"""books - Tools for loading the books"""

# Copyright © 2020  Brett Smith

#

# This program is free software: you can redistribute it and/or modify

# it under the terms of the GNU Affero General Public License as published by

# the Free Software Foundation, either version 3 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU Affero General Public License for more details.

#

# You should have received a copy of the GNU Affero General Public License

# along with this program.  If not, see <https://www.gnu.org/licenses/>.

import datetime

from pathlib import Path

from beancount import loader as bc_loader

from typing import (

    Any,

    Iterable,

    Iterator,

    Mapping,

    NamedTuple,

    Optional,

    Union,

)

from .beancount_types import (

    Error,

    Errors,

    LoadResult,

)

PathLike = Union[str, Path]

Year = Union[int, datetime.date]

class FiscalYear(NamedTuple):

    month: int = 3

    day: int = 1

    def for_date(self, date: Optional[datetime.date]=None) -> int:

        if date is None:

            date = datetime.date.today()

        if (date.month, date.day) < self:

            return date.year - 1

        else:

            return date.year

    def range(self, from_fy: Year, to_fy: Optional[Year]=None) -> Iterable[int]:

        """Return a range of fiscal years

        Both arguments can be either a year (represented as an integer) or a

        date. Dates will be converted into a year by calling for_date() on

        them.

        If the first argument is negative or below 1000, it will be treated as

        an offset. You'll get a range of fiscal years between the second

        argument offset by this amount.

        If the second argument is omitted, it defaults to the current fiscal

        year.

        Note that unlike normal Python ranges, these ranges include the final

        fiscal year.

        Examples:

          range(2015)  # Iterate all fiscal years from 2015 to today, inclusive

          range(-1)  # Iterate the previous fiscal year and current fiscal year

        """

        if not isinstance(from_fy, int):

            from_fy = self.for_date(from_fy)

        if to_fy is None:

            to_fy = self.for_date()

        elif not isinstance(to_fy, int):

            to_fy = self.for_date(to_fy - datetime.timedelta(days=1))

        if from_fy < 1:

            from_fy += to_fy

        elif from_fy < 1000:

            from_fy, to_fy = to_fy, from_fy + to_fy

        return range(from_fy, to_fy + 1)

class Loader:

    """Load Beancount books organized by fiscal year"""

    def __init__(self,

                 books_root: Path,

                 fiscal_year: FiscalYear,

    ) -> None:

        """Set up a books loader

        Arguments:

        * books_root: A Path to a Beancount books checkout.

        * fiscal_year: A FiscalYear object, used to determine what books to

          load for a given date range.

        """

        self.books_root = books_root

        self.fiscal_year = fiscal_year

    def _iter_fy_books(self, fy_range: Iterable[int]) -> Iterator[Path]:

        for year in fy_range:

            path = Path(self.books_root, 'books', f'{year}.beancount')

            if path.exists():

                yield path

    def _load_paths(self, paths: Iterator[Path]) -> LoadResult:

        try:

            entries, errors, options_map = bc_loader.load_file(next(paths))

        except StopIteration:

            entries, errors, options_map = [], [], {}

    ((2019, 2, 1), (2020, 6, 1), [2018, 2019, 2020]),

])

def test_range_two_dates(conservancy_fy, begin_date, end_date, expected):

    actual = list(conservancy_fy.range(datetime.date(*begin_date), datetime.date(*end_date)))

    assert actual == expected

@pytest.mark.parametrize('year_offset', range(3))

def test_range_one_date(cy_fy, year_offset):

    this_year = datetime.date.today().year

    actual = list(cy_fy.range(datetime.date(this_year - year_offset, 1, 1)))

    assert actual == list(range(this_year - year_offset, this_year + 1))

@pytest.mark.parametrize('begin_year,end_year', [

    (2006, 2020),

    (2019, 2020),

    (2020, 2020),

])

def test_range_two_years(conservancy_fy, begin_year, end_year):

    actual = list(conservancy_fy.range(begin_year, end_year))

    assert actual == list(range(begin_year, end_year + 1))

@pytest.mark.parametrize('year_offset', range(3))

def test_range_one_year(cy_fy, year_offset):

    this_year = datetime.date.today().year

    actual = list(cy_fy.range(this_year - year_offset))

    assert actual == list(range(this_year - year_offset, this_year + 1))

@pytest.mark.parametrize('year_offset,month_offset', itertools.product(

    range(-3, 3),

    [-1, 1]

))

def test_range_offset_and_date(conservancy_fy, year_offset, month_offset):

    end_date = datetime.date(2020, conservancy_fy.month + month_offset, 10)

    base_year = end_date.year

    if month_offset < 0:

        base_year -= 1

    if year_offset < 0:

        expected = range(base_year + year_offset, base_year + 1)

    else:

        expected = range(base_year, base_year + year_offset + 1)

    actual = list(conservancy_fy.range(year_offset, end_date))

    assert actual == list(expected)

@pytest.mark.parametrize('year_offset,year', itertools.product(

    range(-3, 3),

    [2010, 2015],

))

def test_range_offset_and_year(conservancy_fy, year_offset, year):

    if year_offset < 0:

        expected = range(year + year_offset, year + 1)

    else:

        expected = range(year, year + year_offset + 1)

    actual = list(conservancy_fy.range(year_offset, year))

    assert actual == list(expected)

@pytest.mark.parametrize('year_offset', range(-3, 3))

def test_range_offset_only(cy_fy, year_offset):

    year = datetime.date.today().year

    if year_offset < 0:

        expected = range(year + year_offset, year + 1)

    else:

        expected = range(year, year + year_offset + 1)

    actual = list(cy_fy.range(year_offset))

    assert actual == list(expected)