cranpose-app-shell 0.1.110

use std::collections::HashMap;

use cranpose_core::NodeId;

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub struct PointerId(pub u32);

impl PointerId {
    pub const PRIMARY: PointerId = PointerId(0);
}

pub struct HitPathTracker {
    paths: HashMap<PointerId, Vec<Vec<NodeId>>>,
}

impl HitPathTracker {
    pub fn new() -> Self {
        Self {
            paths: HashMap::new(),
        }
    }

    pub fn add_hit_path(&mut self, pointer: PointerId, capture_paths: Vec<Vec<NodeId>>) {
        if capture_paths.is_empty() {
            self.paths.remove(&pointer);
        } else {
            self.paths.insert(pointer, capture_paths);
        }
    }

    pub fn get_path(&self, pointer: PointerId) -> Option<&[Vec<NodeId>]> {
        self.paths.get(&pointer).map(Vec::as_slice)
    }

    pub fn dispatch_order(&self, pointer: PointerId) -> Option<Vec<NodeId>> {
        self.get_path(pointer).map(dispatch_order_for_paths)
    }

    pub fn remove_path(&mut self, pointer: PointerId) -> Option<Vec<Vec<NodeId>>> {
        self.paths.remove(&pointer)
    }

    pub fn has_path(&self, pointer: PointerId) -> bool {
        self.paths.contains_key(&pointer)
    }

    pub fn clear(&mut self) {
        self.paths.clear();
    }

    #[cfg(test)]
    pub fn is_empty(&self) -> bool {
        self.paths.is_empty()
    }
}

impl Default for HitPathTracker {
    fn default() -> Self {
        Self::new()
    }
}

#[derive(Default)]
struct DispatchNode {
    children: Vec<NodeId>,
}

pub(crate) fn dispatch_order_for_paths(paths: &[Vec<NodeId>]) -> Vec<NodeId> {
    fn push_unique(nodes: &mut Vec<NodeId>, node_id: NodeId) {
        if !nodes.contains(&node_id) {
            nodes.push(node_id);
        }
    }

    fn visit(node_id: NodeId, tree: &HashMap<NodeId, DispatchNode>, ordered: &mut Vec<NodeId>) {
        if let Some(node) = tree.get(&node_id) {
            for &child in &node.children {
                visit(child, tree, ordered);
            }
        }
        ordered.push(node_id);
    }

    let mut roots = Vec::new();
    let mut tree: HashMap<NodeId, DispatchNode> = HashMap::new();

    for path in paths {
        let mut parent = None;
        for node_id in path.iter().rev().copied() {
            tree.entry(node_id).or_default();
            if let Some(parent_id) = parent {
                let parent_node = tree.entry(parent_id).or_default();
                push_unique(&mut parent_node.children, node_id);
            } else {
                push_unique(&mut roots, node_id);
            }
            parent = Some(node_id);
        }
    }

    let mut ordered = Vec::new();
    for root in roots {
        visit(root, &tree, &mut ordered);
    }
    ordered
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn a_pointer_nobody_touched_has_no_dispatch_order() {
        let tracker = HitPathTracker::new();
        assert_eq!(tracker.dispatch_order(PointerId::PRIMARY), None);
    }

    #[test]
    fn a_dispatch_order_puts_a_shared_ancestor_after_every_child_that_survived() {
        let mut tracker = HitPathTracker::new();
        tracker.add_hit_path(PointerId::PRIMARY, vec![vec![2, 1], vec![4, 1]]);

        let order = tracker
            .dispatch_order(PointerId::PRIMARY)
            .expect("a tracked pointer has an order");

        let ancestor = order
            .iter()
            .position(|node| *node == 1)
            .expect("the ancestor is dispatched");
        for child in [2, 4] {
            let at = order
                .iter()
                .position(|node| *node == child)
                .unwrap_or_else(|| panic!("child {child} was not dispatched"));
            assert!(
                at < ancestor,
                "child {child} was dispatched after its ancestor"
            );
        }
        assert_eq!(
            order.iter().filter(|node| **node == 1).count(),
            1,
            "the shared ancestor was dispatched twice"
        );
    }

    #[test]
    fn test_add_and_get_path() {
        let mut tracker = HitPathTracker::new();
        let paths: Vec<Vec<NodeId>> = vec![vec![1, 2, 3], vec![4, 5]];

        tracker.add_hit_path(PointerId::PRIMARY, paths.clone());

        assert!(tracker.has_path(PointerId::PRIMARY));
        assert_eq!(tracker.get_path(PointerId::PRIMARY), Some(paths.as_slice()));
    }

    #[test]
    fn test_remove_path() {
        let mut tracker = HitPathTracker::new();
        let paths: Vec<Vec<NodeId>> = vec![vec![1]];

        tracker.add_hit_path(PointerId::PRIMARY, paths.clone());
        let removed = tracker.remove_path(PointerId::PRIMARY);

        assert_eq!(removed, Some(paths));
        assert!(!tracker.has_path(PointerId::PRIMARY));
        assert!(tracker.is_empty());
    }

    #[test]
    fn test_clear() {
        let mut tracker = HitPathTracker::new();
        tracker.add_hit_path(PointerId(0), vec![vec![1]]);
        tracker.add_hit_path(PointerId(1), vec![vec![2]]);

        assert!(!tracker.is_empty());

        tracker.clear();

        assert!(tracker.is_empty());
        assert!(!tracker.has_path(PointerId(0)));
        assert!(!tracker.has_path(PointerId(1)));
    }

    #[test]
    fn test_multiple_pointers() {
        let mut tracker = HitPathTracker::new();
        let nodes1: Vec<Vec<NodeId>> = vec![vec![1]];
        let nodes2: Vec<Vec<NodeId>> = vec![vec![2, 3]];

        tracker.add_hit_path(PointerId(0), nodes1.clone());
        tracker.add_hit_path(PointerId(1), nodes2.clone());

        assert_eq!(tracker.get_path(PointerId(0)), Some(nodes1.as_slice()));
        assert_eq!(tracker.get_path(PointerId(1)), Some(nodes2.as_slice()));
    }

    #[test]
    fn test_dispatch_order_keeps_shared_ancestor_after_overlapping_hits() {
        let paths = vec![vec![1, 99], vec![2, 99]];

        assert_eq!(dispatch_order_for_paths(&paths), vec![1, 2, 99]);
    }

    #[test]
    fn dispatch_tree_build_does_not_panic_on_parent_entry_assumption() {
        let source = include_str!("hit_path_tracker.rs");
        let parent_expect = ["expect(\"parent ", "inserted above\")"].concat();

        assert!(!source.contains(parent_expect.as_str()));
        assert!(source.contains("tree.entry(parent_id).or_default()"));
    }
}