rust sort

use std::cmp::Ordering;

enum Fruit {
    Apple(i32),
    Orange(i32),
}

fn process_fruit(_apple_prices: &[i32], _orange_prices: &[i32]) {
    // whatever we do to process fruit, does not matter
}

fn main() {
    let mut fruit : Vec<Fruit> = vec![Fruit::Apple(1), Fruit::Apple(2),
                              Fruit::Orange(4), Fruit::Orange(3),
    ];

    /*
     * Sort fruit by some crazy function - let's say we value oranges more
     * than apples, so when we compare one to the other, we increase
     * the price of oranges by 10.
     */
     
    let fruit_comparator = |x: &Fruit, y: &Fruit| match(x, y) {
        (Fruit::Apple(lhs), Fruit::Apple(rhs)) => {
            lhs.cmp(rhs)
        },
        (Fruit::Apple(lhs), Fruit::Orange(rhs)) => {
            lhs.cmp(&(*rhs + 10))
        },
        (Fruit::Orange(lhs), Fruit::Apple(rhs)) => {
            (lhs + 10).cmp(rhs)
        },
        (Fruit::Orange(lhs), Fruit::Orange(rhs)) => {
            lhs.cmp(rhs)
        },
    };

    fruit.sort_by(fruit_comparator);

    // apples must __only__ contain Fruit::Apple variants
    let mut apple_prices : Vec<i32> = vec![];
    // oranges must __only__ contain Fruit::Orange variants
    let mut orange_prices : Vec<i32> = vec![];

    // TODO generate `fruit_grouped` from an existing sorted `fruit`
    let fruit_sorted_by_price_grouped : Vec<Vec<Fruit>> = {
        let mut groups = Vec::new();
        let mut this_group = Vec::new();
        for f in fruit {
            if this_group.is_empty() || fruit_comparator(&this_group[0], &f) == Ordering::Equal {
                this_group.push(f);
            } else {
                groups.push(this_group);
                this_group = vec![f];
            }
        }
        groups
    };

    for i in fruit_sorted_by_price_grouped {
        for j in i {
            match j {
                Fruit::Apple(price) => {
                    apple_prices.push(price);
                }
                Fruit::Orange(price) => {
                    orange_prices.push(price);
                }
            };
            process_fruit(&apple_prices, &orange_prices);
            apple_prices = vec![];
            orange_prices = vec![];
        }
    }
}