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use crate::{ChangeSet, Rope, State, Transaction};
use smallvec::{smallvec, SmallVec};
/// Undo-tree style history store.
pub struct History {
revisions: Vec<Revision>,
cursor: usize,
}
#[derive(Debug)]
struct Revision {
parent: usize,
children: SmallVec<[(usize, Transaction); 1]>,
/// The transaction to revert to previous state.
revert: Transaction,
// selection before, selection after?
}
impl Default for History {
fn default() -> Self {
// Add a dummy root revision with empty transaction
Self {
revisions: vec![Revision {
parent: 0,
children: SmallVec::new(),
revert: Transaction::from(ChangeSet::new(&Rope::new())),
}],
cursor: 0,
}
}
}
impl History {
pub fn commit_revision(&mut self, transaction: &Transaction, original: &State) {
// TODO: could store a single transaction, if deletes also stored the text they delete
let revert = transaction.invert(original);
let new_cursor = self.revisions.len();
self.revisions.push(Revision {
parent: self.cursor,
children: SmallVec::new(),
revert,
});
// add a reference to the parent
self.revisions
.get_mut(self.cursor)
.unwrap() // TODO: get_unchecked_mut
.children
.push((new_cursor, transaction.clone()));
self.cursor = new_cursor;
}
#[inline]
pub fn at_root(&self) -> bool {
self.cursor == 0
}
pub fn undo(&mut self, state: &mut State) {
if self.at_root() {
// We're at the root of undo, nothing to do.
return;
}
let current_revision = &self.revisions[self.cursor];
// TODO: pass the return value through? It should always succeed
let success = current_revision.revert.apply(state);
if !success {
panic!("Failed to apply undo!");
}
self.cursor = current_revision.parent;
}
pub fn redo(&mut self, state: &mut State) {
let current_revision = &self.revisions[self.cursor];
// for now, simply pick the latest child (linear undo / redo)
if let Some((index, transaction)) = current_revision.children.last() {
let success = transaction.apply(state);
if !success {
panic!("Failed to apply redo!");
}
self.cursor = *index;
}
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_undo_redo() {
let mut history = History::default();
let doc = Rope::from("hello");
let mut state = State::new(doc);
let transaction1 =
Transaction::change(&state, vec![(5, 5, Some(" world!".into()))].into_iter());
// Need to commit before applying!
history.commit_revision(&transaction1, &state);
transaction1.apply(&mut state);
assert_eq!("hello world!", state.doc());
// ---
let transaction2 =
Transaction::change(&state, vec![(6, 11, Some("世界".into()))].into_iter());
// Need to commit before applying!
history.commit_revision(&transaction2, &state);
transaction2.apply(&mut state);
assert_eq!("hello 世界!", state.doc());
// ---
history.undo(&mut state);
assert_eq!("hello world!", state.doc());
history.redo(&mut state);
assert_eq!("hello 世界!", state.doc());
history.undo(&mut state);
history.undo(&mut state);
assert_eq!("hello", state.doc());
// undo at root is a no-op
history.undo(&mut state);
assert_eq!("hello", state.doc());
}
}
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