#![feature(iter_intersperse)]
use std::{
    env,
    ffi::OsString,
    fs,
    os::unix::{
        ffi::{OsStrExt, OsStringExt},
        process::CommandExt,
    },
    process::Command,
};

fn main() {
    let mut child_env = vec![];
    for (key, value) in env::vars_os() {
        let key_bytes: Vec<_> = key.as_bytes().into();
        if key_bytes.ends_with(b"_FILE") && !value.is_empty() {
            match fs::read(&value) {
                Ok(content) => {
                    let key = OsString::from_vec(key_bytes[0..key_bytes.len() - 5].to_owned());
                    child_env.push((key, OsString::from_vec(content)));
                }
                Err(error) => {
                    panic!(
                        "failed to read contents of {value:?} (specified by ${}): {error:?}",
                        key.to_string_lossy()
                    )
                }
            }
        } else {
            child_env.push((key, value))
        }
    }
    let mut args = env::args().skip(1);
    if let Some(cmd) = args.next() {
        let collected: Vec<_> = args.collect();
        let mut child = Command::new(&cmd);
        child.env_clear().envs(child_env);
        for arg in &collected {
            child.arg(arg);
        }
        let err = child.exec(); // Ideally should not return
        panic!("error running command {cmd} with args {collected:?}: {err}");
    } else {
        panic!("no command given");
    }
}