Add diffing & apply

backend/sync_lib/src/operations/operation_sequence.rs

@@ -0,0 +1,126 @@
+use super::{operation, Operation};
+use crate::errors::SyncLibError;
+use log::info;
+use ropey::Rope;
+use similar::utils::diff_graphemes;
+use similar::{utils::TextDiffRemapper, ChangeTag, TextDiff};
+use similar::{Algorithm, DiffableStrRef};
+
+#[derive(Debug)]
+pub struct OperationSequence {
+    operations: Vec<Operation>,
+}
+
+impl OperationSequence {
+    pub fn new(mut operations: Vec<Operation>) -> Self {
+        operations.sort();
+
+        Self { operations }
+    }
+
+    pub fn try_from_string_diff(
+        left: &str,
+        right: &str,
+        diff_ratio_threshold: f32,
+    ) -> Result<Self, SyncLibError> {
+        let diff = TextDiff::configure()
+            .algorithm(Algorithm::Myers)
+            .diff_words(left, right);
+
+        let diff_ratio = 1.0 - diff.ratio();
+        if diff_ratio > diff_ratio_threshold {
+            return Err(SyncLibError::DiffTooLarge {
+                diff_ratio,
+                diff_ratio_limit: diff_ratio_threshold as f32,
+            });
+        }
+
+        let remapper = TextDiffRemapper::from_text_diff(&diff, left, right);
+
+        let mut index = 0;
+        let operations = diff
+            .ops()
+            .iter()
+            .flat_map(move |x| remapper.iter_slices(x))
+            .map(|(tag, text)| match tag {
+                ChangeTag::Equal => {
+                    println!("Equal: {}", text);
+                    index += text.chars().count();
+                    None
+                }
+                ChangeTag::Insert => {
+                    println!("Insert: {}", text);
+                    let result = Some(Operation::new(tag, index as u64, text));
+                    index += text.chars().count();
+                    result
+                }
+                ChangeTag::Delete => {
+                    println!("Delete: {}", text);
+                    Some(Operation::new(tag, index as u64, text))
+                }
+            })
+            .flat_map(Option::into_iter)
+            .collect::<Vec<_>>();
+
+        Ok(Self::new(operations))
+    }
+
+    pub fn apply<'a>(&self, rope_text: &'a mut Rope) -> Result<&'a mut Rope, SyncLibError> {
+        for operation in &self.operations {
+            println!("Applying operation: {:?}", operation);
+            operation.apply(rope_text)?;
+            println!("Text after operation: {}", rope_text);
+        }
+
+        Ok(rope_text)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_calculate_operations() -> Result<(), SyncLibError> {
+        let left = "hello world! How are you?  Adam";
+        let right = "Hello, my friend! How are you doing? Albert";
+
+        let operations = OperationSequence::try_from_string_diff(left, right, 0.6)?;
+
+        insta::assert_debug_snapshot!(operations);
+
+        let mut left = Rope::from_str(left);
+        let new_right = operations.apply(&mut left)?;
+
+        assert_eq!(new_right.to_string(), right);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_calculate_operations_with_large_diff() {
+        let left = "hello world! How are you?  Adam";
+        let right = "Hello, my friend! How are you doing? Albert";
+
+        let result = OperationSequence::try_from_string_diff(left, right, 0.1);
+
+        insta::assert_debug_snapshot!(result);
+    }
+
+    #[test]
+    fn test_calculate_operations_with_no_diff() -> Result<(), SyncLibError> {
+        let left = "hello world!";
+        let right = "hello world!";
+
+        let operations = OperationSequence::try_from_string_diff(left, right, 0.0)?;
+
+        assert_eq!(operations.operations.len(), 0);
+
+        let mut left = Rope::from_str(left);
+        let new_right = operations.apply(&mut left)?;
+
+        assert_eq!(new_right.to_string(), right);
+
+        Ok(())
+    }
+}