# About

This is a demo of using [Haskell](https://haskell.org),
[Nix](https://nixos.org/) and [Miso](https://haskell-miso.org)
to produce a [LynxJS](https://lynxjs.org) application for Android.

The main interest about this demo is that everything is reproducibly built with Nix,
including the building of the `.apk` with `gradle`.

# Requirements

- `nix` [installed](https://nixos.org/download/).
- A host supporting the [Kernel Virtual Machine (KVM) hypervisor](https://developer.android.com/studio/run/emulator-acceleration)
(and having it enabled in its BIOS), or and Android device in debug mode to install the `.apk`.

# Usage

## For an Android emulator

Running:
```console
nix -L run git+https://radicle-mermet.sourcephile.fr/z2BeGZUdNCY3FzYarKMV7XXXuc5os.git#android-emulator-x86_64
```
or alternatively (for hacking):
```console
git clone https://radicle-mermet.sourcephile.fr/z2BeGZUdNCY3FzYarKMV7XXXuc5os.git haskell-miso-nix-demo &&
cd haskell-miso-nix-demo &&
nix -L run .#android-emulator-x86_64
```
or alternatively (for [radicle](https://radicle.xyz) users):
```console
rad clone z2BeGZUdNCY3FzYarKMV7XXXuc5os &&
cd haskell-miso-nix-demo &&
nix -L run .#android-emulator-x86_64
```
should saturate your download link, fill you `/nix/store/`, produce a lot of heat
and eventually spawn an Android emulator running a demo app
where you can increase (resp. decrease) a counter
by tapping on a cat 🐈 (resp. a ramen dish 🍜).

__ResourceWarning:__
because the Haskell compiler (GHC) has to be patched
(otherwise the buttons of the app do not work)
and is not using the same `nixpkgs` as the ones on the public cache
`haskell-miso-cachix.cachix.org`,
this demo requires a lot of CPU cycles and memory space in `/tmp`
to build that patched GHC.

__ResourceWarning:__
besides part of it being in the `/nix/store/`
the actual Android system remains in `/tmp/nix-android-user-home-*` after closing the emulator,
since it weights several gibibits you may want to remove it before your next reboot.

## For an Android device

```console
git clone https://radicle-mermet.sourcephile.fr/z2BeGZUdNCY3FzYarKMV7XXXuc5os.git haskell-miso-nix-demo &&
cd haskell-miso-nix-demo &&
nix -L build .#default &&
adb install result/app-debug.apk
```

__PortabilityNote:__
this demo targets the Android platform 34 which requires Android >= 14,
and all main computer architectures should be supported:
```console
$ aapt dump badging result/app-debug.apk | grep native-code
native-code: 'arm64-v8a' 'armeabi-v7a' 'x86' 'x86_64'
```

# Acknowledgements

- https://github.com/haskell-miso/miso-lynx provided the `counter` example.
- https://github.com/lynx-family/integrating-lynx-demo-projects provided the `JavaEmptyProject`.

# Hack

Java dependencies in `android/deps.json` can be updated with:
```console
nix -L run .#default.update-deps
```

Using `nix -L develop` registers the custom GHC to the host Nix's garbage-collector
in `haskell/cache/gc-roots/ghcjs-ghc`,
manually remove this symbolic link to let `nix-collect-garbage` reclaim it.

## ToDo

- SecurityToDo: sign the APK.