"""balance_sheet.py - Balance sheet report"""

# 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 argparse

import collections

import datetime

import enum

import logging

import operator

import os

import sys

from decimal import Decimal

from pathlib import Path

from typing import (

    Any,

    Callable,

    Collection,

    Dict,

    Hashable,

    Iterable,

    Iterator,

    List,

    Mapping,

    NamedTuple,

    Optional,

    Sequence,

    TextIO,

    Tuple,

    Union,

)

import odf.style  # type:ignore[import]

import odf.table  # type:ignore[import]

from beancount.parser import printer as bc_printer

from . import core

from . import rewrite

from .. import books

from .. import cliutil

from .. import config as configmod

from .. import data

from .. import ranges

EQUITY_ACCOUNTS = frozenset(['Equity', 'Income', 'Expenses'])

PROGNAME = 'balance-sheet-report'

KWArgs = Mapping[str, Any]

class Fund(enum.IntFlag):

    RESTRICTED = enum.auto()

    UNRESTRICTED = enum.auto()

    ANY = RESTRICTED | UNRESTRICTED

class Period(enum.IntFlag):

    OPENING = enum.auto()

    PRIOR = enum.auto()

    MIDDLE = enum.auto()

    PERIOD = enum.auto()

    THRU_PRIOR = OPENING | PRIOR

    THRU_MIDDLE = THRU_PRIOR | MIDDLE

    ANY = THRU_MIDDLE | PERIOD

class BalanceKey(NamedTuple):

    account: data.Account

    classification: data.Account

    period: Period

    fund: Fund

    post_type: Optional[str]

class Balances:

    def __init__(self,

                 postings: Iterable[data.Posting],

                 start_date: datetime.date,

                 stop_date: datetime.date,

                 fund_key: str='project',

                 unrestricted_fund_value: str='Conservancy',

    ) -> None:

        year_diff = (stop_date - start_date).days // 365

        if year_diff == 0:

            self.prior_range = ranges.DateRange(

                cliutil.diff_year(start_date, -1),

                cliutil.diff_year(stop_date, -1),

            )

            self.period_desc = "Period"

        else:

            self.prior_range = ranges.DateRange(

                cliutil.diff_year(start_date, -year_diff),

                start_date,

            )

            self.period_desc = f"Year{'s' if year_diff > 1 else ''}"

        self.middle_range = ranges.DateRange(self.prior_range.stop, start_date)

        self.period_range = ranges.DateRange(start_date, stop_date)

        self.balances: Mapping[BalanceKey, core.MutableBalance] \

            = collections.defaultdict(core.MutableBalance)

        for post in postings:

            post_date = post.meta.date

            if post_date >= stop_date:

                continue

            elif post_date in self.period_range:

                period = Period.PERIOD

            elif post_date in self.middle_range:

                period = Period.MIDDLE

            elif post_date in self.prior_range:

                period = Period.PRIOR

            else:

                period = Period.OPENING

            if post.meta.get(fund_key) == unrestricted_fund_value:

                fund = Fund.UNRESTRICTED

            else:

                fund = Fund.RESTRICTED

            try:

                classification_s = post.account.meta['classification']

                if isinstance(classification_s, str):

                    classification = data.Account(classification_s)

                else:

                    raise TypeError()

            except (KeyError, TypeError):

                classification = post.account

            if post.account.root_part() == 'Expenses':

                post_type = post.meta.get('expense-type')

            else:

                post_type = None

            key = BalanceKey(post.account, classification, period, fund, post_type)

            self.balances[key] += post.at_cost()

    def total(self,

              account: Union[None, str, Collection[str]]=None,

              classification: Optional[str]=None,

              period: int=Period.ANY,

              fund: int=Fund.ANY,

              post_type: Optional[str]=None,

    ) -> core.Balance:

        if isinstance(account, str):

            account = (account,)

        retval = core.MutableBalance()

        for key, balance in self.balances.items():

            if not (account is None or key.account.is_under(*account)):

                pass

            elif not (classification is None

                      or key.classification.is_under(classification)):

                pass

            elif not period & key.period:

                pass

            elif not fund & key.fund:

                pass

            elif not (post_type is None or post_type == key.post_type):

                pass

            else:

                retval += balance

        return retval

    def classifications(self,

                        account: str,

                        sort_period: Optional[int]=None,

    ) -> Sequence[data.Account]:

        if sort_period is None:

            if account in EQUITY_ACCOUNTS:

                sort_period = Period.PERIOD

            else:

                sort_period = Period.ANY

        class_bals: Mapping[data.Account, core.MutableBalance] \

            = collections.defaultdict(core.MutableBalance)

        for key, balance in self.balances.items():

            if not key.account.is_under(account):

                pass

            elif key.period & sort_period:

                class_bals[key.classification] += balance

            else:

