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helix/helix-core/src/history.rs

606 lines
20 KiB
Rust

use crate::{Assoc, ChangeSet, Range, Rope, State, Transaction};
use once_cell::sync::Lazy;
use regex::Regex;
use std::num::NonZeroUsize;
use std::time::{Duration, Instant};
/// Stores the history of changes to a buffer.
///
/// Currently the history is represented as a vector of revisions. The vector
/// always has at least one element: the empty root revision. Each revision
/// with the exception of the root has a parent revision, a [Transaction]
/// that can be applied to its parent to transition from the parent to itself,
/// and an inversion of that transaction to transition from the parent to its
/// latest child.
///
/// When using `u` to undo a change, an inverse of the stored transaction will
/// be applied which will transition the buffer to the parent state.
///
/// Each revision with the exception of the last in the vector also has a
/// last child revision. When using `U` to redo a change, the last child transaction
/// will be applied to the current state of the buffer.
///
/// The current revision is the one currently displayed in the buffer.
///
/// Committing a new revision to the history will update the last child of the
/// current revision, and push a new revision to the end of the vector.
///
/// Revisions are committed with a timestamp. :earlier and :later can be used
/// to jump to the closest revision to a moment in time relative to the timestamp
/// of the current revision plus (:later) or minus (:earlier) the duration
/// given to the command. If a single integer is given, the editor will instead
/// jump the given number of revisions in the vector.
///
/// Limitations:
/// * Changes in selections currently don't commit history changes. The selection
/// will only be updated to the state after a committed buffer change.
/// * The vector of history revisions is currently unbounded. This might
/// cause the memory consumption to grow significantly large during long
/// editing sessions.
/// * Because delete transactions currently don't store the text that they
/// delete, we also store an inversion of the transaction.
///
/// Using time to navigate the history: <https://github.com/helix-editor/helix/pull/194>
#[derive(Debug)]
pub struct History {
revisions: Vec<Revision>,
current: usize,
}
/// A single point in history. See [History] for more information.
#[derive(Debug)]
struct Revision {
parent: usize,
last_child: Option<NonZeroUsize>,
transaction: Transaction,
// We need an inversion for undos because delete transactions don't store
// the deleted text.
inversion: Transaction,
timestamp: Instant,
}
impl Default for History {
fn default() -> Self {
// Add a dummy root revision with empty transaction
Self {
revisions: vec![Revision {
parent: 0,
last_child: None,
transaction: Transaction::from(ChangeSet::new(&Rope::new())),
inversion: Transaction::from(ChangeSet::new(&Rope::new())),
timestamp: Instant::now(),
}],
current: 0,
}
}
}
impl History {
pub fn commit_revision(&mut self, transaction: &Transaction, original: &State) {
self.commit_revision_at_timestamp(transaction, original, Instant::now());
}
pub fn commit_revision_at_timestamp(
&mut self,
transaction: &Transaction,
original: &State,
timestamp: Instant,
) {
let inversion = transaction
.invert(&original.doc)
// Store the current cursor position
.with_selection(original.selection.clone());
let new_current = self.revisions.len();
self.revisions[self.current].last_child = NonZeroUsize::new(new_current);
self.revisions.push(Revision {
parent: self.current,
last_child: None,
transaction: transaction.clone(),
inversion,
timestamp,
});
self.current = new_current;
}
#[inline]
pub fn current_revision(&self) -> usize {
self.current
}
#[inline]
pub const fn at_root(&self) -> bool {
self.current == 0
}
/// Undo the last edit.
pub fn undo(&mut self) -> Option<&Transaction> {
if self.at_root() {
return None;
}
let current_revision = &self.revisions[self.current];
self.current = current_revision.parent;
Some(&current_revision.inversion)
}
/// Redo the last edit.
pub fn redo(&mut self) -> Option<&Transaction> {
let current_revision = &self.revisions[self.current];
let last_child = current_revision.last_child?;
self.current = last_child.get();
Some(&self.revisions[last_child.get()].transaction)
}
// Get the position of last change
pub fn last_edit_pos(&self) -> Option<usize> {
if self.current == 0 {
return None;
}
let current_revision = &self.revisions[self.current];
let primary_selection = current_revision
.inversion
.selection()
.expect("inversion always contains a selection")
.primary();
let (_from, to, _fragment) = current_revision
.transaction
.changes_iter()
// find a change that matches the primary selection
.find(|(from, to, _fragment)| Range::new(*from, *to).overlaps(&primary_selection))
// or use the first change
.or_else(|| current_revision.transaction.changes_iter().next())
.unwrap();
let pos = current_revision
.transaction
.changes()
.map_pos(to, Assoc::After);
Some(pos)
}
fn lowest_common_ancestor(&self, mut a: usize, mut b: usize) -> usize {
use std::collections::HashSet;
let mut a_path_set = HashSet::new();
let mut b_path_set = HashSet::new();
loop {
a_path_set.insert(a);
b_path_set.insert(b);
if a_path_set.contains(&b) {
return b;
}
if b_path_set.contains(&a) {
return a;
}
a = self.revisions[a].parent; // Relies on the parent of 0 being 0.
b = self.revisions[b].parent; // Same as above.
