# The Mia! Accounting Flask Project.
# Author: imacat@mail.imacat.idv.tw (imacat), 2023/3/4

#  Copyright (c) 2023 imacat.
#
#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.
"""The date period.

This file is largely taken from the NanoParma ERP project, first written in
2021/9/16 by imacat (imacat@nanoparma.com).

"""
import calendar
import datetime
import re
import typing as t

from accounting.locale import gettext


class Period:
    """A date period."""

    def __init__(self, start: datetime.date | None, end: datetime.date | None):
        """Constructs a new date period.

        :param start: The start date, or None from the very beginning.
        :param end: The end date, or None till no end.
        """
        self.start: datetime.date | None = start
        """The start of the period."""
        self.end: datetime.date | None = end
        """The end of the period."""
        self.is_default: bool = False
        """Whether the is the default period."""
        self.is_this_month: bool = False
        """Whether the period is this month."""
        self.is_last_month: bool = False
        """Whether the period is last month."""
        self.is_since_last_month: bool = False
        """Whether the period is since last month."""
        self.is_this_year: bool = False
        """Whether the period is this year."""
        self.is_last_year: bool = False
        """Whether the period is last year."""
        self.is_today: bool = False
        """Whether the period is today."""
        self.is_yesterday: bool = False
        """Whether the period is yesterday."""
        self.is_all: bool = start is None and end is None
        """Whether the period is all time."""
        self.spec: str = ""
        """The period specification."""
        self.desc: str = ""
        """The text description."""
        self.is_a_month: bool = False
        """Whether the period is a whole month."""
        self.is_type_month: bool = False
        """Whether the period is for the month chooser."""
        self.is_a_year: bool = False
        """Whether the period is a whole year."""
        self.is_a_day: bool = False
        """Whether the period is a single day."""
        self._set_properties()

    def _set_properties(self) -> None:
        """Sets the following properties.

        * self.spec
        * self.desc
        * self.is_a_month
        * self.is_type_month
        * self.is_a_year
        * self.is_a_day

        Override this method to set the properties in the subclasses, to skip
        the calculation.

        :return: None.
        """
        self.spec = PeriodSpecification(self).spec
        self.desc = PeriodDescription(self).desc
        if self.start is None or self.end is None:
            return
        self.is_a_month = self.start.day == 1 \
            and self.end == _month_end(self.start)
        self.is_type_month = self.is_a_month
        self.is_a_year = self.start == datetime.date(self.start.year, 1, 1) \
            and self.end == datetime.date(self.start.year, 12, 31)
        self.is_a_day = self.start == self.end

    @classmethod
    def get_instance(cls, spec: str | None = None) -> t.Self:
        """Returns a period instance.

        :param spec: The period specification, or omit for the default.
        :return: The period instance.
        :raise ValueError: When the period is invalid.
        """
        if spec is None:
            return ThisMonth()
        named_periods: dict[str, t.Type[t.Callable[[], Period]]] = {
            "this-month": lambda: ThisMonth(),
            "last-month": lambda: LastMonth(),
            "since-last-month": lambda: SinceLastMonth(),
            "this-year": lambda: ThisYear(),
            "last-year": lambda: LastYear(),
            "today": lambda: Today(),
            "yesterday": lambda: Yesterday(),
            "all-time": lambda: AllTime(),
        }
        if spec in named_periods:
            return named_periods[spec]()
        start: datetime.date
        end: datetime.date
        start, end = _parse_period_spec(spec)
        if start is not None and end is not None and start > end:
            raise ValueError
        return cls(start, end)

    def is_year(self, year: int) -> bool:
        """Returns whether the period is the specific year period.

        :param year: The year.
        :return: True if the period is the year period, or False otherwise.
        """
        if not self.is_a_year:
            return False
        return self.start.year == year

    @property
    def is_type_arbitrary(self) -> bool:
        """Returns whether this period is an arbitrary period.

        :return: True if this is an arbitrary period, or False otherwise.
        """
        return not self.is_type_month and not self.is_a_year \
            and not self.is_a_day

    @property
    def before(self) -> t.Self | None:
        """Returns the period before this period.

        :return: The period before this period.
        """
        if self.start is None:
            return None
        return Period(None, self.start - datetime.timedelta(days=1))


class PeriodSpecification:
    """The period specification composer."""

    def __init__(self, period: Period):
        """Constructs the period specification composer.

        :param period: The period.
        """
        self.__start: datetime.date = period.start
        self.__end: datetime.date = period.end
        self.spec: str = self.__get_spec()

    def __get_spec(self) -> str:
        """Returns the period specification.

