feat: handle error when fetching file for future day

aoc/input_file.py

@@ -1,3 +1,4 @@
+import datetime
 import pathlib
 
 import requests
@@ -15,8 +16,21 @@ def download(year: int, day: int, session_token: str | None) -> bytes:
     response = requests.get(url, cookies=cookies)
 
     if response.status_code != 200:
+        status = response.status_code
+
+        # https://stackoverflow.com/a/39079819/11286805
+        local_tz = datetime.datetime.now(datetime.timezone.utc).astimezone().tzinfo
+
+        now = datetime.datetime.now(local_tz)
+        release = datetime.datetime(year, 12, day, 5, tzinfo=datetime.UTC)
+
+        if now < release:
             raise exceptions.AocError(
-            f"failed to fetch input file {year}/{day:02} (http:{response.status_code})"
+                f"unreleased input file {year}/{day:02} (http:{status})"
+            )
+
+        raise exceptions.AocError(
+            f"failed to fetch input file {year}/{day:02} (http:{status})"
             " - is AOC_SESSION_TOKEN environment variable set?"
         )