Iteratation through children first about indextree HOT 8 CLOSED

use indextree::{Arena, NodeEdge};

pub fn main() {
    let mut arena = Arena::new();
    let n1 = arena.new_node(("1", 0));
    let n1_1 = arena.new_node(("1_1", 1));
    n1.append(n1_1, &mut arena);
    let n1_2 = arena.new_node(("1_2", 1));
    n1.append(n1_2, &mut arena);
    {
        let n1_2_1 = arena.new_node(("1_2_1", 2));
        n1_2.append(n1_2_1, &mut arena);
    }
    let n1_3 = arena.new_node(("1_3", 1));
    n1.append(n1_3, &mut arena);
    {
        let n1_3_1 = arena.new_node(("1_3_1", 2));
        n1_3.append(n1_3_1, &mut arena);
        let n1_3_2 = arena.new_node(("1_3_2", 2));
        n1_3.append(n1_3_2, &mut arena);
        let n1_3_3 = arena.new_node(("1_3_3", 2));
        n1_3.append(n1_3_3, &mut arena);
    }

    let iter = n1.traverse(&arena).filter_map(|ev| match ev {
        NodeEdge::Start(_) => None,
        NodeEdge::End(id) => Some(id),
    });
    for id in iter {
        let (v, level) = arena[id].get();
        println!("{}", format!("{:>width$}", v, width = 4 * level));
    }
}

// This must return `Some(_)` since the last item to be iterated
// by `.traverse(...)` should be `NodeEdge::End(root_id)`.
let mut next_id = root_id
    .traverse(&arena)
    .find_map(|ev| match ev {
        NodeEdge::Start(_) => None,
        NodeEdge::End(id) => Some(id),
    });
while let Some(current_id) = next_id {
    let current = arena[current_id];
    next_id = if current_id == root_id {
        // This will be the last node to iterate.
        None
    } else if let Some(next_sib_id) = current.next_sibling() {
        // This will return `Some(_)` since the last item to be iterated
        // by `.traverse(...)` should be `NodeEdge::End(next_sib_id)`.
        next_sib_id
            .traverse(&arena)
            .find_map(|ev| match ev {
                NodeEdge::Start(_) => None,
                NodeEdge::End(id) => Some(id),
            })
    } else {
        // No more following siblings. Go to the parent node.
        current.parent()
    }

    todo!("Do your work here");
}

// This must return `Some(_)` since the last item to be iterated
// by `.traverse(...)` should be `NodeEdge::End(root_id)`.
let mut next_id = root_id
    .traverse(&arena)
    .find_map(|ev| match ev {
        NodeEdge::Start(_) => None,
        NodeEdge::End(id) => Some(id),
    });
while let Some(current_id) = next_id {
    next_id = if current_id == root_id {
        // This will be the last node to iterate.
        None
    } else if let Some(next_sib_id) = arena[current_id].next_sibling() {
        // This will return `Some(_)` since the last item to be iterated
        // by `.traverse(...)` should be `NodeEdge::End(next_sib_id)`.
        next_sib_id
            .traverse(&arena)
            .find_map(|ev| match ev {
                NodeEdge::Start(_) => None,
                NodeEdge::End(id) => Some(id),
            })
    } else {
        // No more following siblings. Go to the parent node.
        arena[current_id].parent()
    }

    todo!("Do your work here");
}