# Decodal

Decodal is a small deterministic DSL for describing, composing, validating, and materializing structured data.

It is designed around a lightweight Rust library:

- host-supplied imports through `SourceLoader`
- no filesystem access in the library core
- concrete and abstract values with constraints and defaults
- deterministic expression evaluation
- optional regex support behind a Cargo feature
- browser playground support through WebAssembly

## Library crate

Embedded hosts should depend on `decodal` and provide imports with a `SourceLoader`.

```toml
[dependencies]
decodal = "0.1"
```

## Derive support

For embedded Rust applications, Decodal can generate a schema and typed decoder from a Rust struct with the `derive` feature.

```toml
[dependencies]
decodal = { version = "0.1", features = ["derive"] }
```

```rust
use decodal::{Decodal, DecodalDecode, DecodalSchema, Engine};

#[derive(Decodal)]
struct Service {
    name: String,
    #[decodal(gt = 443, default = 8443)]
    port: i64,
    #[decodal(rename = "feature.enable", default = true)]
    feature_enabled: bool,
}
```

The derive implements:

- `DecodalSchema`, which produces a host schema for `Engine::bind_global`
- `DecodalDecode`, which converts materialized `Data` into the Rust struct

## CLI

A standalone CLI is kept in this repository as the `decodal-cli` workspace package.
It builds a `decodal` binary, but it is not the primary crates.io package.

Run a Decodal file from the repository:

```sh
cargo run -q -p decodal-cli -- examples/advanced/main.dcdl
```

Enable optional regex support when needed:

```sh
cargo run -q -p decodal-cli --features regex -- examples/regex/main.dcdl
```

## Web playground

The static documentation site and browser playground live under:

```text
site/decodal-site/
```

## License

Licensed under either of:

- Apache License, Version 2.0
- MIT license

at your option.
