Refactor

backend/reconcile/src/operation_transformation/merge_context.rs

@@ -0,0 +1,34 @@
+use crate::operation_transformation::{operation, Operation};
+
+#[derive(Debug, Clone, Default)]
+pub struct MergeContext {
+    pub last_delete: Option<Operation>,
+    pub shift: i64,
+}
+
+impl MergeContext {
+    /// Replace the last delete operation (if there was one) with a new one while
+    /// applying it to the shift.
+    pub fn replace_delete(&mut self, delete: Option<Operation>) {
+        if let Some(produced_last_delete) = self.last_delete.take() {
+            self.shift -= produced_last_delete.len() as i64;
+        }
+
+        self.last_delete = delete;
+    }
+
+    /// Remove the last delete operation (if there was one) in case it is behind the
+    /// threshold operation.
+    pub fn consume_delete_if_behind_operation(&mut self, threshold_operation: &Operation) {
+        match self.last_delete.as_ref() {
+            Some(last_delete)
+                if threshold_operation.start_index() as i64 + self.shift
+                    > last_delete.end_index() as i64 =>
+            {
+                self.shift -= last_delete.len() as i64;
+                self.last_delete = None;
+            }
+            _ => {}
+        }
+    }
+}