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use std::collections::HashMap;
#[derive(Eq, PartialEq, Debug)]
pub struct HashMapDiff<K, V>
where
K: Eq + std::hash::Hash,
{
pub updated: HashMap<K, V>,
pub removed: HashMap<K, V>,
}
pub fn hash_map_diff<'a, K, V>(
lhs: &'a HashMap<K, V>,
rhs: &'a HashMap<K, V>,
) -> HashMapDiff<&'a K, &'a V>
where
K: Eq + std::hash::Hash + Clone,
V: Eq + Clone,
{
let mut removed: HashMap<&'a K, &'a V> = HashMap::new();
for (key, value) in lhs {
if !rhs.contains_key(key) {
removed.insert(key, value);
}
}
let mut updated: HashMap<&'a K, &'a V> = HashMap::new();
for (key, new_value) in rhs {
if let Some(old_value) = lhs.get(key) {
if new_value != old_value {
updated.insert(key, new_value);
}
} else {
updated.insert(key, new_value);
}
}
HashMapDiff { updated, removed }
}
#[cfg(test)]
mod should {
use super::*;
#[test]
fn detect_removed_elements() {
let old_hash_map = [("key1", 1), ("key2", 2)].into();
let new_hash_map = [("key2", 2)].into();
let diff = hash_map_diff(&old_hash_map, &new_hash_map);
let expected_diff = HashMapDiff {
updated: HashMap::new(),
removed: [(&"key1", &1)].into(),
};
assert_eq!(diff, expected_diff);
}
#[test]
fn detect_changed_values() {
let old_hash_map = [("key1", 1), ("key2", 2)].into();
let new_hash_map = [("key1", 1), ("key2", 3)].into();
let diff = hash_map_diff(&old_hash_map, &new_hash_map);
let expected_diff = HashMapDiff {
updated: [(&"key2", &3)].into(),
removed: HashMap::new(),
};
assert_eq!(diff, expected_diff);
}
#[test]
fn detect_new_keys() {
let old_hash_map = [("key1", 1)].into();
let new_hash_map = [("key1", 1), ("key3", 3)].into();
let diff = hash_map_diff(&old_hash_map, &new_hash_map);
let expected_diff = HashMapDiff {
updated: [(&"key3", &3)].into(),
removed: HashMap::new(),
};
assert_eq!(diff, expected_diff);
}
#[test]
fn usage_test() {
let lhs = [("unchanged", 1), ("removed", 2), ("changed", 3)].into();
let rhs = [("unchanged", 1), ("changed", 5), ("added", 4)].into();
let received_diff = hash_map_diff(&lhs, &rhs);
let expected_diff = HashMapDiff {
updated: [(&"changed", &5), (&"added", &4)].into(),
removed: [(&"removed", &2)].into(),
};
assert_eq!(received_diff, expected_diff);
}
}