}
}
/// List of nodes on the way from `n` to 'a`. Doesn't include `a`.
/// Includes `n` unless `a == n`. `a` must be an ancestor of `n`.
fn path_up(&self, mut n: usize, a: usize) -> Vec<usize> {
let mut path = Vec::new();
while n != a {
path.push(n);
n = self.revisions[n].parent;
}
path
}
/// Create a [`Transaction`] that will jump to a specific revision in the history.
fn jump_to(&mut self, to: usize) -> Vec<Transaction> {
let lca = self.lowest_common_ancestor(self.current, to);
let up = self.path_up(self.current, lca);
let down = self.path_up(to, lca);
self.current = to;
let up_txns = up.iter().map(|&n| self.revisions[n].inversion.clone());
let down_txns = down
.iter()
.rev()
.map(|&n| self.revisions[n].transaction.clone());
up_txns.chain(down_txns).collect()
}
/// Creates a [`Transaction`] that will undo `delta` revisions.
fn jump_backward(&mut self, delta: usize) -> Vec<Transaction> {
self.jump_to(self.current.saturating_sub(delta))
}
/// Creates a [`Transaction`] that will redo `delta` revisions.
fn jump_forward(&mut self, delta: usize) -> Vec<Transaction> {
self.jump_to(
self.current
.saturating_add(delta)
.min(self.revisions.len() - 1),
)
}
/// Helper for a binary search case below.
fn revision_closer_to_instant(&self, i: usize, instant: Instant) -> usize {
let dur_im1 = instant.duration_since(self.revisions[i - 1].timestamp);
let dur_i = self.revisions[i].timestamp.duration_since(instant);
use std::cmp::Ordering::*;
match dur_im1.cmp(&dur_i) {
Less => i - 1,
Equal | Greater => i,
}
}
/// Creates a [`Transaction`] that will match a revision created at around
/// `instant`.
fn jump_instant(&mut self, instant: Instant) -> Vec<Transaction> {
let search_result = self
.revisions
.binary_search_by(|rev| rev.timestamp.cmp(&instant));
let revision = match search_result {
Ok(revision) => revision,
Err(insert_point) => match insert_point {
0 => 0,
n if n == self.revisions.len() => n - 1,
i => self.revision_closer_to_instant(i, instant),
},
};
self.jump_to(revision)
}
/// Creates a [`Transaction`] that will match a revision created `duration` ago
/// from the timestamp of current revision.
fn jump_duration_backward(&mut self, duration: Duration) -> Vec<Transaction> {
match self.revisions[self.current].timestamp.checked_sub(duration) {
Some(instant) => self.jump_instant(instant),
None => self.jump_to(0),
}
}
/// Creates a [`Transaction`] that will match a revision created `duration` in
/// the future from the timestamp of the current revision.
fn jump_duration_forward(&mut self, duration: Duration) -> Vec<Transaction> {
match self.revisions[self.current].timestamp.checked_add(duration) {
Some(instant) => self.jump_instant(instant),
None => self.jump_to(self.revisions.len() - 1),
}
}
/// Creates an undo [`Transaction`].
pub fn earlier(&mut self, uk: UndoKind) -> Vec<Transaction> {
use UndoKind::*;
match uk {
Steps(n) => self.jump_backward(n),
TimePeriod(d) => self.jump_duration_backward(d),
}
}
/// Creates a redo [`Transaction`].
pub fn later(&mut self, uk: UndoKind) -> Vec<Transaction> {
use UndoKind::*;
match uk {
Steps(n) => self.jump_forward(n),
TimePeriod(d) => self.jump_duration_forward(d),
}
}
}
/// Whether to undo by a number of edits or a duration of time.
