"""funds.py - Funds report from Beancount

This tool produces a report of account balances for restricted funds,
including income, expenses, and realized gain/loss over a given time period.
Restricted funds are designated with the "project" metadata.

Specify the date range you want to report with the ``--begin`` and ``--end``
options.

Select the accounts you want to report with the ``--account`` option. You can
specify this option multiple times. The report will include at least one sheet
for each account you specify. Subaccounts will be reported on that sheet as
well.

Select the postings you want to report by passing metadata search terms in
``name=value`` format.

Run ``ledger-report --help`` for abbreviations and other options.

Examples
--------

Generate a report of all restricted funds in ODS format over the last year::

      fund-report

Query a specific restricted fund and get a quick balance on the terminal::

      fund-report <PROJECT>
"""
# 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 locale
import logging
import sys

from typing import (
    Dict,
    Iterable,
    Iterator,
    Mapping,
    Optional,
    Sequence,
    TextIO,
    Tuple,
)
from ..beancount_types import (
    MetaValue,
)

from pathlib import Path

import odf.table  # type:ignore[import]

from beancount.parser import printer as bc_printer

from . import core
from .. import books
from .. import cliutil
from .. import config as configmod
from .. import data

AccountsMap = Mapping[data.Account, core.PeriodPostings]
FundPosts = Tuple[MetaValue, AccountsMap]

EQUITY_ACCOUNTS = ['Equity', 'Income', 'Expenses']
INFO_ACCOUNTS = [
    'Assets:Receivable',
    'Assets:Prepaid',
    'Liabilities:Payable',
    'Liabilities:UnearnedIncome',
]
PROGNAME = 'fund-report'
UNRESTRICTED_FUND = 'Conservancy'
logger = logging.getLogger('conservancy_beancount.reports.fund')

class ODSReport(core.BaseODS[FundPosts, None]):
    def __init__(self, start_date: datetime.date, stop_date: datetime.date) -> None:
        super().__init__()
        self.start_date = start_date
        self.stop_date = stop_date
        self.unrestricted: AccountsMap = {}

    def section_key(self, row: FundPosts) -> None:
        return None

    def start_spreadsheet(self) -> None:
        self.use_sheet("Fund Report")
        for width in [2.5, 1.5, 1.2, 1.2, 1.2, 1.5]:
            col_style = self.column_style(width)
            self.sheet.addElement(odf.table.TableColumn(stylename=col_style))
        center_bold = self.merge_styles(self.style_centertext, self.style_bold)
        self.add_row(
            self.string_cell(
                "Fund", stylename=self.merge_styles(self.style_endtext, self.style_bold),
            ),
            self.multiline_cell(["Balance as of", self.start_date.isoformat()],
                                stylename=center_bold),
            self.string_cell("Income", stylename=center_bold),
            self.string_cell("Expenses", stylename=center_bold),
            self.multiline_cell(["Realized", "Gain/Loss"], stylename=center_bold),
            self.multiline_cell(["Balance as of", self.stop_date.isoformat()],
                                stylename=center_bold),
        )
        self.lock_first_row()
        self.add_row()
        self.add_row(self.string_cell(
            f"Fund Report From {self.start_date.isoformat()} To {self.stop_date.isoformat()}",
            stylename=center_bold,
            numbercolumnsspanned=6,
        ))
        self.add_row()

    def _row_balances(self, accounts_map: AccountsMap) -> Iterable[core.Balance]:
        acct_order = ['Income', 'Expenses', 'Equity']
        key_order = [core.OPENING_BALANCE_NAME, *acct_order, core.ENDING_BALANCE_NAME]
        balances: Dict[str, core.Balance] = {key: core.MutableBalance() for key in key_order}
        for acct_s, balance in core.account_balances(accounts_map, acct_order):
            if acct_s in balances:
                balances[acct_s] = balance
            else:
                acct_root, _, _ = acct_s.partition(':')
                balances[acct_root] += balance
        for key in key_order:
            if key == 'Expenses':
                yield balances[key]
            else:
                yield -balances[key]

