This codebase has been set up to work with heroku.

Create a file .envvars with the following content.

!#/bin/bash
export ENV=debug
export PAYPAL_MODE=sandbox
export PAYPAL_CLIENT_ID=EBWKjlELKMYqRNQ6sYvFo64FtaRLRR5BdHEESmha49TM
export PAYPAL_CLIENT_SECRET=EO422dn3gQLgDbuwqTjzrFgFtaRLRR5BdHEESmha49TM
export FIREBASE_TOKEN=sDsdf324fRMtKc6zojplvjaOW5MnyuhQzKTrq8wj
export FIREBASE_URL=https://your-project.firebaseio.com
export APP_BASE_URL=http://ulkkbc1e933e.laurenceputra.koding.io:3000
export APP_PAYPAL_SUCCESS_CALLBACK=/payment/execute/
export APP_PAYPAL_CANCEL_CALLBACK=/payment/cancel/

Replace PAYPAL_CLIENT_ID and PAYPAL_CLIENT_SECRET with the tokens you get from PayPal Developer's Dashboard after you have created an application. Use sandbox for PAYPAL_MODE until your application is ready to go live.

For the Firebase envars, get the FIREBASE_TOKEN from the Secrets section when viewing the dashboard for your Firebase Application. And of course, replace the FIREBASE_URL with your firebase URL.

The APP_* envars are for you to define the endpoints PayPal should redirect your users to when the payment process is completed or cancelled. Change the APP_BASE_URL to your base URL without the trailing slash.

Once you have created the .envvars file, run

source .envvars

before you start the server. You can simply start the server by typing npm start. Do note that if this is your first time running the server, you will have to do an npm install to install all the dependencies.

Heroku's setup is slightly simpler. Once you have created the applicaiton, go to the settings tab of your applicaiton's dashboard, and click on Reveal Config Vars. Click on edit, and fill in the config vars similar to what you have done for Koding.com above, and replace the values with your values.

Once you have entered the details, click on the save button. and simply connect your Heroku account to Github and you can deploy your code from Heroku without much hassle.

##Code

For simplicity reasons, most of the code is placed in the index.js file. Do note that you should organise your code properly for maintainability purposes when you are writing an application for your startup. A recommended framework to use for projects that need proper code organisation would be KrakenJS, which is built on top of many other powerful open source projects.

If you are interested in understanding the implementation of the PayPal billing agreement/subscription endpoints, feel free to go through the code. The code has been documented to explain the process and rationale behind it. If you still have any questions about the code, open an issue here.

There are 3 main endpoints for this server.

The /payment/create-plan endpoint creates the plans based on what you have indicated in the model.js file. You will only need to run this once.

The /payment/initiate/:planId endpoint connects with PayPal to start the checkout process, and redirects the user to PayPal.

The /payment/execute/ is redirected from PayPal. This is the point where you should store in Firebase that your user has paid for a certain plan.