"""ledger.py - General ledger report from Beancount

This tool produces a spreadsheet that shows postings in Beancount, organized
by account.

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
--------

Report all activity related to a given project::

    ledger-report project=NAME

Get all Assets postings for a given month to help with reconciliation::

    ledger-report -a Assets -b 2018-05-01 -e 2018-06-01
"""
# 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 itertools
import operator
import logging
import sys

from typing import (
    Callable,
    Dict,
    Iterable,
    Iterator,
    List,
    Mapping,
    Optional,
    Sequence,
    TextIO,
    Tuple,
)

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
from .. import ranges
from .. import rtutil

PostTally = List[Tuple[int, data.Account]]

PROGNAME = 'ledger-report'
logger = logging.getLogger('conservancy_beancount.reports.ledger')

class LedgerODS(core.BaseODS[data.Posting, data.Account]):
    CORE_COLUMNS: Sequence[str] = [
        'Date',
        data.Metadata.human_name('entity'),
        'Description',
        'Original Amount',
        'Booked Amount',
    ]
    ACCOUNT_COLUMNS: Dict[str, Sequence[str]] = collections.OrderedDict([
        ('Income', ['project', 'rt-id', 'receipt', 'income-type']),
        ('Expenses', ['project', 'rt-id', 'receipt', 'approval', 'expense-allocation']),
        ('Equity', ['rt-id']),
        ('Assets:Receivable', ['project', 'rt-id', 'invoice', 'approval', 'contract', 'purchase-order']),
        ('Liabilities:Payable', ['project', 'rt-id', 'invoice', 'approval', 'contract', 'purchase-order']),
        ('Assets:PayPal', ['rt-id', 'paypal-id', 'receipt', 'approval']),
        ('Assets', ['rt-id', 'receipt', 'approval', 'bank-statement']),
        ('Liabilities', ['rt-id', 'receipt', 'approval', 'bank-statement']),
    ])
    COLUMN_STYLES: Mapping[str, str] = {
        'Date': '',
        'Description': 'col_1_75',
        data.Metadata.human_name('paypal-id'): 'col_1_5',
    }
    # Excel 2003 was limited to 65,536 rows per worksheet.
    # While we can probably count on all our users supporting more modern
    # formats (Excel 2007 supports over 1 million rows per worksheet),
    # keeping the default limit conservative seems good to avoid running into
    # other limits (like the number of hyperlinks per worksheet), plus just
    # better for human organization and readability.
    SHEET_SIZE = 65000

    def __init__(self,
                 start_date: datetime.date,
                 stop_date: datetime.date,
                 sheet_names: Optional[Sequence[str]]=None,
                 rt_wrapper: Optional[rtutil.RT]=None,
                 sheet_size: Optional[int]=None,
    ) -> None:
        if sheet_names is None:
            sheet_names = list(self.ACCOUNT_COLUMNS)
        if sheet_size is None:
            sheet_size = self.SHEET_SIZE
        super().__init__(rt_wrapper)
        self.date_range = ranges.DateRange(start_date, stop_date)
        self.required_sheet_names = sheet_names
        self.sheet_size = sheet_size

    @classmethod
    def _group_tally(
            cls,
            tally_by_account: PostTally,
            key: Callable[[data.Account], Optional[str]],
    ) -> Dict[str, PostTally]:
        retval: Dict[str, PostTally] = collections.defaultdict(list)
        for count, account in tally_by_account:
            item_key = key(account)
            if item_key is not None:
                retval[item_key].append((count, account))
        return retval

    @classmethod
    def _split_sheet(
            cls,
            tally_by_account: PostTally,
            sheet_size: int,
            sheet_name: str,
    ) -> Iterator[str]:
        total = 0
        for index, (count, account) in enumerate(tally_by_account):
            total += count
            if total > sheet_size:
                break
        else:
            # All the accounts fit in this sheet.
            yield sheet_name
            return
        if index == 0 and len(tally_by_account) == 1:
            # With one account, we can't split any further, so warn and stop.
            logger.warning(
                "%s has %s rows, over size %s",
                account, f'{count:,g}', f'{sheet_size:,g}',
            )
            yield sheet_name
            return
        group_func = operator.methodcaller('root_part', sheet_name.count(':') + 2)
        maybe_split = cls._group_tally(tally_by_account[:index], group_func)
        must_split = cls._group_tally(tally_by_account[index:], group_func)
        for subkey, must_split_tally in sorted(must_split.items()):
            split_names = cls._split_sheet(
                maybe_split.get(subkey, []) + must_split_tally, sheet_size, subkey,
            )
            # We must be willing to split out at least as many sheets as there
            # are accounts that didn't fit. Do that first.
            yield from itertools.islice(split_names, len(must_split_tally))
            # After that, we can be in one of two cases:
            # 1. There is no next sheet. All the accounts, including the
            #    maybe_splits and must_splits, fit on planned subsheets.
            #    Update state to note we don't need a sheet for them anymore.
            # 2. The next sheet is named `subkey`, and is planned to include
            #    all of our maybe_split accounts. However, we don't need to
            #    yield that sheet name, because those accounts already fit in
            #    the sheet we're planning, and it would be a needless split.
            next_sheet_name = next(split_names, None)
            if next_sheet_name is None:
                maybe_split.pop(subkey, None)
            else:
                assert next_sheet_name == subkey
                assert not any(split_names)
        if maybe_split:
            yield sheet_name

