Automatic Swift bindings generation for rust-lightning.

To install using Swift Package Manager, add the following line to the depedencies array of your Package.swift:

.package(url: "https://github.com/lightningdevkit/ldk-swift/", exact: "0.0.118")

Be sure to also include "LightningDevKit" into your packages target like so:

targets: [
 .target(
 name: "YourPackage",
 dependencies: [
 .product(name: "LightningDevKit", package: "ldk-swift")
 ]),
 ...
]

If you're importing directly into Xcode, just copy and paste https://github.com/lightningdevkit/ldk-swift/ into the system dialog when you click "Add Package..."

In order to use the automatically generated bindings, simply drag *.xcframework file into an Xcode project.

The *.xcframework files are either available on the Releases page, or can be compiled from scratch.

• A machine running macOS
• Xcode
• Python3
• Rust
• NPM
• GNU sed (optional, but will cut your compile times significantly!)

For Rust specifically, there are a couple additional requirements that can be installed once the Rust toolchain is set up:

rustup toolchain install nightly
rustup target add aarch64-apple-darwin aarch64-apple-ios x86_64-apple-ios
cargo install cbindgen

In order to generate these bindings from scratch, you will need to clone two dependency repositories:

rust-lightning , (a specific branch built for bindings compatibility):

git clone --branch 0.0.125-bindings https://github.com/lightningdevkit/rust-lightning /path/to/rust-lightning

ldk-c-bindings :

git clone --branch main https://github.com/lightningdevkit/ldk-c-bindings /path/to/ldk-c-bindings

Take note of where you clone these directories, it's best you save the absolute path somewhere handy for the rest of the remaining steps.

Now, navigate to the ldk-c-bindings directory and run the genbindings.sh script:

pushd path/to/ldk-c-bindings
./genbindings.sh /path/to/rust-lightning true
popd

lightning = { git = "https://github.com/thebluematt/rust-lightning", branch = "2023-07-0.0.116-java-bindings", default-features = false }
lightning-persister = { git = "https://github.com/thebluematt/rust-lightning", branch = "2023-07-0.0.116-java-bindings", default-features = false }
lightning-invoice = { git = "https://github.com/thebluematt/rust-lightning", branch = "2023-07-0.0.116-java-bindings", default-features = false }
lightning-background-processor = { git = "https://github.com/thebluematt/rust-lightning", branch = "2023-07-0.0.116-java-bindings", default-features = false }
lightning-rapid-gossip-sync = { git = "https://github.com/thebluematt/rust-lightning", branch = "2023-07-0.0.116-java-bindings", default-features = false }

cd /path/to/rust-lightning
git rev-parse HEAD

To generate the Swift files, navigate to the ldk-swift repository and run the following:

export LDK_SWIFT_GENERATOR_INPUT_HEADER_PATH="/path/to/ldk-c-bindings/lightning-c-bindings/include/lightning.h"
npm i && npm run tsc && node ./src/index.mjs

Now, the contents of ./ci/LDKSwift/Sources/LDKSwift/bindings will have been completely regenerated.

To make sure the correct bindings files are referenced in the project, open ./xcode/LDKFramework/LDK.xcodeproj.

In the sidebar, navigate to the LDK/bindings group, and delete it by removing references.

Then, open a Finder window, and drag the bindings folder (./ci/LDKSwift/Sources/LDKSwift/bindings) into the same location in Xcode that you just deleted.

Finally, make sure you leave the "Copy items if needed" box unchecked, and pick at least LightningDevKit as a target to add the references to. Depending on what you intend to do later on, it's easiest to simply add it to all the targets.

Navigate (cd) to the ./scripts folder, and run the following Python script:

python3 ./build_bulk_libldks.py /path/to/ldk-c-bindings

This command will take a while, but it will eventually produce a set of binaries for all the platform/architecture combinations we're trying to support. Those binaries should adhere to the ./bindings/bin/release/<platform>/ folder pattern.

Each of those folders will contain an architectures directory with subdirectories such as arm64 or x86_64, as well as a libldk.a file, which is the lipo product of all the targeted architectures.

With all the binaries generated, still in the ./src/scripts directory, you just need to run one last Python script to produce the framework:

python3 ./generate_xcframework.py /path/to/ldk-c-bindings

Once the script finishes running, you should see LightningDevKit.xcframework in the ./bindings/bin/release folder. Drag that into your project, and you're done!