# Native language bindings for BDK
The workspace in this repository creates the `libbdkffi` multi-language library for the rust based
[bdk] library from the [Bitcoin Dev Kit] project. The `bdk-ffi-bindgen` package builds a tool for
generating the actual language binding code used to access the `libbdkffi` library.
Each supported language has its own repository that includes this project as a [git submodule].
The rust code in this project is a wrapper around the [bdk] library to expose it's APIs in a
uniform way using the [mozilla/uniffi-rs] bindings generator for each supported target language.
## Supported target languages and platforms
The below repositories include instructions for using, building, and publishing the native
language binding for [bdk] supported by this project.
| Language | Platform | Repository |
| -------- | ------------ | ------------ |
| Kotlin | jvm | [bdk-kotlin] |
| Kotlin | android | [bdk-kotlin] |
| Swift | iOS, macOS | [bdk-swift] |
| Python | linux, macOS | [bdk-python] |
## Language bindings generator tool
Use the `bdk-ffi-bindgen` tool to generate language binding code for the above supported languages.
To run `bdk-ffi-bindgen` and see the available options use the command:
```shell
cargo run -p bdk-ffi-bindgen -- --help
```
[bdk]: https://github.com/bitcoindevkit/bdk
[Bitcoin Dev Kit]: https://github.com/bitcoindevkit
[git submodule]: https://git-scm.com/book/en/v2/Git-Tools-Submodules
[uniffi-rs]: https://github.com/mozilla/uniffi-rs
[bdk-kotlin]: https://github.com/bitcoindevkit/bdk-kotlin
[bdk-swift]: https://github.com/bitcoindevkit/bdk-swift
[bdk-python]: https://github.com/bitcoindevkit/bdk-python
## Contributing
### Adding new structs and functions
See the [UniFFI User Guide](https://mozilla.github.io/uniffi-rs/)
#### For pass by value objects
1. create new rust struct with only fields that are supported UniFFI types
1. update mapping `bdk.udl` file with new `dictionary`
#### For pass by reference values
1. create wrapper rust struct/impl with only fields that are `Sync + Send`
1. update mapping `bdk.udl` file with new `interface`
## Goals
1. Language bindings should feel idiomatic in target languages/platforms
1. Adding new targets should be easy
1. Getting up and running should be easy
1. Contributing should be easy
1. Get it right, then automate
# bdk-kotlin
This project builds .jar and .aar packages for the `jvm` and `android` platforms that provide
[Kotlin] language bindings for the [`bdk`] library. The Kotlin language bindings are created by the
[`bdk-ffi`] project which is included as a git submodule of this repository.
## How to Use
To use the Kotlin language bindings for [`bdk`] in your `jvm` or `android` project add the
following to your gradle dependencies:
```groovy
repositories {
mavenCentral()
}
dependencies {
// for jvm
implementation 'org.bitcoindevkit:bdk-jvm:'
// OR for android
implementation 'org.bitcoindevkit:bdk-android:'
}
```
You may then import and use the `org.bitcoindevkit` library in your Kotlin code. For example:
```kotlin
import org.bitcoindevkit.*
// ...
val externalDescriptor = "wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/0/*)"
val internalDescriptor = "wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/1/*)"
val databaseConfig = DatabaseConfig.Memory
val blockchainConfig =
BlockchainConfig.Electrum(
ElectrumConfig("ssl://electrum.blockstream.info:60002", null, 5u, null, 10u)
)
val wallet = Wallet(externalDescriptor, internalDescriptor, Network.TESTNET, databaseConfig, blockchainConfig)
val newAddress = wallet.getNewAddress()
```
### Example Projects
#### `bdk-android`
* [Devkit Wallet](https://github.com/thunderbiscuit/devkit-wallet)
* [Padawan Wallet](https://github.com/thunderbiscuit/padawan-wallet)
#### `bdk-jvm`
* [Tatooine Faucet](https://github.com/thunderbiscuit/tatooine)
