💫 Welcome! 🎉

This backend exercise involves building a Node.js/Express.js app that will serve a REST API. We imagine you should spend around 3 hours at implement this feature.

Data Models

All models are defined in src/model.js

Profile

A profile can be either a client or a contractor. clients create contracts with contractors. contractor does jobs for clients and get paid. Each profile has a balance property.

Contract

A contract between and client and a contractor. Contracts have 3 statuses, new, in_progress, terminated. contracts are considered active only when in status in_progress Contracts group jobs within them.

Job

contractor get paid for jobs by clients under a certain contract.

Application Flow

1. Authentication: Users authenticate by including their profile_id in the request headers. The getProfile middleware retrieves the profile from the cache or database and attaches it to the request object.

2. Retrieving Contracts: Clients and contractors can access their respective contracts via the /contracts endpoint. Only non-terminated contracts are returned.

3. Managing Jobs:

   • Unpaid jobs can be retrieved via the /jobs/unpaid endpoint, which lists all unpaid jobs for the authenticated user.
   • Clients can pay for jobs using the /jobs/:job_id/pay endpoint. The payment process updates the balances of both the client and the contractor.

4. Admin Reports:

   • The /admin/best-profession endpoint provides insights into the most profitable profession within a specified date range.
   • The /admin/best-clients endpoint returns the top clients who paid the most for jobs during a specified period.

Getting Set Up

The exercise requires Node.js to be installed. We recommend using the LTS version.

1. Start by creating a local repository for this folder.

2. In the repo root directory, run npm install to gather all dependencies.

3. Next, npm run seed will seed the local SQLite database. Warning: This will drop the database if it exists. The database lives in a local file database.sqlite3.

4. Then run npm start which should start both the server and the React client.

❗️ Make sure you commit all changes to the master branch!

Technical Notes

• The server is running with nodemon which will automatically restart for you when you modify and save a file.

• The database provider is SQLite, which will store data in a file local to your repository called database.sqlite3. The ORM Sequelize is on top of it. You should only have to interact with Sequelize - please spend some time reading sequelize documentation before starting the exercise.

• To authenticate users use the getProfile middleware that is located under src/middleware/getProfile.js. users are authenticated by passing profile_id in the request header. after a user is authenticated his profile will be available under req.profile. make sure only users that are on the contract can access their contracts.

• The server is running on port 3001.

APIs To Implement

Below is a list of the required API's for the application.

1. GET /contracts/:id - This API is broken 😵! it should return the contract only if it belongs to the profile calling. better fix that!

2. GET /contracts - Returns a list of contracts belonging to a user (client or contractor), the list should only contain non terminated contracts.

3. GET /jobs/unpaid - Get all unpaid jobs for a user (either a client or contractor), for active contracts only.

4. POST /jobs/:job_id/pay - Pay for a job, a client can only pay if his balance >= the amount to pay. The amount should be moved from the client's balance to the contractor balance.

5. POST /balances/deposit/:userId - Deposits money into the the the balance of a client, a client can't deposit more than 25% his total of jobs to pay. (at the deposit moment)

6. GET /admin/best-profession?start=<date>&end=<date> - Returns the profession that earned the most money (sum of jobs paid) for any contactor that worked in the query time range.

7. GET /admin/best-clients?start=<date>&end=<date>&limit=<integer> - returns the clients the paid the most for jobs in the query time period. limit query parameter should be applied, default limit is 2.

 [
    {
        "id": 1,
        "fullName": "Reece Moyer",
        "paid" : 100.3
    },
    {
        "id": 200,
        "fullName": "Debora Martin",
        "paid" : 99
    },
    {
        "id": 22,
        "fullName": "Debora Martin",
        "paid" : 21
    }
]

Improvements for Production-Level Application

To enhance this application for production use, consider the following improvements:

1. Error Handling: Implement a centralized error handling middleware to capture and manage errors across the application gracefully.

2. Logging: Integrate a logging library (e.g., Winston or Morgan) to log important events and errors, aiding in debugging and monitoring application health.

3. Database Migration: Implement migrations for the SQLite database to manage schema changes efficiently. This will help in maintaining the database structure during the deployment process.

4. Rate Limiting: Use rate-limiting middleware to protect the APIs from excessive requests, enhancing security and performance.

5. Performance Optimization: Evaluate and optimize query performance, particularly for endpoints that may return large datasets. Consider implementing pagination where applicable.

6. Code Optimization: The code can be more extendible with custom exceptions and various design patterns like factory pattern can be used to create objects or services. For instance, if you have different types of jobs or contracts with specific logic, a factory can instantiate them etc.

7. Input validation and proper logging: Input validation at multiple edge cases can be more optimized with custom logging and exception handling

Going Above and Beyond the Requirements

Given the time expectations of this exercise, we don't expect anyone to submit anything super fancy, but if you find yourself with extra time, any extra credit item(s) that showcase your unique strengths would be awesome! 🙌

It would be great for example if you'd write some unit test / simple frontend demostrating calls to your fresh APIs.

Submitting the Assignment

When you have finished the assignment, zip your repo (make sure to include .git folder) and send us the zip.

Thank you and good luck! 🙏