277 lines
9.8 KiB
Rust
277 lines
9.8 KiB
Rust
#[cfg(feature = "serde")]
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use serde::{Deserialize, Serialize};
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use super::{CursorPosition, Operation, TextWithCursors, ordered_operation::OrderedOperation};
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use crate::{
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diffs::{myers::diff, raw_operation::RawOperation},
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operation_transformation::{
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merge_context::MergeContext,
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utils::{cook_operations::cook_operations, elongate_operations::elongate_operations},
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},
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tokenizer::{Tokenizer, word_tokenizer::word_tokenizer},
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utils::{side::Side, string_builder::StringBuilder},
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};
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/// A text document and a sequence of operations that can be applied to the text
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/// document. `EditedText` supports merging two sequences of operations using
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/// the principles of Operational Transformation.
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///
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/// It's mainly created through the `from_strings` method, then merged with
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/// another `EditedText` derived from the same original text and then applied to
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/// the original text to get the reconciled text of concurrent edits.
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///
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/// In addition to text and operations, it also keeps track of cursor positions
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/// in the original text. The cursor positions are updated when the operations
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/// are applied, so that the cursor positions can be used to restore the
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/// cursor positions in the updated text.
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#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
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#[derive(Debug, Clone, PartialEq, Default)]
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pub struct EditedText<'a, T>
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where
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T: PartialEq + Clone + std::fmt::Debug,
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{
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text: &'a str,
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operations: Vec<OrderedOperation<T>>,
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pub(crate) cursors: Vec<CursorPosition>,
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}
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impl<'a> EditedText<'a, String> {
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/// Create an `EditedText` from the given original (old) and updated (new)
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/// strings. The returned `EditedText` represents the changes from the
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/// original to the updated text. When the return value is applied to
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/// the original text, it will result in the updated text. The default
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/// word tokenizer is used to tokenize the text which splits the text on
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/// whitespaces.
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#[must_use]
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pub fn from_strings(original: &'a str, updated: TextWithCursors<'a>) -> Self {
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Self::from_strings_with_tokenizer(original, updated, &word_tokenizer)
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}
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}
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impl<'a, T> EditedText<'a, T>
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where
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T: PartialEq + Clone + std::fmt::Debug,
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{
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/// Create an `EditedText` from the given original (old) and updated (new)
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/// strings. The returned `EditedText` represents the changes from the
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/// original to the updated text. When the return value is applied to
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/// the original text, it will result in the updated text. The tokenizer
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/// function is used to tokenize the text.
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pub fn from_strings_with_tokenizer(
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original: &'a str,
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updated: TextWithCursors<'a>,
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tokenizer: &Tokenizer<T>,
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) -> Self {
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let original_tokens = (tokenizer)(original);
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let updated_tokens = (tokenizer)(&updated.text);
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let diff: Vec<RawOperation<T>> = diff(&original_tokens, &updated_tokens);
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Self::new(
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original,
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cook_operations(elongate_operations(diff)).collect(),
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updated.cursors,
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)
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}
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/// Create a new `EditedText` with the given operations.
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/// The operations must be in the order in which they are meant to be
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/// applied. The operations must not overlap.
