Expense-serverless

This application implements a simple Expense-Tracker application using AWS Lambda and Serverless framework, The idea is that the user can login to his/her profile to keep track of their expenses by adding the name and the ammount they spent, users will have the option to upload a file e.g receipts, images, etc, Each user is authenticated and will have it's own profile.

Functionality of the application

This application will allow creating/removing/updating/fetching Expense items. Each Expense item can optionally have an attachment image. Each user only has access to Expense items that he/she has created.

Functions implemented

The following functions were implemented and configured in the serverless.yml file:

• Auth - this function implements a custom authorizer for API Gateway that should be added to all other functions.

• GetExpenses - returns all Expenses for a current user. A user id can be extracted from a JWT token that is sent by the frontend

It should return data that looks like this:

{
  "items": [
    {
      "userId": "123",
      "expenseId": "123546",
      "createdAt": "2019-07-27T20:01:45.424Z",
      "name": "Car Payment",
      "date": "2019-07-29T20:01:45.424Z",
      "amount": 275.00,
      "attachmentUrl": "http://example.com/image.png"
    },
    {
     "userId": "456",
      "expenseId": "129856",
      "createdAt": "2020-07-27T20:01:45.424Z",
      "name": "Rent",
      "date": "2020-07-29T20:01:45.424Z",
      "amount": 950.00,
      "attachmentUrl": "http://example.com/image.png"
    },
  ]
}

• CreateExpense - creates a new Expense for a current user. A shape of data send by a client application to this function can be found in the CreateExpenseRequest.ts file

It receives a new Expense item to be created in JSON format that looks like this:

{
      "expenseId": "123546",
      "createdAt": "2019-07-27T20:01:45.424Z",
      "name": "Car Payment",
      "date": "2019-07-29T20:01:45.424Z",
      "amount": 275.00,
      "attachmentUrl": "http://example.com/image.png"
}

It should return a new Expense item that looks like this:

{
  "item": {
      "userId": "123",
      "expenseId": "123546",
      "createdAt": "2019-07-27T20:01:45.424Z",
      "name": "Car Payment",
      "date": "2019-07-29T20:01:45.424Z",
      "amount": 275.00,
      "attachmentUrl": "http://example.com/image.png"
  }
}

• UpdateExpense - updates an Expense item created by a current user. A shape of data send by a client application to this function can be found in the UpdateExpenseRequest.ts file

It receives an object that contains three fields that can be updated in a Expense item:

{
  "name": "Phone bill",
  "date": "2019-07-29T20:01:45.424Z",
  "amount": 150.00
}

The id of an item that should be updated is passed as a URL parameter.

It should return an empty body.

• DeleteExpense - deletes an Expense item created by a current user. Expects an id of an Expense item to remove.

It should return an empty body.

• GenerateUploadUrl - returns a pre-signed URL that can be used to upload an attachment file for an Expense item.

It should return a JSON object that looks like this:

{
  "uploadUrl": "https://s3-bucket-name.s3.eu-west-2.amazonaws.com/image.png"
}

All functions are already connected to appropriate events from API Gateway.

An id of a user can be extracted from a JWT token passed by a client.

Necessary resources are implemented in the resources section of the serverless.yml file such as DynamoDB table and S3 bucket.

How to run the application

Backend

To deploy an application run the following commands:

cd backend
npm install
sls deploy -v

Frontend

To run a client application first edit the client/src/config.ts file to set correct parameters. And then run the following commands:

cd client
npm install
npm run start

This should start a development server with the React application that will interact with the serverless Expense application.