#[derive(Debug, PartialEq, Clone, Copy)]
pub enum UndoKind {
Steps(usize),
TimePeriod(std::time::Duration),
}
/// A subset of systemd.time time span syntax units.
const TIME_UNITS: &[(&[&str], &str, u64)] = &[
(&["seconds", "second", "sec", "s"], "seconds", 1),
(&["minutes", "minute", "min", "m"], "minutes", 60),
(&["hours", "hour", "hr", "h"], "hours", 60 * 60),
(&["days", "day", "d"], "days", 24 * 60 * 60),
];
/// Checks if the duration input can be turned into a valid duration. It must be a
/// positive integer and denote the [unit of time.](`TIME_UNITS`)
/// Examples of valid durations:
/// * `5 sec`
/// * `5 min`
/// * `5 hr`
/// * `5 days`
static DURATION_VALIDATION_REGEX: Lazy<Regex> =
Lazy::new(|| Regex::new(r"^(?:\d+\s*[a-z]+\s*)+$").unwrap());
/// Captures both the number and unit as separate capture groups.
static NUMBER_UNIT_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"(\d+)\s*([a-z]+)").unwrap());
/// Parse a string (e.g. "5 sec") and try to convert it into a [`Duration`].
fn parse_human_duration(s: &str) -> Result<Duration, String> {
if !DURATION_VALIDATION_REGEX.is_match(s) {
return Err("duration should be composed \
of positive integers followed by time units"
.to_string());
}
let mut specified = [false; TIME_UNITS.len()];
let mut seconds = 0u64;
for cap in NUMBER_UNIT_REGEX.captures_iter(s) {
let (n, unit_str) = (&cap[1], &cap[2]);
let n: u64 = n.parse().map_err(|_| format!("integer too large: {}", n))?;
let time_unit = TIME_UNITS
.iter()
.enumerate()
.find(|(_, (forms, _, _))| forms.iter().any(|f| f == &unit_str));
if let Some((i, (_, unit, mul))) = time_unit {
if specified[i] {
return Err(format!("{} specified more than once", unit));
}
specified[i] = true;
let new_seconds = n.checked_mul(*mul).and_then(|s| seconds.checked_add(s));
match new_seconds {
Some(ns) => seconds = ns,
None => return Err("duration too large".to_string()),
}
} else {
return Err(format!("incorrect time unit: {}", unit_str));
}
}
Ok(Duration::from_secs(seconds))
}
impl std::str::FromStr for UndoKind {
type Err = String;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let s = s.trim();
if s.is_empty() {
Ok(Self::Steps(1usize))
} else if let Ok(n) = s.parse::<usize>() {
Ok(UndoKind::Steps(n))
} else {
Ok(Self::TimePeriod(parse_human_duration(s)?))
}
}
}
#[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.doc, vec![(5, 5, Some(" world!".into()))].into_iter());
// Need to commit before applying!
history.commit_revision(&transaction1, &state);
transaction1.apply(&mut state.doc);
assert_eq!("hello world!", state.doc);
// ---
let transaction2 =
Transaction::change(&state.doc, vec![(6, 11, Some("".into()))].into_iter());
// Need to commit before applying!
history.commit_revision(&transaction2, &state);
transaction2.apply(&mut state.doc);
assert_eq!("hello !", state.doc);
// ---
fn undo(history: &mut History, state: &mut State) {
if let Some(transaction) = history.undo() {
transaction.apply(&mut state.doc);
}
}
fn redo(history: &mut History, state: &mut State) {
if let Some(transaction) = history.redo() {
transaction.apply(&mut state.doc);
}
}
undo(&mut history, &mut state);
assert_eq!("hello world!", state.doc);
redo(&mut history, &mut state);
assert_eq!("hello !", state.doc);
undo(&mut history, &mut state);
undo(&mut history, &mut state);
assert_eq!("hello", state.doc);
// undo at root is a no-op
undo(&mut history, &mut state);
assert_eq!("hello", state.doc);
}
#[test]
fn test_earlier_later() {
let mut history = History::default();
let doc = Rope::from("a\n");
let mut state = State::new(doc);
fn undo(history: &mut History, state: &mut State) {
if let Some(transaction) = history.undo() {
transaction.apply(&mut state.doc);
}
}
fn earlier(history: &mut History, state: &mut State, uk: UndoKind) {
let txns = history.earlier(uk);
for txn in txns {
txn.apply(&mut state.doc);
}
}
fn later(history: &mut History, state: &mut State, uk: UndoKind) {
let txns = history.later(uk);
for txn in txns {
txn.apply(&mut state.doc);
}
}
fn commit_change(
history: &mut History,
state: &mut State,
change: crate::transaction::Change,
instant: Instant,
