use super::funejson::Value;
use super::dates_add_days::epoch_day_from_iso;

/// Calendar days from one date to another: end minus start, negative when the
/// end is earlier. Both dates are parsed strictly, so an impossible date fails
/// rather than being rolled into the next month.
///
/// # Panics
/// Panics if either date is malformed or impossible.
pub fn days_between(start_iso: &str, end_iso: &str) -> i64 {
    epoch_day_from_iso(end_iso) - epoch_day_from_iso(start_iso)
}

pub fn fune_vector(args: &[Value]) -> Value {
    Value::Int(days_between(args[0].as_str(), args[1].as_str()))
}