Drill 23: Find the core line — Error handling patterns

use std::fs;
use thiserror::Error;

#[derive(Debug, Error)]
enum ReadError {
    #[error("file not found: {0}")]
    NotFound(String),
    #[error("could not read file: {0}")]
    Io(#[from] std::io::Error),
}

fn read_title(path: &str) -> Result<String, ReadError> {
    let text = fs::read_to_string(path)?;
    Ok(text.trim().to_string())
}

fn pick(values: Vec<i32>) -> Option<i32> {
    values.first().copied()
}

fn main() {
    match pick(vec![3, 5, 8]) {
        Some(first) => println!("first {}", first),
        None => println!("empty"),
    }

    match read_title("notes.txt") {
        Ok(title) => println!("title {}", title),
        Err(err) => println!("error {}", err),
    }
}