From 3ec60bfb0010d12f2c7cef726aa581d75a142705 Mon Sep 17 00:00:00 2001
From: Michael Kirk <michael.code@endoftheworl.de>
Date: Thu, 5 May 2022 10:55:43 -0700
Subject: [PATCH] scaffold rstar edge set intersector

Copied the "SimpleEdgeSetIntersector" into a new struct. I'll add the
actual RTree implementation in a follow up, and hopefully this way it'll
be easier to compare the two implementations.
---
 .../relate/geomgraph/geometry_graph.rs        | 11 +++-
 .../algorithm/relate/geomgraph/index/mod.rs   |  2 +
 .../index/rstar_edge_set_intersector.rs       | 59 +++++++++++++++++++
 3 files changed, 70 insertions(+), 2 deletions(-)
 create mode 100644 geo/src/algorithm/relate/geomgraph/index/rstar_edge_set_intersector.rs

diff --git a/geo/src/algorithm/relate/geomgraph/geometry_graph.rs b/geo/src/algorithm/relate/geomgraph/geometry_graph.rs
index a699c06ea2..77efbc1da1 100644
--- a/geo/src/algorithm/relate/geomgraph/geometry_graph.rs
+++ b/geo/src/algorithm/relate/geomgraph/geometry_graph.rs
@@ -1,5 +1,7 @@
 use super::{
-    index::{EdgeSetIntersector, SegmentIntersector, SimpleEdgeSetIntersector},
+    index::{
+        EdgeSetIntersector, RstarEdgeSetIntersector, SegmentIntersector, SimpleEdgeSetIntersector,
+    },
     CoordNode, CoordPos, Direction, Edge, Label, LineIntersector, PlanarGraph, TopologyPosition,
 };
 
@@ -97,7 +99,12 @@ where
     fn create_edge_set_intersector() -> Box<dyn EdgeSetIntersector<F>> {
         // PERF: faster algorithms exist. This one was chosen for simplicity of implementation and
         //       debugging
-        Box::new(SimpleEdgeSetIntersector::new())
+        // Slow, but simple and good for debugging
+        // Box::new(SimpleEdgeSetIntersector::new())
+
+        // Should be much faster for sparse intersections, while not much slower than
+        // SimpleEdgeSetIntersector in the dense case
+        Box::new(RstarEdgeSetIntersector::new())
     }
 
     fn boundary_nodes(&self) -> impl Iterator<Item = &CoordNode<F>> {
diff --git a/geo/src/algorithm/relate/geomgraph/index/mod.rs b/geo/src/algorithm/relate/geomgraph/index/mod.rs
index 06c4b2c21c..ae48b3db93 100644
--- a/geo/src/algorithm/relate/geomgraph/index/mod.rs
+++ b/geo/src/algorithm/relate/geomgraph/index/mod.rs
@@ -1,7 +1,9 @@
 mod edge_set_intersector;
+mod rstar_edge_set_intersector;
 mod segment_intersector;
 mod simple_edge_set_intersector;
 
 pub(crate) use edge_set_intersector::EdgeSetIntersector;
+pub(crate) use rstar_edge_set_intersector::RstarEdgeSetIntersector;
 pub(crate) use segment_intersector::SegmentIntersector;
 pub(crate) use simple_edge_set_intersector::SimpleEdgeSetIntersector;
diff --git a/geo/src/algorithm/relate/geomgraph/index/rstar_edge_set_intersector.rs b/geo/src/algorithm/relate/geomgraph/index/rstar_edge_set_intersector.rs
new file mode 100644
index 0000000000..91619f9197
--- /dev/null
+++ b/geo/src/algorithm/relate/geomgraph/index/rstar_edge_set_intersector.rs
@@ -0,0 +1,59 @@
+use super::super::Edge;
+use super::{EdgeSetIntersector, SegmentIntersector};
+use crate::GeoFloat;
+
+use std::cell::RefCell;
+use std::rc::Rc;
+
+pub(crate) struct RstarEdgeSetIntersector;
+
+impl RstarEdgeSetIntersector {
+    pub fn new() -> Self {
+        RstarEdgeSetIntersector
+    }
+
+    fn compute_intersects<F: GeoFloat>(
+        &mut self,
+        edge0: &Rc<RefCell<Edge<F>>>,
+        edge1: &Rc<RefCell<Edge<F>>>,
+        segment_intersector: &mut SegmentIntersector<F>,
+    ) {
+        let edge0_coords_len = edge0.borrow().coords().len() - 1;
+        let edge1_coords_len = edge1.borrow().coords().len() - 1;
+        for i0 in 0..edge0_coords_len {
+            for i1 in 0..edge1_coords_len {
+                segment_intersector.add_intersections(edge0, i0, edge1, i1);
+            }
+        }
+    }
+}
+
+impl<F: GeoFloat> EdgeSetIntersector<F> for RstarEdgeSetIntersector {
+    fn compute_intersections_within_set(
+        &mut self,
+        edges: &[Rc<RefCell<Edge<F>>>],
+        check_for_self_intersecting_edges: bool,
+        segment_intersector: &mut SegmentIntersector<F>,
+    ) {
+        for edge0 in edges.iter() {
+            for edge1 in edges.iter() {
+                if check_for_self_intersecting_edges || edge0.as_ptr() != edge1.as_ptr() {
+                    self.compute_intersects(edge0, edge1, segment_intersector);
+                }
+            }
+        }
+    }
+
+    fn compute_intersections_between_sets(
+        &mut self,
+        edges0: &[Rc<RefCell<Edge<F>>>],
+        edges1: &[Rc<RefCell<Edge<F>>>],
+        segment_intersector: &mut SegmentIntersector<F>,
+    ) {
+        for edge0 in edges0 {
+            for edge1 in edges1 {
+                self.compute_intersects(edge0, edge1, segment_intersector);
+            }
+        }
+    }
+}