Add design info for FeelGood project page (#24)

* Add design info for FeelGood project page

Still needs service-specific steps taken, helpful hints, etc; those
sections say "More info coming soon."

* Add Ballmer gif for Chris

* Add links to GitHub repo code examples

The links are currently broken because the PRs are waiting for approval.

* Add S3 implementation notes in feelgood.md

* Fix publish function link to point to the publish function instead of the subscription function

* Add SNS abbreviation

Co-authored-by: Taylor <taysulli@gmail.com>
Co-authored-by: Anish Prasad <33945547+anishprasad01@users.noreply.github.com>

_docs/feelgood.md

@@ -8,4 +8,160 @@ permalink: /feelgood.html
 
 # FeelGood, an Example Project for AWS
 
-More information coming soon!
+The hackathon organizers wanted to build an application that facilitates 
+self-service for good vibes and positivity.
+
+From that ideal, the project grew to provide additional registration 
+options to facilitate laughs and silliness.
+
+Read about the project and how we built it!
+
+## Goals
+
+* **Text Messages**: uplifting content, delivered straight to your phone.
+* **Mix and Match Subscriptions**: users should be able to register for 
+  message streams that fit their personality.
+* **Fully Cloud Hosted**: The end-to-end deployment should be fully hosted 
+  in the cloud, without running a VM or using local computing resources.
+
+TL;DR: `automatic, supersonic, hypnotic, funky fresh`
+
+## User Experience
+
+1. A user goes to the application's website to sign up for messages.
+   <div style="width:100%;height:0;padding-bottom:56%;position:relative;"><iframe src="https://giphy.com/embed/fQZX2aoRC1Tqw" width="100%" height="100%" style="position:absolute" frameBorder="0" class="giphy-embed" allowFullScreen></iframe></div><p><a href="https://giphy.com/gifs/fQZX2aoRC1Tqw">via GIPHY</a></p>
+
+2. The user subscribes to a topic.
+    <div style="width:100%;height:0;padding-bottom:75%;position:relative;"><iframe src="https://giphy.com/embed/mgqefqwSbToPe" width="100%" height="100%" style="position:absolute" frameBorder="0" class="giphy-embed" allowFullScreen></iframe></div><p><a href="https://giphy.com/gifs/mrw-joke-advice-mgqefqwSbToPe">via GIPHY</a></p>
+
+3. The user gets a welcome message after subscribing to a topic of their choice. 
+   They can continue to subscribe to other topics they are interested in.
+    <div style="width:100%;height:0;padding-bottom:100%;position:relative;"><iframe src="https://giphy.com/embed/10a9ikXNvR9MXe" width="100%" height="100%" style="position:absolute" frameBorder="0" class="giphy-embed" allowFullScreen></iframe></div><p><a href="https://giphy.com/gifs/john-boyega-10a9ikXNvR9MXe">via GIPHY</a></p>
+
+4. At set times during the day, the user gets a text message reminding them to:
+    * Feel good
+    * Drink water
+    * Laugh
+    * Commune with their crow friends
+
+    Of course, the messages they actually get are dependent on which topics 
+    they subscribed to.
+
+    <div style="width:100%;height:0;padding-bottom:60%;position:relative;"><iframe src="https://giphy.com/embed/QBd2kLB5qDmysEXre9" width="100%" height="100%" style="position:absolute" frameBorder="0" class="giphy-embed" allowFullScreen></iframe></div><p><a href="https://giphy.com/gifs/time-mr-bean-look-at-the-QBd2kLB5qDmysEXre9">via GIPHY</a></p>
+    <div style="width:100%;height:0;padding-bottom:113%;position:relative;"><iframe src="https://giphy.com/embed/wqd5THxOO39KM" width="100%" height="100%" style="position:absolute" frameBorder="0" class="giphy-embed" allowFullScreen></iframe></div><p><a href="https://giphy.com/gifs/laughing-the-big-bang-theory-wqd5THxOO39KM">via GIPHY</a></p>
+
+## Architecture
+
+To realize these desired behaviors & user experiences, we used AWS services 
+and deployed the application to the cloud. The application's design is 
+described below.
+
+### User Subscription
+
+* An [S3 bucket](https://docs.aws.amazon.com/AmazonS3/latest/dev/WebsiteHosting.html) 
+  is used to host the subscription site. We configured 
+  [domain redirection for a custom domain](https://www.freecodecamp.org/news/simple-site-hosting-with-amazon-s3-and-https-5e78017f482a/) 
+  and SSL certificates for HTTP/S traffic.
+* The user interacts with the site as they would any other.
+* Upon clicking the `Submit` button, a JavaScript function makes an 
+  [HTTP POST](https://en.wikipedia.org/wiki/POST_%28HTTP%29) request 
+  to the application's API, sending the user's data from the website's 
+  subscription form. The API endpoint is connected to a Lambda function using  
+  [API Gateway](https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-getting-started-with-rest-apis.html).
+* The Lambda function takes the JSON payload delivered by the POST request, 
+  which contains the user's phone number and selected topic. The function 
+  then:
+    * Validates the phone number for correct formatting 
+    * Looks up the [Amazon Resource Name](https://docs.aws.amazon.com/general/latest/gr/aws-arns-and-namespaces.html) 
+      (ARN) for the selected topic
+    * Invokes the [Simple Notification Service](https://aws.amazon.com/sns/) (SNS) SDK
+    * Makes a `subscribe()` call to SNS, passing the user's data and topic ARN
+* SNS saves the user's phone number as a subscriber under the specified topic.
+* If the Lambda function processes successfully, it will return a success code 
+  to the API Gateway method, which in turn returns the HTTP 200 status to the 
