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use crate::{NeverConflict, StateMachine};
use serde::de::DeserializeOwned;
use serde::{Deserialize, Serialize};
use std::fmt::Debug;
#[derive(Serialize, Deserialize, Clone, PartialEq, Debug)]
pub struct Constant<T: Clone + PartialEq + Debug + Unpin + Send + Sync> {
value: T,
}
impl<T: Send + Sync> Constant<T>
where
T: 'static + Serialize + DeserializeOwned + Unpin + Send + Clone + PartialEq + Debug,
{
pub fn new(initial: T) -> Self {
Constant { value: initial }
}
pub fn value(&self) -> &T {
&self.value
}
}
impl<T: Send + Sync> StateMachine for Constant<T>
where
T: 'static + Serialize + DeserializeOwned + Unpin + Send + Clone + PartialEq + Debug,
{
type Transition = InvalidTransition;
type Conflict = NeverConflict;
fn apply(&mut self, _transition_event: InvalidTransition) -> Result<(), NeverConflict> {
panic!("Constant should never receive transition event.");
}
}
#[derive(Serialize, Deserialize, Clone, PartialEq, Debug)]
pub struct InvalidTransition;
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_replace() {
let constant = Constant::new(5);
assert_eq!(5, *constant.value());
}
}