replaceable.rs

/// Types that implement this trait provide the rules
/// for replacing objects of the same type.
pub trait Replaceable {
    type Key: Eq;
    fn unique_key(&self) -> Self::Key;
    fn should_replace(&self, other: &Self) -> bool;
}

/// Trait implemented for collections that can be
/// filtered using replacement rules
pub trait ReplacementFiltering {
    fn filter_and_replace(self) -> Self;
}

/// Implementation of replacement filtering on Vec 
impl<T> ReplacementFiltering for Vec<T> where T: Replaceable {
    fn filter_and_replace(self) -> Self {
        let mut result: Vec<T> = vec![];
        for next in self {
            match result.iter().enumerate().find(|(_, e)| (*e).unique_key() == next.unique_key()) {
                Some((index, existing)) => {
                    if next.should_replace(existing) {
                        result.remove(index);
                        result.insert(index, next);
                    }
                },
                None => result.push(next)
            }
        }

        result
    }
}