Set up a BFS iterator over the node tree

otg/core/src/types.rs

@@ -3,9 +3,9 @@ use config::define_config;
 use config_derive::ConfigOption;
 use serde::{Deserialize, Serialize};
 use sgf::GameNode;
-use uuid::Uuid;
+use std::{cell::RefCell, collections::VecDeque, fmt, path::PathBuf, time::Duration};
-use std::{cell::RefCell, fmt, path::PathBuf, time::Duration};
 use thiserror::Error;
+use uuid::Uuid;
 
 define_config! {
     LibraryPath(LibraryPath),
@@ -235,12 +235,12 @@ impl GameState {
 //
 // So, what is the maximum depth of the tree? Follow all paths and see how far I get in every case.
 // I could do this by just generating an intermediate tree and numbering each level.
-
 pub struct Tree<T> {
     nodes: Vec<Node<T>>,
 }
 
-struct Node<T> {
+#[derive(Debug)]
+pub struct Node<T> {
     id: usize,
     node: T,
     parent: Option<usize>,
@@ -294,6 +294,17 @@ impl<T> Tree<T> {
         )
     }
 
+    // Since I know the width of a node, now I want to figure out its placement in the larger
+    // scheme of things.
+    //
+    // One thought I have is that I could just develop a grid virtually and start placing nodes.
+    // Whenever I notice a collision, I can just move the node over. But I'd like to see if I can
+    // be a bit smarter than doing it as just a vec into which I place things, as though it's a
+    // game board. So, given a game node, I want to figure out it's position along the X axis.
+    //
+    // Just having the node is greatly insufficient. I can get better results if I'm calculating
+    // the position of its children.
+    //
     // indent represents the indentation that should be applied to all children in this tree. It
     // amounts to the position of the parent node.
     pub fn position(&self, indent: usize, idx: usize) -> (usize, usize) {
@@ -310,12 +321,22 @@ impl<T> Tree<T> {
                 println!("[{}] sibling width {}", idx, sibling_width);
                 (node.depth, indent + sibling_width)
             }
-            
+
             // Root nodes won't have a parent, so just put them in the first column
             None => (0, 0),
         }
     }
 
+    // Given a node, do a postorder traversal to figure out the width of the node based on all of
+    // its children. This is equivalent to the widest of all of its children at all depths.
+    //
+    // There are some collapse rules that I could take into account here, but that I haven't
+    // figured out yet. If two nodes are side by side, and one of them has some wide children but
+    // the other has no children, then they are effectively the same width. The second node only
+    // needs to be moved out if it has children that would overlap the children of the first node.
+    //
+    // My algorithm right now is likely to generate unnecessarily wide trees in a complex game
+    // review.
     fn width(&self, id: usize) -> usize {
         println!("[{}] calculating width", id);
         let node = &self.nodes[id];
@@ -333,6 +354,12 @@ impl<T> Tree<T> {
 
         width
     }
+
+    fn bfs_iter<'a>(&'a self) -> BFSIter<T> {
+        let mut queue = VecDeque::new();
+        queue.push_back(&self.nodes[0]);
+        BFSIter { tree: self, queue }
+    }
 }
 
 impl<'a> From<&'a GameNode> for Tree<Uuid> {
@@ -365,9 +392,30 @@ impl<'a> From<&'a GameNode> for Tree<Uuid> {
     }
 }
 
+pub struct BFSIter<'a, T> {
+    tree: &'a Tree<T>,
+    queue: VecDeque<&'a Node<T>>,
+}
+
+impl<'a, T> Iterator for BFSIter<'a, T> {
+    type Item = &'a Node<T>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let retval = self.queue.pop_front();
+        if let Some(ref retval) = retval {
+            retval
+                .children
+                .iter()
+                .for_each(|idx| self.queue.push_back(&self.tree.nodes[*idx]));
+        }
+        retval
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
+    use cool_asserts::assert_matches;
     use sgf::{Move, MoveNode};
 
     #[test]
@@ -498,4 +546,45 @@ mod test {
         assert_eq!(tree.position(0, 6), (1, 3));
         assert_eq!(tree.position(0, 7), (1, 4));
     }
+
+    #[test]
+    fn breadth_first_iter() {
+        let mut node_a = MoveNode::new(sgf::Color::Black, Move::Move("dp".to_owned()));
+        let mut node_b = MoveNode::new(sgf::Color::Black, Move::Move("dp".to_owned()));
+        let mut node_c = MoveNode::new(sgf::Color::Black, Move::Move("dp".to_owned()));
+        let node_d = MoveNode::new(sgf::Color::Black, Move::Move("dp".to_owned()));
+        let node_e = MoveNode::new(sgf::Color::Black, Move::Move("dp".to_owned()));
+        let node_f = MoveNode::new(sgf::Color::Black, Move::Move("dp".to_owned()));
+        let node_g = MoveNode::new(sgf::Color::Black, Move::Move("dp".to_owned()));
+        let mut node_h = MoveNode::new(sgf::Color::Black, Move::Move("dp".to_owned()));
+        let node_i = MoveNode::new(sgf::Color::Black, Move::Move("dp".to_owned()));
+
+        node_c.children.push(GameNode::MoveNode(node_d.clone()));
+        node_c.children.push(GameNode::MoveNode(node_e.clone()));
+        node_c.children.push(GameNode::MoveNode(node_f.clone()));
+
+        node_b.children.push(GameNode::MoveNode(node_c.clone()));
+
+        node_h.children.push(GameNode::MoveNode(node_i.clone()));
+
+        node_a.children.push(GameNode::MoveNode(node_b.clone()));
+        node_a.children.push(GameNode::MoveNode(node_g.clone()));
+        node_a.children.push(GameNode::MoveNode(node_h.clone()));
+
+        let game_tree = GameNode::MoveNode(node_a.clone());
+
+        let tree = Tree::from(&game_tree);
+
+        let mut iter = tree.bfs_iter();
+
+        assert_matches!(iter.next(), Some(Node { node: uuid, .. }) => assert_eq!(*uuid, node_a.id));
+        assert_matches!(iter.next(), Some(Node { node: uuid, .. }) => assert_eq!(*uuid, node_b.id));
+        assert_matches!(iter.next(), Some(Node { node: uuid, .. }) => assert_eq!(*uuid, node_g.id));
+        assert_matches!(iter.next(), Some(Node { node: uuid, .. }) => assert_eq!(*uuid, node_h.id));
+        assert_matches!(iter.next(), Some(Node { node: uuid, .. }) => assert_eq!(*uuid, node_c.id));
+        assert_matches!(iter.next(), Some(Node { node: uuid, .. }) => assert_eq!(*uuid, node_i.id));
+        assert_matches!(iter.next(), Some(Node { node: uuid, .. }) => assert_eq!(*uuid, node_d.id));
+        assert_matches!(iter.next(), Some(Node { node: uuid, .. }) => assert_eq!(*uuid, node_e.id));
+        assert_matches!(iter.next(), Some(Node { node: uuid, .. }) => assert_eq!(*uuid, node_f.id));
+    }
 }