"""Delphi TDateTime implementation."""

import decimal

from dfdatetime import definitions
from dfdatetime import factory
from dfdatetime import interface


class DelphiDateTimeEpoch(interface.DateTimeEpoch):
    """Delphi TDateTime epoch."""

    def __init__(self):
        """Initializes a Delphi TDateTime epoch."""
        super().__init__(1899, 12, 30)


class DelphiDateTime(interface.DateTimeValues):
    """Delphi TDateTime timestamp.

    The Delphi TDateTime timestamp is a floating point value that contains
    the number of days since 1899-12-30 00:00:00 (also known as the epoch).
    Negative values represent date and times predating the epoch.

    The maximal correct date supported by TDateTime values is limited to:
    9999-12-31 23:59:59.999

    Attributes:
      is_local_time (bool): True if the date and time value is in local time.
    """

    # The difference between December 30, 1899 and January 1, 1970 in days.
    _DELPHI_TO_POSIX_BASE = 25569

    _EPOCH = DelphiDateTimeEpoch()

    def __init__(self, precision=None, time_zone_offset=None, timestamp=None):
        """Initializes a Delphi TDateTime timestamp.

        Args:
          precision (Optional[str]): precision of the date and time value, which
              should be one of the PRECISION_VALUES in definitions.
          time_zone_offset (Optional[int]): time zone offset in number of minutes
              from UTC or None if not set.
          timestamp (Optional[float]): Delphi TDateTime timestamp.
        """
        super().__init__(
            precision=precision or definitions.PRECISION_1_MILLISECOND,
            time_zone_offset=time_zone_offset,
        )
        self._timestamp = timestamp

    @property
    def timestamp(self):
        """float: Delphi TDateTime timestamp or None if not set."""
        return self._timestamp

    def _GetNormalizedTimestamp(self):
        """Retrieves the normalized timestamp.

        Returns:
          decimal.Decimal: normalized timestamp, which contains the number of
              seconds since January 1, 1970 00:00:00 and a fraction of second used
              for increased precision, or None if the normalized timestamp cannot be
              determined.
        """
        if self._normalized_timestamp is None:
            if self._timestamp is not None:
                self._normalized_timestamp = (
                    decimal.Decimal(self._timestamp) - self._DELPHI_TO_POSIX_BASE
                )
                self._normalized_timestamp *= definitions.SECONDS_PER_DAY

                if self._time_zone_offset:
                    self._normalized_timestamp -= self._time_zone_offset * 60

        return self._normalized_timestamp

    def CopyFromDateTimeString(self, time_string):
        """Copies a Delphi TDateTime timestamp from a string.

        Args:
          time_string (str): date and time value formatted as:
              YYYY-MM-DD hh:mm:ss.######[+-]##:##

              Where # are numeric digits ranging from 0 to 9 and the seconds
              fraction can be either 3, 6 or 9 digits. The time of day, seconds
              fraction and time zone offset are optional. The default time zone
              is UTC.

        Raises:
          ValueError: if the time string is invalid or not supported.
        """
        date_time_values = self._CopyDateTimeFromString(time_string)

        year = date_time_values.get("year", 0)
        month = date_time_values.get("month", 0)
        day_of_month = date_time_values.get("day_of_month", 0)
        hours = date_time_values.get("hours", 0)
        minutes = date_time_values.get("minutes", 0)
        seconds = date_time_values.get("seconds", 0)
        nanoseconds = date_time_values.get("nanoseconds", 0)
        time_zone_offset = date_time_values.get("time_zone_offset")

        if year > 9999:
            raise ValueError(f"Unsupported year value: {year:d}.")

        timestamp = self._GetNumberOfSecondsFromElements(
            year, month, day_of_month, hours, minutes, seconds
        )
        timestamp = float(timestamp) / definitions.SECONDS_PER_DAY
        timestamp += self._DELPHI_TO_POSIX_BASE
        timestamp += float(nanoseconds) / definitions.NANOSECONDS_PER_DAY

        self._normalized_timestamp = None
        self._timestamp = timestamp
        self._time_zone_offset = time_zone_offset

    def CopyToDateTimeString(self):
        """Copies the Delphi TDateTime timestamp to a date and time string.

        Returns:
          str: date and time value formatted as: "YYYY-MM-DD hh:mm:ss.######" or
              None if the timestamp is missing.
        """
        if self._timestamp is None:
            return None

        number_of_seconds = self._timestamp * definitions.SECONDS_PER_DAY

        number_of_days, hours, minutes, seconds = self._GetTimeValues(
            int(number_of_seconds)
        )
        # The maximum date supported by TDateTime values is limited to:
        # 9999-12-31 23:59:59.999 (approximate 2958465 days since epoch).
        # The minimum date is unknown hence assuming it is limited to:
        # 0001-01-01 00:00:00.000 (approximate -693593 days since epoch).

        if number_of_days < -693593 or number_of_days > 2958465:
            return None

        year, month, day_of_month = self._GetDateValuesWithEpoch(
            number_of_days, self._EPOCH
        )
        microseconds = int(
            (number_of_seconds % 1) * definitions.MICROSECONDS_PER_SECOND
        )
        return (
            f"{year:04d}-{month:02d}-{day_of_month:02d} "
            f"{hours:02d}:{minutes:02d}:{seconds:02d}.{microseconds:06d}"
        )

    def CopyToSerializableDict(self):
        """Copies the date time value to a serializable dictionary.

        Returns:
          dict[str, object]: serializable dictionary.
        """
        serializable_dict = self._CreateSerializableDict()

        serializable_dict["timestamp"] = self._timestamp

        return serializable_dict


factory.Factory.RegisterDateTimeValues(DelphiDateTime)
