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helix/helix-core/src/transaction.rs

777 lines
24 KiB
Rust

use crate::{Range, Rope, Selection, Tendril};
use std::borrow::Cow;
/// (from, to, replacement)
pub type Change = (usize, usize, Option<Tendril>);
// TODO: pub(crate)
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Operation {
/// Move cursor by n characters.
Retain(usize),
/// Delete n characters.
Delete(usize),
/// Insert text at position.
Insert(Tendril),
}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum Assoc {
Before,
After,
}
#[derive(Debug, Default, Clone, PartialEq, Eq)]
pub struct ChangeSet {
pub(crate) changes: Vec<Operation>,
/// The required document length. Will refuse to apply changes unless it matches.
len: usize,
len_after: usize,
}
impl ChangeSet {
pub fn with_capacity(capacity: usize) -> Self {
Self {
changes: Vec::with_capacity(capacity),
len: 0,
len_after: 0,
}
}
#[must_use]
pub fn new(doc: &Rope) -> Self {
let len = doc.len_chars();
Self {
changes: Vec::new(),
len,
len_after: len,
}
}
// TODO: from iter
#[doc(hidden)] // used by lsp to convert to LSP changes
pub fn changes(&self) -> &[Operation] {
&self.changes
}
// Changeset builder operations: delete/insert/retain
fn delete(&mut self, n: usize) {
use Operation::*;
if n == 0 {
return;
}
self.len += n;
if let Some(Delete(count)) = self.changes.last_mut() {
*count += n;
} else {
self.changes.push(Delete(n));
}
}
fn insert(&mut self, fragment: Tendril) {
use Operation::*;
if fragment.is_empty() {
return;
}
// Avoiding std::str::len() to account for UTF-8 characters.
self.len_after += fragment.chars().count();
let new_last = match self.changes.as_mut_slice() {
[.., Insert(prev)] | [.., Insert(prev), Delete(_)] => {
prev.push_str(&fragment);
return;
}
[.., last @ Delete(_)] => std::mem::replace(last, Insert(fragment)),
_ => Insert(fragment),
};
self.changes.push(new_last);
}
fn retain(&mut self, n: usize) {
use Operation::*;
if n == 0 {
return;
}
self.len += n;
self.len_after += n;
if let Some(Retain(count)) = self.changes.last_mut() {
*count += n;
} else {
self.changes.push(Retain(n));
}
}
/// Combine two changesets together.
/// In other words, If `this` goes `docA` → `docB` and `other` represents `docB` → `docC`, the
/// returned value will represent the change `docA` → `docC`.
pub fn compose(self, other: Self) -> Self {
assert!(self.len_after == other.len);
// composing fails in weird ways if one of the sets is empty
// a: [] len: 0 len_after: 1 | b: [Insert(Tendril<UTF8>(inline: "\n")), Retain(1)] len 1
if self.changes.is_empty() {
return other;
}
if other.changes.is_empty() {
return self;
}
let len = self.changes.len();
let mut changes_a = self.changes.into_iter();
let mut changes_b = other.changes.into_iter();
let mut head_a = changes_a.next();
let mut head_b = changes_b.next();
let mut changes = Self::with_capacity(len); // TODO: max(a, b), shrink_to_fit() afterwards
loop {
use std::cmp::Ordering;
use Operation::*;
match (head_a, head_b) {
// we are done
(None, None) => {
break;
}
// deletion in A
(Some(Delete(i)), b) => {
changes.delete(i);
head_a = changes_a.next();
head_b = b;
}
// insertion in B
(a, Some(Insert(current))) => {
changes.insert(current);
head_a = a;
head_b = changes_b.next();
}
(None, val) | (val, None) => unreachable!("({:?})", val),
(Some(Retain(i)), Some(Retain(j))) => match i.cmp(&j) {
Ordering::Less => {
changes.retain(i);
head_a = changes_a.next();
head_b = Some(Retain(j - i));
}
Ordering::Equal => {
changes.retain(i);
head_a = changes_a.next();
head_b = changes_b.next();
}
Ordering::Greater => {
changes.retain(j);
head_a = Some(Retain(i - j));
head_b = changes_b.next();
}
},
(Some(Insert(mut s)), Some(Delete(j))) => {
let len = s.chars().count();
match len.cmp(&j) {
Ordering::Less => {
head_a = changes_a.next();
head_b = Some(Delete(j - len));
}
Ordering::Equal => {
head_a = changes_a.next();
head_b = changes_b.next();
}
Ordering::Greater => {
// TODO: cover this with a test
// figure out the byte index of the truncated string end
let (pos, _) = s.char_indices().nth(j).unwrap();
s.replace_range(0..pos, "");
head_a = Some(Insert(s));
head_b = changes_b.next();
}
}
}
(Some(Insert(s)), Some(Retain(j))) => {
let len = s.chars().count();
match len.cmp(&j) {
Ordering::Less => {
changes.insert(s);
head_a = changes_a.next();
head_b = Some(Retain(j - len));
}
Ordering::Equal => {
changes.insert(s);
head_a = changes_a.next();
head_b = changes_b.next();
}
Ordering::Greater => {
// figure out the byte index of the truncated string end
let (pos, _) = s.char_indices().nth(j).unwrap();
let mut before = s;
let after = before.split_off(pos);
changes.insert(before);
head_a = Some(Insert(after));
head_b = changes_b.next();
}
}
}
(Some(Retain(i)), Some(Delete(j))) => match i.cmp(&j) {
Ordering::Less => {
changes.delete(i);
head_a = changes_a.next();
head_b = Some(Delete(j - i));
}
Ordering::Equal => {
changes.delete(j);
head_a = changes_a.next();
head_b = changes_b.next();
}
Ordering::Greater => {
changes.delete(j);
head_a = Some(Retain(i - j));
head_b = changes_b.next();
}
},
};
}
// starting len should still equal original starting len
debug_assert!(changes.len == self.len);
changes
}
/// Given another change set starting in the same document, maps this
/// change set over the other, producing a new change set that can be
/// applied to the document produced by applying `other`. When
/// `before` is `true`, order changes as if `this` comes before
/// `other`, otherwise (the default) treat `other` as coming first.