    def write_row(self, row: FundPosts) -> None:
        fund, accounts_map = row
        if fund == UNRESTRICTED_FUND:
            assert not self.unrestricted
            self.unrestricted = accounts_map
            return
        self.add_row(
            self.string_cell(fund, stylename=self.style_endtext),
            *(self.balance_cell(bal) for bal in self._row_balances(accounts_map)),
        )

    def write(self, rows: Iterable[FundPosts]) -> None:
        super().write(rows)
        if self.unrestricted:
            self.add_row()
            self.write_row(("Unrestricted", self.unrestricted))


class TextReport:
    def __init__(self,
                 start_date: datetime.date,
                 stop_date: datetime.date,
                 out_file: TextIO) -> None:
        self.start_date = start_date
        self.stop_date = stop_date
        self.out_file = out_file

    def _account_balances(self,
                          fund: str,
                          account_map: AccountsMap,
    ) -> Iterator[Tuple[str, Sequence[str]]]:
        total_fmt = f'{fund} balance as of {{}}'
        for acct_s, balance in core.account_balances(account_map, EQUITY_ACCOUNTS):
            if acct_s is core.OPENING_BALANCE_NAME:
                acct_s = total_fmt.format(self.start_date.isoformat())
            elif acct_s is core.ENDING_BALANCE_NAME:
                acct_s = total_fmt.format(self.stop_date.isoformat())
            yield acct_s, (-balance).format(None, sep='\0').split('\0')
        for _, account in core.sort_and_filter_accounts(account_map, INFO_ACCOUNTS):
            balance = account_map[account].stop_bal
            if not balance.is_zero():
                balance = core.normalize_amount_func(account)(balance)
                yield account, balance.format(None, sep='\0').split('\0')

    def write(self, rows: Iterable[FundPosts]) -> None:
        output = [
            line
            for fund, account_map in rows
            for line in self._account_balances(fund, account_map)
        ]
        acct_width = max(len(acct_s) for acct_s, _ in output) + 2
        bal_width = max(len(s) for _, bal_s in output for s in bal_s)
        bal_width = max(bal_width, 8)
        line_fmt = f'{{:>{acct_width}}}  {{:>{bal_width}}}'
        print(line_fmt.replace('{:>', '{:^').format("ACCOUNT", "BALANCE"),
              file=self.out_file)
        fund_start = f' balance as of {self.start_date.isoformat()}'
        for acct_s, bal_seq in output:
            if acct_s.endswith(fund_start):
                print(line_fmt.format('―' * acct_width, '―' * bal_width),
                      file=self.out_file)
            bal_iter = iter(bal_seq)
            print(line_fmt.format(acct_s, next(bal_iter)), file=self.out_file)
            for bal_s in bal_iter:
                print(line_fmt.format('', bal_s), file=self.out_file)


class ReportType(enum.Enum):
    TEXT = TextReport
    ODS = ODSReport
    TXT = TEXT
    SPREADSHEET = ODS

    @classmethod
    def from_arg(cls, s: str) -> 'ReportType':
        try:
            return cls[s.upper()]
        except KeyError:
            raise ValueError(f"no report type matches {s!r}") from None


