use std::iter::{FromIterator, IntoIterator};
use serde::{Deserialize, Serialize};
use crate::crdt::crdt::*;
/// Simple CRDT Map
///
/// This types defines a CRDT for a map from keys to values. Values are CRDT types which
/// can have their own updating logic.
///
/// Internally, the map is stored as a vector of keys and values, sorted by ascending key order.
/// This is why the key type `K` must implement `Ord` (and also to ensure a unique serialization,
/// such that two values can be compared for equality based on their hashes). As a consequence,
/// insertions take `O(n)` time. This means that Map should be used for reasonably small maps.
/// However, note that even if we were using a more efficient data structure such as a `BTreeMap`,
/// the serialization cost `O(n)` would still have to be paid at each modification, so we are
/// actually not losing anything here.
#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
pub struct Map<K, V> {
vals: Vec<(K, V)>,
}
impl<K, V> Map<K, V>
where
K: Clone + Ord,
V: Clone + Crdt,
{
/// Create a new empty map CRDT
pub fn new() -> Self {
Self { vals: vec![] }
}
/// Returns a map that contains a single mapping from the specified key to the specified value.
/// This can be used to build a delta-mutator:
/// when merged with another map, the value will be added or CRDT-merged if a previous
/// value already exists.
#[must_use = "CRDT mutators are meant to be merged into a CRDT and not ignored."]
pub fn put_mutator(k: K, v: V) -> Self {
Self { vals: vec![(k, v)] }
}
/// Add a value to the map
pub fn put(&mut self, k: K, v: V) {
self.merge(&Self::put_mutator(k, v));
}
/// Removes all values from the map
pub fn clear(&mut self) {
self.vals.clear();
}
/// Get a reference to the value assigned to a key
pub fn get(&self, k: &K) -> Option<&V> {
match self.vals.binary_search_by(|(k2, _)| k2.cmp(k)) {
Ok(i) => Some(&self.vals[i].1),
Err(_) => None,
}
}
/// Gets a reference to all of the items, as a slice. Usefull to iterate on all map values.
pub fn items(&self) -> &[(K, V)] {
&self.vals[..]
}
/// Returns the number of items in the map
pub fn len(&self) -> usize {
self.vals.len()
}
/// Returns true if the map is empty
pub fn is_empty(&self) -> bool {
self.len() == 0
}
}
impl<K, V> Crdt for Map<K, V>
where
K: Clone + Ord,
V: Clone + Crdt,
{
fn merge(&mut self, other: &Self) {
for (k, v2) in other.vals.iter() {
match self.vals.binary_search_by(|(k2, _)| k2.cmp(k)) {
Ok(i) => {
self.vals[i].1.merge(v2);
}
Err(i) => {
self.vals.insert(i, (k.clone(), v2.clone()));
}
}
}
}
}
impl<K, V> Default for Map<K, V>
where
K: Clone + Ord,
V: Clone + Crdt,
{
fn default() -> Self {
Self::new()
}
}
/// A crdt map can be created from an iterator of key-value pairs.
/// Note that all keys in the iterator must be distinct:
/// this function will throw a panic if it is not the case.
impl<K, V> FromIterator<(K, V)> for Map<K, V>
where
K: Clone + Ord,
V: Clone + Crdt,
{
fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self {
let mut vals: Vec<(K, V)> = iter.into_iter().collect();
vals.sort_by_cached_key(|tup| tup.0.clone());
// sanity check
for i in 1..vals.len() {
if vals[i - 1].0 == vals[i].0 {
panic!("Duplicate key in crdt::Map resulting from .from_iter() or .collect()");
}
}
Self { vals }
}
}
