"""Enhanced Beancount data structures for Conservancy

The classes in this module are interface-compatible with Beancount's core data

structures, and provide additional business logic that we want to use

throughout Conservancy tools.

"""

# 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 collections

import datetime

import decimal

import functools

from beancount.core import account as bc_account

from beancount.core import amount as bc_amount

from beancount.core import convert as bc_convert

from beancount.core import position as bc_position

from typing import (

    cast,

    overload,

    Callable,

    Hashable,

    Iterable,

    Iterator,

    MutableMapping,

    Optional,

    Sequence,

    TypeVar,

    Union,

)

from .beancount_types import (

    Directive,

    MetaKey,

    MetaValue,

    Posting as BasePosting,

    Transaction,

)

DecimalCompat = Union[decimal.Decimal, int]

LINK_METADATA = frozenset([

    'approval',

    'check',

    'contract',

    'invoice',

    'purchase-order',

    'receipt',

    'rt-id',

    'statement',

])

class Account(str):

    """Account name string

    This is a string that names an account, like Assets:Bank:Checking

    or Income:Donations. This class provides additional methods for common

    account name parsing and queries.

    """

        elif stop is None:

            return self[self._find_part_slice(start)]

        else:

            part_slice = slice(start, stop)

        return self.split(self.SEP)[part_slice]

    def root_part(self, count: int=1) -> str:

        """Return the first part(s) of the account name as a string"""

        try:

            stop = self._find_part_slice(count - 1).stop

        except IndexError:

            return self

        else:

            return self[:stop]

class Amount(bc_amount.Amount):

    """Beancount amount after processing

    Beancount's native Amount class declares number to be Optional[Decimal],

    because the number is None when Beancount first parses a posting that does

    not have an amount, because the user wants it to be automatically balanced.

    As part of the loading process, Beancount replaces those None numbers

    with the calculated amount, so it will always be a Decimal. This class

    overrides the type declaration accordingly, so the type checker knows

    that our code doesn't have to consider the possibility that number is

    None.

    """

    number: decimal.Decimal

    # beancount.core._Amount is the plain namedtuple.

    # beancore.core.Amount adds instance methods to it.

    # b.c.Amount.__New__ calls `b.c._Amount.__new__`, which confuses type

    # checking. See <https://github.com/python/mypy/issues/1279>.

    # It works fine if you use super(), which is better practice anyway.

    # So we override __new__ just to call _Amount.__new__ this way.

    def __new__(cls, number: decimal.Decimal, currency: str) -> 'Amount':

        return super(bc_amount.Amount, Amount).__new__(cls, number, currency)

class Metadata(MutableMapping[MetaKey, MetaValue]):

    """Transaction or posting metadata

    This class wraps a Beancount metadata dictionary with additional methods

    for common parsing and query tasks.

    """

    __slots__ = ('meta',)

    def __init__(self, source: MutableMapping[MetaKey, MetaValue]) -> None:

        self.meta = source

    def __iter__(self) -> Iterator[MetaKey]:

        return iter(self.meta)

    def __len__(self) -> int:

        return len(self.meta)

    def __getitem__(self, key: MetaKey) -> MetaValue:

        return self.meta[key]

    def __setitem__(self, key: MetaKey, value: MetaValue) -> None:

        self.meta[key] = value

    def __delitem__(self, key: MetaKey) -> None:

        del self.meta[key]

    def get_links(self, key: MetaKey) -> Sequence[str]:

        try:

            value = self.meta[key]

        except KeyError:

            return ()

        if isinstance(value, str):

            return value.split()

        else:

            raise TypeError("{} metadata is a {}, not str".format(

                key, type(value).__name__,

            ))

    @overload

    def first_link(self, key: MetaKey, default: None=None) -> Optional[str]: ...

    @overload

    def first_link(self, key: MetaKey, default: str) -> str: ...

    def first_link(self, key: MetaKey, default: Optional[str]=None) -> Optional[str]:

        try:

            return self.get_links(key)[0]

        except (IndexError, TypeError):

            return default

class PostingMeta(Metadata):

    """Combined access to posting metadata with its parent transaction metadata

    This lets you access posting metadata through a single dict-like object.

    If you try to look up metadata that doesn't exist on the posting, it will

    look for the value in the parent transaction metadata instead.

    You can set and delete metadata as well. Changes only affect the metadata

    of the posting, never the transaction. Changes are propagated to the

    underlying Beancount data structures.

    Functionally, you can think of this as identical to:

      collections.ChainMap(post.meta, txn.meta)

    Under the hood, this class does a little extra work to avoid creating

    posting metadata if it doesn't have to.

    """

    __slots__ = ('txn', 'index', 'post')

    def __init__(self,

                 txn: Transaction,

                 index: int,

                 post: Optional[BasePosting]=None,

    ) -> None:

        if post is None:

            post = txn.postings[index]

        self.txn = txn

        self.index = index

        self.post = post

        if post.meta is None:

            self.meta = self.txn.meta

        else:

            self.meta = collections.ChainMap(post.meta, txn.meta)

    def __getitem__(self, key: MetaKey) -> MetaValue:

        try:

            return super().__getitem__(key)

        except KeyError:

            if key == 'entity' and self.txn.payee is not None:

                return self.txn.payee

            else:

                raise

    def __setitem__(self, key: MetaKey, value: MetaValue) -> None:

        if self.post.meta is None:

            self.post = self.post._replace(meta={key: value})