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fn new(
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text: &'a str,
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operations: Vec<OrderedOperation<T>>,
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mut cursors: Vec<CursorPosition>,
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) -> Self {
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operations
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.iter()
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.zip(operations.iter().skip(1))
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.for_each(|(previous, next)| {
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debug_assert!(
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previous.operation.start_index() <= next.operation.start_index(),
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"{} must not come before {} yet it does",
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previous.operation,
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next.operation
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);
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});
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cursors.sort_by_key(|cursor| cursor.char_index);
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Self {
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text,
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operations,
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cursors,
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}
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}
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#[must_use]
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pub fn merge(self, other: Self) -> Self {
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debug_assert_eq!(
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self.text, other.text,
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"`EditedText`-s must be derived from the same text to be mergable"
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);
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let mut left_merge_context = MergeContext::default();
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let mut right_merge_context = MergeContext::default();
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let mut merged_cursors = Vec::with_capacity(self.cursors.len() + other.cursors.len());
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let mut left_cursors = self.cursors.into_iter().peekable();
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let mut right_cursors = other.cursors.into_iter().peekable();
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let mut merged_operations: Vec<OrderedOperation<T>> =
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Vec::with_capacity(self.operations.len() + other.operations.len());
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let mut left_iter = self.operations.into_iter();
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let mut right_iter = other.operations.into_iter();
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let mut maybe_left_op = left_iter.next();
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let mut maybe_right_op = right_iter.next();
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loop {
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let (side, OrderedOperation { operation, order }) =
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match (maybe_left_op.clone(), maybe_right_op.clone()) {
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(Some(left_op), Some(right_op)) => {
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if left_op < right_op {
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(Side::Left, left_op)
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} else {
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(Side::Right, right_op)
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}
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}
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(Some(left_op), None) => (Side::Left, left_op),
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(None, Some(right_op)) => (Side::Right, right_op),
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(None, None) => break,
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};
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if side == Side::Left {
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maybe_left_op = left_iter.next();
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} else {
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maybe_right_op = right_iter.next();
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}
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let original_start = operation.start_index() as i64;
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let original_end = operation.end_index();
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let original_length = operation.len() as i64;
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let result = match side {
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Side::Left => operation.merge_operations_with_context(
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&mut right_merge_context,
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&mut left_merge_context,
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),
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Side::Right => operation.merge_operations_with_context(
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&mut left_merge_context,
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&mut right_merge_context,
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),
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};
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if let Some(ref op @ (Operation::Insert { .. } | Operation::Equal { .. })) = result {
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let shift =
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op.start_index() as i64 - original_start + op.len() as i64 - original_length;
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match side {
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Side::Left => {
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while let Some(cursor) =
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left_cursors.next_if(|cursor| cursor.char_index <= original_end + 1)
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{
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merged_cursors.push(cursor.with_index(
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(op.start_index() as i64).max(cursor.char_index as i64 + shift)
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as usize,
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));
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}
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}
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Side::Right => {
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while let Some(cursor) =
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right_cursors.next_if(|cursor| cursor.char_index <= original_end + 1)
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{
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merged_cursors.push(cursor.with_index(
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(op.start_index() as i64).max(cursor.char_index as i64 + shift)
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as usize,
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));
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}
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}
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}
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}
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merged_operations.extend(result.into_iter().map(|op| OrderedOperation {
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order,
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operation: op,
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}));
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}
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let last_index = merged_operations
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.iter()
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.filter(|operation| {
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matches!(
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operation.operation,
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Operation::Insert { .. } | Operation::Equal { .. }
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)
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})
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.next_back()
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.map_or(0, |op| op.operation.end_index());
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for cursor in left_cursors.chain(right_cursors) {
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merged_cursors.push(cursor.with_index(last_index));
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}
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Self::new(self.text, merged_operations, merged_cursors)
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}
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/// Apply the operations to the text and return the resulting text.
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#[must_use]
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pub fn apply(&self) -> String {
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let mut builder: StringBuilder<'_> = StringBuilder::new(self.text);
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for OrderedOperation { operation, .. } in &self.operations {
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builder = operation.apply(builder);
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}
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builder.build()
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}
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}
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#[cfg(test)]
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mod tests {
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use std::env;
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use insta::assert_debug_snapshot;
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use pretty_assertions::assert_eq;
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use super::*;
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#[test]
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fn test_calculate_operations() {
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let left = "hello world! How are you? Adam";
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let right = "Hello, my friend! How are you doing? Albert";
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let operations = EditedText::from_strings(left, right.into());
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insta::assert_debug_snapshot!(operations);
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let new_right = operations.apply();
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assert_eq!(new_right.to_string(), right);
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}
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#[test]
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fn test_calculate_operations_with_no_diff() {
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let text = "hello world!";
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let operations = EditedText::from_strings(text, text.into());
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assert_debug_snapshot!(operations);
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let new_right = operations.apply();
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assert_eq!(new_right.to_string(), text);
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}
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#[test]
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fn test_calculate_operations_with_insert() {
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let original = "hello world! ...";
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let left = "Hello world! I'm Andras.";
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let right = "Hello world! How are you?";
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let expected = "Hello world! How are you? I'm Andras.";
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let operations_1 = EditedText::from_strings(original, left.into());
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let operations_2 = EditedText::from_strings(original, right.into());
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let operations = operations_1.merge(operations_2);
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assert_eq!(operations.apply(), expected);
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}
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}
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