# OPA-WASM

This directory contains a library that implements various low-level
operations for policies compiled into WebAssembly (WASM). Specifically, the
library implements:

* JSON parsing
* JSON AST (e.g., comparison, iteration, lookup, etc.)
* String operations
* Memory allocation

This library does not make any backwards compatibility guarantees.

## Development

You should have Docker installed to build and test changes to the library. We
commit the output of the build (`opa.wasm`) into the repository so it's
important for the build output to be reproducible.

You can build the library by running `make build`. This will produce WASM
executables under the `_obj` directory.

You can test the library by running `make test`. By default the test runner
does not print messages when tests pass. If you run `make test VERBOSE=1` it
will log all of the tests that were run.

You can run `make hack` to start a shell inside the builder image. This is
useful if you need to interact with low-level WASM tooling like
`wasm-objdump`, `wasm2wat`, etc. or LLVM itself.

You must manually push the builder image if you make changes to it (run `make
builder` to produce a new Docker image).

## Vendoring

If you make changes to the library, run the `make generate` in the parent
directory and commit the results back to the repository. The `generate`
target will:

1. Build the OPA-WASM library
2. Copy the library into the [internal/compiler/wasm/opa](../internal/compiler/wasm/opa) directory.
3. Run the tool to generate the [internal/compiler/wasm/opa/opa.go](../internal/compiler/wasm/opa/opa.go) file.