use std::path::PathBuf;

use clap::Parser;

mod repl;
mod sandbox;
mod stdlib;

/// Runs a Lua script in a customized environment, or an interactive REPL when
/// no script path is given.
#[derive(Parser, Debug)]
#[command(version, about)]
struct Args {
    /// Path to the Lua script to execute. Omit to start an interactive REPL.
    filepath: Option<PathBuf>,
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    env_logger::Builder::from_env(env_logger::Env::default().default_filter_or("warn")).init();

    let args = Args::parse();

    let lua = sandbox::create_sandboxed_lua()?;

    let Some(filepath) = args.filepath else {
        return repl::run(&lua).await;
    };

    let source = tokio::fs::read_to_string(&filepath).await?;

    // Skip a leading shebang line like stock Lua's luaL_loadfilex does (it
    // skips any first line starting with '#'). The newline is kept so error
    // messages still report correct line numbers.
    let chunk = if source.starts_with('#') {
        &source[source.find('\n').unwrap_or(source.len())..]
    } else {
        source.as_str()
    };

    lua.load(chunk)
        // "@" marks the chunk name as a file path in error messages / tracebacks
        .set_name(format!("@{}", filepath.display()))
        .exec_async()
        .await?;

    Ok(())
}