fn parse_path(s: &std::ffi::OsStr) -> Result<std::path::PathBuf, &'static str> {

    Ok(s.into())

}

fn parse_args() -> Result<Args, pico_args::Error> {

    let mut pargs = pico_args::Arguments::from_env();

    // Help has a higher priority and should be handled separately.

    if pargs.contains(["-h", "--help"]) {

        print!("{}", HELP);

        std::process::exit(0);

    }

    let args = Args {

        input: pargs.value_from_os_str("--input", parse_path)?,

        output_dir: pargs.value_from_os_str("--output-dir", parse_path)?,

    let remaining_arguments = pargs.finish();

    if !remaining_arguments.is_empty() {

        eprintln!("There are unused arguments:");

        for remaining in remaining_arguments {

            if let Ok(remaining) = remaining.into_string() {

                eprintln!("Unused argument: {}", remaining);

            }

        print!("{}", HELP);

        std::process::exit(1);

    }

    Ok(args)

}

fn main() {

    let args = match parse_args() {

        Ok(v) => v,

        Err(e) => {

            eprintln!("Error: {}.", e);

            std::process::exit(1);

    harvest(&args.input, &args.output_dir);

}