1 files changed, 94 insertions, 0 deletions

diff --git a/crates/libsyntax2/src/yellow/red.rs b/crates/libsyntax2/src/yellow/red.rs
new file mode 100644
index 000000000..13ad44c65
--- /dev/null
+++ b/crates/libsyntax2/src/yellow/red.rs
@@ -0,0 +1,94 @@
+use parking_lot::RwLock;
+use {yellow::{GreenNode, RedPtr}, TextUnit};
+
+#[derive(Debug)]
+pub(crate) struct RedNode {
+    green: GreenNode,
+    parent: Option<ParentData>,
+    children: RwLock<Box<[Option<RedNode>]>>,
+}
+
+#[derive(Debug)]
+struct ParentData {
+    parent: RedPtr,
+    start_offset: TextUnit,
+    index_in_parent: usize,
+}
+
+impl RedNode {
+    pub fn new_root(green: GreenNode) -> RedNode {
+        RedNode::new(green, None)
+    }
+
+    fn new_child(
+        green: GreenNode,
+        parent: RedPtr,
+        start_offset: TextUnit,
+        index_in_parent: usize,
+    ) -> RedNode {
+        let parent_data = ParentData {
+            parent,
+            start_offset,
+            index_in_parent,
+        };
+        RedNode::new(green, Some(parent_data))
+    }
+
+    fn new(green: GreenNode, parent: Option<ParentData>) -> RedNode {
+        let n_children = green.children().len();
+        let children = (0..n_children)
+            .map(|_| None)
+            .collect::<Vec<_>>()
+            .into_boxed_slice();
+        RedNode {
+            green,
+            parent,
+            children: RwLock::new(children),
+        }
+    }
+
+    pub(crate) fn green(&self) -> &GreenNode {
+        &self.green
+    }
+
+    pub(crate) fn start_offset(&self) -> TextUnit {
+        match &self.parent {
+            None => 0.into(),
+            Some(p) => p.start_offset,
+        }
+    }
+
+    pub(crate) fn n_children(&self) -> usize {
+        self.green.children().len()
+    }
+
+    pub(crate) fn get_child(&self, idx: usize) -> Option<RedPtr> {
+        if idx >= self.n_children() {
+            return None;
+        }
+        match &self.children.read()[idx] {
+            Some(child) => return Some(RedPtr::new(child)),
+            None => (),
+        };
+        let green_children = self.green.children();
+        let start_offset = self.start_offset()
+            + green_children[..idx]
+            .iter()
+            .map(|x| x.text_len())
+            .sum::<TextUnit>();
+        let child =
+            RedNode::new_child(green_children[idx].clone(), RedPtr::new(self), start_offset, idx);
+        let mut children = self.children.write();
+        if children[idx].is_none() {
+            children[idx] = Some(child)
+        }
+        Some(RedPtr::new(children[idx].as_ref().unwrap()))
+    }
+
+    pub(crate) fn parent(&self) -> Option<RedPtr> {
+        Some(self.parent.as_ref()?.parent)
+    }
+    pub(crate) fn index_in_parent(&self) -> Option<usize> {
+        Some(self.parent.as_ref()?.index_in_parent)
+    }
+}