///
/// Given two changes `A` and `B`, `A.compose(B.map(A))` and
/// `B.compose(A.map(B, true))` will produce the same document. This
/// provides a basic form of [operational
/// transformation](https://en.wikipedia.org/wiki/Operational_transformation),
/// and can be used for collaborative editing.
pub fn map(self, _other: Self) -> Self {
unimplemented!()
}
/// Returns a new changeset that reverts this one. Useful for `undo` implementation.
/// The document parameter expects the original document before this change was applied.
pub fn invert(&self, original_doc: &Rope) -> Self {
assert!(original_doc.len_chars() == self.len);
let mut changes = Self::with_capacity(self.changes.len());
let mut pos = 0;
for change in &self.changes {
use Operation::*;
match change {
Retain(n) => {
changes.retain(*n);
pos += n;
}
Delete(n) => {
let text = Cow::from(original_doc.slice(pos..pos + *n));
changes.insert(Tendril::from(text.as_ref()));
pos += n;
}
Insert(s) => {
let chars = s.chars().count();
changes.delete(chars);
}
}
}
changes
}
/// Returns true if applied successfully.
pub fn apply(&self, text: &mut Rope) -> bool {
if text.len_chars() != self.len {
return false;
}
let mut pos = 0;
for change in &self.changes {
use Operation::*;
match change {
Retain(n) => {
pos += n;
}
Delete(n) => {
text.remove(pos..pos + *n);
// pos += n;
}
Insert(s) => {
text.insert(pos, s);
pos += s.chars().count();
}
}
}
true
}
/// `true` when the set is empty.
#[inline]
pub fn is_empty(&self) -> bool {
self.changes.is_empty() || self.changes == [Operation::Retain(self.len)]
}
/// Map a position through the changes.
///
/// `assoc` indicates which size to associate the position with. `Before` will keep the
/// position close to the character before, and will place it before insertions over that
/// range, or at that point. `After` will move it forward, placing it at the end of such
/// insertions.
pub fn map_pos(&self, pos: usize, assoc: Assoc) -> usize {
use Operation::*;
let mut old_pos = 0;
let mut new_pos = 0;
let mut iter = self.changes.iter().peekable();
while let Some(change) = iter.next() {
let len = match change {
Delete(i) | Retain(i) => *i,
Insert(_) => 0,
};
let mut old_end = old_pos + len;
match change {
Retain(_) => {
if old_end > pos {
return new_pos + (pos - old_pos);
}
new_pos += len;
}
Delete(_) => {
// in range
if old_end > pos {
return new_pos;
}
}
Insert(s) => {
let ins = s.chars().count();
// a subsequent delete means a replace, consume it
if let Some(Delete(len)) = iter.peek() {
iter.next();
old_end = old_pos + len;
// in range of replaced text
if old_end > pos {
// at point or tracking before
if pos == old_pos || assoc == Assoc::Before {
return new_pos;
} else {
// place to end of insert
return new_pos + ins;
}
}
} else {
// at insert point
if old_pos == pos {
// return position before inserted text
if assoc == Assoc::Before {
return new_pos;
} else {
// after text
return new_pos + ins;
}
}
}
new_pos += ins;
}
}
old_pos = old_end;
}
if pos > old_pos {
panic!(
"Position {} is out of range for changeset len {}!",
pos, old_pos
)
}
new_pos
}
pub fn changes_iter(&self) -> ChangeIterator {
ChangeIterator::new(self)
}
}
/// Transaction represents a single undoable unit of changes. Several changes can be grouped into
/// a single transaction.
