Add `.ib.venues` for mkt-venue-closure checkers

Introduce set of helper-fns for detecting venue open/close status,
session start/end times, and related time-gap detection using
`pendulum`.

Deats,
- add `iter_sessions()` to yield `pendulum.Interval`s from
  a `ContractDetails` instance.
- add `is_venue_open()` to check if active at a given time.
- add `is_venue_closure()` to detect valid closure gaps.
- add `sesh_times()` to extract weekday-agnostic open/close times.
- add `has_weekend()` to check for Sat/Sun in interval.
- move in lowlevel `is_current_time_in_range()` for checking a
  datetime within a `sesh: pendulum.Interval`.

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

piker/brokers/ib/venues.py

@@ -0,0 +1,151 @@
+# piker: trading gear for hackers
+# Copyright (C) Tyler Goodlet (in stewardship for pikers)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+'''
+(Multi-)venue mgmt helpers.
+
+IB generally supports all "legacy" trading venues, those mostly owned
+by ICE and friends.
+
+'''
+from __future__ import annotations
+from datetime import (  # noqa
+    datetime,
+    date,
+    tzinfo as TzInfo,
+)
+from typing import (
+    Iterator,
+    TYPE_CHECKING,
+)
+
+from pendulum import (
+    now,
+    Duration,
+    Interval,
+    Time,
+)
+
+if TYPE_CHECKING:
+    from ib_insync import (
+        TradingSession,
+        ContractDetails,
+    )
+
+
+def has_weekend(
+    period: Interval,
+) -> bool:
+    has_weekend: bool = False
+    for dt in period:
+        if dt.day_of_week in [0, 6]: # 0=Sunday, 6=Saturday
+            has_weekend = True
+            break
+
+    return has_weekend
+
+
+def is_current_time_in_range(
+    sesh: Interval,
+    when: datetime|None = None,
+) -> bool:
+    '''
+    Check if current time is within the datetime range.
+
+    Use any/the-same timezone as provided by `start_dt.tzinfo` value
+    in the range.
+
+    '''
+    when: datetime = when or now()
+    return when in sesh
+
+
+def iter_sessions(
+    con_deats: ContractDetails,
+) -> Iterator[Interval]:
+    '''
+    Yield `pendulum.Interval`s for all
+    `ibas.ContractDetails.tradingSessions() -> TradingSession`s.
+
+    '''
+    sesh: TradingSession
+    for sesh in con_deats.tradingSessions():
+        yield Interval(*sesh)
+
+
+def sesh_times(
+    con_deats: ContractDetails,
+) -> tuple[Time, Time]:
+    '''
+    Based on the earliest trading session provided by the IB API,
+    get the (day-agnostic) times for the start/end.
+
+    '''
+    earliest_sesh: Interval = next(iter_sessions(con_deats))
+    return (
+        earliest_sesh.start.time(),
+        earliest_sesh.end.time(),
+    )
+    # ^?TODO, use `.diff()` to get point-in-time-agnostic period?
+    # https://pendulum.eustace.io/docs/#difference
+
+
+def is_venue_open(
+    con_deats: ContractDetails,
+    when: datetime|Duration|None = None,
+) -> bool:
+    '''
+    Check if market-venue is open during `when`, which defaults to
+    "now".
+
+    '''
+    sesh: Interval
+    for sesh in iter_sessions(con_deats):
+        if is_current_time_in_range(
+            sesh=sesh,
+            when=when,
+        ):
+            return True
+
+    return False
+
+
+def is_venue_closure(
+    gap: Interval,
+    con_deats: ContractDetails,
+) -> bool:
+    '''
+    Check if a provided time-`gap` is just an (expected) trading
+    venue closure period.
+
+    '''
+    open: Time
+    close: Time
+    open, close = sesh_times(con_deats)
+    # TODO! ensure this works!
+    # breakpoint()
+    if (
+        (
+            gap.start.time() == close
+            and
+            gap.end.time() == open
+        )
+        or
+        has_weekend(gap)
+    ):
+        return True
+
+    return False