    @classmethod
    def plan_sheets(
            cls,
            tally_by_account: Mapping[data.Account, int],
            base_sheets: Sequence[str],
            sheet_size: int,
    ) -> Sequence[str]:
        sorted_tally: PostTally = [
            (count, account)
            for account, count in tally_by_account.items()
        ]
        sorted_tally.sort()
        split_tally = cls._group_tally(
            sorted_tally,
            operator.methodcaller('is_under', *base_sheets),
        )
        return [
            sheet_name
            for key in base_sheets
            for sheet_name in cls._split_sheet(split_tally[key], sheet_size, key)
        ]

    @staticmethod
    def _sort_and_filter_accounts(
            accounts: Iterable[data.Account],
            order: Sequence[str],
    ) -> Iterator[Tuple[int, data.Account]]:
        index_map = {s: ii for ii, s in enumerate(order)}
        retval: Mapping[int, List[data.Account]] = collections.defaultdict(list)
        for account in accounts:
            acct_key = account.is_under(*order)
            if acct_key is not None:
                retval[index_map[acct_key]].append(account)
        for key in sorted(retval):
            acct_list = retval[key]
            acct_list.sort()
            for account in acct_list:
                yield key, account

    def section_key(self, row: data.Posting) -> data.Account:
        return row.account

    def start_sheet(self, sheet_name: str) -> None:
        self.use_sheet(sheet_name.replace(':', ' '))
        columns_key = data.Account(sheet_name).is_under(*self.ACCOUNT_COLUMNS)
        # columns_key must not be None because ACCOUNT_COLUMNS has an entry
        # for all five root accounts.
        assert columns_key is not None
        self.metadata_columns = self.ACCOUNT_COLUMNS[columns_key]
        self.sheet_columns: Sequence[str] = [
            *self.CORE_COLUMNS,
            *(data.Metadata.human_name(meta_key) for meta_key in self.metadata_columns),
        ]
        for col_name in self.sheet_columns:
            self.sheet.addElement(odf.table.TableColumn(
                stylename=self.COLUMN_STYLES.get(col_name, 'col_1_25'),
            ))
        self.add_row(*(
            self.string_cell(col_name, stylename=self.style_bold)
            for col_name in self.sheet_columns
        ))
        self.lock_first_row()

    def _report_section_balance(self, key: data.Account, date_key: str) -> None:
        uses_opening = key.is_under('Assets', 'Equity', 'Liabilities')
        if date_key == 'start':
            if not uses_opening:
                return
            date = self.date_range.start
            description = "Opening Balance"
        else:
            date = self.date_range.stop
            description = "Ending Balance" if uses_opening else "Period Total"
        balance = self.norm_func(
            self.account_groups[key].balance_at_cost_by_date(date)
        )
        self.add_row(
            self.date_cell(date, stylename=self.merge_styles(
                self.style_bold, self.style_date,
            )),
            odf.table.TableCell(),
            self.string_cell(description, stylename=self.style_bold),
            odf.table.TableCell(),
            self.balance_cell(balance, stylename=self.style_bold),
        )

    def start_section(self, key: data.Account) -> None:
        self.add_row()
        self.add_row(
            odf.table.TableCell(),
            self.string_cell(
                f"{key} Ledger"
                f" From {self.date_range.start.isoformat()}"
                f" To {self.date_range.stop.isoformat()}",
                stylename=self.style_bold,
                numbercolumnsspanned=len(self.sheet_columns) - 1,
            ),
        )
        self.norm_func = core.normalize_amount_func(key)
        self._report_section_balance(key, 'start')

    def end_section(self, key: data.Account) -> None:
        self._report_section_balance(key, 'stop')

    def write_row(self, row: data.Posting) -> None:
        if row.meta.date not in self.date_range:
            return
        elif row.cost is None:
            amount_cell = odf.table.TableCell()
        else:
            amount_cell = self.currency_cell(self.norm_func(row.units))
        self.add_row(
            self.date_cell(row.meta.date),
            self.string_cell(row.meta.get('entity') or ''),
            self.string_cell(row.meta.txn.narration),
            amount_cell,
            self.currency_cell(self.norm_func(row.at_cost())),
            *(self.meta_links_cell(row.meta.report_links(key))
              if key in data.LINK_METADATA
              else self.string_cell(row.meta.get(key, ''))
              for key in self.metadata_columns),
        )

    def _combined_balance_row(self,
                              date: datetime.date,
                              balance_accounts: Sequence[str],
    ) -> None:
        balance = -sum((
            related.balance_at_cost_by_date(date)
            for account, related in self.account_groups.items()
            if account.is_under(*balance_accounts)
        ), core.MutableBalance())
        self.add_row(
            self.string_cell(
                f"Balance as of {date.isoformat()}",
                stylename=self.merge_styles(self.style_bold, self.style_endtext),
            ),
            self.balance_cell(balance, stylename=self.style_bold),
        )

