# Buzzer

A simple buzzer implementation using web technologies.

## Usage

### Preconditions

You need a JDK, version 11 upwards.

### Build

Until artifact storage is provided, start the service using `gradlew run` from within the project directory.

Alternatively, you can create the artifact using `gradlew shadowJar`. The output will be written to `<projectDir>/build/libs/`. Then run it using `java -jar <JarFile>`.

After it successfully launched, you have access to two clients.

### Player-Client

All participants should call `http://<yourHost>:8888/` or `http://<yourHost>:8888/clients/player`.

Now, they only need to enter their name on top, and they're set.

To trigger the buzzer, they just need to push the large surface. After a short amount of time they will be notified whether they were the fastest players (button turns green) or not (it turns red).

### Game-Master-Client

You can access this client from `http://<yourhost>:8888/clients/master/`.

Your surface consists of three parts. After a game has started, and some player decided they want to do the turn, these have the following functions:
* On top, there's a large surface showing you the fastest player if any.
* Below, you will see the order of players who pushed the button within *500ms* after the fastest player (including the initial push). This information is included solely for transparency reasons and might be used to resolve obvious "Whoops, my beer tipped, and I accidentally activated the button!"-like situations to some extent.
* A "reset"-button is located at the bottom. Clicking this will prepare the app for the next round. It will forget about all buttons pushed, and re-enable the buttons on the player's clients.

## Troubleshooting & Tips

* Before starting the game, test that each of the player's client works properly, by letting each one put their button after each other, resetting after each turn.
* If the players or clients can't connect to your game server, make sure it's not blocked by the firewall. The app requires access to port 8888 for tcp connections.
* Make sure each player's clients are released after you reset the round. If this is not the case, wait a few seconds and try again (and also check the players network connection and power save settings).

## Technology

This project contains a weird mixture of technologies that I wanted to play around with:

* Currently, there is no check for uniqueness of player names, and the name is used as identifier (that's the simplest way to be consistent across reconnects). Make sure each player uses a different name!
* The server-portion is based on the [ktor][ktor] framework, a rather lightweight, code-configured web servicing library.
* The clients' HTML files are created on the fly using the domain specific HTML language provided by [kotlinx-html][kotlinxhtml].
* Javascript and data binding in the clients is achieved by embedding [alpine-js][alpinejs], in conjunction with a few extension functions to integrate it into kotlinx-html. 
* Client-side websockets are made resilient with [robust-websocket][robustws]. Honestly, it's a shame how much time you need to invest nowadays to find a plain JS utility library that can just be included without running it through a full `npm` build pipeline for even a small task like this…

## Roadmap

* Configure startup (IP and port)
* Keep history of previous rounds.
* Ship utility JS libs as asset, don't rely on CDN and internet connectivity.

[kotlinxhtml]: https://github.com/Kotlin/kotlinx.html
[alpinejs]: https://alpinejs.dev
[ktor]: https://ktor.io
[robustws]: https://github.com/nathanboktae/robust-websocket