core.common: move listify to core.utils.itertools, use better typing annotations for it

also some minor refactoring of my.rss

my/rss/feedbin.py

@@ -2,24 +2,22 @@
 Feedbin RSS reader
 """
 
-from my.config import feedbin as config
-
+import json
 from pathlib import Path
-from typing import Sequence
+from typing import Iterator, Sequence
 
-from my.core.common import listify, get_files
+from my.core import get_files, stat, Stats
 from my.core.compat import fromisoformat
-from .common import Subscription
+from .common import Subscription, SubscriptionState
+
+from my.config import feedbin as config
 
 
 def inputs() -> Sequence[Path]:
     return get_files(config.export_path)
 
 
-import json
-
-@listify
-def parse_file(f: Path):
+def parse_file(f: Path) -> Iterator[Subscription]:
     raw = json.loads(f.read_text())
     for r in raw:
         yield Subscription(
@@ -30,19 +28,14 @@ def parse_file(f: Path):
         )
 
 
-from typing import Iterable
-from .common import SubscriptionState
-def states() -> Iterable[SubscriptionState]:
+def states() -> Iterator[SubscriptionState]:
     for f in inputs():
         # TODO ugh. depends on my naming. not sure if useful?
         dts = f.stem.split('_')[-1]
         dt = fromisoformat(dts)
-        subs = parse_file(f)
+        subs = list(parse_file(f))
         yield dt, subs
 
 
-def stats():
-    from more_itertools import ilen, last
-    return {
-        'subscriptions': ilen(last(states())[1])
-    }
+def stats() -> Stats:
+    return stat(states)