    def write_balance_sheet(self) -> None:
        balance_accounts = ['Equity', 'Income', 'Expenses']
        # FIXME: This is a hack to exclude non-project Equity accounts from
        # project reports.
        if balance_accounts[0] not in self.required_sheet_names:
            balance_accounts[0] = 'Equity:Funds'
        self.use_sheet("Balance")
        column_style = self.replace_child(
            self.document.automaticstyles, odf.style.Style, name='col_3',
        )
        column_style.setAttribute('family', 'table-column')
        column_style.addElement(odf.style.TableColumnProperties(columnwidth='3in'))
        for _ in range(2):
            self.sheet.addElement(odf.table.TableColumn(stylename=column_style))
        self.add_row(
            self.string_cell("Account", stylename=self.style_bold),
            self.string_cell("Balance", stylename=self.style_bold),
        )
        self.lock_first_row()
        self.add_row()
        self.add_row(self.string_cell(
            f"Ledger From {self.date_range.start.isoformat()}"
            f" To {self.date_range.stop.isoformat()}",
            stylename=self.merge_styles(self.style_centertext, self.style_bold),
            numbercolumnsspanned=2,
        ))
        self.add_row()
        self._combined_balance_row(self.date_range.start, balance_accounts)
        for _, account in self._sort_and_filter_accounts(
                self.account_groups, balance_accounts,
        ):
            related = self.account_groups[account]
            # start_bal - stop_bal == -(stop_bal - start_bal)
            balance = related.balance_at_cost_by_date(self.date_range.start)
            balance -= related.balance_at_cost_by_date(self.date_range.stop)
            if not balance.is_zero():
                self.add_row(
                    self.string_cell(account, stylename=self.style_endtext),
                    self.balance_cell(balance),
                )
        self._combined_balance_row(self.date_range.stop, balance_accounts)

    def write(self, rows: Iterable[data.Posting]) -> None:
        self.account_groups = dict(core.RelatedPostings.group_by_account(rows))
        self.write_balance_sheet()
        tally_by_account_iter = (
            (account, sum(1 for post in related if post.meta.date in self.date_range))
            for account, related in self.account_groups.items()
        )
        tally_by_account = {
            account: count
            for account, count in tally_by_account_iter
            if count
        }
        sheet_names = self.plan_sheets(
            tally_by_account, self.required_sheet_names, self.sheet_size,
        )
        using_sheet_index = -1
        for sheet_index, account in self._sort_and_filter_accounts(
                tally_by_account, sheet_names,
        ):
            while using_sheet_index < sheet_index:
                using_sheet_index += 1
                self.start_sheet(sheet_names[using_sheet_index])
            super().write(self.account_groups[account])
        for index in range(using_sheet_index + 1, len(sheet_names)):
            self.start_sheet(sheet_names[index])


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, or 30 days from today if the start
date was also not specified.
""")
    parser.add_argument(
        '--account', '-a',
        dest='sheet_names',
        metavar='ACCOUNT',
        action='append',
        help="""Show this account in the report. You can specify this option
multiple times. If not specified, the default set adapts to your search
criteria.
""")
    parser.add_argument(
        '--sheet-size', '--size',
        metavar='SIZE',
        type=int,
        default=LedgerODS.SHEET_SIZE,
        help="""Try to limit sheets to this many rows. The report will
automatically create new sheets to make this happen. When that's not possible,
it will issue a warning.
""")
    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 the balance and outgoing reports, and a generated
filename for other 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.sheet_names is None:
        if any(term.meta_key == 'project' for term in args.search_terms):
            args.sheet_names = ['Income', 'Expenses', 'Assets:Receivable', 'Liabilities:Payable']
        else:
            args.sheet_names = list(LedgerODS.ACCOUNT_COLUMNS)
    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()

    today = datetime.date.today()
    if args.start_date is None:
        args.start_date = diff_year(today, -1)
        if args.stop_date is None:
            args.stop_date = today + datetime.timedelta(days=30)
    elif args.stop_date is None:
        args.stop_date = diff_year(args.start_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 = data.Posting.from_entries(entries)
    for search_term in args.search_terms:
        postings = search_term.filter_postings(postings)

    rt_wrapper = config.rt_wrapper()
    if rt_wrapper is None:
        logger.warning("could not initialize RT client; spreadsheet links will be broken")
    report = LedgerODS(
        args.start_date,
        args.stop_date,
        args.sheet_names,
        rt_wrapper,
        args.sheet_size,
    )
    report.write(postings)
    if not report.account_groups:
        logger.warning("no matching postings found to report")
        returncode |= ReturnFlag.NOTHING_TO_REPORT

    if args.output_file is None:
        out_dir_path = config.repository_path() or Path()
        args.output_file = out_dir_path / 'LedgerReport_{}_{}.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)
    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())