Add multiregion function object reader support

flowboost/openfoam/data/base.py

@@ -97,21 +97,39 @@ def discover_function_objects(self) -> dict[str, dict[str, list[Path]]]:
 
         function_objects = {}
         for function_dir in filter(Path.is_dir, self.post_processing_path.iterdir()):
-            time_dirs = self._time_dirs_for_function_object(function_dir)
-
-            function_objects[function_dir.name] = {
-                time_dir.name: sorted(
-                    (path for path in time_dir.iterdir() if path.is_file()),
-                    key=lambda path: path.name,
-                )
-                for time_dir in time_dirs
-            }
+            direct_outputs = self._files_by_time_directory(function_dir)
+            if direct_outputs:
+                function_objects[function_dir.name] = direct_outputs
+
+            # Multi-region function objects often add one extra nesting level:
+            # postProcessing/<region>/<functionObject>/<time>/...
+            for nested_function_dir in filter(Path.is_dir, function_dir.iterdir()):
+                nested_outputs = self._files_by_time_directory(nested_function_dir)
+                if nested_outputs:
+                    function_objects[
+                        f"{function_dir.name}/{nested_function_dir.name}"
+                    ] = nested_outputs
 
         return function_objects
 
     def _time_dirs_for_function_object(self, fo_folder: Path) -> list[Path]:
         return list(filter(Path.is_dir, fo_folder.iterdir()))
 
+    def _files_by_time_directory(self, fo_folder: Path) -> dict[str, list[Path]]:
+        """Return a time->files mapping when *fo_folder* has standard output."""
+        time_dirs = self._time_dirs_for_function_object(fo_folder)
+        outputs = {
+            time_dir.name: sorted(
+                (path for path in time_dir.iterdir() if path.is_file()),
+                key=lambda path: path.name,
+            )
+            for time_dir in time_dirs
+        }
+
+        # Only treat the folder as a function-object output when at least one
+        # time directory contains files.
+        return {time: files for time, files in outputs.items() if files}
+
     # -- simple_function_object_reader ------------------------------------
 
     @overload
@@ -160,6 +178,8 @@ def simple_function_object_reader(
                 at_time=at_time,
             )
 
+        function_object_name = function_object_name.strip("/")
+
         function_objects = self.discover_function_objects()
 
         if function_object_name not in function_objects:

tests/flowboost/openfoam/test_data_unit.py

@@ -196,3 +196,42 @@ def test_simple_reader_loads_single_extensionless_output(self, tmp_path):
             {"column_1": 0.1, "column_2": 1.0},
             {"column_1": 0.2, "column_2": 2.0},
         ]
+
+    def test_discovers_multiregion_function_objects(self, tmp_path):
+        fo_file = (
+            tmp_path
+            / "postProcessing"
+            / "fluid"
+            / "cylinderT"
+            / "0"
+            / "surfaceFieldValue.dat"
+        )
+        fo_file.parent.mkdir(parents=True)
+        fo_file.write_text("# Time\tareaAverage(T)\n0.1\t297.0\n0.2\t298.0\n")
+
+        data = PolarsData(path=tmp_path)
+        discovered = data.discover_function_objects()
+
+        assert discovered["fluid/cylinderT"]["0"] == [fo_file]
+
+    def test_simple_reader_loads_multiregion_function_object(self, tmp_path):
+        fo_file = (
+            tmp_path
+            / "postProcessing"
+            / "fluid"
+            / "cylinderT"
+            / "0"
+            / "surfaceFieldValue.dat"
+        )
+        fo_file.parent.mkdir(parents=True)
+        fo_file.write_text("# Time\tareaAverage(T)\n0.1\t297.0\n0.2\t298.0\n")
+
+        data = PolarsData(path=tmp_path)
+        df = data.simple_function_object_reader("/fluid/cylinderT")
+
+        assert df is not None
+        assert df.columns == ["Time", "areaAverage(T)"]
+        assert df.to_dicts() == [
+            {"Time": 0.1, "areaAverage(T)": 297.0},
+            {"Time": 0.2, "areaAverage(T)": 298.0},
+        ]