From ebf78d104b90dbbb3b41cc3fbec75bf39dd836f2 Mon Sep 17 00:00:00 2001
From: Huite Bootsma <huitebootsma@gmail.com>
Date: Sat, 12 Aug 2023 12:34:37 +0200
Subject: [PATCH] Add Ugrid2d.bounding_polygon

---
 docs/api.rst            |  1 +
 docs/changelog.rst      |  4 ++++
 tests/test_ugrid2d.py   |  7 +++++++
 xugrid/ugrid/ugrid2d.py | 16 ++++++++++++++++
 4 files changed, 28 insertions(+)

diff --git a/docs/api.rst b/docs/api.rst
index 9bd632543..4fc251fc8 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -257,6 +257,7 @@ UGRID2D Topology
     Ugrid2d.bounds
     Ugrid2d.edge_bounds
     Ugrid2d.face_bounds
+    Ugrid2d.polygon_bounds
 
     Ugrid2d.node_node_connectivity
     Ugrid2d.node_edge_connectivity
diff --git a/docs/changelog.rst b/docs/changelog.rst
index f142a4ec4..cf9314e1b 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -32,6 +32,8 @@ Added
 - :meth:`xugrid.UgridDatasetAccessor.rename` and
   :meth:`xugrid.UgridDataArrayAccessor.rename` to rename both topology and the
   associated dimensions.
+- :meth:`xugrid.Ugrid2d.polygon_bounds` has been added to get a polygon
+  describing the bounds of the grid.
 
 Fixed
 ~~~~~
@@ -46,6 +48,8 @@ Fixed
   reference system).
 - :meth:`xugrid.UgridDatasetAccessor.to_geodataframe` will no longer error when
   converting a UgridDataset that does not contain any variables.
+- :meth:`xugrid.OverlapRegridder.regrid` will no longer give incorrect results
+  on repeated calls with the "mode" method.
 
 Changed
 ~~~~~~~
diff --git a/tests/test_ugrid2d.py b/tests/test_ugrid2d.py
index 2d7c79f3c..e772a6bd8 100644
--- a/tests/test_ugrid2d.py
+++ b/tests/test_ugrid2d.py
@@ -901,6 +901,13 @@ def test_from_geodataframe():
     assert isinstance(grid, xugrid.Ugrid2d)
 
 
+def test_bounding_polygon():
+    grid = grid2d()
+    polygon = grid.bounding_polygon()
+    assert isinstance(polygon, shapely.Polygon)
+    assert np.allclose(grid.bounds, polygon.bounds)
+
+
 def test_to_shapely():
     grid = grid2d()
 
diff --git a/xugrid/ugrid/ugrid2d.py b/xugrid/ugrid/ugrid2d.py
index 754c7f08a..33782602e 100644
--- a/xugrid/ugrid/ugrid2d.py
+++ b/xugrid/ugrid/ugrid2d.py
@@ -1671,3 +1671,19 @@ def to_shapely(self, dim):
                 f"Dimension {dim} is not a face, node, or edge dimension of the"
                 " Ugrid2d topology."
             )
+
+    def bounding_polygon(self) -> "shapely.Polygon":  # type: ignore # noqa
+        """
+        Construct the bounding polygon of the grid.
+        
+        This polygon may include holes if the grid also contains holes.
+        """
+        import shapely
+
+        def _bbox_area(bounds):
+            return (bounds[2] - bounds[0]) * (bounds[3] - bounds[1])
+
+        edges = self.node_coordinates[self.boundary_node_connectivity]
+        collection = shapely.polygonize(shapely.linestrings(edges))
+        polygon = max(collection.geoms, key=lambda x: _bbox_area(x.bounds))
+        return polygon