pub const COLORS : [&str; 16] = [
    "#000000", "#1D2B53", "#7E2553", "#008751",
    "#AB5236", "#5F574F", "#C2C3C7", "#FFF1E8",
    "#FF004D", "#FFA300", "#FFEC27", "#00E436",
    "#29ADFF", "#83769C", "#FF77A8", "#FFCCAA"
];

#[derive(Clone,Copy,PartialEq,Debug)]
pub struct Color([u8 ; 3]);

impl From<Color> for String {
    fn from(color: Color) -> String {
	format!("#{:02x}{:02x}{:02x}", color.0[0], color.0[1], color.0[2])
    }
}

impl TryFrom<String> for Color {
    type Error = &'static str;
    
    fn try_from(s: String) -> Result<Color, Self::Error> {
	let ("#", rest) = s[..].split_at(1) else {
	    return Err("Badly formated color: should start with '#'");
	};
	if rest.len() != 6 {
	    return Err("Badly formated color");
	}
	let Ok(r) = u8::from_str_radix(&rest[0..2], 16) else {
	    return Err("Badly formated color");
	};
	let Ok(g) = u8::from_str_radix(&rest[2..4], 16) else {
	    return Err("Badly formated color");
	};
	let Ok(b) = u8::from_str_radix(&rest[4..6], 16) else {
	    return Err("Badly formated color");
	};

	Ok(Color([r,g,b]))
    }
}

#[test]
fn test_string_to_color() {
    let c : Result<Color, _> = "#ff0042".to_string().try_into();
    assert_eq!(c, Ok(Color([0xff, 0x00, 0x42])));

    let c : Result<Color, _> = "ff0042".to_string().try_into();
    assert_eq!(c, Err("Badly formated color: should start with '#'"));

    let c : Result<Color, _> = "#ff004242".to_string().try_into();
    assert_eq!(c, Err("Badly formated color"));
    
    let c : Result<Color, _> = "#ffg042".to_string().try_into();
    assert_eq!(c, Err("Badly formated color"));    
}

#[test]
fn test_color_to_string() {
    let s : String = Color([0xff, 0x00, 0x42]).into();
    assert_eq!(s, "#ff0042");
}