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//! Module used to communicate changes in the data structures.
use core::mem;
#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};
#[cfg(feature = "std")]
use std::sync::mpsc::{Sender, SyncSender};
/// Slot wrapper that adds some additional functionality.
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[repr(transparent)]
#[derive(Clone, Debug)]
pub(crate) struct Socket<S>(Option<S>);
impl<S> Socket<S> {
pub const fn new(slot: S) -> Socket<S> {
Socket(Some(slot))
}
pub fn connect(&mut self, slot: Option<S>) -> Option<S> {
mem::replace(&mut self.0, slot)
}
pub fn disconnect(&mut self) -> Option<S> {
self.0.take()
}
}
impl<S> Default for Socket<S> {
fn default() -> Self {
Socket(None)
}
}
impl<S: Slot> Socket<S> {
pub fn emit(&mut self, event: impl FnOnce() -> Event) {
if let Some(slot) = &mut self.0 {
slot.on_emit(event());
}
}
pub fn emit_if(&mut self, cond: bool, event: impl FnOnce() -> Event) {
if cond {
self.emit(event);
}
}
}
/// Describes an event on the structures.
///
/// See [`Slot`] for more information.
#[derive(Clone, Debug, PartialEq)]
#[non_exhaustive]
pub enum Event {
/// Emitted when the structures ability to undo has changed.
Undo(bool),
/// Emitted when the structures ability to redo has changed.
Redo(bool),
/// Emitted when the saved state has changed.
Saved(bool),
/// Emitted when the root has changed.
Root(usize),
/// Emitted when the index has changed.
Index(usize),
}
/// Handles events.
///
/// # Examples
/// ```
/// # use std::sync::mpsc;
/// # use undo::{Add, Record, Event};
/// let (sender, receiver) = mpsc::channel();
/// let mut iter = receiver.try_iter();
///
/// let mut target = String::new();
/// let mut record = Record::builder()
/// .connect(sender)
/// .build();
///
/// record.edit(&mut target, Add('a'));
/// assert_eq!(iter.next(), Some(Event::Undo(true)));
/// assert_eq!(iter.next(), Some(Event::Saved(false)));
/// assert_eq!(iter.next(), Some(Event::Index(1)));
/// assert_eq!(iter.next(), None);
///
/// record.undo(&mut target);
/// assert_eq!(iter.next(), Some(Event::Undo(false)));
/// assert_eq!(iter.next(), Some(Event::Redo(true)));
/// assert_eq!(iter.next(), Some(Event::Saved(true)));
/// assert_eq!(iter.next(), Some(Event::Index(0)));
/// assert_eq!(iter.next(), None);
/// ```
pub trait Slot {
/// Receives an event that describes the state change done to the structures.
fn on_emit(&mut self, event: Event);
}
impl Slot for () {
fn on_emit(&mut self, _: Event) {}
}
impl<F: FnMut(Event)> Slot for F {
fn on_emit(&mut self, event: Event) {
self(event)
}
}
#[cfg(feature = "std")]
impl Slot for Sender<Event> {
fn on_emit(&mut self, event: Event) {
self.send(event).ok();
}
}
#[cfg(feature = "std")]
impl Slot for SyncSender<Event> {
fn on_emit(&mut self, event: Event) {
self.send(event).ok();
}
}