                # Ensure the balance exists in the mapping

                class_bals[key.classification]

        norm_func = core.normalize_amount_func(f'{account}:RootsOK')

        def sortkey(acct: data.Account) -> Hashable:

            prefix, _, _ = acct.rpartition(':')

            balance = norm_func(class_bals[acct])

            try:

                max_bal = max(amount.number for amount in balance.values())

            except ValueError:

                max_bal = Decimal(0)

            return prefix, -max_bal

        return sorted(class_bals, key=sortkey)

    def iter_accounts(self, root: str) -> Sequence[data.Account]:

        start_date = self.period_range.start

        stop_date = self.period_range.stop

        return sorted(

            account

            for account in data.Account.iter_accounts(root)

            if account.meta.open_date < stop_date

            and (account.meta.close_date is None

                 or account.meta.close_date > start_date)

        )

class Report(core.BaseODS[Sequence[None], None]):

    C_CASH = 'Cash'

    NO_BALANCE = core.Balance()

    SPACE = ' ' * 4

    def __init__(self,

                 balances: Balances,

                 *,

                 date_fmt: str='%B %d, %Y',

    ) -> None:

        super().__init__()

        self.balances = balances

        self.period_desc = balances.period_desc

        self.date_fmt = date_fmt

        one_day = datetime.timedelta(days=1)

        date = balances.period_range.stop - one_day

        self.period_name = date.strftime(date_fmt)

        date = balances.prior_range.stop - one_day

        self.opening_name = date.strftime(date_fmt)

        self.last_totals_row = odf.table.TableRow()

    def section_key(self, row: Sequence[None]) -> None:

        raise NotImplementedError("balance_sheet.Report.section_key")

    def init_styles(self) -> None:

        super().init_styles()

        self.style_header = self.merge_styles(self.style_bold, self.style_centertext)

        self.style_huline = self.merge_styles(

            self.style_header,

            self.border_style(core.Border.BOTTOM, '1pt'),

        )

    def write_all(self) -> None:

        self.write_financial_position()

        self.write_activities()

        self.write_functional_expenses()

        self.write_cash_flows()

        self.write_trial_balances()

    def walk_classifications(self, cseq: Iterable[data.Account]) \

        -> Iterator[Tuple[str, Optional[data.Account]]]:

        last_prefix: Sequence[str] = []

        for classification in cseq:

            parts = classification.split(':')

            tail = parts.pop()

            space = self.SPACE * len(parts)

            if parts != last_prefix:

                yield f'{space[len(self.SPACE):]}{parts[-1]}', None

                last_prefix = parts

            yield f'{space}{tail}', classification

    def walk_classifications_by_account(

            self,

            account: str,

            sort_period: Optional[int]=None,

    ) -> Iterator[Tuple[str, Optional[data.Account]]]:

        return self.walk_classifications(self.balances.classifications(

            account, sort_period,

        ))

    def start_sheet(self,

                    sheet_name: str,

                    *headers: Iterable[str],

                    totals_prefix: Sequence[str]=(),

                    first_width: Union[float, str]=3,

                    width: Union[float, str]=1.5,

                    title_fmt: str="DRAFT Statement of {sheet_name}",

    ) -> None:

        header_cells: Sequence[odf.table.TableCell] = [

            odf.table.TableCell(),

            *(self.multiline_cell(header_lines, stylename=self.style_huline)

              for header_lines in headers),

            *(self.multiline_cell([*totals_prefix, date_s], stylename=self.style_huline)

              for date_s in [self.period_name, self.opening_name]),

        ]

        self.col_count = len(header_cells)

        self.use_sheet(sheet_name)

        for index in range(self.col_count):

            col_style = self.column_style(width if index else first_width)

            self.sheet.addElement(odf.table.TableColumn(stylename=col_style))

        start_date = self.balances.period_range.start.strftime(self.date_fmt)

        self.add_row(

            self.multiline_cell([

                title_fmt.format(sheet_name=sheet_name),

                f"{start_date}—{self.period_name}",

            ], numbercolumnsspanned=self.col_count, stylename=self.style_header)