) {
let txn = Transaction::change(&state.doc, vec![change].into_iter());
history.commit_revision_at_timestamp(&txn, state, instant);
txn.apply(&mut state.doc);
}
let t0 = Instant::now();
let t = |n| t0.checked_add(Duration::from_secs(n)).unwrap();
commit_change(&mut history, &mut state, (1, 1, Some(" b".into())), t(0));
assert_eq!("a b\n", state.doc);
commit_change(&mut history, &mut state, (3, 3, Some(" c".into())), t(10));
assert_eq!("a b c\n", state.doc);
commit_change(&mut history, &mut state, (5, 5, Some(" d".into())), t(20));
assert_eq!("a b c d\n", state.doc);
undo(&mut history, &mut state);
assert_eq!("a b c\n", state.doc);
commit_change(&mut history, &mut state, (5, 5, Some(" e".into())), t(30));
assert_eq!("a b c e\n", state.doc);
undo(&mut history, &mut state);
undo(&mut history, &mut state);
assert_eq!("a b\n", state.doc);
commit_change(&mut history, &mut state, (1, 3, None), t(40));
assert_eq!("a\n", state.doc);
commit_change(&mut history, &mut state, (1, 1, Some(" f".into())), t(50));
assert_eq!("a f\n", state.doc);
use UndoKind::*;
earlier(&mut history, &mut state, Steps(3));
assert_eq!("a b c d\n", state.doc);
later(&mut history, &mut state, TimePeriod(Duration::new(20, 0)));
assert_eq!("a\n", state.doc);
earlier(&mut history, &mut state, TimePeriod(Duration::new(19, 0)));
assert_eq!("a b c d\n", state.doc);
earlier(
&mut history,
&mut state,
TimePeriod(Duration::new(10000, 0)),
);
assert_eq!("a\n", state.doc);
later(&mut history, &mut state, Steps(50));
assert_eq!("a f\n", state.doc);
earlier(&mut history, &mut state, Steps(4));
assert_eq!("a b c\n", state.doc);
later(&mut history, &mut state, TimePeriod(Duration::new(1, 0)));
assert_eq!("a b c\n", state.doc);
later(&mut history, &mut state, TimePeriod(Duration::new(5, 0)));
assert_eq!("a b c d\n", state.doc);
later(&mut history, &mut state, TimePeriod(Duration::new(6, 0)));
assert_eq!("a b c e\n", state.doc);
later(&mut history, &mut state, Steps(1));
assert_eq!("a\n", state.doc);
}
#[test]
fn test_parse_undo_kind() {
use UndoKind::*;
// Default is one step.
assert_eq!("".parse(), Ok(Steps(1)));
// An integer means the number of steps.
assert_eq!("1".parse(), Ok(Steps(1)));
assert_eq!(" 16 ".parse(), Ok(Steps(16)));
// Duration has a strict format.
let validation_err = Err("duration should be composed \
of positive integers followed by time units"
.to_string());
assert_eq!(" 16 33".parse::<UndoKind>(), validation_err);
assert_eq!(" seconds 22 ".parse::<UndoKind>(), validation_err);
assert_eq!(" -4 m".parse::<UndoKind>(), validation_err);
assert_eq!("5s 3".parse::<UndoKind>(), validation_err);
// Units are u64.
assert_eq!(
"18446744073709551616minutes".parse::<UndoKind>(),
Err("integer too large: 18446744073709551616".to_string())
);
// Units are validated.
assert_eq!(
"1 millennium".parse::<UndoKind>(),
Err("incorrect time unit: millennium".to_string())
);
// Units can't be specified twice.
assert_eq!(
"2 seconds 6s".parse::<UndoKind>(),
Err("seconds specified more than once".to_string())
);
// Various formats are correctly handled.
assert_eq!(
"4s".parse::<UndoKind>(),
Ok(TimePeriod(Duration::from_secs(4)))
);
assert_eq!(
"2m".parse::<UndoKind>(),
Ok(TimePeriod(Duration::from_secs(120)))
);
assert_eq!(
"5h".parse::<UndoKind>(),
Ok(TimePeriod(Duration::from_secs(5 * 60 * 60)))
);
assert_eq!(
"3d".parse::<UndoKind>(),
Ok(TimePeriod(Duration::from_secs(3 * 24 * 60 * 60)))
);
assert_eq!(
"1m30s".parse::<UndoKind>(),
Ok(TimePeriod(Duration::from_secs(90)))
);
assert_eq!(
"1m 20 seconds".parse::<UndoKind>(),
Ok(TimePeriod(Duration::from_secs(80)))
);
assert_eq!(
" 2 minute 1day".parse::<UndoKind>(),
Ok(TimePeriod(Duration::from_secs(24 * 60 * 60 + 2 * 60)))
);
assert_eq!(
"3 d 2hour 5 minutes 30sec".parse::<UndoKind>(),
Ok(TimePeriod(Duration::from_secs(
3 * 24 * 60 * 60 + 2 * 60 * 60 + 5 * 60 + 30
)))
);
// Sum overflow is handled.
assert_eq!(
"18446744073709551615minutes".parse::<UndoKind>(),
Err("duration too large".to_string())
);
assert_eq!(
"1 minute 18446744073709551615 seconds".parse::<UndoKind>(),
Err("duration too large".to_string())
);
}
}