        :return: The period specification.
        """
        if self.__start is None and self.__end is None:
            return "-"
        if self.__end is None:
            return self.__get_since_spec()
        if self.__start is None:
            return self.__get_until_spec()
        try:
            return self.__get_year_spec()
        except ValueError:
            pass
        try:
            return self.__get_month_spec()
        except ValueError:
            pass
        return self.__get_day_spec()

    def __get_since_spec(self) -> str:
        """Returns the period specification without the end day.

        :return: The period specification without the end day
        """
        if self.__start.month == 1 and self.__start.day == 1:
            return self.__start.strftime("%Y-")
        if self.__start.day == 1:
            return self.__start.strftime("%Y-%m-")
        return self.__start.strftime("%Y-%m-%d-")

    def __get_until_spec(self) -> str:
        """Returns the period specification without the start day.

        :return: The period specification without the start day
        """
        if self.__end.month == 12 and self.__end.day == 31:
            return self.__end.strftime("-%Y")
        if (self.__end + datetime.timedelta(days=1)).day == 1:
            return self.__end.strftime("-%Y-%m")
        return self.__end.strftime("-%Y-%m-%d")

    def __get_year_spec(self) -> str:
        """Returns the period specification as a year range.

        :return: The period specification as a year range.
        :raise ValueError: The period is not a year range.
        """
        if self.__start.month != 1 or self.__start.day != 1 \
                or self.__end.month != 12 or self.__end.day != 31:
            raise ValueError
        if self.__start.year == self.__end.year:
            return "%04d" % self.__start.year
        return "%04d-%04d" % (self.__start.year, self.__end.year)

    def __get_month_spec(self) -> str:
        """Returns the period specification as a month range.

        :return: The period specification as a month range.
        :raise ValueError: The period is not a month range.
        """
        if self.__start.day != 1 or self.__end != _month_end(self.__end):
            raise ValueError
        if self.__start.year == self.__end.year \
                and self.__start.month == self.__end.month:
            return "%04d-%02d" % (self.__start.year, self.__start.month)
        return "%04d-%02d-%04d-%02d" % (
            self.__start.year, self.__start.month,
            self.__end.year, self.__end.month)

    def __get_day_spec(self) -> str:
        """Returns the period specification as a day range.

        :return: The period specification as a day range.
        :raise ValueError: The period is a month or year range.
        """
        if self.__start == self.__end:
            return "%04d-%02d-%02d" % (
                self.__start.year, self.__start.month, self.__start.day)
        return "%04d-%02d-%02d-%04d-%02d-%02d" % (
            self.__start.year, self.__start.month, self.__start.day,
            self.__end.year, self.__end.month, self.__end.day)


class PeriodDescription:
    """The period description composer."""

    def __init__(self, period: Period):
        """Constructs the period description composer.

        :param period: The period.
        """
        self.__start: datetime.date = period.start
        self.__end: datetime.date = period.end
        self.desc: str = self.__get_desc()

    def __get_desc(self) -> str:
        """Returns the period description.

        :return: The period description.
        """
        if self.__start is None and self.__end is None:
            return gettext("for all time")
        if self.__start is None:
            return self.__get_until_desc()
        if self.__end is None:
            return self.__get_since_desc()
        try:
            return self.__get_year_desc()
        except ValueError:
            pass
        try:
            return self.__get_month_desc()
        except ValueError:
            pass
        return self.__get_day_desc()

    def __get_since_desc(self) -> str:
        """Returns the description without the end day.

        :return: The description without the end day.
        """
        def get_start_desc() -> str:
            """Returns the description of the start day.

            :return: The description of the start day.
            """
            if self.__start.month == 1 and self.__start.day == 1:
                return str(self.__start.year)
            if self.__start.day == 1:
                return self.__format_month(self.__start)
            return self.__format_date(self.__start)

        return gettext("since %(start)s", start=get_start_desc())

    def __get_until_desc(self) -> str:
        """Returns the description without the start day.

        :return: The description without the start day.
        """
        def get_end_desc() -> str:
            """Returns the description of the end day.

            :return: The description of the end day.
            """
            if self.__end.month == 12 and self.__end.day == 31:
                return str(self.__end.year)
            if (self.__end + datetime.timedelta(days=1)).day == 1:
                return self.__format_month(self.__end)
            return self.__format_date(self.__end)

        return gettext("until %(end)s", end=get_end_desc())

    def __get_year_desc(self) -> str:
        """Returns the description as a year range.

