"""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 = [], [], {}

        for load_path in paths:

            new_entries, new_errors, new_options = bc_loader.load_file(load_path)

            # We only want transactions from the new fiscal year.

            # We don't want the opening balance, duplicate definitions, etc.

            fy_filename = str(load_path.parent.parent / load_path.name)

            entries.extend(

                entry for entry in new_entries

                if entry.meta.get('filename') == fy_filename

            )

            errors.extend(new_errors)

        return entries, errors, options_map

    def _path_year(self, path: Path) -> int:

        return int(path.stem)

    def load_all(self, from_year: Optional[Year]=None) -> LoadResult:

        """Load all of the books from a starting FY

        This method loads all of the books, starting from the fiscal year you

        specify.

        * Pass in a date to start from the FY for that date.

        * Pass in an integer >= 1000 to start from that year.

        * Pass in a smaller integer to start from an FY relative to today

          (e.g., -2 starts two FYs before today).

        * Pass is no argument to load all books from the first available FY.

        This method finds books by globbing the filesystem. It still loads

        each fiscal year in sequence to provide the best cache utilization.

        """

        path = Path(self.books_root, 'books')

        fy_paths = list(path.glob('[1-9][0-9][0-9][0-9].beancount'))

        fy_paths.sort(key=self._path_year)

        if from_year is not None:

            if not isinstance(from_year, int):

                from_year = self.fiscal_year.for_date(from_year)

            elif from_year < 1000:

                from_year = self.fiscal_year.for_date() + from_year

            for index, path in enumerate(fy_paths):

                if self._path_year(path) >= from_year:

                    fy_paths = fy_paths[index:]

                    break

            else:

                fy_paths = []

        return self._load_paths(iter(fy_paths))

    def load_fy_range(self,

                      from_fy: Year,

                      to_fy: Optional[Year]=None,

    ) -> LoadResult:

        """Load books for a range of fiscal years

        This method generates a range of fiscal years by calling

        FiscalYear.range() with its arguments. It loads all the books within

        that range.

        """

        fy_range = self.fiscal_year.range(from_fy, to_fy)

        fy_paths = self._iter_fy_books(fy_range)

        return self._load_paths(fy_paths)

    @classmethod

    def load_none(cls, config_path: Optional[PathLike]=None, lineno: int=0) -> LoadResult:

        """Load no books and generate an error about it

        This is a convenience method for reporting tools that already handle

        general Beancount errors. If a configuration problem prevents them from

        loading the books, they can call this method in place of a regular

        loading method, and then continue on their normal code path.

        The path and line number given in the arguments will be named as the

        source of the error.

        """

        source = {

            'filename': str(config_path or 'conservancy_beancount.ini'),

            'lineno': lineno,

        }

        errors: Errors = [Error(source, "no books to load in configuration", None)]

        return [], errors, {}

"""test_books_fiscal_year - Unit tests for books.FiscalYear"""

# 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

import itertools

import pytest

from conservancy_beancount import books

@pytest.fixture(scope='module')

def conservancy_fy():

    return books.FiscalYear(3, 1)

@pytest.fixture(scope='module')

def cy_fy():

    return books.FiscalYear(1, 1)

# Not bothering because it's too much trouble to override __new__

# @pytest.mark.parametrize('month,day', [

#     (0, 0),

#     (2, 29),

#     (4, 31),

#     (13, 15),

#     (-1, 1),

#     (1, -5),

# ])

# def test_values_checked(month, day):

#     with pytest.raises(ValueError):

#         books.FiscalYear(month, day)

def test_attribute_access():

    fy = books.FiscalYear(2, 15)

    assert fy.month == 2

    assert fy.day == 15

    with pytest.raises(AttributeError):

        fy.year

@pytest.mark.parametrize('month,day,expected', [

    (1, 1, 2019),

    (2, 15, 2019),

    (2, 28, 2019),

    (2, 29, 2019),

    (3, 1, 2020),

    (3, 9, 2020),

    (6, 1, 2020),

    (12, 31, 2020),

])

def test_for_date(conservancy_fy, month, day, expected):

    date = datetime.date(2020, month, day)

    assert conservancy_fy.for_date(date) == expected

def test_for_date_default_today(cy_fy):

    assert cy_fy.for_date() == datetime.date.today().year

@pytest.mark.parametrize('begin_date,end_date,expected', [

    ((2020, 3, 1), (2021, 2, 28), [2020]),

    ((2020, 1, 1), (2020, 3, 1), [2019]),

    ((2020, 1, 1), (2020, 3, 5), [2019, 2020]),

    ((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)