Merge crates

src/operation_transformation/edited_text.rs

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