# 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 source and structured-value imports through `ImportLoader`
- shared host environments for production and semantic editor tooling
- no filesystem access in the library core
- concrete and abstract values with constraints and defaults
- asymmetric range refinement with `narrower as wider`
- homogeneous associative-array schemas with `{...valueSchema}`
- 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 an `ImportLoader`.

```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
```

## Language server

The `decodal-language-service` crate provides transport-independent evaluation and completion, while `decodal-lsp` exposes it through the Language Server Protocol with live semantic diagnostics and document formatting.
Its library API accepts the same host environment used for production evaluation, so application-defined globals and structured import routing remain available in the editor.

```toml
[dependencies]
decodal = "0.2.0"
decodal-language-service = "0.2.0"
decodal-lsp = "0.2.0"
```

Run the default filesystem-backed server from the repository:

```sh
cargo run -q -p decodal-lsp
```

Embedded applications can implement `decodal_lsp::LspEnvironment` for their existing `HostEnvironment` and construct it from the `InitializeParams` passed to `decodal_lsp::run_stdio`.

## Web playground

The static documentation site and browser playground live under:

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

Browser hosts can use `decodal-wasm`. Its `DecodalLanguageService` accepts JavaScript-owned `globals`, `loadImport`, and `completeImport` callbacks; filesystem and virtual-project policy remain outside the package.

## License

Licensed under either of:

- Apache License, Version 2.0
- MIT license

at your option.