        )

        self.add_row()

        self.add_row(*header_cells)

    def write_classifications_by_account(

            self,

            account: str,

            balance_kwargs: Sequence[KWArgs],

            exclude_classifications: Collection[str]=frozenset(),

            text_prefix: str='',

            norm_func: Optional[Callable[[core.Balance], core.Balance]]=None,

    ) -> Sequence[core.Balance]:

        if norm_func is None:

            norm_func = core.normalize_amount_func(f'{account}:RootsOK')

        assert len(balance_kwargs) + 1 == self.col_count, \

            "called write_classifications with wrong number of balance_kwargs"

        retval = [core.MutableBalance() for _ in balance_kwargs]

        for text, classification in self.walk_classifications_by_account(account):

            text_cell = self.string_cell(text_prefix + text)

            if classification is None:

                if not text[0].isspace():

                    self.add_row()

                self.add_row(text_cell)

            elif classification in exclude_classifications:

                pass

            else:

                row = self.add_row(text_cell)

                for kwargs, total_bal in zip(balance_kwargs, retval):

                    balance = norm_func(self.balances.total(

                        classification=classification, **kwargs,

                    ))

                    row.addElement(self.balance_cell(balance))

                    total_bal += balance

        return retval

    def write_totals_row(

            self,

            text: str,

            *balances: Sequence[core.Balance],

            stylename: Union[None, str, odf.style.Style]=None,

            leading_rows: Optional[int]=None,

    ) -> odf.table.TableRow:

        if leading_rows is None:

            if (self.sheet.lastChild is self.last_totals_row

                or stylename is self.style_bottomline):

                leading_rows = 1

            else:

                leading_rows = 0

        expect_len = self.col_count - 1

        assert all(len(seq) == expect_len for seq in balances), \

            "called write_totals_row with the wrong length of balance columns"

        for _ in range(leading_rows):

            self.add_row()

        self.last_totals_row = self.add_row(

            self.string_cell(text),

            *(self.balance_cell(

                sum(sum_bals, core.MutableBalance()),

                stylename=stylename,

            ) for sum_bals in zip(*balances)),

        )

        return self.last_totals_row

    def write_financial_position(self) -> None:

        self.start_sheet("Financial Position")

        balance_kwargs: Sequence[KWArgs] = [

            {'period': Period.ANY},

            {'period': Period.THRU_PRIOR},

        ]

        asset_totals = self.write_classifications_by_account('Assets', balance_kwargs)

        self.write_totals_row(

            "Total Assets", asset_totals, stylename=self.style_bottomline,

        )

        self.add_row()

        self.add_row()

        liabilities = self.write_classifications_by_account('Liabilities', balance_kwargs)

        self.write_totals_row(

            "Total Liabilities", liabilities, stylename=self.style_endtotal,

        )

        self.add_row()

        self.add_row()

        equity_totals = [core.MutableBalance() for _ in balance_kwargs]

        self.add_row(self.string_cell("Net Assets", stylename=self.style_bold))

        self.add_row()

        for fund in [Fund.UNRESTRICTED, Fund.RESTRICTED]:

            preposition = "Without" if fund is Fund.UNRESTRICTED else "With"

            row = self.add_row(self.string_cell(f"{preposition} donor restrictions"))

            for kwargs, total_bal in zip(balance_kwargs, equity_totals):

                balance = -self.balances.total(account=EQUITY_ACCOUNTS, fund=fund, **kwargs)

                row.addElement(self.balance_cell(balance))

                total_bal += balance

        self.write_totals_row(

            "Total Net Assets", equity_totals, stylename=self.style_total,

        )

        self.write_totals_row(

            "Total Liabilities and Net Assets",

            liabilities, equity_totals,

            stylename=self.style_bottomline,

        )

    def write_activities(self) -> None:

        self.start_sheet(

            "Activities",

            ["Without Donor", "Restrictions"],

            ["With Donor", "Restrictions"],

            totals_prefix=[f"Total {self.period_desc} Ended"],

        )

        bal_kwargs: Sequence[Dict[str, Any]] = [

            {'period': Period.PERIOD, 'fund': Fund.UNRESTRICTED},

            {'period': Period.PERIOD, 'fund': Fund.RESTRICTED},

            {'period': Period.PERIOD},

            {'period': Period.PRIOR},

        ]

        self.add_row(self.string_cell("Support and Revenue", stylename=self.style_bold))

        self.add_row()

        income_totals = self.write_classifications_by_account('Income', bal_kwargs)

        self.write_totals_row("", income_totals, stylename=self.style_total)

        self.add_row()

        self.add_row(

            self.string_cell("Net Assets released from restrictions:"),

        )

        released = self.balances.total(

            account=('Expenses', 'Equity'),

            period=Period.PERIOD,

            fund=Fund.RESTRICTED,

        )

        other_totals = [core.MutableBalance() for _ in bal_kwargs]

        other_totals[0] += released

        other_totals[1] -= released

        self.write_totals_row("Satisfaction of program restrictions", other_totals)

        self.write_totals_row(

            "Total Support and Revenue",

            income_totals, other_totals,

            stylename=self.style_endtotal,

        )

        period_expenses = core.MutableBalance()

        prior_expenses = core.MutableBalance()

        self.add_row()

        self.add_row(self.string_cell("Expenses", stylename=self.style_bold))

        self.add_row()

        for text, type_value in [

                ("Program services", 'program'),

                ("Management and administrative services", 'management'),