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// Lazy pre-order traversal over arbitrary tree-sitter trees
// extern
use tree_sitter::{Node, Tree, TreeCursor};
pub struct PreOrder<'a> {
cursor: TreeCursor<'a>,
done: bool,
}
impl<'a> PreOrder<'a> {
pub fn new(tree: &'a Tree) -> Self {
Self {
cursor: tree.walk(),
done: false,
}
}
}
// Traverse the tree in root-left-right fashion
impl<'a> Iterator for PreOrder<'a> {
type Item = Node<'a>;
fn next(&mut self) -> Option<Self::Item> {
if self.done {
return None;
}
// capture the root node
let node = self.cursor.node();
// if this node has a child, move there and return the root, or
// if this node has a sibling, move there and return the root
if self.cursor.goto_first_child() || self.cursor.goto_next_sibling() {
return Some(node);
}
loop {
// we are done retracing all the way back to the root node
if !self.cursor.goto_parent() {
self.done = true;
break;
}
if self.cursor.goto_next_sibling() {
break;
}
}
Some(node)
}
}
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