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#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Colour {
    pub red: u8,
    pub green: u8,
    pub blue: u8,
}

#[derive(Debug)]
pub struct InvalidRgb;

impl Colour {
    pub(crate) fn from(string: &str) -> Result<Colour, InvalidRgb> {
        let values: Vec<&str> = string.trim_matches(',').split(',').collect();

        if values.len() != 3 {
            return Err(InvalidRgb);
        }

        let red: u8 = values[0].parse().unwrap_or(0);
        let green: u8 = values[1].parse().unwrap_or(0);
        let blue: u8 = values[2].parse().unwrap_or(0);

        Ok(Colour { red, green, blue })
    }
}

impl ToString for Colour {
    fn to_string(&self) -> String {
        format!("{},{},{}", self.red, self.green, self.blue)
    }
}

#[cfg(test)]
mod test {
    use crate::Colour;

    #[test]
    fn colour_from_string() {
        assert_eq!(
            Colour::from("0,255,0").unwrap(),
            Colour { red: 0, green: 255, blue: 0 }
        );
    }

    #[test]
    fn colour_to_string() {
        assert_eq!(Colour { red: 22, green: 33, blue: 44, }.to_string(), "22,33,44".to_string());
    }

    #[test]
    fn colour_missing_value() {
        assert!(Colour::from("0,0").is_err());
    }

    #[test]
    fn colour_ambiguous_value() {
        assert!(Colour::from("0,0,").is_err());
    }

    #[test]
    fn colour_extraneous_value() {
        assert!(Colour::from("0,0,0,0").is_err());
    }
}