rawtx - lightning network wallet

rawtx is an open-source lightning network wallet powered by lnd which allows you to send and receive Bitcoins both on blockchain and lightning network.

Here's what it looks like:

You can get it from Play Store on Android or App Store for iOS.

If you're interested in compiling it from scratch, would like to know how it works or looking to contribute, please keep reading.

High level overview

Uses lnd as a daemon/library because it fully conforms to the BOLT specifications and is easy to cross-compile and run on mobile platforms.
rawtx is cross compiled using xgo. xgo brings up a docker image with all the build tools required for compiling Go into different platforms. It also supports building an .aar package for Android and a .framework package for iOS.
The UI/app is built using react-native, which gives us the performance of a native app with development convenience of Javascript.
Architecture looks like: react-native -> (glue) -> lnd
- glue here is the native code (Java on Android and objC on iOS) that allows react-native to manage and call lnd. glue let's us:
  - start, stop and query the state of lnd,
  - write, read files, scan QR codes,
  - make REST calls to lnd,
  - on Android, manages the background lnd process.
To support multiple wallets, the app has a wallet.conf that keeps track of all wallets. multi-wallet support from the very beginning sets user expectations and allows things like:
- running Bitcoin and Litecoin(when ready) wallets side-by-side,
- running multiple Bitcoin wallets (testnet or mainnet when ready),
- allows adding remote wallets(coming soon) for those running their own nodes,
  - also will enable monitoring of multiple remote nodes when prometheus is merged into lnd,
- allows shipping 2 binary versions of lnd (ex: lnd upgrades from 0.4.2 to 0.5),
  - it's possible that there will be backwards-incompatible changes, by having 2 binaries we can use the new binary for new wallets and old binary for existing wallets, prompting the user to switch funds,
  - makes it possible to ship a new lnd version and detect regression on newly created wallets, etc.
- allows having additional implementations like c-lightning for some wallets.
On Android, the lnd daemon is isolated in it's own process, so it's easier to manage and when it hangs or shutdowns, the whole process is removed, keeping the app's own process "clean" and makes it more difficult for native code to crash the app.
On iOS, lnd runs in the same process as the main app and there are far more restrictions on memory/cpu/processes, so when the wallet is closed, the user can't reopen another wallet without quitting the app.

gomobile is a common option used by other developers for cross-compiling, we believe xgo is better because:

gomobile is experimental with no end-user support, few documentation, xgo is simply a docker image and tool to run a cgo cross-compilation (cgo is part of golang, used by many big/important projects, also used internally by gomobile), so xgo will be more predictable and reliable,
gomobile requires modifications to lnd's codebase in order to compile (ex: gomobile can't export anything in main package). With xgo, we can just git pull and compile without any new modifications to lnd's codebase.
gomobile tries to export every functions it finds so that the Go project can be used as a library on mobile, this is both unnecessary and problematic. Unnecessary because we run lnd as a daemon, therefore we don't need access to it's internals and problematic because not everything is exportable to mobile (ex: if it comes across a big integer, it doesn't have an equivalent on JVM, it will fail with unsupported type).

Building from source

Please note: when you compile and run from the development version from the source code by default, there is a lot of overhead. The profile server will be open on port :6060, lnd log levels will be set to info and app logs will be set at the info level. This will lead to performance problems and overheating of your phone, if you don't want to develop but still compile from source code, look into documentation on how to build a release build of react-native project.

If you run into libfishhook.a related errors on XCode, patch: facebook/react-native#19579 into node_modules/react-native/ code.

If you run into config.h not found: facebook/react-native#14382

1. Requirements

You need to install:

2. Cross compiling lnd

Go to lnd folder
Apply the rawtx patch (lnd.patch in this repo, this exports hooks which allows us to start/stop lnd)
```
git apply lnd.patch
```
Note: if you run into problems with the patch, you can always use the newmerge branch from our own fork of lnd: https://github.com/rawtxapp/lnd/tree/newmerge.
Depending on which platform you're targeting, compile using xgo:
- Android, run:
```
dep ensure && xgo -out rtx_export --targets=android/aar  ./
```
This will produce an rtx_export-android-16.aar file and you need to copy it in the app's directory at rawtx/android/rtx_export-android-16/rtx_export-android-16.aar.
- iOS, run:
```
dep ensure && xgo -out rtx_export --targets=ios/framework ./
```
This will produce a rtx_export-ios-5.0-framework/Rtx_export.framework/ folder and you need to copy it to rawtx/ios/rtxnative/Rtx_export.framework.
Once the native libraries are copied, just go to the app's folder, run npm install and run react-native run-android or open XCode from the ios/ folder and launch the application. As mentioned previously, these will be development builds by default and will be slower than optimized builds.
...
Enjoy!

Contributing

There's still a lot of work that needs to be done, if you know JS/Java or objC and would like to contribute to the app/UI layer, here's a list of possible features. If you know golang, you can head over to lnd to contribute at the lightning layer.

Some TODOs/features:

integrate autopilot,
support streaming lnd APIs,
litecoin integration,
better UI for payments/invoices list screen,
advanced/simple modes,
possibility of pointing to remote node,
satoshi, mbtc, US$ units for balances,
settings,
dark theme,
a specific activity just for handling lightning: links,
translations.

In-depth overview of the code

Coming soon.