        :return: The description as a year range.
        :raise ValueError: The period is not a year range.
        """
        if self.__start.month != 1 or self.__start.day != 1 \
                or self.__end.month != 12 or self.__end.day != 31:
            raise ValueError
        start: str = str(self.__start.year)
        if self.__start.year == self.__end.year:
            return self.__get_in_desc(start)
        return self.__get_from_to_desc(start, str(self.__end.year))

    def __get_month_desc(self) -> str:
        """Returns the description as a month range.

        :return: The description as a month range.
        :raise ValueError: The period is not a month range.
        """
        if self.__start.day != 1 or self.__end != _month_end(self.__end):
            raise ValueError
        start: str = self.__format_month(self.__start)
        if self.__start.year == self.__end.year \
                and self.__start.month == self.__end.month:
            return self.__get_in_desc(start)
        if self.__start.year == self.__end.year:
            return self.__get_from_to_desc(start, str(self.__end.month))
        return self.__get_from_to_desc(start, self.__format_month(self.__end))

    def __get_day_desc(self) -> str:
        """Returns the description as a day range.

        :return: The description as a day range.
        :raise ValueError: The period is a month or year range.
        """
        start: str = self.__format_day(self.__start)
        if self.__start == self.__end:
            return self.__get_in_desc(start)
        if self.__start.year == self.__end.year \
                and self.__start.month == self.__end.month:
            return self.__get_from_to_desc(start, str(self.__end.day))
        if self.__start.year == self.__end.year:
            end_month_day: str = f"{self.__end.month}/{self.__end.day}"
            return self.__get_from_to_desc(start, end_month_day)
        return self.__get_from_to_desc(start, self.__format_day(self.__end))

    @staticmethod
    def __format_date(date: datetime.date) -> str:
        """Formats a date.

        :param date: The date.
        :return: The formatted date.
        """
        return f"{date.year}/{date.month}/{date.day}"

    @staticmethod
    def __format_month(month: datetime.date) -> str:
        """Formats a month.

        :param month: The month.
        :return: The formatted month.
        """
        return f"{month.year}/{month.month}"

    @staticmethod
    def __format_day(day: datetime.date) -> str:
        """Formats a day.

        :param day: The day.
        :return: The formatted day.
        """
        return f"{day.year}/{day.month}/{day.day}"

    @staticmethod
    def __get_in_desc(period: str) -> str:
        """Returns the description of a whole year, month, or day.

        :param period: The time period.
        :return: The description of a whole year, month, or day.
        """
        return gettext("in %(period)s", period=period)

    @staticmethod
    def __get_from_to_desc(start: str, end: str) -> str:
        """Returns the description of a separated start and end.

        :param start: The start.
        :param end: The end.
        :return: The description of the separated start and end.
        """
        return gettext("in %(start)s-%(end)s", start=start, end=end)


class ThisMonth(Period):
    """The period of this month."""
    def __init__(self):
        today: datetime.date = datetime.date.today()
        this_month_start: datetime.date \
            = datetime.date(today.year, today.month, 1)
        super().__init__(this_month_start, _month_end(today))
        self.is_default = True
        self.is_this_month = True

    def _set_properties(self) -> None:
        self.spec = "this-month"
        self.desc = gettext("This month")
        self.is_a_month = True
        self.is_type_month = True


class LastMonth(Period):
    """The period of this month."""
    def __init__(self):
        today: datetime.date = datetime.date.today()
        year: int = today.year
        month: int = today.month - 1
        if month < 1:
            year = year - 1
            month = 12
        start: datetime.date = datetime.date(year, month, 1)
        super().__init__(start, _month_end(start))
        self.is_last_month = True

    def _set_properties(self) -> None:
        self.spec = "last-month"
        self.desc = gettext("Last month")
        self.is_a_month = True
        self.is_type_month = True


class SinceLastMonth(Period):
    """The period of this month."""
    def __init__(self):
        today: datetime.date = datetime.date.today()
        year: int = today.year
        month: int = today.month - 1
        if month < 1:
            year = year - 1
            month = 12
        start: datetime.date = datetime.date(year, month, 1)
        super().__init__(start, None)
        self.is_since_last_month = True

    def _set_properties(self) -> None:
        self.spec = "since-last-month"
        self.desc = gettext("Since last month")
        self.is_type_month = True


class ThisYear(Period):
    """The period of this year."""
    def __init__(self):
        year: int = datetime.date.today().year
        start: datetime.date = datetime.date(year, 1, 1)
        end: datetime.date = datetime.date(year, 12, 31)
        super().__init__(start, end)
        self.is_this_year = True

