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117 lines
5.5 KiB
Markdown
117 lines
5.5 KiB
Markdown
As a learning and practice exercise I built a [crate] for interacting with the
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[Lobsters](https://lobste.rs/) programming community website. It's built on the
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asynchronous Rust ecosystem. To demonstrate the crate I also built a terminal
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user interface (TUI).
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<figure>
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<img style="border: 2px solid black" src="/images/2019/lobsters-tui.png" alt="Screenshot of Lobsters TUI" />
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<figcaption>A screenshot of the TUI in <a href="https://github.com/jwilm/alacritty">Alacritty</a></figcaption>
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</figure>
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## Try It
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[](https://crates.io/crates/lobsters)
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Pre-built binaries with no runtime dependencies are available for:
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- FreeBSD 12 amd64
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- Linux armv6 (Raspberry Pi)
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- Linux x86_64
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- MacOS
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- NetBSD 8 amd64
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- OpenBSD 6.5 amd64
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<a class="action-button action-button-ghost" href="https://git.sr.ht/~wezm/lobsters#download">Downloads</a>
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<a class="action-button action-button-ghost" href="https://git.sr.ht/~wezm/lobsters">Source Code</a>
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The TUI uses the following key bindings:
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* `j` or `↓` — Move cursor down
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* `k` or `↑` — Move cursor up
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* `h` or `←` — Scroll view left
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* `l` or `→` — Scroll view right
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* `Enter` — Open story URL in browser
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* `c` — Open story comments in browser
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* `q` or `Esc` — Quit
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As mentioned in the introduction the motivation for starting the client was to
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practice using the async Rust ecosystem and it kind of spiralled from there.
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The resulting TUI is functional but not especially useful, since it just opens
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links in your browser. I can imagine it being slightly more useful if you could
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also view and reply to comments without leaving the UI.
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## Building It
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The client proved to be an interesting challenge, mostly because Lobsters
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doesn't have a full API. This meant I had to learn how to set up and use a
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cookie jar along side [reqwest] in order to make authenticated requests.
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Logging in requires supplying a cross-site request forgery token, which Rails
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uses to prevent CSRF attacks. To handle this I need to first fetch the login
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page, note the token, then POST to the login endpoint. I could have tried to
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extract the token from the markup with a regex or substring matching but
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instead used [kuchiki] to parse the HTML and then match on the `meta` element
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in the `head`.
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Once I added support for writing with the client (posting comments), not just
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reading, I thought I best not test against the real site. Fortunately the site's
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code is open source. I took this as an opportunity to use [my new-found Docker
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knowledge][alpine-docker] and run it with Docker Compose. That turned out
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pretty easy since I was able to base it on one of the Dockerfiles for a Rails
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app I run. If you're curious the [Alpine Linux] based `Dockerfile` and
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`docker-compose.yml` can be viewed in [this
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paste](https://paste.sr.ht/%7Ewezm/6da6b05677f80069b166433b19ef2209176f036f).
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After I had the basics of the client worked out I thought it would be neat to
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fetch the front page stories and render them in the terminal in a style similar
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to the site itself. I initially did this with [ansi_term]. It looked good but
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lacked interactivity so I looked into ways to build a TUI along the lines of
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[tig]. I built it several times with different crates, switching each time I
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hit a limitation. I tried:
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* [easycurses], which lived up to it's name and produced a working result
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quickly. I'd recommend this if your needs aren't too fancy, however I needed
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more control than it provided.
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* [pancurses] didn't seem to be able to use colors outside the core 16 from
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ncurses.
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Finally I ended up going a bit lower-level and used [termion]. It does
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everything itself but at the same time you lose the conveniences ncurses
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provides. It also doesn't support Windows, so my plans of supporting that were
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thwarted. Some time after I had the `termion` version working I revisited
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[tui-rs], which I had initially dismissed as unsuitable for my task. In
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hindsight it would probably have been perfect, but we're here now.
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In addition to async and TUI I also learned more about:
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- Building a robust and hopefully user friendly command line tool.
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- Documenting a library.
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- Publishing crates.
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- Dockerising a Rails app that uses MySQL.
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- How to build and publish pre-built binaries for many platforms.
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- How to accept a password in the terminal without echoing it.
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- Setting up multi-platform [CI builds on Sourcehut][builds].
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Whilst the library and UI aren't especially useful the exercise was worth it. I got
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to practice a bunch of things and learn some new ones at the same time.
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<img src="/images/lobsters.png" alt="" width="16" class="lobsters"> [Comments on Lobsters](https://lobste.rs/s/nono6k/what_i_learnt_building_lobsters_tui_rust)
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<div class="seperator"><hr class="left">✦<hr class="right"></div>
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Previous Post: [Cross Compiling Rust for FreeBSD With Docker](/technical/2019/03/cross-compile-freebsd-rust-binary-with-docker/)
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Next Post: [An Illustrated Guide to Useful Command Line Tools](/technical/2019/10/useful-command-line-tools/)
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[repo]: https://git.sr.ht/~wezm/lobsters
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[ansi_term]: https://crates.io/crates/ansi_term
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[tig]: https://jonas.github.io/tig/
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[pancurses]: https://crates.io/crates/pancurses
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[tui-rs]: https://crates.io/crates/tui
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[termion]: https://crates.io/crates/termion
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[builds]: https://man.sr.ht/builds.sr.ht/
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[reqwest]: https://crates.io/crates/reqwest
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[kuchiki]: https://crates.io/crates/kuchiki
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[alpine-docker]: /technical/2019/02/alpine-linux-docker-infrastructure/
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[easycurses]: https://crates.io/crates/easycurses
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[Alpine Linux]: https://alpinelinux.org/
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[crate]: https://crates.io/crates/lobsters
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