rustlings-exercises-completed/exercises/iterators/iterators5.rs

// iterators5.rs
// Let's define a simple model to track Rustlings exercise progress. Progress
// will be modelled using a hash map. The name of the exercise is the key and
// the progress is the value. Two counting functions were created to count the
// number of exercises with a given progress. These counting functions use
// imperative style for loops. Recreate this counting functionality using
// iterators. Only the two iterator methods (count_iterator and
// count_collection_iterator) need to be modified.
// Execute `rustlings hint iterators5` or use the `hint` watch subcommand for a hint.
//
// Make the code compile and the tests pass.

use std::collections::HashMap;

#[derive(Clone, Copy, PartialEq, Eq)]
enum Progress {
    None,
    Some,
    Complete,
}

fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
    let mut count = 0;
    for val in map.values() {
        if val == &value {
            count += 1;
        }
    }
    count
}

fn count_iterator(map: &HashMap<String, Progress>, value: Progress) -> usize {
    // map is a hashmap with String keys and Progress values.
    // map = { "variables1": Complete, "from_str": None, ... }
    map.values()
        .map(|x| match x {
            Progress::Complete => 1,
            _ => 0,
        })
        .sum()
}

fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
    let mut count = 0;
    for map in collection {
        for val in map.values() {
            if val == &value {
                count += 1;
            }
        }
    }
    count
}

fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
    // collection is a slice of hashmaps.
    // collection = [{ "variables1": Complete, "from_str": None, ... },
    //     { "variables2": Complete, ... }, ... ]
    collection.iter().map(|x| count_iterator(x, value)).sum()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn count_complete() {
        let map = get_map();
        assert_eq!(3, count_iterator(&map, Progress::Complete));
    }

    #[test]
    fn count_equals_for() {
        let map = get_map();
        assert_eq!(
            count_for(&map, Progress::Complete),
            count_iterator(&map, Progress::Complete)
        );
    }

    #[test]
    fn count_collection_complete() {
        let collection = get_vec_map();
        assert_eq!(
            6,
            count_collection_iterator(&collection, Progress::Complete)
        );
    }

    #[test]
    fn count_collection_equals_for() {
        let collection = get_vec_map();
        assert_eq!(
            count_collection_for(&collection, Progress::Complete),
            count_collection_iterator(&collection, Progress::Complete)
        );
    }

    fn get_map() -> HashMap<String, Progress> {
        use Progress::*;

        let mut map = HashMap::new();
        map.insert(String::from("variables1"), Complete);
        map.insert(String::from("functions1"), Complete);
        map.insert(String::from("hashmap1"), Complete);
        map.insert(String::from("arc1"), Some);
        map.insert(String::from("as_ref_mut"), None);
        map.insert(String::from("from_str"), None);

        map
    }

    fn get_vec_map() -> Vec<HashMap<String, Progress>> {
        use Progress::*;

        let map = get_map();

        let mut other = HashMap::new();
        other.insert(String::from("variables2"), Complete);
        other.insert(String::from("functions2"), Complete);
        other.insert(String::from("if1"), Complete);
        other.insert(String::from("from_into"), None);
        other.insert(String::from("try_from_into"), None);

        vec![map, other]
    }
}