1 files changed, 83 insertions, 0 deletions
diff --git a/app/utils/metadata_parser.py b/app/utils/metadata_parser.py
new file mode 100644
index 0000000..1ed49ab
--- /dev/null
+++ b/app/utils/metadata_parser.py
@@ -0,0 +1,83 @@
+###############################################################################
+# Copyright (c) 2017 Koren Lev (Cisco Systems), Yaron Yogev (Cisco Systems)   #
+# and others                                                                  #
+#                                                                             #
+# All rights reserved. This program and the accompanying materials            #
+# are made available under the terms of the Apache License, Version 2.0       #
+# which accompanies this distribution, and is available at                    #
+# http://www.apache.org/licenses/LICENSE-2.0                                  #
+###############################################################################
+import json
+import os
+from abc import abstractmethod, ABCMeta
+
+from utils.util import get_extension
+
+
+class MetadataParser(metaclass=ABCMeta):
+
+    def __init__(self):
+        super().__init__()
+        self.errors = []
+
+    @abstractmethod
+    def get_required_fields(self) -> list:
+        pass
+
+    def validate_metadata(self, metadata: dict) -> bool:
+        if not isinstance(metadata, dict):
+            raise ValueError('metadata needs to be a valid dict')
+
+        # make sure metadata json contains all fields we need
+        required_fields = self.get_required_fields()
+        if not all([field in metadata for field in required_fields]):
+            raise ValueError("Metadata json should contain "
+                             "all the following fields: {}"
+                             .format(', '.join(required_fields)))
+        return True
+
+    @staticmethod
+    def _load_json_file(file_path: str):
+        with open(file_path) as data_file:
+            return json.load(data_file)
+
+    def _parse_json_file(self, file_path: str):
+        metadata = self._load_json_file(file_path)
+
+        # validate metadata correctness
+        if not self.validate_metadata(metadata):
+            return None
+
+        return metadata
+
+    @staticmethod
+    def check_metadata_file_ok(file_path: str):
+        extension = get_extension(file_path)
+        if extension != 'json':
+            raise ValueError("Extension '{}' is not supported. "
+                             "Please provide a .json metadata file."
+                             .format(extension))
+
+        if not os.path.isfile(file_path):
+            raise ValueError("Couldn't load metadata file. "
+                             "Path '{}' doesn't exist or is not a file"
+                             .format(file_path))
+
+    def parse_metadata_file(self, file_path: str) -> dict:
+        # reset errors in case same parser is used to read multiple inputs
+        self.errors = []
+        self.check_metadata_file_ok(file_path)
+
+        # Try to parse metadata file if it has one of the supported extensions
+        metadata = self._parse_json_file(file_path)
+        self.check_errors()
+        return metadata
+
+    def check_errors(self):
+        if self.errors:
+            raise ValueError("Errors encountered during "
+                             "metadata file parsing:\n{}"
+                             .format("\n".join(self.errors)))
+
+    def add_error(self, msg):
+        self.errors.append(msg)