### How to build
_Note that Kotlin version `1.6.10` or later is required to build the library._
1. Clone this repository and initialize and update its [`bdk-ffi`] submodule.
```shell
git clone https://github.com/bitcoindevkit/bdk-kotlin
git submodule update --init
```
2. Follow the "General" bdk-ffi ["Getting Started (Developer)"] instructions.
3. If building on MacOS install required intel and m1 jvm targets
```sh
rustup target add x86_64-apple-darwin aarch64-apple-darwin
```
4. Install required targets
```sh
rustup target add x86_64-linux-android aarch64-linux-android armv7-linux-androideabi
```
5. Install Android SDK and Build-Tools for API level 30+
6. Setup `$ANDROID_SDK_ROOT` and `$ANDROID_NDK_ROOT` path variables (which are required by the
build tool), for example (NDK major version 21 is required):
```shell
export ANDROID_SDK_ROOT=~/Android/Sdk
export ANDROID_NDK_ROOT=$ANDROID_SDK_ROOT/ndk/21.
```
7. Build kotlin bindings
```sh
# build JVM library
cd bdk-jvm
./gradlew buildJvmLib
# build Android library
cd bdk-android
./gradlew buildAndroidLib
```
8. Start android emulator (must be x86_64) and run tests
```sh
./gradlew connectedAndroidTest
```
## How to publish
### Publish to your local maven repo
```shell
# bdk-jvm
cd bdk-jvm
./gradlew publishToMavenLocal --exclude-task signMavenPublication
# bdk-android
cd bdk-android
./gradlew publishToMavenLocal --exclude-task signMavenPublication
```
Note that the commands assume you don't need the local libraries to be signed. If you do wish to sign them, simply set your `~/.gradle/gradle.properties` signing key values like so:
```properties
signing.gnupg.keyName=
signing.gnupg.passphrase=
```
and use the `publishToMavenLocal` task without excluding the signing task:
```shell
./gradlew publishToMavenLocal
```
## Verifying Signatures
Both libraries and all their corresponding artifacts are signed with a PGP key you can find in the
root of this repository. To verify the signatures follow the below steps:
1. Import the PGP key in your keyring.
```shell
# Navigate to the root of the repository and import the ./PGP-BDK-BINDINGS.asc public key
gpg --import ./PGP-BDK-BINDINGS.asc
# Alternatively, you can import the key directly from a public key server
gpg --keyserver keyserver.ubuntu.com --receive-key 2768C43E8803C6A3
# Verify that the correct key was imported
gpg --list-keys
# You should see the below output
pub ed25519 2022-08-31 [SC]
88AD93AC4589FD090FF3B8D12768C43E8803C6A3
uid [ unknown] bitcoindevkit-bindings
sub cv25519 2022-08-31 [E]
```
2. Download the binary artifacts and corresponding signature files.
- from [bdk-jvm]
- `bdk-jvm-.jar`
- `bdk-jvm-.jar.asc`
- from [bdk-android]
- `bdk-android-.aar`
- `bdk-android-.aar.asc`
3. Verify the signatures.
```shell
gpg --verify bdk-jvm-.jar.asc
gpg --verify bdk-android-.aar.asc
# you should see a "Good signature" result
gpg: Good signature from "bitcoindevkit-bindings " [unknown]
```
### PGP Metadata
Full key ID: `88AD 93AC 4589 FD09 0FF3 B8D1 2768 C43E 8803 C6A3`
Fingerprint: `2768C43E8803C6A3`
Name: `bitcoindevkit-bindings`
Email: `bindings@bitcoindevkit.org`
[Kotlin]: https://kotlinlang.org/
[Android Studio]: https://developer.android.com/studio/
[`bdk`]: https://github.com/bitcoindevkit/bdk
[`bdk-ffi`]: https://github.com/bitcoindevkit/bdk-ffi
["Getting Started (Developer)"]: https://github.com/bitcoindevkit/bdk-ffi#getting-started-developer
[Gradle Nexus Publish Plugin]: https://github.com/gradle-nexus/publish-plugin
[bdk-jvm]: https://search.maven.org/artifact/org.bitcoindevkit/bdk-jvm/0.9.0/jar
[bdk-android]: https://search.maven.org/artifact/org.bitcoindevkit/bdk-android/0.9.0/aar
## Thanks
This project is made possible thanks to the wonderful work by the [mozilla/uniffi-rs] team.
[mozilla/uniffi-rs]: https://github.com/mozilla/uniffi-rs