the first commit

path_util.py

@@ -0,0 +1,49 @@
+# Copyright 2019 Novartis Institutes for BioMedical Research Inc. Licensed
+# under the Apache License, Version 2.0 (the "License"); you may not use
+# this file except in compliance with the License. You may obtain a copy
+# of the License at http://www.apache.org/licenses/LICENSE-2.0. Unless
+# required by applicable law or agreed to in writing, software distributed
+# under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES
+# OR CONDITIONS OF ANY KIND, either express or implied. See the License for
+# the specific language governing permissions and limitations under the License.
+
+import os
+
+from flask_api import status
+
+import env
+from cellxgene_exception import CellxgeneException
+
+
+def get_dataset(path):
+    if path == "/" or path == "":
+        raise CellxgeneException(
+            "No matching dataset found.", status.HTTP_404_NOT_FOUND
+        )
+
+    trimmed = path[:-1] if path[-1] == "/" else path
+
+    try:
+        get_file_path(trimmed)
+        return trimmed
+    except CellxgeneException:
+        split = os.path.split(trimmed)
+        return get_dataset(split[0])
+
+
+def validate_path(file_path):
+    if not os.path.exists(file_path):
+        raise CellxgeneException(
+            "File does not exist: " + file_path, status.HTTP_400_BAD_REQUEST
+        )
+    if not os.path.isfile(file_path):
+        raise CellxgeneException(
+            "Path is not file: " + file_path, status.HTTP_400_BAD_REQUEST
+        )
+    return
+
+
+def get_file_path(dataset):
+    file_path = os.path.join(env.cellxgene_data, dataset)
+    validate_path(file_path)
+    return file_path