use structopt::StructOpt;
use std::{error::Error, fmt};
use std::io::prelude::*;
use std::io::BufReader;
use std::fs::File;
use std::path::PathBuf;
#[derive(Debug)]
struct FileNotFoundError(String);
impl Error for FileNotFoundError {}
impl fmt::Display for FileNotFoundError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Oh no, something bad went down")
    }
}
#[derive(Debug, StructOpt)]
struct Opts {
    pattern: String,
    #[structopt(parse(from_os_str))]
    path: PathBuf
}
fn main() -> Result<(), Box<dyn std::error::Error>> {
    let opts = Opts::from_args();
    println!("{:?}", opts);
    let file = match File::open(&opts.path) {
        Ok(content) => { content },
        Err(error) => { return Err(Box::new(FileNotFoundError(format!("Error reading `{}`: {}", &opts.path.to_str().unwrap(), error)))) }
    };
    let reader = BufReader::new(file);
    for (num, line) in reader.lines().enumerate() {
        let value = line?;
        if value.contains(&opts.pattern) {
            println!("{}. {}", num, value);
        }
    }
    Ok(())
}