2 files changed, 258 insertions, 0 deletions

diff --git a/src/algo/mod.rs b/src/algo/mod.rs
index c1644d16d..d2de70fd4 100644
--- a/src/algo/mod.rs
+++ b/src/algo/mod.rs
@@ -1 +1,123 @@
 pub mod walk;
+
+use {SyntaxNodeRef, TextUnit, TextRange};
+
+pub fn find_leaf_at_offset(node: SyntaxNodeRef, offset: TextUnit) -> LeafAtOffset {
+    let range = node.range();
+    assert!(
+        contains_offset_nonstrict(range, offset),
+        "Bad offset: range {:?} offset {:?}", range, offset
+    );
+    if range.is_empty() {
+        return LeafAtOffset::None;
+    }
+
+    if node.is_leaf() {
+        return LeafAtOffset::Single(node);
+    }
+
+    let mut children = node.children()
+        .filter(|child| {
+            let child_range = child.range();
+            !child_range.is_empty() && contains_offset_nonstrict(child_range, offset)
+        });
+
+    let left = children.next().unwrap();
+    let right = children.next();
+    assert!(children.next().is_none());
+    return if let Some(right) = right {
+        match (find_leaf_at_offset(left, offset), find_leaf_at_offset(right, offset)) {
+            (LeafAtOffset::Single(left), LeafAtOffset::Single(right)) =>
+                LeafAtOffset::Between(left, right),
+            _ => unreachable!()
+        }
+    } else {
+        find_leaf_at_offset(left, offset)
+    };
+}
+
+#[derive(Clone, Copy, Debug)]
+pub enum LeafAtOffset<'a> {
+    None,
+    Single(SyntaxNodeRef<'a>),
+    Between(SyntaxNodeRef<'a>, SyntaxNodeRef<'a>)
+}
+
+impl<'a> LeafAtOffset<'a> {
+    pub fn right_biased(self) -> Option<SyntaxNodeRef<'a>> {
+        match self {
+            LeafAtOffset::None => None,
+            LeafAtOffset::Single(node) => Some(node),
+            LeafAtOffset::Between(_, right) => Some(right)
+        }
+    }
+
+    pub fn left_biased(self) -> Option<SyntaxNodeRef<'a>> {
+        match self {
+            LeafAtOffset::None => None,
+            LeafAtOffset::Single(node) => Some(node),
+            LeafAtOffset::Between(left, _) => Some(left)
+        }
+    }
+}
+
+impl<'f> Iterator for LeafAtOffset<'f> {
+    type Item = SyntaxNodeRef<'f>;
+
+    fn next(&mut self) -> Option<SyntaxNodeRef<'f>> {
+        match *self {
+            LeafAtOffset::None => None,
+            LeafAtOffset::Single(node) => { *self = LeafAtOffset::None; Some(node) }
+            LeafAtOffset::Between(left, right) => { *self = LeafAtOffset::Single(right); Some(left) }
+        }
+    }
+}
+
+
+pub fn find_covering_node(root: SyntaxNodeRef, range: TextRange) -> SyntaxNodeRef {
+    assert!(is_subrange(root.range(), range));
+    let (left, right) = match (
+        find_leaf_at_offset(root, range.start()).right_biased(),
+        find_leaf_at_offset(root, range.end()).left_biased()
+    ) {
+        (Some(l), Some(r)) => (l, r),
+        _ => return root
+    };
+
+    common_ancestor(left, right)
+}
+
+fn common_ancestor<'a>(n1: SyntaxNodeRef<'a>, n2: SyntaxNodeRef<'a>) -> SyntaxNodeRef<'a> {
+    for p in ancestors(n1) {
+        if ancestors(n2).any(|a| a == p) {
+            return p;
+        }
+    }
+    panic!("Can't find common ancestor of {:?} and {:?}", n1, n2)
+}
+
+pub fn ancestors<'a>(node: SyntaxNodeRef<'a>) -> impl Iterator<Item=SyntaxNodeRef<'a>> {
+    Ancestors(Some(node))
+}
+
+#[derive(Debug)]
+struct Ancestors<'a>(Option<SyntaxNodeRef<'a>>);
+
+impl<'a> Iterator for Ancestors<'a> {
+    type Item = SyntaxNodeRef<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0.take().map(|n| {
+            self.0 = n.parent();
+            n
+        })
+    }
+}
+
+fn contains_offset_nonstrict(range: TextRange, offset: TextUnit) -> bool {
+    range.start() <= offset && offset <= range.end()
+}
+
+fn is_subrange(range: TextRange, subrange: TextRange) -> bool {
+    range.start() <= subrange.start() && subrange.end() <= range.end()
+}
diff --git a/src/algo/search.rs b/src/algo/search.rs
new file mode 100644
