color.ceylon

abstract class Color() of Red | Green | Blue | Rgb {}

class Red() extends Color() {}
class Green() extends Color() {}
class Blue() extends Color() {}
class Rgb(r, g, b) extends Color() {
    shared Integer r;
    shared Integer g;
    shared Integer b;
}

String intToHex(Integer num, Integer min) {
    value s = formatInteger(num, 16);
    return s.padLeading(min, '0');
}

String toHex(Color root) {
    switch (root)
    case (is Red) { return "#FF0000"; }
    case (is Green) { return "#00FF00"; }
    case (is Blue) { return "#0000FF"; }
    case (is Rgb) {
        value hex = "#" + intToHex(root.r, 2) + intToHex(root.g, 2) + intToHex(root.b, 2);
        return hex.uppercased;
    }
}

void run() {
    value color = Rgb(100, 1, 255);
    print(toHex(color));
}