use std::fs::File;
use std::io::ErrorKind;

fn main() {
    // panic!("crash and burn");

    // let f = File::open("hello.txt");

    // let f = match f {
    //     Ok(file) => file,
    //     Err(error) => match error.kind() {
    //         ErrorKind::NotFound => match File::create("hello.txt") {
    //             Ok(fc) => fc,
    //             Err(e) => panic!("Problem creating the file: {:?}", e),
    //         },
    //         other_error => {
    //             panic!("Problem opening file: {:?}", other_error)
    //         }
    //     },
    // };

    // Rustacean style
    // let f = File::open("hello.txt").unwrap_or_else(|error| {
    //     if error.kind() == ErrorKind::NotFound {
    //         File::create("hello.txt").unwrap_or_else(|error| {
    //             panic!("Problem creating the file: {:?}", error);
    //         })
    //     } else {
    //         panic!("Problem opening file: {:?}", error);
    //     }
    // });

    // Shortcut
    // let f = File::open("hello.txt").unwrap();

    // let f = File::open("hello.txt").expect("Failed to open hello.txt");

    // Propagating
    use std::io;
    use std::io::Read;

    // fn read_username_from_file() -> Result<String, io::Error> {
    //     let f = File::open("hello.txt");

    //     let mut f = match f {
    //         Ok(file) => file,
    //         Err(e) => return Err(e),
    //     };

    //     let mut s = String::new();

    //     match f.read_to_string(&mut s) {
    //         Ok(_) => Ok(s),
    //         Err(e) => Err(e),
    //     }
    // }

    // Propagating shortcut
    // fn read_username_from_file() -> Result<String, io::Error> {
    //     let mut f = File::open("hello.txt")?;
    //     let mut s = String::new();
    //     f.read_to_string(&mut s)?;
    //     Ok(s)
    // }

    // Chaining
    // fn read_username_from_file() -> Result<String, io::Error> {
    //     let mut s = String::new();

    //     File::open("hello.txt")?.read_to_string(&mut s)?;

    //     Ok(s)
    // }

    // Using `fs::read_to_string`
    use std::fs;
    fn read_username_from_file() -> Result<String, io::Error> {
        fs::read_to_string("hello.txt")
    }

    let r = read_username_from_file();
    println!("{:?}", r);
}