# SnarkyJS bindings

This repository collects code needed by [SnarkyJS](https://github.com/o1-labs/snarkyjs) to bind to lower layers of the proof system and the Mina transaction logic, which are written in Rust and OCaml.

The repo is included as a git submodule in the [SnarkyJS repo](https://github.com/o1-labs/snarkyjs) under `src/bindings`, and typically used from there.

**Directory structure**

- `/compiled` - compiled JS and Wasm artifacts produced by `js_of_ocaml` and `wasm-bindgen` from Rust and OCaml source code. We keep these artifacts in the source tree so that developing on SnarkyJS can be done with standard JS tooling and doesn't require setting up the full OCaml/Rust build pipeline.
- `/crypto` - pure TS implementations of a subset of the crypto primitives we use, including finite field and elliptic curve arithmetic. This is used by mina-signer (a pure TS package) to hash and sign transactions.
- `/js` - JS-side wrappers for the artifacts located in `/compiled`, which differs between the Node.js and web versions of SnarkyJS. Includes code for setting up workers to support using `rayon` in Rust.
- `/kimchi` - bindings to the [Kimchi proof system](https://o1-labs.github.io/proof-systems/kimchi/overview.html) which is implemented in Rust. This contains a Wasm compatibility layer written in Rust as well as a `js_of_ocaml`-to-`wasm-bindgen` glue layer written in JS.
- `/lib` - miscellaneous low-level TypeScript which underpins SnarkyJS and provides generic ways to connect with a proof system and blockchain protocol.
- `/mina-transaction` - TS types and modules which specialize the generic tooling in `/lib` to Mina's zkApp protocol; mostly auto-generated from OCaml.
- `/ocaml` - OCaml library exposing Snarky, Pickles and parts of the Mina transaction logic to JS. Also, OCaml scripts which help auto-generating TypeScript for Mina- and crypto-related types and constants.
- `/scripts` - scripts which build parts of SnarkyJS from their OCaml and Rust sources, including the contents of `/compiled` and other generated TS files.
- `MINA_COMMIT` - commit hash pointing to the commit of the [Mina repo](https://github.com/MinaProtocol/mina) that build artifacts in this repo where generated from.

## Building the SnarkyJS bindings

To instrument the scripts and build the SnarkyJS bindings from source, you need to work from the [Mina monorepo](https://github.com/MinaProtocol/mina).

Inside the Mina repo, you'll find the [SnarkyJS repo](https://github.com/o1-labs/snarkyjs) as a git submodule under `src/lib/snarkyjs`. Inside `snarkyjs`, the `snarkyjs-bindings` repo is located at `src/bindings`. To make sure you have all nested submodules checked out, run (from the Mina root):

```sh
git submodule update --init --recursive
```

Then, switch to the SnarkyJS root in `src/lib/snarkyjs`. There are two different commands available, `npm run make` and `npm run bindings`, which you need for different purposes:

```
npm run make
```

This command will

- regenerate TS files in the snarkyjs-bindings source tree
- build the JS/Wasm artifacts for Node.js (also contained in `/compiled/node-bindings`), but only move them to their place in the `snarkyjs/dist/node` folder which is not part of the source tree.

> ℹ️ Use `npm run make` if you are developing on or testing the OCaml/Rust layers of SnarkyJS, and want to rebuild.

```
npm run bindings
```

This command will

- do everything `npm run make` does, plus
- build the web version of the SnarkyJS bindings, plus
- place the generated artifacts in the source tree, under `/compiled`
- update the `MINA_COMMIT` file

> ℹ️ Use `npm run bindings` to update the source tree after you have finished a batch of work / a PR which touches the OCaml/Rust layers. SnarkyJS CI depends on these artifacts, so this is a required step before merging such changes.