Add apply_merge_context to cursor

backend/reconcile/src/lib.rs

@@ -1,11 +1,10 @@
-mod cursor;
 mod diffs;
 mod operation_transformation;
 mod tokenizer;
 mod utils;
 
-pub use cursor::{CursorPosition, TextWithCursors};
 pub use operation_transformation::{
-    EditedText, reconcile, reconcile_with_cursors, reconcile_with_tokenizer,
+    CursorPosition, EditedText, TextWithCursors, reconcile, reconcile_with_cursors,
+    reconcile_with_tokenizer,
 };
 pub use tokenizer::{Tokenizer, token::Token};

backend/reconcile/src/operation_transformation/cursor.rs

@@ -0,0 +1,65 @@
+use std::borrow::Cow;
+
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
+use super::merge_context::MergeContext;
+use crate::operation_transformation::Operation;
+
+// CursorPosition is a wrapper around usize to represent the position of an
+// identifiable cursor in a text document based on the character index.
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Default)]
+pub struct CursorPosition {
+    pub id: usize,
+    pub char_index: usize,
+}
+
+impl CursorPosition {
+    pub fn apply_merge_context<T>(&self, context: &MergeContext<T>) -> Self
+    where
+        T: PartialEq + Clone + std::fmt::Debug,
+    {
+        let char_index = match context.last_operation() {
+            Some(Operation::Delete { index, .. }) => (*index) as i64,
+            _ => self.char_index as i64 + context.shift,
+        };
+
+        CursorPosition {
+            id: self.id,
+            char_index: char_index.max(0) as usize,
+        }
+    }
+}
+
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Default)]
+pub struct TextWithCursors<'a> {
+    pub text: Cow<'a, str>,
+    pub cursors: Vec<CursorPosition>,
+}
+
+impl<'a> TextWithCursors<'a> {
+    pub fn new(text: &'a str, cursors: Vec<CursorPosition>) -> Self {
+        Self {
+            text: text.into(),
+            cursors,
+        }
+    }
+
+    pub fn new_owned(text: String, cursors: Vec<CursorPosition>) -> Self {
+        Self {
+            text: text.into(),
+            cursors,
+        }
+    }
+}
+
+impl<'a> From<&'a str> for TextWithCursors<'a> {
+    fn from(text: &'a str) -> Self {
+        Self {
+            text: text.into(),
+            cursors: Vec::new(),
+        }
+    }
+}