parse_args.rs

#[derive(Debug)]
struct Frame {
    width: u32,
    height: u32,
}

#[derive(Debug)]
enum ParseError {
    TooFewArgs,
    TooManyArgs,
    InvalidInteger(String),
}

fn parse_args() -> Result<Frame, ParseError> {
    use self::ParseError::*;

    let mut args = std::env::args().skip(1);

    let width_str = match args.next() {
        None => return Err(TooFewArgs),
        Some(width_str) => width_str,
    };

    let height_str = match args.next() {
        None => return Err(TooFewArgs),
        Some(height_str) => height_str,
    };

    match args.next() {
        Some(_) => return Err(TooManyArgs),
        None => (),
    }

    let width = match width_str.parse() {
        Err(_) => return Err(InvalidInteger(width_str)),
        Ok(width) => width,
    };

    let height = match height_str.parse() {
        Err(_) => return Err(InvalidInteger(height_str)),
        Ok(height) => height,
    };

    Ok(Frame {
        width,
        height,
    })
}