Christmas in July

It’s Independence Day when I’m writing this, which seems like a good time to write about my winter holiday cards from last year. In a previous blog post, I wrote about a small project I made with my naitian.holiday domain name. However, that wasn’t the original purpose for the domain. The first use for the domain was digital holiday cards for some of my friends.

Table of Contents

Planning

AKA all the things I wanted to do but didn’t.

There were a couple of clear requirements that were non-negotiable:

  1. There had to be at least some form of authentication (so not everyone can see everyone else’s card)
  2. Emails would be sent out notifying people of their cards.
  3. Cards need to be personalized with:
    • Greeting
    • Name (duh)
    • Message

Later, I also decided a couple more requirements, both for fun and for education:

  1. Everything would be compiled and hosted statically on S3.
  2. In the theme of using AWS for everything, I’d also send email notifications with Amazon’s Simple Email Service (SES) and handle domain name / certificates with Route53.
  3. Each person would only see pretty URLs (e.g. naitian.holiday/nate)
  4. Cards would include these draggable Polaroid-style pictures from my Google Photos.

Implementation

AKA what I ended up doing

Infrastructure

I will be totally honest with you and say I don’t actually remember all the details to the infrastructure on AWS, but it wasn’t super complex. The gist is:

  • All the static files are hosted with S3’s static website hosting.
  • I used Cloudfront as the CDN for the S3 files.
  • I have a hosted zone for naitian.holiday in Route53 which points to the Cloudfront endpoint (which in turn points to the S3 bucket).
  • Photos were hosted on Google Photos

Design

Aesthetically, I decided to go for a festive red with a subtle gradient. I chose a classy serif typeface and drew this freaking amazing Christmas non-denominational holiday tree.

Build Process

Each card was defined as a yaml file. I wrote a Python script to read these yaml files and used markdown to render them into HTML files. At the same time, I generated the SES email template data for bulk sending the notification emails.

I also had a Makefile which would run the rendering script, compile the SCSS into CSS, minify CSS and JS, and push everything to S3. There were also Make steps which would send a test email and send out the actual emails.

Authentication

One of the most interesting parts of this whole exercise was figuring out a good authentication method. I definitely did not want to make anyone sign in or create any accounts (partly also because I wanted this to be a totally static site).

I ended up compromising with a “good-enough” authentication plan, which I had to alter a little bit to also keep the pretty URLs. Here’s how it ended up working:

  1. When a card is rendered, it is actually placed in a directory named after its SHA256 hash.
  2. This hash is used as an auth token in the link.
  3. Not only is an HTML file generated with the card’s content, another HTML page is generated with Javascript for authentication and a hidden input field containing a SHA256 hash of the token.
  4. When a user navigates to the site (e.g. naitian.holidy/nate), they are actually navigating to the page with only the auth code.
    • On the client side, the token (if it’s present) is hashed and compared to the correct token.
    • If incorrect, the user is rejected.
  5. If correct, there is an XHR request that fetches the actual HTML and displays it.

This means the user would have a hard time even realizing that any authentication had occurred in the first place.

To recap, for each card, the path structure looked like this:

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naitian.holiday/<SHA256>/index.html   <- this is the HTML for the card
naitian.holiday/nate/index.html       <- this is the HTML for authentication

Of course, I also added a robots.txt which disallowed any crawling. This makes it pretty difficult to find the (very much public) SHA256 paths of any of the cards.

So, while not airtight, this worked well enough to prevent people from just typing in names of other people to see their cards.

I also stored the tokens in local storage, so after the first visit, the token isn’t actually required.

Nifty.

Email Notifications

Emails were surprisingly straightforward to set up. I used the Simple Email Service from Amazon. Initially, I planned to do a lot more CSS for the HTML emails, but ultimately decided against it for two reasons: it would have been more work to implement and try to test, and I felt like it would feel more personal if it was more “raw”.

I had a make rule which would send just test emails to myself and a different rule to send out the emails for real.