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use core::future::Future;
use crate::awaitable::{IntoStateMachine, Superstate, SuperstateExt};
use crate::Outcome;
use crate::StateOrSuperstate;
/// An enum that represents the leaf states of the state machine.
pub trait State<M>
where
Self: Sized,
M: IntoStateMachine<State = Self>,
for<'b> M::Superstate<'b>: Superstate<M>,
{
/// Call the handler for the current state and let it handle the given event.
fn call_handler(
&mut self,
shared_storage: &mut M,
event: &M::Event<'_>,
context: &mut M::Context<'_>,
) -> impl Future<Output = Outcome<Self>>;
#[allow(unused)]
/// Call the entry action for the current state.
fn call_entry_action(
&mut self,
shared_storage: &mut M,
context: &mut M::Context<'_>,
) -> impl Future<Output = ()> {
core::future::ready(())
}
#[allow(unused)]
/// Call the exit action for the current state.
fn call_exit_action(
&mut self,
shared_storage: &mut M,
context: &mut M::Context<'_>,
) -> impl Future<Output = ()> {
core::future::ready(())
}
/// Return the superstate of the current state, if there is one.
fn superstate(&mut self) -> Option<M::Superstate<'_>> {
None
}
}
/// Extensions for `State` trait.
pub trait StateExt<M>: State<M>
where
M: IntoStateMachine<State = Self>,
for<'b> M::Superstate<'b>: Superstate<M>,
{
/// Check if two states are the same.
fn same_state(lhs: &Self, rhs: &Self) -> bool {
core::mem::discriminant(lhs) == core::mem::discriminant(rhs)
}
/// Get the depth of the current state.
fn depth(&mut self) -> usize {
match self.superstate() {
Some(mut superstate) => superstate.depth() + 1,
None => 1,
}
}
/// Get the depth of the common ancestor of two states.
fn common_ancestor_depth(source: &mut Self, target: &mut Self) -> usize {
if Self::same_state(source, target) {
return source.depth();
}
match (source.superstate(), target.superstate()) {
(Some(source), Some(target)) => M::Superstate::common_ancestor_depth(source, target),
_ => 0,
}
}
/// Get the transition path that needs to be taken to get from the source state to
/// the target state. The returned tuple respectively represents the levels that need
/// to be exited, and the levels that need to be entered.
fn transition_path(&mut self, target: &mut Self) -> (usize, usize) {
if Self::same_state(self, target) {
return (1, 1);
}
let source_depth = self.depth();
let target_depth = target.depth();
if let (Some(source), Some(target)) = (self.superstate(), target.superstate()) {
let common_state_depth = M::Superstate::common_ancestor_depth(source, target);
(
source_depth - common_state_depth,
target_depth - common_state_depth,
)
} else {
(source_depth, target_depth)
}
}
/// Handle the given event in the current state.
fn handle(
&mut self,
shared_storage: &mut M,
event: &M::Event<'_>,
context: &mut M::Context<'_>,
) -> impl Future<Output = Outcome<Self>> {
async move {
M::before_dispatch(
shared_storage,
StateOrSuperstate::State(self),
event,
context,
)
.await;
let outcome = self.call_handler(shared_storage, event, context).await;
M::after_dispatch(
shared_storage,
StateOrSuperstate::State(self),
event,
context,
)
.await;
match outcome {
Outcome::Handled => Outcome::Handled,
Outcome::Super => match self.superstate() {
Some(mut superstate) => loop {
M::before_dispatch(
shared_storage,
StateOrSuperstate::Superstate(&superstate),
event,
context,
)
.await;
let outcome = superstate
.call_handler(shared_storage, event, context)
.await;
M::after_dispatch(
shared_storage,
StateOrSuperstate::Superstate(&superstate),
event,
context,
)
.await;
match outcome {
Outcome::Handled => break Outcome::Handled,
Outcome::Super => match superstate.superstate() {
Some(superstate_of_superstate) => {
superstate = superstate_of_superstate
}
None => break Outcome::Handled,
},
Outcome::Transition(state) => break Outcome::Transition(state),
}
},
None => Outcome::Super,
},
Outcome::Transition(state) => Outcome::Transition(state),
}
}
}
/// Starting from the current state, climb a given amount of levels and execute all the
/// entry actions while going back down to the current state.
fn enter(
&mut self,
shared_storage: &mut M,
context: &mut M::Context<'_>,
mut levels: usize,
) -> impl Future<Output = ()> {
async move {
// For each level we need to enter, climb that number of levels and excecute
// the superstate's entry action. We then decrement `levels` and again climb
// up the tree and execute the next entry action. We keep doing this until
// `levels` is equal to 1, which means the only entry action left to excecute
// is the state's own.
while levels > 1 {
if let Some(mut superstate) = self.superstate() {
for _ in 2..levels {
superstate = match superstate.superstate() {
Some(superstate) => superstate,
None => break,
}
}
superstate.call_entry_action(shared_storage, context).await;
}
levels -= 1;
}
if levels == 1 {
self.call_entry_action(shared_storage, context).await;
}
}
}
/// Starting from the current state, climb a given amount of levels and execute all the
/// the exit actions while going up to a certain superstate.
fn exit(
&mut self,
shared_storage: &mut M,
context: &mut M::Context<'_>,
mut levels: usize,
) -> impl Future<Output = ()> {
async move {
// First we need to excucute that state's own exit action.
if levels >= 1 {
self.call_exit_action(shared_storage, context).await;
}
// For each level we need to exit, climb up one level in the tree and
// execute the superstate's exit action, then decrement `levels`. As long as
// `levels` is greater then 1, we keep climbing up the three and excecute
// that superstate exit action.
if let Some(mut superstate) = self.superstate() {
while levels > 1 {
superstate.call_exit_action(shared_storage, context).await;
superstate = match superstate.superstate() {
Some(superstate) => superstate,
None => break,
};
levels -= 1;
}
}
}
}
}
impl<T, M> StateExt<M> for T
where
Self: State<M>,
M: IntoStateMachine<State = T>,
for<'b> M::Superstate<'b>: Superstate<M>,
{
}