reminder-bot/bot/services/time_service.py

"""Time and timezone utilities."""

from datetime import datetime, time, timedelta
from zoneinfo import ZoneInfo
from typing import Optional

from bot.logging_config import get_logger

logger = get_logger(__name__)


class TimeService:
    """Service for time-related operations."""

    def __init__(self, timezone: str = "Europe/Moscow"):
        """
        Initialize TimeService.

        Args:
            timezone: Timezone name (e.g., "Europe/Moscow")
        """
        self.timezone = ZoneInfo(timezone)
        logger.info(f"TimeService initialized with timezone: {timezone}")

    def get_now(self) -> datetime:
        """
        Get current datetime in configured timezone (as naive).

        Returns:
            Current datetime in local timezone (Moscow), naive
        """
        # Get aware datetime in configured timezone, then strip timezone
        aware_now = datetime.now(self.timezone)
        return aware_now.replace(tzinfo=None)

    def combine_date_time(self, date: datetime, time_of_day: time) -> datetime:
        """
        Combine date and time as naive datetime.

        Args:
            date: Date component
            time_of_day: Time component

        Returns:
            Combined naive datetime
        """
        return datetime.combine(date.date(), time_of_day)

    def calculate_first_run_time(
        self,
        time_of_day: time,
        from_datetime: Optional[datetime] = None,
    ) -> datetime:
        """
        Calculate the nearest future occurrence of time_of_day (today or tomorrow).
        Used for new reminders and resume.

        Args:
            time_of_day: Desired time of day
            from_datetime: Base datetime (defaults to now)

        Returns:
            Next run datetime (today if time hasn't passed, otherwise tomorrow)
        """
        if from_datetime is None:
            from_datetime = self.get_now()

        next_run = self.combine_date_time(from_datetime, time_of_day)

        if next_run <= from_datetime:
            next_run += timedelta(days=1)

        return next_run

    def calculate_next_run_with_interval(
        self,
        time_of_day: time,
        days_interval: int,
        from_datetime: Optional[datetime] = None,
    ) -> datetime:
        """
        Calculate next run datetime using interval offset from now.
        Used when interval is changed.

        Args:
            time_of_day: Desired time of day
            days_interval: Days between reminders
            from_datetime: Base datetime (defaults to now)

        Returns:
            Datetime at time_of_day, days_interval days from from_datetime
        """
        if from_datetime is None:
            from_datetime = self.get_now()

        target_date = from_datetime + timedelta(days=days_interval)
        return self.combine_date_time(target_date, time_of_day)

    def calculate_next_occurrence(
        self,
        current_run: datetime,
        days_interval: int,
    ) -> datetime:
        """
        Calculate next occurrence after a completed/sent reminder.
        Guarantees the result is in the future.

        Args:
            current_run: Current run datetime
            days_interval: Days between reminders

        Returns:
            Next occurrence datetime (always in the future)
        """
        now = self.get_now()
        next_run = current_run + timedelta(days=days_interval)

        while next_run <= now:
            next_run += timedelta(days=days_interval)

        return next_run

    def add_hours(self, dt: datetime, hours: int) -> datetime:
        """
        Add hours to a datetime.

        Args:
            dt: Base datetime
            hours: Hours to add

        Returns:
            New datetime
        """
        return dt + timedelta(hours=hours)

    def format_next_run(self, next_run: datetime) -> str:
        """
        Format next run datetime for display.

        Args:
            next_run: Next run datetime (naive UTC)

        Returns:
            Formatted string
        """
        now = self.get_now()

        # If it's today
        if next_run.date() == now.date():
            return f"сегодня в {next_run.strftime('%H:%M')}"

        # If it's tomorrow
        tomorrow = (now + timedelta(days=1)).date()
        if next_run.date() == tomorrow:
            return f"завтра в {next_run.strftime('%H:%M')}"

        # Otherwise, show full date
        return next_run.strftime("%d.%m.%Y в %H:%M")


# Global instance
_time_service: Optional[TimeService] = None


def get_time_service(timezone: Optional[str] = None) -> TimeService:
    """
    Get global TimeService instance.

    Args:
        timezone: Timezone name (only used for first initialization)

    Returns:
        TimeService instance
    """
    global _time_service
    if _time_service is None:
        if timezone is None:
            from bot.config import get_config
            timezone = get_config().timezone
        _time_service = TimeService(timezone)
    return _time_service