#[derive(Debug, Default, Clone, PartialEq, Eq)]
pub struct Transaction {
changes: ChangeSet,
selection: Option<Selection>,
}
impl Transaction {
/// Create a new, empty transaction.
pub fn new(doc: &Rope) -> Self {
Self {
changes: ChangeSet::new(doc),
selection: None,
}
}
/// Changes made to the buffer.
pub fn changes(&self) -> &ChangeSet {
&self.changes
}
/// When set, explicitly updates the selection.
pub fn selection(&self) -> Option<&Selection> {
self.selection.as_ref()
}
/// Returns true if applied successfully.
pub fn apply(&self, doc: &mut Rope) -> bool {
if self.changes.is_empty() {
return true;
}
// apply changes to the document
self.changes.apply(doc)
}
/// Generate a transaction that reverts this one.
pub fn invert(&self, original: &Rope) -> Self {
let changes = self.changes.invert(original);
Self {
changes,
selection: None,
}
}
pub fn compose(mut self, other: Self) -> Self {
self.changes = self.changes.compose(other.changes);
// Other selection takes precedence
self.selection = other.selection;
self
}
pub fn with_selection(mut self, selection: Selection) -> Self {
self.selection = Some(selection);
self
}
/// Generate a transaction from a set of changes.
pub fn change<I>(doc: &Rope, changes: I) -> Self
where
I: Iterator<Item = Change>,
{
let len = doc.len_chars();
let (lower, upper) = changes.size_hint();
let size = upper.unwrap_or(lower);
let mut changeset = ChangeSet::with_capacity(2 * size + 1); // rough estimate
let mut last = 0;
for (from, to, tendril) in changes {
// Verify ranges are ordered and not overlapping
debug_assert!(last <= from);
// Retain from last "to" to current "from"
changeset.retain(from - last);
let span = to - from;
match tendril {
Some(text) => {
changeset.insert(text);
changeset.delete(span);
}
None => changeset.delete(span),
}
last = to;
}
changeset.retain(len - last);
Self::from(changeset)
}
/// Generate a transaction with a change per selection range.
pub fn change_by_selection<F>(doc: &Rope, selection: &Selection, f: F) -> Self
where
F: FnMut(&Range) -> Change,
{
Self::change(doc, selection.iter().map(f))
}
/// Insert text at each selection head.
pub fn insert(doc: &Rope, selection: &Selection, text: Tendril) -> Self {
Self::change_by_selection(doc, selection, |range| {
(range.head, range.head, Some(text.clone()))
})
}
pub fn changes_iter(&self) -> ChangeIterator {
self.changes.changes_iter()
}
}
impl From<ChangeSet> for Transaction {
fn from(changes: ChangeSet) -> Self {
Self {
changes,
selection: None,
}
}
}
pub struct ChangeIterator<'a> {
iter: std::iter::Peekable<std::slice::Iter<'a, Operation>>,
pos: usize,
}
impl<'a> ChangeIterator<'a> {
fn new(changeset: &'a ChangeSet) -> Self {
let iter = changeset.changes.iter().peekable();
Self { iter, pos: 0 }
}
}
impl<'a> Iterator for ChangeIterator<'a> {
type Item = Change;
fn next(&mut self) -> Option<Self::Item> {
use Operation::*;
loop {
match self.iter.next()? {
Retain(len) => {
self.pos += len;
}
Delete(len) => {
let start = self.pos;
self.pos += len;
return Some((start, self.pos, None));
}
Insert(s) => {
let start = self.pos;
// a subsequent delete means a replace, consume it
if let Some(Delete(len)) = self.iter.peek() {
self.iter.next();
self.pos += len;
return Some((start, self.pos, Some(s.clone())));
} else {
return Some((start, start, Some(s.clone())));
}
}
}
}
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::history::State;
#[test]
fn composition() {
use Operation::*;
let a = ChangeSet {
changes: vec![
Retain(5),
Insert(" test!".into()),
Retain(1),
Delete(2),
Insert("abc".into()),
],
len: 8,
len_after: 15,
};
let b = ChangeSet {
changes: vec![Delete(10), Insert("世orld".into()), Retain(5)],
len: 15,
len_after: 10,
};
let mut text = Rope::from("hello xz");
// should probably return cloned text
let composed = a.compose(b);
assert_eq!(composed.len, 8);
assert!(composed.apply(&mut text));
assert_eq!(text, "世orld! abc");
}
#[test]
fn invert() {
use Operation::*;
let changes = ChangeSet {
changes: vec![Retain(4), Insert("test".into()), Delete(5), Retain(3)],
len: 12,
len_after: 11,
