What I Learnt Building a Lobsters TUI in Rust Published on Thu, 25 April 2019

As a learning and practice exercise I built a crate for interacting with the Lobsters programming community website. It’s built on the asynchronous Rust ecosystem. To demonstrate the crate I also built a terminal user interface (TUI).

A screenshot of the TUI in Alacritty

Try It

Pre-built binaries with no runtime dependencies are available for:

FreeBSD 12 amd64

Linux armv6 (Raspberry Pi)

Linux x86_64

MacOS

NetBSD 8 amd64

OpenBSD 6.5 amd64

Downloads Source Code

The TUI uses the following key bindings:

j or ↓ — Move cursor down

or — Move cursor down k or ↑ — Move cursor up

or — Move cursor up h or ← — Scroll view left

or — Scroll view left l or → — Scroll view right

or — Scroll view right Enter — Open story URL in browser

— Open story URL in browser c — Open story comments in browser

— Open story comments in browser q or Esc — Quit

As mentioned in the introduction the motivation for starting the client was to practice using the async Rust ecosystem and it kind of spiralled from there. The resulting TUI is functional but not especially useful, since it just opens links in your browser. I can imagine it being slightly more useful if you could also view and reply to comments without leaving the UI.

Building It

The client proved to be an interesting challenge, mostly because Lobsters doesn’t have a full API. This meant I had to learn how to set up and use a cookie jar along side reqwest in order to make authenticated requests. Logging in requires supplying a cross-site request forgery token, which Rails uses to prevent CSRF attacks. To handle this I need to first fetch the login page, note the token, then POST to the login endpoint. I could have tried to extract the token from the markup with a regex or substring matching but instead used kuchiki to parse the HTML and then match on the meta element in the head .

Once I added support for writing with the client (posting comments), not just reading, I thought I best not test against the real site. Fortunately the site’s code is open source. I took this as an opportunity to use my new-found Docker knowledge and run it with Docker Compose. That turned out pretty easy since I was able to base it on one of the Dockerfiles for a Rails app I run. If you’re curious the Alpine Linux based Dockerfile and docker-compose.yml can be viewed in this paste.

After I had the basics of the client worked out I thought it would be neat to fetch the front page stories and render them in the terminal in a style similar to the site itself. I initially did this with ansi_term. It looked good but lacked interactivity so I looked into ways to build a TUI along the lines of tig. I built it several times with different crates, switching each time I hit a limitation. I tried:

easycurses, which lived up to it’s name and produced a working result quickly. I’d recommend this if your needs aren’t too fancy, however I needed more control than it provided.

pancurses didn’t seem to be able to use colors outside the core 16 from ncurses.

Finally I ended up going a bit lower-level and used termion. It does everything itself but at the same time you lose the conveniences ncurses provides. It also doesn’t support Windows, so my plans of supporting that were thwarted. Some time after I had the termion version working I revisited tui-rs, which I had initially dismissed as unsuitable for my task. In hindsight it would probably have been perfect, but we’re here now.

In addition to async and TUI I also learned more about:

Building a robust and hopefully user friendly command line tool.

Documenting a library.

Publishing crates.

Dockerising a Rails app that uses MySQL.

How to build and publish pre-built binaries for many platforms.

How to accept a password in the terminal without echoing it.

Setting up multi-platform CI builds on Sourcehut.

Whilst the library and UI aren’t especially useful the exercise was worth it. I got to practice a bunch of things and learn some new ones at the same time.

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