Localize notification_utils to the API

This changeset pulls in all of the notification_utils code directly into the API and removes it as an external dependency.  We are doing this to cut down on operational maintenance of the project and will begin removing parts of it no longer needed for the API.

Signed-off-by: Carlo Costino <carlo.costino@gsa.gov>

notifications_utils/letter_timings.py

@@ -0,0 +1,180 @@
+from collections import namedtuple
+from datetime import datetime, time, timedelta
+
+import pytz
+from govuk_bank_holidays.bank_holidays import BankHolidays
+
+from notifications_utils.countries.data import Postage
+from notifications_utils.timezones import utc_string_to_aware_gmt_datetime
+
+LETTER_PROCESSING_DEADLINE = time(17, 30)
+CANCELLABLE_JOB_LETTER_STATUSES = [
+    "created",
+    "cancelled",
+    "virus-scan-failed",
+    "validation-failed",
+    "technical-failure",
+    "pending-virus-check",
+]
+
+
+non_working_days_dvla = BankHolidays(
+    use_cached_holidays=True,
+    weekend=(5, 6),
+)
+non_working_days_royal_mail = BankHolidays(
+    use_cached_holidays=True,
+    weekend=(6,),  # Only Sunday (day 6 of the week) is a non-working day
+)
+
+
+def set_gmt_hour(day, hour):
+    return (
+        day.astimezone(pytz.timezone("Europe/London"))
+        .replace(hour=hour, minute=0)
+        .astimezone(pytz.utc)
+    )
+
+
+def get_next_work_day(date, non_working_days):
+    next_day = date + timedelta(days=1)
+    if non_working_days.is_work_day(
+        date=next_day.date(),
+        division=BankHolidays.ENGLAND_AND_WALES,
+    ):
+        return next_day
+    return get_next_work_day(next_day, non_working_days)
+
+
+def get_next_dvla_working_day(date):
+    """
+    Printing takes place monday to friday, excluding bank holidays
+    """
+    return get_next_work_day(date, non_working_days=non_working_days_dvla)
+
+
+def get_next_royal_mail_working_day(date):
+    """
+    Royal mail deliver letters on monday to saturday
+    """
+    return get_next_work_day(date, non_working_days=non_working_days_royal_mail)
+
+
+def get_delivery_day(date, *, days_to_deliver):
+    next_day = get_next_royal_mail_working_day(date)
+    if days_to_deliver == 1:
+        return next_day
+    return get_delivery_day(next_day, days_to_deliver=(days_to_deliver - 1))
+
+
+def get_min_and_max_days_in_transit(postage):
+    return {
+        # first class post is printed earlier in the day, so will
+        # actually transit on the printing day, and be delivered the next
+        # day, so effectively spends no full days in transit
+        "first": (0, 0),
+        "second": (1, 2),
+        Postage.EUROPE: (3, 5),
+        Postage.REST_OF_WORLD: (5, 7),
+    }[postage]
+
+
+def get_earliest_and_latest_delivery(print_day, postage):
+    for days_to_transit in get_min_and_max_days_in_transit(postage):
+        yield get_delivery_day(print_day, days_to_deliver=1 + days_to_transit)
+
+
+def get_letter_timings(upload_time, postage):
+    LetterTimings = namedtuple(
+        "LetterTimings", "printed_by, is_printed, earliest_delivery, latest_delivery"
+    )
+
+    # shift anything after 5:30pm to the next day
+    processing_day = utc_string_to_aware_gmt_datetime(upload_time) + timedelta(
+        hours=6, minutes=30
+    )
+    print_day = get_next_dvla_working_day(processing_day)
+
+    earliest_delivery, latest_delivery = get_earliest_and_latest_delivery(
+        print_day, postage
+    )
+
+    # print deadline is 3pm BST
+    printed_by = set_gmt_hour(print_day, hour=15)
+    now = (
+        datetime.utcnow()
+        .replace(tzinfo=pytz.utc)
+        .astimezone(pytz.timezone("Europe/London"))
+    )
+
+    return LetterTimings(
+        printed_by=printed_by,
+        is_printed=(now > printed_by),
+        earliest_delivery=set_gmt_hour(earliest_delivery, hour=16),
+        latest_delivery=set_gmt_hour(latest_delivery, hour=16),
+    )
+
+
+def letter_can_be_cancelled(notification_status, notification_created_at):
+    """
+    If letter does not have status of created or pending-virus-check
+        => can't be cancelled (it has already been processed)
+
+    If it's after 5.30pm local time and the notification was created today before 5.30pm local time
+        => can't be cancelled (it will already be zipped up to be sent)
+    """
+    if notification_status not in ("created", "pending-virus-check"):
+        return False
+
+    if too_late_to_cancel_letter(notification_created_at):
+        return False
+    return True
+
+
+def too_late_to_cancel_letter(notification_created_at):
+    time_created_at = notification_created_at
+    day_created_on = time_created_at.date()
+
+    current_time = datetime.utcnow()
+    current_day = current_time.date()
+    if (
+        _after_letter_processing_deadline()
+        and _notification_created_before_today_deadline(notification_created_at)
+    ):
+        return True
+    if (
+        _notification_created_before_that_day_deadline(notification_created_at)
+        and day_created_on < current_day
+    ):
+        return True
+    if (current_day - day_created_on).days > 1:
+        return True
+
+
+def _after_letter_processing_deadline():
+    current_utc_datetime = datetime.utcnow()
+    bst_time = current_utc_datetime.time()
+
+    return bst_time >= LETTER_PROCESSING_DEADLINE
+
+
+def _notification_created_before_today_deadline(notification_created_at):
+    current_bst_datetime = datetime.utcnow()
+    todays_deadline = current_bst_datetime.replace(
+        hour=LETTER_PROCESSING_DEADLINE.hour,
+        minute=LETTER_PROCESSING_DEADLINE.minute,
+    )
+
+    notification_created_at_in_bst = notification_created_at
+
+    return notification_created_at_in_bst <= todays_deadline
+
+
+def _notification_created_before_that_day_deadline(notification_created_at):
+    notification_created_at_bst_datetime = notification_created_at
+    created_at_day_deadline = notification_created_at_bst_datetime.replace(
+        hour=LETTER_PROCESSING_DEADLINE.hour,
+        minute=LETTER_PROCESSING_DEADLINE.minute,
+    )
+
+    return notification_created_at_bst_datetime <= created_at_day_deadline