use rust2fun::prelude::*;

fn get_credit_card(user: User) -> CreditCard {
    // Get credit card for user
}

fn print_credit_card(card: CreditCard) {
    // Print credit card details
}

fn print_credit_card_of<F>(user: F)
    where
        F: Functor<CreditCard, Param=User>,
        F::Target<CreditCard>: Functor<(), Param=CreditCard>,
{
    user.map(get_credit_card).map(print_credit_card);
}

fn user(id: u32) -> Option<User> {
    // Get user from database
}

fn all_users() -> Vec<User> {
    // Get all users from database
}

print_credit_card_of(user(1));
print_credit_card_of(all_users());

fn validate_number(number: CreditCardNumber) -> ValidatedNev<CreditCardNumber, Error> {
    // Validating credit card number
}

fn validate_expiration(date: Date) -> ValidatedNev<Date, Error> {
    // Validating expiration date
}

fn validate_cvv(cvv: Code) -> ValidatedNev<Code, Error> {
    // Validating CVV code
}

fn validate_credit_card(
    number: CreditCardNumber,
    expiration: Date,
    cvv: Code,
) -> ValidatedNev<CreditCard, Error> {
    ValidatedNev::pure(CreditCard::new)
        .ap3(validate_number(number),
             validate_expiration(expiration),
             validate_cvv(cvv))
}

fn validate_credit_card(
    number: CreditCardNumber,
    expiration: Date,
    cvv: Code,
) -> ValidatedNev<CreditCard, Error> { 
    MapN::map3(validate_number(number),
               validate_expiration(expiration),
               validate_cvv(cvv),
               CreditCard::new)
}

fn get_opening_prices() -> Vec<(AssetId, i32)> {
  // Get opening prices from an external service
}

fn get_closing_prices() -> Vec<(AssetId, i32)> {
  // Get closing prices from an external service
}

fn get_asset_name(id: AssetId) -> Option<String> {
  // Recover asset name for the given id
}

let profits: Vec<(String, i32)> = bind! {
    for (id_open, opening_price) in get_opening_prices();
    for (id_close, closing_price) in get_closing_prices();
    let diff = closing_price - opening_price;
    for name in OptionToVec.apply(get_asset_name(id_open)),
        if id_open == id_close && diff > 0;
    (name, diff)
};