hyperlight-js-runtime 0.2.1

/*
Copyright 2026  The Hyperlight Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
use std::path::{Path, PathBuf};
use std::{env, fs};

use anyhow::{Context as _, Result};
use clap::Parser;
use tracing::instrument;

struct Host;

impl hyperlight_js_runtime::host::Host for Host {
    fn resolve_module(&self, base: String, name: String) -> Result<String> {
        let base = PathBuf::from(base);
        let path = base.join(&name);

        let path = path
            .canonicalize()
            .with_context(|| format!("Resolving module {name:?} from {base:?}"))?;
        Ok(path.display().to_string())
    }

    fn load_module(&self, name: String) -> Result<String> {
        fs::read_to_string(&name).with_context(|| format!("Loading module {name:?}"))
    }
}

const EXAMPLES: &str = "\u{001b}[1;4mExamples:\u{001b}[0m
  Run a handler script located at ./handler.js with an event '{\"name\":\"hyperlight-js-runtime\"}':
    $ cat ./handler.js
    function handler(event) {
        return `hello ${event.name}`
    }

    $ hyperlight-js-runtime ./handler.js '{\"name\":\"hyperlight-js-runtime\"}'
    Handler result: \"hello hyperlight-js-runtime\"

  Example handler script (index.js) and module (math.js):
    $ cat ./index.js
    import * as math from './math.js';
    function handler(event) {
        console.log(JSON.stringify(event));
        return math.add(event.a, 41);
    }

    $ cat ./math.js
    const add = (a, b) => a + b;
    export { add };

    $ hyperlight-js-runtime ./index.js '{\"a\":1,\"b\":[1,2,3]}'
    {\"a\":1,\"b\":[1,2,3]}
    Handler result: 42
";

/// Run a JavaScript handler script with a given event as they would have been run inside `hyperlight-js`.
///
/// The handler script is expected to export a function named `handler` that takes a single argument
/// (the event) and returns a value.
#[derive(clap::Parser)]
#[command(version, about)]
#[clap(after_help = EXAMPLES)]
struct Cli {
    /// The path to the JavaScript handler script file.
    file: PathBuf,

    /// The event to pass to the handler function as a JSON string.
    event: String,
}

#[instrument(skip_all, level = "info")]
fn main() -> Result<()> {
    let Cli { file, event } = Cli::parse();

    let handler_script = fs::read_to_string(&file)
        .with_context(|| format!("Reading handler script from {:?}", file))?;

    let handler_pwd = file.parent().unwrap_or_else(|| Path::new("."));

    env::set_current_dir(handler_pwd).with_context(|| {
        format!("Setting current directory to handler script directory {handler_pwd:?}")
    })?;

    let mut runtime = hyperlight_js_runtime::JsRuntime::new(Host)?;

    runtime.register_host_function("fs", "readFile", move |path: String| -> Result<String> {
        Ok(fs::read_to_string(&path)?)
    })?;

    runtime.register_handler("handler".to_string(), handler_script, String::from("."))?;

    let result = runtime.run_handler("handler".to_string(), event, false)?;
    println!("Handler result: {result}");

    Ok(())
}