"""Date and time utilities."""

import re
from datetime import datetime

from abacus_common_logic.constants.constants import (
    DATE_FORMAT,
    DATETIME_FORMAT,
    OPERATING_TIMEZONE,
    SYSTEM_TIMEZONE,
)

DATE_REGEXP = r'([0-9]{4})-(1[0-2]|0[1-9])-(3[01]|0[1-9]|[12][0-9])'
TIME_REGEXP = r'([01][0-9]|2[0123]):([0-5][0-9]):([0-5][0-9])'
ISO_DATETIME_REGEXP = re.compile(
    rf'^{DATE_REGEXP}T{TIME_REGEXP}\.\d\d\d\d\d\d([\+-]\d\d:\d\d)?$'
)


def safe_format_date(date, fmt=DATE_FORMAT):
    """Format a date."""
    return date and date.strftime(fmt)


def safe_format_datetime(date_time, fmt=DATETIME_FORMAT):
    """Format datetime to string value."""
    return date_time and date_time.strftime(fmt)


def parse_date(date_string, fmt=DATE_FORMAT):
    """Attempt to parse a date string using provided date format."""
    return datetime.strptime(date_string, fmt).date()


def parse_datetime(datetime_string, fmt=DATETIME_FORMAT):
    """Parse a datetime string and return datetime object."""
    return datetime.strptime(datetime_string, fmt)


def current_timestamp(timezone=SYSTEM_TIMEZONE):
    """Return the current timestamp in the internal system timezone."""
    return datetime.now(timezone)


def operating_date(timestamp, operating_tz=OPERATING_TIMEZONE):
    """Given a timestamp, return its date in the operating timezone.

    If the timestamp is not timezone-aware, it is assumed to be in UTC.
    """
    with_tz = (
        timestamp if timestamp.tzinfo else timestamp.replace(tzinfo=SYSTEM_TIMEZONE)
    )
    return with_tz.astimezone(operating_tz).date()


def is_iso_datetime(str_datetime):
    """Check if given string value matches iso datetime format."""
    return bool(ISO_DATETIME_REGEXP.match(str_datetime))