class ReturnFlag(enum.IntFlag):
    LOAD_ERRORS = 1
    NOTHING_TO_REPORT = 8


def parse_arguments(arglist: Optional[Sequence[str]]=None) -> argparse.Namespace:
    parser = argparse.ArgumentParser(prog=PROGNAME)
    cliutil.add_version_argument(parser)
    parser.add_argument(
        '--begin', '--start', '-b',
        dest='start_date',
        metavar='DATE',
        type=cliutil.date_arg,
        help="""Date to start reporting entries, inclusive, in YYYY-MM-DD format.
The default is one year ago.
""")
    parser.add_argument(
        '--end', '--stop', '-e',
        dest='stop_date',
        metavar='DATE',
        type=cliutil.date_arg,
        help="""Date to stop reporting entries, exclusive, in YYYY-MM-DD format.
The default is a year after the start date.
""")
    parser.add_argument(
        '--report-type', '-t',
        metavar='TYPE',
        type=ReportType.from_arg,
        help="""Type of report to generate. `text` gives a plain two-column text
report listing accounts and balances over the period, and is the default when
you search for a specific project/fund. `ods` produces a higher-level
spreadsheet, meant to provide an overview of all funds, and is the default when
you don't specify a project/fund.
""")
    parser.add_argument(
        '--output-file', '-O',
        metavar='PATH',
        type=Path,
        help="""Write the report to this file, or stdout when PATH is `-`.
The default is stdout for text reports, and a generated filename for ODS
reports.
""")
    cliutil.add_loglevel_argument(parser)
    parser.add_argument(
        'search_terms',
        metavar='FILTER',
        type=cliutil.SearchTerm.arg_parser('project', 'rt-id'),
        nargs=argparse.ZERO_OR_MORE,
        help="""Report on postings that match this criteria. The format is
NAME=TERM. TERM is a link or word that must exist in a posting's NAME
metadata to match. A single ticket number is a shortcut for
`rt-id=rt:NUMBER`. Any other word is a shortcut for `project=TERM`.
""")
    args = parser.parse_args(arglist)
    if args.report_type is None:
        if any(term.meta_key == 'project' for term in args.search_terms):
            args.report_type = ReportType.TEXT
        else:
            args.report_type = ReportType.ODS
    return args

def diff_year(date: datetime.date, diff: int) -> datetime.date:
    new_year = date.year + diff
    try:
        return date.replace(year=new_year)
    except ValueError:
        # The original date is Feb 29, which doesn't exist in the new year.
        if diff < 0:
            return datetime.date(new_year, 2, 28)
        else:
            return datetime.date(new_year, 3, 1)

def main(arglist: Optional[Sequence[str]]=None,
         stdout: TextIO=sys.stdout,
         stderr: TextIO=sys.stderr,
         config: Optional[configmod.Config]=None,
) -> int:
    args = parse_arguments(arglist)
    cliutil.set_loglevel(logger, args.loglevel)
    if config is None:
        config = configmod.Config()
        config.load_file()

    if args.stop_date is None:
        if args.start_date is None:
            args.stop_date = datetime.date.today()
        else:
            args.stop_date = diff_year(args.start_date, 1)
    if args.start_date is None:
        args.start_date = diff_year(args.stop_date, -1)

    returncode = 0
    books_loader = config.books_loader()
    if books_loader is None:
        entries, load_errors, _ = books.Loader.load_none(config.config_file_path())
    else:
        entries, load_errors, _ = books_loader.load_fy_range(args.start_date, args.stop_date)
    for error in load_errors:
        bc_printer.print_error(error, file=stderr)
        returncode |= ReturnFlag.LOAD_ERRORS

    postings = (
        post
        for post in data.Posting.from_entries(entries)
        if post.meta.date < args.stop_date
    )
    for search_term in args.search_terms:
        postings = search_term.filter_postings(postings)
    fund_postings = {
        key: related
        for key, related in core.RelatedPostings.group_by_meta(postings, 'project')
        if isinstance(key, str)
    }
    period_cls = core.PeriodPostings.with_start_date(args.start_date)
    fund_map = collections.OrderedDict(
        (fund, dict(period_cls.group_by_account(fund_postings[fund])))
        for fund in sorted(fund_postings, key=lambda s: locale.strxfrm(s.casefold()))
    )
    if not fund_map:
        logger.warning("no matching postings found to report")
        returncode |= ReturnFlag.NOTHING_TO_REPORT
    elif args.report_type is ReportType.TEXT:
        out_file = cliutil.text_output(args.output_file, stdout)
        report = TextReport(args.start_date, args.stop_date, out_file)
        report.write(fund_map.items())
    else:
        ods_report = ODSReport(args.start_date, args.stop_date)
        ods_report.write(fund_map.items())
        if args.output_file is None:
            out_dir_path = config.repository_path() or Path()
            args.output_file = out_dir_path / 'FundReport_{}_{}.ods'.format(
                args.start_date.isoformat(), args.stop_date.isoformat(),
            )
            logger.info("Writing report to %s", args.output_file)
        ods_file = cliutil.bytes_output(args.output_file, stdout)
        ods_report.save_file(ods_file)
    return 0 if returncode == 0 else 16 + returncode

entry_point = cliutil.make_entry_point(__name__, PROGNAME)

if __name__ == '__main__':
    exit(entry_point())