index 000000000..46404f537
--- /dev/null
+++ b/src/algo/search.rs
@@ -0,0 +1,136 @@
+use {Node, NodeType, TextUnit, TextRange};
+use ::visitor::{visitor, process_subtree_bottom_up};
+
+pub fn child_of_type(node: Node, ty: NodeType) -> Option<Node> {
+    node.children().find(|n| n.ty() == ty)
+}
+
+pub fn children_of_type<'f>(node: Node<'f>, ty: NodeType) -> Box<Iterator<Item=Node<'f>> + 'f> {
+    Box::new(node.children().filter(move |n| n.ty() == ty))
+}
+
+pub fn subtree<'f>(node: Node<'f>) -> Box<Iterator<Item=Node<'f>> + 'f> {
+    Box::new(node.children().flat_map(subtree).chain(::std::iter::once(node)))
+}
+
+pub fn descendants_of_type<'f>(node: Node<'f>, ty: NodeType) -> Vec<Node<'f>> {
+    process_subtree_bottom_up(
+        node,
+        visitor(Vec::new())
+            .visit_nodes(&[ty], |node, nodes| nodes.push(node))
+    )
+}
+
+pub fn child_of_type_exn(node: Node, ty: NodeType) -> Node {
+    child_of_type(node, ty).unwrap_or_else(|| {
+        panic!("No child of type {:?} for {:?}\
+                ----\
+                {}\
+                ----", ty, node.ty(), node.text())
+    })
+}
+
+
+pub fn ancestors(node: Node) -> Ancestors {
+    Ancestors(Some(node))
+}
+
+pub struct Ancestors<'f>(Option<Node<'f>>);
+
+impl<'f> Iterator for Ancestors<'f> {
+    type Item = Node<'f>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let current = self.0;
+        self.0 = current.and_then(|n| n.parent());
+        current
+    }
+}
+
+pub fn is_leaf(node: Node) -> bool {
+    node.children().next().is_none() && !node.range().is_empty()
+}
+
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub enum Direction {
+    Left, Right
+}
+
+pub fn sibling(node: Node, dir: Direction) -> Option<Node> {
+    let (parent, idx) = child_position(node)?;
+    let idx = match dir {
+        Direction::Left => idx.checked_sub(1)?,
+        Direction::Right => idx + 1,
+    };
+    parent.children().nth(idx)
+}
+
+pub mod ast {
+    use {Node, AstNode, TextUnit, AstChildren};
+    use visitor::{visitor, process_subtree_bottom_up};
+    use super::{ancestors, find_leaf_at_offset, LeafAtOffset};
+
+    pub fn ancestor<'f, T: AstNode<'f>>(node: Node<'f>) -> Option<T> {
+        ancestors(node)
+            .filter_map(T::wrap)
+            .next()
+    }
+
+    pub fn ancestor_exn<'f, T: AstNode<'f>>(node: Node<'f>) -> T {
+        ancestor(node).unwrap()
+    }
+
+    pub fn children_of_type<'f, N: AstNode<'f>>(node: Node<'f>) -> AstChildren<N> {
+        AstChildren::new(node.children())
+    }
+
+    pub fn descendants_of_type<'f, N: AstNode<'f>>(node: Node<'f>) -> Vec<N> {
+        process_subtree_bottom_up(
+            node,
+            visitor(Vec::new())
+                .visit::<N, _>(|node, acc| acc.push(node))
+        )
+    }
+
+    pub fn node_at_offset<'f, T: AstNode<'f>>(node: Node<'f>, offset: TextUnit) -> Option<T> {
+        match find_leaf_at_offset(node, offset) {
+            LeafAtOffset::None => None,
+            LeafAtOffset::Single(node) => ancestor(node),
+            LeafAtOffset::Between(left, right) => ancestor(left).or_else(|| ancestor(right)),
+        }
+    }
+}
+
+pub mod traversal {
+    use {Node};
+
+    pub fn bottom_up<'f, F: FnMut(Node<'f>)>(node: Node<'f>, mut f: F)
+    {
+        go(node, &mut f);
+
+        fn go<'f, F: FnMut(Node<'f>)>(node: Node<'f>, f: &mut F) {
+            for child in node.children() {
+                go(child, f)
+            }
+            f(node);
+        }
+    }
+}
+
+fn child_position(child: Node) -> Option<(Node, usize)> {
+    child.parent()
+        .map(|parent| {
+            (parent, parent.children().position(|n| n == child).unwrap())
+        })
+}
+
+fn common_ancestor<'f>(n1: Node<'f>, n2: Node<'f>) -> Node<'f> {
+    for p in ancestors(n1) {
+        if ancestors(n2).any(|a| a == p) {
+            return p;
+        }
+    }
+    panic!("Can't find common ancestor of {:?} and {:?}", n1, n2)
+}
+