Various fixes

server-rs/src/parsing/bounds.rs

@@ -1,11 +1,29 @@
 use axum::http::StatusCode;
 
-/// Compute the lat/lon bounding box of an H3 cell, with a configurable buffer in degrees.
+/// Check if two bounding boxes intersect.
+/// Both boxes are (south, west, north, east) / (min_lat, min_lon, max_lat, max_lon).
+#[inline]
+pub fn bounds_intersect(
+    a_south: f64,
+    a_west: f64,
+    a_north: f64,
+    a_east: f64,
+    b_south: f64,
+    b_west: f64,
+    b_north: f64,
+    b_east: f64,
+) -> bool {
+    a_west <= b_east && a_east >= b_west && a_south <= b_north && a_north >= b_south
+}
+
+/// Compute the lat/lon bounding box of an H3 cell in degrees, with a configurable buffer in degrees.
+/// Returns (south, west, north, east) / (min_lat, min_lon, max_lat, max_lon).
 pub fn h3_cell_bounds(cell: h3o::CellIndex, buffer: f64) -> (f64, f64, f64, f64) {
     let boundary = cell.boundary();
     let (mut min_lat, mut max_lat) = (f64::INFINITY, f64::NEG_INFINITY);
     let (mut min_lon, mut max_lon) = (f64::INFINITY, f64::NEG_INFINITY);
     for vertex in boundary.iter() {
+        // h3o LatLng::lat()/lng() return degrees
         let lat = vertex.lat();
         let lon = vertex.lng();
         if lat < min_lat {
@@ -81,4 +99,42 @@ mod tests {
         assert!((buf_max_lat - max_lat - 0.1).abs() < 1e-10);
         assert!((buf_max_lon - max_lon - 0.1).abs() < 1e-10);
     }
+
+    #[test]
+    fn h3_cell_bounds_returns_degrees_not_radians() {
+        // Cell "8928308280fffff" is in San Francisco area (~37.77°N, ~-122.4°W)
+        let cell = h3o::CellIndex::from_str("8928308280fffff").unwrap();
+        let (min_lat, min_lon, max_lat, max_lon) = h3_cell_bounds(cell, 0.0);
+
+        // If h3o returned radians, values would be < π ≈ 3.14
+        // Latitude ~37.77° proves we're getting degrees, not radians
+        assert!(min_lat > 30.0 && min_lat < 45.0, "min_lat {} should be ~37° (degrees)", min_lat);
+        assert!(max_lat > 30.0 && max_lat < 45.0, "max_lat {} should be ~37° (degrees)", max_lat);
+
+        // Longitude ~-122° also proves degrees (radians would be < π)
+        assert!(min_lon < -100.0, "min_lon {} should be ~-122° (degrees)", min_lon);
+        assert!(max_lon < -100.0, "max_lon {} should be ~-122° (degrees)", max_lon);
+    }
+
+    #[test]
+    fn bounds_intersect_overlapping() {
+        // Two overlapping boxes
+        assert!(bounds_intersect(0.0, 0.0, 2.0, 2.0, 1.0, 1.0, 3.0, 3.0));
+        // Box B is inside box A
+        assert!(bounds_intersect(0.0, 0.0, 10.0, 10.0, 2.0, 2.0, 5.0, 5.0));
+        // Box A is inside box B
+        assert!(bounds_intersect(2.0, 2.0, 5.0, 5.0, 0.0, 0.0, 10.0, 10.0));
+        // Touching at edge
+        assert!(bounds_intersect(0.0, 0.0, 1.0, 1.0, 1.0, 0.0, 2.0, 1.0));
+    }
+
+    #[test]
+    fn bounds_intersect_non_overlapping() {
+        // Box B is to the right of box A
+        assert!(!bounds_intersect(0.0, 0.0, 1.0, 1.0, 0.0, 2.0, 1.0, 3.0));
+        // Box B is above box A
+        assert!(!bounds_intersect(0.0, 0.0, 1.0, 1.0, 2.0, 0.0, 3.0, 1.0));
+        // Completely separate
+        assert!(!bounds_intersect(0.0, 0.0, 1.0, 1.0, 5.0, 5.0, 6.0, 6.0));
+    }
 }