1 files changed, 62 insertions, 0 deletions
diff --git a/pysite/utils/time.py b/pysite/utils/time.py
new file mode 100644
index 00000000..334408a4
--- /dev/null
+++ b/pysite/utils/time.py
@@ -0,0 +1,62 @@
+from datetime import datetime, timedelta
+
+from rethinkdb import make_timezone
+
+
+UNITS = {
+    's': lambda value: value,
+    'm': lambda value: value * 60,
+    'h': lambda value: value * 60 * 60,
+    'd': lambda value: value * 60 * 60 * 24,
+    'w': lambda value: value * 60 * 60 * 24 * 7
+}
+
+
+def parse_duration(duration: str) -> datetime:
+    """
+    Parses a string like '3w' into a datetime 3 weeks from now.
+
+    Also supports strings like 1w2d or 1h25m.
+
+    This function is adapted from a bot called ROWBOAT, written by b1naryth1ef.
+    See https://github.com/b1naryth1ef/rowboat/blob/master/rowboat/util/input.py
+
+    :param duration: a string containing the number and a time unit shorthand.
+    :return: A datetime representing now + the duration
+    """
+
+    if not duration:
+        raise ValueError("No duration provided.")
+
+    value = 0
+    digits = ''
+
+    for char in duration:
+
+        # Add all numbers to the digits string
+        if char.isdigit():
+            digits += char
+            continue
+
+        # If it's not a number and not one of the letters in UNITS, it must be invalid.
+        if char not in UNITS or not digits:
+            raise ValueError("Invalid duration")
+
+        # Otherwise, call the corresponding lambda to convert the value, and keep iterating.
+        value += UNITS[char](int(digits))
+        digits = ''
+
+    return datetime.now(make_timezone("00:00")) + timedelta(seconds=value + 1)
+
+
+def is_expired(rdb_datetime: datetime) -> bool:
+    """
+    Takes a rethinkdb datetime (timezone aware) and
+    figures out if it has expired yet.
+
+    Always compares with UTC 00:00
+
+    :param rdb_timestamp: A datetime as stored in rethinkdb.
+    :return: True if the datetime is in the past.
+    """
+    return datetime.now(make_timezone("00:00")) > rdb_datetime