rss module: prettify & reorganize to allow for easily adding extra modules

my/rss/common.py

@@ -0,0 +1,44 @@
+# shared Rss stuff
+from datetime import datetime
+from typing import NamedTuple, Optional, List, Dict
+
+
+class Subscription(NamedTuple):
+    title: str
+    url: str
+    id: str # TODO not sure about it...
+    # eh, not all of them got reasonable 'created' time
+    created_at: Optional[datetime]
+    subscribed: bool=True
+
+from typing import Iterable, Tuple, Sequence
+
+# snapshot of subscriptions at time
+SubscriptionState = Tuple[datetime, Sequence[Subscription]]
+
+
+def compute_subscriptions(*sources: Iterable[SubscriptionState]) -> List[Subscription]:
+    """
+    Keeps track of everything I ever subscribed to.
+    In addition, keeps track of unsubscribed as well (so you'd remember when and why you unsubscribed)
+    """
+    from itertools import chain
+    states = list(chain.from_iterable(sources))
+    # TODO keep 'source'/'provider'/'service' attribute?
+
+    by_url: Dict[str, Subscription] = {}
+    # ah. dates are used for sorting
+    for when, state in sorted(states):
+        # TODO use 'when'?
+        for feed in state:
+            if feed.url not in by_url:
+                by_url[feed.url] = feed
+
+    _, last_state = max(states, key=lambda x: x[0])
+    last_urls = {f.url for f in last_state}
+
+    res = []
+    for u, x in sorted(by_url.items()):
+        present = u in last_urls
+        res.append(x._replace(subscribed=present))
+    return res