};
let doc = Rope::from("世界3 hello xz");
let revert = changes.invert(&doc);
let mut doc2 = doc.clone();
changes.apply(&mut doc2);
// a revert is different
assert_ne!(changes, revert);
assert_ne!(doc, doc2);
// but inverting a revert will give us the original
assert_eq!(changes, revert.invert(&doc2));
// applying a revert gives us back the original
revert.apply(&mut doc2);
assert_eq!(doc, doc2);
}
#[test]
fn map_pos() {
use Operation::*;
// maps inserts
let cs = ChangeSet {
changes: vec![Retain(4), Insert("!!".into()), Retain(4)],
len: 8,
len_after: 10,
};
assert_eq!(cs.map_pos(0, Assoc::Before), 0); // before insert region
assert_eq!(cs.map_pos(4, Assoc::Before), 4); // at insert, track before
assert_eq!(cs.map_pos(4, Assoc::After), 6); // at insert, track after
assert_eq!(cs.map_pos(5, Assoc::Before), 7); // after insert region
// maps deletes
let cs = ChangeSet {
changes: vec![Retain(4), Delete(4), Retain(4)],
len: 12,
len_after: 8,
};
assert_eq!(cs.map_pos(0, Assoc::Before), 0); // at start
assert_eq!(cs.map_pos(4, Assoc::Before), 4); // before a delete
assert_eq!(cs.map_pos(5, Assoc::Before), 4); // inside a delete
assert_eq!(cs.map_pos(5, Assoc::After), 4); // inside a delete
// TODO: delete tracking
// stays inbetween replacements
let cs = ChangeSet {
changes: vec![
Insert("ab".into()),
Delete(2),
Insert("cd".into()),
Delete(2),
],
len: 4,
len_after: 4,
};
assert_eq!(cs.map_pos(2, Assoc::Before), 2);
assert_eq!(cs.map_pos(2, Assoc::After), 2);
}
#[test]
fn transaction_change() {
let mut doc = Rope::from("hello world!\ntest 123");
let transaction = Transaction::change(
&doc,
// (1, 1, None) is a useless 0-width delete that gets factored out
vec![(1, 1, None), (6, 11, Some("void".into())), (12, 17, None)].into_iter(),
);
transaction.apply(&mut doc);
assert_eq!(doc, Rope::from_str("hello void! 123"));
}
#[test]
fn changes_iter() {
let doc = Rope::from("hello world!\ntest 123");
let changes = vec![(6, 11, Some("void".into())), (12, 17, None)];
let transaction = Transaction::change(&doc, changes.clone().into_iter());
assert_eq!(transaction.changes_iter().collect::<Vec<_>>(), changes);
}
#[test]
fn optimized_composition() {
let mut state = State {
doc: "".into(),
selection: Selection::point(0),
};
let t1 = Transaction::insert(&state.doc, &state.selection, Tendril::from("h"));
t1.apply(&mut state.doc);
state.selection = state.selection.clone().map(t1.changes());
let t2 = Transaction::insert(&state.doc, &state.selection, Tendril::from("e"));
t2.apply(&mut state.doc);
state.selection = state.selection.clone().map(t2.changes());
let t3 = Transaction::insert(&state.doc, &state.selection, Tendril::from("l"));
t3.apply(&mut state.doc);
state.selection = state.selection.clone().map(t3.changes());
let t4 = Transaction::insert(&state.doc, &state.selection, Tendril::from("l"));
t4.apply(&mut state.doc);
state.selection = state.selection.clone().map(t4.changes());
let t5 = Transaction::insert(&state.doc, &state.selection, Tendril::from("o"));
t5.apply(&mut state.doc);
state.selection = state.selection.clone().map(t5.changes());
assert_eq!(state.doc, Rope::from_str("hello"));
// changesets as follows:
// h
// retain 1, e
// retain 2, l
let changes = t1
.changes
.compose(t2.changes)
.compose(t3.changes)
.compose(t4.changes)
.compose(t5.changes);
use Operation::*;
assert_eq!(changes.changes, &[Insert("hello".into())]);
// instead of insert h, insert e, insert l, insert l, insert o
}
#[test]
fn combine_with_empty() {
let empty = Rope::from("");
let a = ChangeSet::new(&empty);
let mut b = ChangeSet::new(&empty);
b.insert("a".into());
let changes = a.compose(b);
use Operation::*;
assert_eq!(changes.changes, &[Insert("a".into())]);
}
#[test]
fn combine_with_utf8() {
const TEST_CASE: &str = "Hello, これはヘリックスエディターです!";
let empty = Rope::from("");
let a = ChangeSet::new(&empty);
let mut b = ChangeSet::new(&empty);
b.insert(TEST_CASE.into());
let changes = a.compose(b);
use Operation::*;
assert_eq!(changes.changes, &[Insert(TEST_CASE.into())]);
assert_eq!(changes.len_after, TEST_CASE.chars().count());
}
}