    def _set_properties(self) -> None:
        self.spec = "this-year"
        self.desc = gettext("This year")
        self.is_a_year = True


class LastYear(Period):
    """The period of last year."""
    def __init__(self):
        year: int = datetime.date.today().year
        start: datetime.date = datetime.date(year - 1, 1, 1)
        end: datetime.date = datetime.date(year - 1, 12, 31)
        super().__init__(start, end)
        self.is_last_year = True

    def _set_properties(self) -> None:
        self.spec = "last-year"
        self.desc = gettext("Last year")
        self.is_a_year = True


class Today(Period):
    """The period of today."""
    def __init__(self):
        today: datetime.date = datetime.date.today()
        super().__init__(today, today)
        self.is_today = True

    def _set_properties(self) -> None:
        self.spec = "today"
        self.desc = gettext("Today")
        self.is_a_day = True


class Yesterday(Period):
    """The period of yesterday."""
    def __init__(self):
        yesterday: datetime.date \
            = datetime.date.today() - datetime.timedelta(days=1)
        super().__init__(yesterday, yesterday)
        self.is_yesterday = True

    def _set_properties(self) -> None:
        self.spec = "yesterday"
        self.desc = gettext("Yesterday")
        self.is_a_day = True


class AllTime(Period):
    """The period of all time."""
    def __init__(self):
        super().__init__(None, None)
        self.is_all = True

    def _set_properties(self) -> None:
        self.spec = "all-time"
        self.desc = gettext("All")


class TemplatePeriod(Period):
    """The period template."""
    def __init__(self):
        super().__init__(None, None)

    def _set_properties(self) -> None:
        self.spec = "PERIOD"


class YearPeriod(Period):
    """A year period."""

    def __init__(self, year: int):
        """Constructs a year period.

        :param year: The year.
        """
        start: datetime.date = datetime.date(year, 1, 1)
        end: datetime.date = datetime.date(year, 12, 31)
        super().__init__(start, end)


DATE_SPEC_RE: str = r"(\d{4})(?:-(\d{2})(?:-(\d{2}))?)?"
"""The regular expression of a date specification."""


def _parse_period_spec(text: str) \
        -> tuple[datetime.date | None, datetime.date | None]:
    """Parses the period specification.

    :param text: The period specification.
    :return: The start and end day of the period.  The start and end day
        may be None.
    :raise ValueError: When the date is invalid.
    """
    if text == "-":
        return None, None
    m = re.match(f"^{DATE_SPEC_RE}$", text)
    if m is not None:
        return __get_start(m[1], m[2], m[3]), \
               __get_end(m[1], m[2], m[3])
    m = re.match(f"^{DATE_SPEC_RE}-$", text)
    if m is not None:
        return __get_start(m[1], m[2], m[3]), None
    m = re.match(f"-{DATE_SPEC_RE}$", text)
    if m is not None:
        return None, __get_end(m[1], m[2], m[3])
    m = re.match(f"^{DATE_SPEC_RE}-{DATE_SPEC_RE}$", text)
    if m is not None:
        return __get_start(m[1], m[2], m[3]), \
               __get_end(m[4], m[5], m[6])
    raise ValueError


def __get_start(year: str, month: str | None, day: str | None)\
        -> datetime.date:
    """Returns the start of the period from the date representation.

    :param year: The year.
    :param month: The month, if any.
    :param day: The day, if any.
    :return: The start of the period.
    :raise ValueError: When the date is invalid.
    """
    if day is not None:
        return datetime.date(int(year), int(month), int(day))
    if month is not None:
        return datetime.date(int(year), int(month), 1)
    return datetime.date(int(year), 1, 1)


def __get_end(year: str, month: str | None, day: str | None)\
        -> datetime.date:
    """Returns the end of the period from the date representation.

    :param year: The year.
    :param month: The month, if any.
    :param day: The day, if any.
    :return: The end of the period.
    :raise ValueError: When the date is invalid.
    """
    if day is not None:
        return datetime.date(int(year), int(month), int(day))
    if month is not None:
        year_n: int = int(year)
        month_n: int = int(month)
        day_n: int = calendar.monthrange(year_n, month_n)[1]
        return datetime.date(year_n, month_n, day_n)
    return datetime.date(int(year), 12, 31)


def _month_end(date: datetime.date) -> datetime.date:
    """Returns the end day of month for a date.

    :param date: The date.
    :return: The end day of the month of that day.
    """
    day: int = calendar.monthrange(date.year, date.month)[1]
    return datetime.date(date.year, date.month, day)