OneCAD/vendor/truck-shapeops/src/transversal/polyline_construction/mod.rs

use rustc_hash::{FxHashMap as HashMap, FxHashSet as HashSet};
use std::collections::VecDeque;
use truck_base::{cgmath64::*, tolerance::*};
use truck_meshalgo::prelude::PolylineCurve;

pub fn construct_polylines(lines: &[(Point3, Point3)]) -> Vec<PolylineCurve<Point3>> {
    let mut graph: Graph = lines.iter().collect();
    let mut res = Vec::new();
    while !graph.is_empty() {
        let (mut idx, node) = graph.get_one();
        let mut wire: VecDeque<_> = vec![node.coord].into();
        while let Some((idx0, pt)) = graph.get_a_next_node(idx) {
            idx = idx0;
            wire.push_back(pt);
        }
        let mut idx = PointIndex::from(wire[0]);
        while let Some((idx0, pt)) = graph.get_a_next_node(idx) {
            idx = idx0;
            wire.push_front(pt);
        }
        res.push(PolylineCurve(wire.into()));
    }
    res
}

#[derive(Clone, Debug, Copy, Hash, PartialEq, Eq)]
struct PointIndex([i64; 3]);

impl From<Point3> for PointIndex {
    #[inline(always)]
    fn from(pt: Point3) -> PointIndex {
        let idx = pt.add_element_wise(TOLERANCE) / (2.0 * TOLERANCE);
        PointIndex(idx.cast::<i64>().unwrap().into())
    }
}

struct Node {
    coord: Point3,
    adjacency: HashSet<PointIndex>,
}

impl Node {
    #[inline(always)]
    fn new(coord: Point3, adjacency: HashSet<PointIndex>) -> Node { Node { coord, adjacency } }

    fn pop_one_adjacency(&mut self) -> PointIndex {
        let idx = *self.adjacency.iter().next().unwrap();
        self.adjacency.remove(&idx);
        idx
    }
}

struct Graph(HashMap<PointIndex, Node>);

impl std::ops::Deref for Graph {
    type Target = HashMap<PointIndex, Node>;
    #[inline(always)]
    fn deref(&self) -> &Self::Target { &self.0 }
}

impl std::ops::DerefMut for Graph {
    #[inline(always)]
    fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 }
}

impl Graph {
    fn add_half_edge(&mut self, pt0: Point3, pt1: Point3) {
        let idx0 = pt0.into();
        let idx1 = pt1.into();
        if let Some(node) = self.get_mut(&idx0) {
            node.adjacency.insert(idx1);
        } else {
            let mut set = HashSet::default();
            set.insert(idx1);
            self.insert(idx0, Node::new(pt0, set));
        }
    }

    fn add_edge(&mut self, line: (Point3, Point3)) {
        if !line.0.near(&line.1) {
            self.add_half_edge(line.0, line.1);
            self.add_half_edge(line.1, line.0);
        }
    }

    #[inline(always)]
    fn get_one(&self) -> (PointIndex, &Node) {
        let (idx, node) = self.iter().next().unwrap();
        (*idx, node)
    }

    fn get_a_next_node(&mut self, idx: PointIndex) -> Option<(PointIndex, Point3)> {
        let node = self.get_mut(&idx)?;
        let idx0 = node.pop_one_adjacency();
        if node.adjacency.is_empty() {
            self.remove(&idx);
        }
        let node = self.get_mut(&idx0)?;
        node.adjacency.remove(&idx);
        let pt = node.coord;
        if node.adjacency.is_empty() {
            self.remove(&idx0);
        }
        Some((idx0, pt))
    }
}

impl<'a> FromIterator<&'a (Point3, Point3)> for Graph {
    fn from_iter<I: IntoIterator<Item = &'a (Point3, Point3)>>(iter: I) -> Graph {
        let mut res = Graph(HashMap::default());
        iter.into_iter().for_each(|line| res.add_edge(*line));
        res
    }
}

#[cfg(test)]
mod tests;