basic subscriptions system

1 files changed, 84 insertions, 0 deletions

diff --git a/python/atoma/utils.py b/python/atoma/utils.py
new file mode 100644
index 0000000..4dc1ab5
--- /dev/null
+++ b/python/atoma/utils.py
@@ -0,0 +1,84 @@
+from datetime import datetime, timezone
+from xml.etree.ElementTree import Element
+from typing import Optional
+
+import dateutil.parser
+from defusedxml.ElementTree import parse as defused_xml_parse, ParseError
+
+from .exceptions import FeedXMLError, FeedParseError
+
+ns = {
+    'content': 'http://purl.org/rss/1.0/modules/content/',
+    'feed': 'http://www.w3.org/2005/Atom'
+}
+
+
+def parse_xml(xml_content):
+    try:
+        return defused_xml_parse(xml_content)
+    except ParseError:
+        raise FeedXMLError('Not a valid XML document')
+
+
+def get_child(element: Element, name,
+              optional: bool=True) -> Optional[Element]:
+    child = element.find(name, namespaces=ns)
+
+    if child is None and not optional:
+        raise FeedParseError(
+            'Could not parse feed: "{}" does not have a "{}"'
+            .format(element.tag, name)
+        )
+
+    elif child is None:
+        return None
+
+    return child
+
+
+def get_text(element: Element, name, optional: bool=True) -> Optional[str]:
+    child = get_child(element, name, optional)
+    if child is None:
+        return None
+
+    if child.text is None:
+        if optional:
+            return None
+
+        raise FeedParseError(
+            'Could not parse feed: "{}" text is required but is empty'
+            .format(name)
+        )
+
+    return child.text.strip()
+
+
+def get_int(element: Element, name, optional: bool=True) -> Optional[int]:
+    text = get_text(element, name, optional)
+    if text is None:
+        return None
+
+    return int(text)
+
+
+def get_datetime(element: Element, name,
+                 optional: bool=True) -> Optional[datetime]:
+    text = get_text(element, name, optional)
+    if text is None:
+        return None
+
+    return try_parse_date(text)
+
+
+def try_parse_date(date_str: str) -> Optional[datetime]:
+    try:
+        date = dateutil.parser.parse(date_str, fuzzy=True)
+    except (ValueError, OverflowError):
+        return None
+
+    if date.tzinfo is None:
+        # TZ naive datetime, make it a TZ aware datetime by assuming it
+        # contains UTC time
+        date = date.replace(tzinfo=timezone.utc)
+
+    return date