use mlua::{ExternalResult, Lua, LuaSerdeExt, Result};

#[tokio::main]
async fn main() -> Result<()> {
    let lua = Lua::new();
    let globals = lua.globals();
    globals.set("null", lua.null())?;

    let fetch_json = lua.create_async_function(|lua, uri: String| async move {
        let resp = reqwest::get(&uri)
            .await
            .and_then(|resp| resp.error_for_status())
            .to_lua_err()?;
        let json = resp.json::<serde_json::Value>().await.to_lua_err()?;
        lua.to_value(&json)
    })?;
    globals.set("fetch_json", fetch_json)?;

    let f = lua
        .load(
            r#"
            function print_r(t, indent)
                local indent = indent or ''
                for k, v in pairs(t) do
                    io.write(indent, tostring(k))
                    if type(v) == "table" then io.write(':\n') print_r(v, indent..'  ')
                    else io.write(': ', v == null and "null" or tostring(v), '\n') end
                end
            end

            local res = fetch_json(...)
            print_r(res)
        "#,
        )
        .into_function()?;

    f.call_async("https://httpbin.org/anything?arg0=val0").await
}