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use core::convert::Infallible;
use core::fmt::Debug;
use num::bigint::BigUint;
use serde::{Deserialize, Serialize};
use crate::{CmRDT, CvRDT, Dot, ResetRemove, VClock};
#[derive(Debug, PartialEq, Eq, Clone, Hash, Serialize, Deserialize)]
pub struct GCounter<A: Ord> {
inner: VClock<A>,
}
impl<A: Ord> Default for GCounter<A> {
fn default() -> Self {
Self {
inner: Default::default(),
}
}
}
impl<A: Ord + Clone + Debug> CmRDT for GCounter<A> {
type Op = Dot<A>;
type Validation = Infallible;
fn validate_op(&self, _op: &Self::Op) -> Result<(), Self::Validation> {
Ok(())
}
fn apply(&mut self, op: Self::Op) {
self.inner.apply(op)
}
}
impl<A: Ord + Clone + Debug> CvRDT for GCounter<A> {
type Validation = Infallible;
fn validate_merge(&self, _other: &Self) -> Result<(), Self::Validation> {
Ok(())
}
fn merge(&mut self, other: Self) {
self.inner.merge(other.inner);
}
}
impl<A: Ord> ResetRemove<A> for GCounter<A> {
fn reset_remove(&mut self, clock: &VClock<A>) {
self.inner.reset_remove(&clock);
}
}
impl<A: Ord + Clone> GCounter<A> {
pub fn new() -> Self {
Default::default()
}
pub fn inc(&self, actor: A) -> Dot<A> {
self.inner.inc(actor)
}
pub fn inc_many(&self, actor: A, steps: u64) -> Dot<A> {
let steps = steps + self.inner.get(&actor);
Dot::new(actor, steps)
}
pub fn read(&self) -> BigUint {
self.inner.iter().map(|dot| dot.counter).sum()
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_basic_by_one() {
let mut a = GCounter::new();
let mut b = GCounter::new();
a.apply(a.inc("A"));
b.apply(b.inc("B"));
assert_eq!(a.read(), b.read());
assert_ne!(a, b);
a.apply(a.inc("A"));
assert_eq!(a.read(), b.read() + BigUint::from(1u8));
}
#[test]
fn test_basic_by_many() {
let mut a = GCounter::new();
let mut b = GCounter::new();
let steps = 3;
a.apply(a.inc_many("A", steps));
b.apply(b.inc_many("B", steps));
assert_eq!(a.read(), b.read());
assert_ne!(a, b);
a.apply(a.inc_many("A", steps));
assert_eq!(a.read(), b.read() + BigUint::from(steps));
}
}