Flux Challenge

Database reader of Sith lords

Background

You are Obi-Wan Kenobi's "IT" assistant at the Jedi Council, and your job is to create a User Interface for the Sith Database. Obi-Wan is travelling around the galaxy visiting many planets, doing an investigation. It is rumored that the homeworld of every Dark Jedi has a distinctive Sith emblem marked on their house where they were born/raised, and Obi-Wan wants to check if this rumor is true.

The Jedi Master requested you to make a dashboard-like UI showing a list of Sith lords sorted by apprenticeship (row N is the Sith Lord who was master of the Dark Jedi below at row N+1). The dashboard also shows at the top the current planet which Obi-Wan is visiting at the moment. The UI is supposed to verify if any of those Dark Jedis currently displayed on the list was born at the planet Obi-Wan is currently visiting, and if any, display that Dark Jedi in red.

Requirements

Data for current planet indicator comes from WebSocket connection to ws://localhost:4000 and is displayed at the top of the page.

Make requests to http://localhost:3000/dark-jedis/ to populate the list. The first request must be to get Darth Sidious: http://localhost:3000/dark-jedis/3616
- The HTTP response for one row tells the URL for the next row response.apprentice.url and the previous row response.master.url.
Scroll buttons: up/down buttons, move the list 2 positions
When scrolled, load more rows one at a time to fill in the blanks. Don't cache data, always request new data. (Other users might make live changes (typo fixing etc) to the data and Obi-Wan asked you to always make fresh requests)

Do not make any request for a sith that would be outside the list. Cancel any such obsolete request when the user scrolls.

When either the current planet indicator changes OR loaded new rows: check if there is a displayed Dark Jedi whose home planet matches the current planet. If true, then display that Dark Jedi in red text, and cancel ALL ongoing HTTP requests for rows. Freeze the UI from scrolling until the current planet changes again and there is no red-highlighted Dark Jedi anymore.

The list cannot be scrolled down if the last known sith has no apprentice. The list cannot be scrolled up if the first known sith has no master. Use .css-button-disabled on the buttons to indicate this status.

Use CSS classes from styles.css to style the HTML, which should look roughly like this:

<div class="app-container">
  <div class="css-root">
    <h1 class="css-planet-monitor">Obi-Wan currently on Tatooine</h1>

    <section class="css-scrollable-list">
      <ul class="css-slots">
        <li class="css-slot">
          <h3>Jorak Uln</h3>
          <h6>Homeworld: Korriban</h6>
        </li>
        <li class="css-slot">
          <h3>Skere Kaan</h3>
          <h6>Homeworld: Coruscant</h6>
        </li>
        <li class="css-slot">
          <h3>Na'daz</h3>
          <h6>Homeworld: Ryloth</h6>
        </li>
        <li class="css-slot">
          <h3>Kas'im</h3>
          <h6>Homeworld: Nal Hutta</h6>
        </li>
        <li class="css-slot">
          <h3>Darth Bane</h3>
          <h6>Homeworld: Apatros</h6>
        </li>
      </ul>

      <div class="css-scroll-buttons">
        <button class="css-button-up"></button>
        <button class="css-button-down"></button>
      </div>
    </section>
  </div>
</div>

Submission

Create a directory inside submissions named after your GitHub username. E.g submissions/staltz/.
Place all your client-side code in that repository, must include index.html in your submission folder.
Run the server like this: cd server then npm install (just once) then npm start.
Remember to use styles.css in your index.html solution.
Your solution should be executable by opening submissions/username/index.html in the browser with no build steps.
Send a pull request only when you consider it done. Don't submit Work-In-Progress PRs.

Criteria

Must be JavaScript, running as a web page.
Preferably a Flux-like architecture, but if you feel like you can use anything
Must solve the requirements listed above
As elegant code as possible

There is no "winner", the objective is just to solve the problem by building the UI with the most elegant code as possible. The objective is not just to "solve the problem" (I know it can be rather easily solved), the objective is to solve it as elegantly as possible.

Elegance here is not a subjective criteria. Let's define code elegance to be "the ability of a programmer to easily understand the program's flow and state coordination, being completely familiar with the tools used but completely unfamiliar with the codebase". Special attention is given to "familiar with the tools" and "unfamiliar with the codebase". This means if I know nothing about ClojureScript, a ClojureScript solution to this problem might still be very elegant to an experienced ClojureScript developer. On the other hand, unfamiliarity with the codebase is important to determine that, because usually as you grow familiar with a codebase, you find it easier to understand how it works. Our objective is to make it easy for a peer programmer to join a codebase and quickly understand how it works.

Purpose

This challenge is meant to be solved with Flux or some variation of this architecture, such as architectures with the single state tree and "actions" (Om, Redux, etc). It's my personal belief that Flux does not provide an elegant way of coordinating multiple async data sources, but more experienced Flux users might disagree. This challenge's requirements were tailored to touch Flux's weakest spots, these are not typical web app requirements. On the other hand, analytics and sensors dashboard UIs resemble this challenge a lot. That said, I am open and curious to be proven wrong about Flux. I'm curious about every solution's pros and cons, and I would prefer to discuss over evidence/artifacts instead of with platitude arguments.

Trying out submissions

cd server
npm start

Open http://localhost:3000/s/ in your browser.

staltz/flux-challenge