multicall.rs

use std::{
    env::args_os,
    fs::{hard_link, read_link},
    path::{Path, PathBuf},
    process::exit,
};

use clap::{Clap, IntoApp};

#[derive(Clap, Debug)]
enum Applets {
    True,
    False,
}

#[derive(Clap, Debug)]
#[clap(setting = clap::AppSettings::Multicall)]
struct Args {
    #[clap(
        long,
        default_missing_value = "/usr/local/bin",
        exclusive = true,
        use_delimiter = false
    )]
    install: Option<Option<PathBuf>>,
    #[clap(subcommand)]
    applet: Option<Applets>,
}

fn main() {
    let args = Args::parse();
    if let Some(path) = args.install {
        let path = path.expect("clap Option<Option<T>>'s inner Option<T> should always be present if given default_missing_value");
        let app = Args::into_app();
        let applets: Vec<_> = app.get_subcommands().map(|c| c.get_name()).collect();
        let exec_path = read_link("/proc/self/exe")
            .ok()
            .or_else(|| {
                args_os().next().and_then(|s| {
                    let p: &Path = s.as_ref();
                    if p.is_absolute() {
                        Some(PathBuf::from(s))
                    } else {
                        None
                    }
                })
            })
            .expect(
                "Should be able to read /proc/self/exe or argv0 should be present and absolute",
            );
        let mut dest = PathBuf::from(path);
        for applet in applets {
            if applet == "install" {
                continue;
            }
            dest.push(applet);
            hard_link(&exec_path, &dest).expect("Should be able to hardlink");
            dest.pop();
        }
        exit(0);
    }
    match args.applet {
        Some(Applets::True) => exit(0),
        Some(Applets::False) => exit(1),
        _ => Args::into_app().print_help().unwrap(),
    }
}