#![allow(dead_code)]

mod re;
mod text;

fn main() -> Result<(), Box<dyn std::error::Error>>
{
    let args: Vec<String> = std::env::args().collect();

    if args.len() < 4 {
	println!("Usage: {} <str> <regex> <group>", args[0]);
	println!("Pass `-' as `<str>' to read lines from stdin");
	std::process::exit(1);
    } else {
	let re = re::Regex::compile(&args[2])?;
	let text = &args[1];
	let group: usize = args[3].parse().expect("Invalid group number.");

	if text == "-" {
	    text::stdin_lines(|text| -> Result<bool, re::Error> {
		match re.exec(&text)? {
		    Some(g) if g.len() > group => println!("{}", &g[group]),
		    _ => (),
		}
		Ok(true)
	    })?;
	} else {

	    match re.exec(&text)? {
		Some(g) if g.len() > group => println!("{}", &g[group]),
		_ => (),
	    }
	}
    }
    Ok(())
}