    <div>
      <input
        type="text"
        value={roleName}
        onChange={(e) => setRoleName(e.target.value)}
        placeholder="Enter role name"
      />
      <button onClick={handleSubmit}>Create Role</button>
    </div>
  );
};

export default CreateRoleComponent;

### Step 5: Security and Validation

#### Technical Design & Architecture

**Objective**: Ensure that the role management system is secure and robust, protecting against common vulnerabilities and ensuring data integrity.

**Components**:
1. **Input Validation**: Implementing checks on the frontend and backend to validate user inputs.
2. **Authorization Checks**: Ensuring that users can perform only those actions they are permitted to.
3. **Security Best Practices**: Adopting standard security measures in both frontend and backend.
4. **Error Handling**: Properly handling errors to avoid leaking sensitive information.

#### Implementation Steps

1. **Implement Input Validation**:
- Use frontend validation to catch and inform users of input errors before submission.
- Implement backend validation to catch any malformed or malicious data before processing.

2. **Strengthen Authorization Checks**:
- Ensure that each backend endpoint checks the user’s roles and permissions before performing any action.
- On the frontend, conditionally render components based on the user's roles and permissions.

3. **Adopt Security Best Practices**:
- Use HTTPS for all data in transit.
- Sanitize inputs to prevent SQL Injection, XSS, and other injection attacks.
- Implement proper JWT handling strategies (such as token expiration and refresh tokens).

4. **Implement Comprehensive Error Handling**:
- Avoid sending detailed error messages to the client, which could expose internal workings or vulnerabilities.
- Log errors on the server for debugging while providing generic error messages to users.

5. **Regular Security Audits and Updates**:
- Conduct regular security reviews and updates of your codebase and dependencies.
- Stay informed about new vulnerabilities and apply patches as necessary.

#### Sample Code Snippet (Backend Validation in TypeScript)

Here's an example of backend validation for a role creation endpoint:

import { Request, Response, NextFunction } from 'express';
import { body, validationResult } from 'express-validator';

// Middleware for role creation validation
const validateRoleCreation = [
  body('name').isString().withMessage('Role name must be a string'),
  // additional validations can be added here
  (req: Request, res: Response, next: NextFunction) => {
    const errors = validationResult(req);
    if (!errors.isEmpty()) {
      return res.status(400).json({ errors: errors.array() });
    }
    next();
  }
];

// Sample endpoint using the validation middleware
router.post('/roles', validateRoleCreation, async (req: Request, res: Response) => {
  // Endpoint logic here
});

### Step 6: Testing and Documentation

#### Technical Design & Architecture

**Objective**: Ensure that the role management system is thoroughly tested for functionality, security, and user experience, and that comprehensive documentation is provided for future maintenance and development.

**Components**:
1. **Unit and Integration Tests**: Writing tests for individual components and their integration.
2. **Security Testing**: Conducting tests to identify and fix security vulnerabilities.
3. **User Experience Testing**: Ensuring the system is intuitive and user-friendly.
4. **Documentation**: Creating detailed documentation for the system.

#### Implementation Steps

1. **Develop Unit and Integration Tests**:
- Write unit tests for backend functionalities like role creation, deletion, assignment, and permission checks.
- Develop integration tests that simulate real-world usage scenarios of the role management system.

2. **Conduct Security Testing**:
- Perform penetration testing to identify potential security vulnerabilities.
- Use tools and methodologies to test for common web application vulnerabilities (like SQL injection, XSS).

3. **Perform User Experience Testing**:
- Conduct usability testing sessions to gather feedback on the system's user interface and overall experience.
- Implement A/B testing if necessary to determine the most effective UI/UX design.

4. **Create Comprehensive Documentation**:
- Document the architecture of the role management system, including data models and workflow diagrams.
- Provide detailed API documentation for backend services.
- Include frontend component documentation, detailing how components should be used and interacted with.

5. **Ensure Regular Updates and Maintenance**:
- Plan for regular updates to the testing suite to cover new features and changes.
- Keep the documentation updated with each system update or modification.

#### Sample Code Snippet (Unit Test in TypeScript)

Here’s an example of a unit test for a role creation function:

import { Role } from './roleManagement';
import { createRole } from './roleController';
import { expect } from 'chai';
import 'mocha';

describe('Role Creation', () => {
  it('should create a new role', async () => {
    const roleName = 'Test Role';
    const role = await createRole(roleName);

    expect(role).to.be.an('object');
    expect(role.name).to.equal(roleName);
  });

  // Additional tests for error cases, input validation, etc.
});

### Potential Additional Steps or Considerations:

- **Deployment Strategy**: Determine how you will deploy your application, whether on a cloud platform or on-premises. Consider containerization (e.g., using Docker) and continuous integration/continuous deployment (CI/CD) pipelines.
- **Performance Optimization**: Analyze and optimize the performance of both the backend and frontend, especially under load.
- **Scalability Assessment**: Plan for scaling the system as the number of users or the amount of data grows.
- **User Feedback and Iteration**: After deployment, gather user feedback to identify areas for improvement and iterate on the product.
- **Monitoring and Logging**: Set up monitoring and logging mechanisms to track the system's health and usage patterns.
- **Compliance and Legal Considerations**: Ensure compliance with relevant laws and regulations (like GDPR, HIPAA, etc.), if applicable.