+  user's browser. The Lambda function also publishes a text message to the user's 
+  provided number, which confirms subscription and welcomes the user.
+
+[View the website code here.](https://github.com/UWB-ACM/feelgood/blob/master/website/)
+
+[View the subscription Lambda function here.](https://github.com/UWB-ACM/feelgood/blob/master/subscribe/lambda_function.py)
+
+Here's a diagram of the system's flow of logic:
+
+![FeelGood subscription mechanism](/assets/feelgood_sub.png)
+
+### User Notification
+
+* To send messages out at regular intervals, we used CloudWatch Events 
+  to create [rules which get invoked on a time schedule](https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/Create-CloudWatch-Events-Scheduled-Rule.html).
+* When creating the Event rule, the message publication function 
+  [was selected as the target](https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/RunLambdaSchedule.html).
+* Upon being invoked, the Lambda function:
+    * Chooses 4 messages to publish (one for each possible topic)
+    * Looks up the ARN for each topic
+    * Invokes the [Simple Notification Service](https://aws.amazon.com/sns/) SDK
+    * Makes 4 `publish()` calls to SNS, where each call uses a different message and topic ARN
+* SNS receives the SDK invocation to publish a message and distributes 
+  the message for each topic to all subscribers for that topic. Each topic 
+  is handled asynchronously.
+
+[View the publication Lambda function here.](https://github.com/UWB-ACM/feelgood/blob/master/publish/lambda_function.py)
+
+Here's a diagram of the subsystem's flow of logic:
+
+![FeelGood publication mechanism](/assets/feelgood_pub.png)
+
+## Implementation Notes
+
+The specific instructions, how-tos, and details we encountered are organized 
+here by AWS product.
+
+### S3 & Website Construction
+
+We used to the following resources as a guide for configuring S3 buckets to host the subscription website:
+
+- [Setting Up a Static Website Using a Custom Domain Name Registered with Route 53](https://docs.aws.amazon.com/AmazonS3/latest/dev/website-hosting-custom-domain-walkthrough.html)<br>
+  This guide walks through how to register a custom domain using Route 53 and create/configure two S3 buckets to serve as containers for the contents of your website.
+
+- [Setting up a Static Website](https://docs.aws.amazon.com/AmazonS3/latest/dev/HostingWebsiteOnS3Setup.html)<br>
+  If you don't wish to buy a custom domain, use this guide instead. Your website will still be publicly accessible with a link that resembles the following: `http://your-bucket-name.s3-website-your-aws-region.amazonaws.com`
+
+- [Obtaining an SSL Certificate for a Custom Domain](https://aws.amazon.com/premiumsupport/knowledge-center/cloudfront-serve-static-website/)<br>
+  This guide explains how to use CloudFront to request an SSL certificate for your custom domain in order to serve content over an HTTPS protocol. Make sure to scroll down to the section titled `Using a website endpoint as the origin with anonymous (public) access allowed`, which aligns with the configuration outlined in the two previous S3 setup guides.
+
+- [Updating Existing Content with a CloudFront Distribution](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/UpdatingExistingObjects.html)<br>
+  If using CloudFront to serve your site over HTTPS, you will find updating the content of the site is not as simple as changing out the files in the S3 bucket due to CloudFront's caching properties. This guide outlines two workarounds: using versioned file names, and [invalidating the object](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/Invalidation.html) within CloudFront which prompts it to reload objects the source.
+
+- [Collecting and Submitting Form Data to Other AWS Services using HTML and jQuery AJAX requsts](https://aws.amazon.com/blogs/architecture/create-dynamic-contact-forms-for-s3-static-websites-using-aws-lambda-amazon-api-gateway-and-amazon-ses/)<br>
+  The `Your “Contact Us” Form` section of this guide covers how to create a simple web form using HTML, and `Connecting it all Together` covers how to use [jQuery AJAX calls](https://api.jquery.com/jquery.ajax/) to send the data collected in the form to other AWS services to complete the subscription process.
+
+### API Gateway
+
+More info coming soon.
+
+### Lambda
+
+More info coming soon.
+
+### SNS
+
+More info coming soon.
+
+### CloudWatch
+
+More info coming soon.
+
+## Gotchas & Lessons Learned
+
+1. Amazon SNS may have reliability issues that are outside of your control; 
+   *message delivery to subscribers is not guaranteed*. If high availability or 
+   reliability is important to your application, consider incorporating 
+   an API-accessible service which specializes in SMS, such as 
+   [Twilio](https://www.twilio.com/).
+2. Always, _always_, _**always**_ set up robust logging. AWS streamlines 
+   setup of logging and performance monitoring for many services via 
+   [CloudWatch](https://aws.amazon.com/cloudwatch/). This was particularly 
+   useful when troubleshooting unreliable message delivery to subscribers, 
+   monitoring S3 usage, and monitoring the frequency of API requests.
+
+<div style="width:100%;height:0;padding-bottom:75%;position:relative;"><iframe src="https://giphy.com/embed/3KVChGOKcyyRO" width="100%" height="100%" style="position:absolute" frameBorder="0" class="giphy-embed" allowFullScreen></iframe></div><p><a href="https://giphy.com/gifs/steve-yahoo-retirement-3KVChGOKcyyRO">via GIPHY</a></p>