const ORDINALS: [&str; 12] = [
    "first",
    "second",
    "third",
    "fourth",
    "fifth",
    "sixth",
    "seventh",
    "eighth",
    "ninth",
    "tenth",
    "eleventh",
    "twelfth",
];

const GIFTS: [&str; 12] = [
    "Twelve drummers drumming",
    "Eleven pipers piping",
    "Ten lords a-leaping",
    "Nine ladies dancing",
    "Eight maids a-milking",
    "Seven swans a-swimming",
    "Six geese a-laying",
    "Five golden rings",
    "Four calling birds",
    "Three french hens",
    "Two turtle doves",
    "and a partridge in a pear tree.",
];

fn format_verse(day: &str, gifts: &str) -> String {
    format!("On the {} day of Christmas, my true love gave to me: \n{}\n", day, gifts)
}

fn main() {
    for n in 0..12 {
        let verse: String = match n {
            0 => format_verse("first", "A partridge in a pear tree."),
            _ => {
                // The highest index is 11, and we want
                // the highest index to start, so we can
                // easily have the cumulative list each verse.
                let gift_index = 11 - n;

                // Get the slice of the array of gifts, from
                // the index to the end of the array
                let gifts = &GIFTS[gift_index..]
                    .to_vec() // So we have the join method that returns a string
                    .join(",\n");

                format_verse(ORDINALS[n], gifts)
            }
        };

        // For some reason, the println! macro only takes string literals
        println!("{}", verse);
    }
}