            )

            groups[f'{post.account} {post_invoice} {post_entity}'].append(post)

        type_self = type(self)

        for group_key, posts in groups.items():

            yield group_key, type_self(posts, _can_own=True)

    def is_paid(self, default: Optional[bool]=None) -> Optional[bool]:

        if self.accrual_type is None:

            return default

        else:

            return self.end_balance.le_zero()

    def is_zero(self, default: Optional[bool]=None) -> Optional[bool]:

        if self.accrual_type is None:

            return default

        else:

            return self.end_balance.is_zero()

    def since_last_nonzero(self) -> 'AccrualPostings':

        for index, (post, balance) in enumerate(self.iter_with_balance()):

            if balance.is_zero():

                start_index = index

        try:

            empty = start_index == index

        except NameError:

            empty = True

        return self if empty else self[start_index + 1:]

    @property

    def rt_id(self) -> Union[str, None, Sentinel]:

        return self._single_item(self.first_meta_links('rt-id', None))

class BaseReport:

    def __init__(self, out_file: TextIO) -> None:

        self.out_file = out_file

        self.logger = logger.getChild(type(self).__name__)

    def _report(self, posts: AccrualPostings, index: int) -> Iterable[str]:

        raise NotImplementedError("BaseReport._report")

    def run(self, groups: PostGroups) -> None:

        for index, invoice in enumerate(groups):

            for line in self._report(groups[invoice], index):

                print(line, file=self.out_file)

class AgingODS(core.BaseODS[AccrualPostings, Optional[data.Account]]):

    COLUMNS = [

        'Date',

        'Invoice Amount',

        'Booked Amount',

    ]

    COL_COUNT = len(COLUMNS)

    def __init__(self,

                 rt_wrapper: rtutil.RT,

                 date: datetime.date,

                 logger: logging.Logger,

    ) -> None:

        super().__init__(rt_wrapper)

        self.date = date

        self.logger = logger

    def init_styles(self) -> None:

        super().init_styles()

        self.style_widecol = self.replace_child(

            self.document.automaticstyles,

            odf.style.Style,

            name='WideCol',

        )

        self.style_widecol.setAttribute('family', 'table-column')

        self.style_widecol.addElement(odf.style.TableColumnProperties(

            columnwidth='1.25in',

        ))

    def section_key(self, row: AccrualPostings) -> Optional[data.Account]:

        if isinstance(row.account, str):

            return row.account

        else:

            return None

    def start_spreadsheet(self) -> None:

        for accrual_type in AccrualAccount:

            self.use_sheet(accrual_type.name.title())

            for index in range(self.COL_COUNT):

                stylename = self.style_widecol if index else ''

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

            self.add_row(*(

                self.string_cell(name, stylename=self.style_bold)

                for name in self.COLUMNS

            ))

            self.lock_first_row()

    def start_section(self, key: Optional[data.Account]) -> None:

        if key is None:

            return

        self.age_thresholds = list(AccrualAccount.by_account(key).value.aging_thresholds)

        self.age_balances = [core.MutableBalance() for _ in self.age_thresholds]

        accrual_date = self.date - datetime.timedelta(days=self.age_thresholds[-1])

                age_range = f"Over {age_text}"

            else:

                age_range = f"{age_text}–{last_age_text}"

            self.add_row(

                self.string_cell(

                    f"Total Aged {age_range}: ",

                    stylename=text_style,

                    numbercolumnsspanned=text_span,

                ),

                *(odf.table.TableCell() for _ in range(1, text_span)),

                self.balance_cell(balance),

            )

            last_age_text = age_text

            total_balance += balance

        self.add_row(

            self.string_cell(

                "Total Unpaid: ",

                stylename=text_style,

                numbercolumnsspanned=text_span,

            ),

            *(odf.table.TableCell() for _ in range(1, text_span)),

            self.balance_cell(total_balance),

        )

    def write_row(self, row: AccrualPostings) -> None:

        age = (self.date - row[0].meta.date).days

        if row.end_balance.ge_zero():

            for index, threshold in enumerate(self.age_thresholds):

                if age >= threshold:

                    self.age_balances[index] += row.end_balance

                    break

            else:

                return

        raw_balance = row.balance()

        if row.accrual_type is not None:

            raw_balance = row.accrual_type.normalize_amount(raw_balance)

        if raw_balance == row.end_balance:

            amount_cell = odf.table.TableCell()

        else:

            amount_cell = self.balance_cell(raw_balance)

        projects = {post.meta.get('project') or None for post in row}

        projects.discard(None)

        self.add_row(

            self.date_cell(row[0].meta.date),

            self.multiline_cell(row.entities()),

            amount_cell,

            self.balance_cell(row.end_balance),

            self.multiline_cell(sorted(projects)),

        )

class AgingReport(BaseReport):

    def __init__(self,

                 rt_wrapper: rtutil.RT,

                 out_file: BinaryIO,

                 date: Optional[datetime.date]=None,

    ) -> None:

        if date is None:

            date = datetime.date.today()

        self.out_bin = out_file

        self.logger = logger.getChild(type(self).__name__)

        self.ods = AgingODS(rt_wrapper, date, self.logger)

    def run(self, groups: PostGroups) -> None:

        rows: List[AccrualPostings] = []

        for group in groups.values():

            if group.is_zero():

                # Cheap optimization: don't slice and dice groups we're not

                # going to report anyway.

                continue

            elif group.accrual_type is None:

                group = group.since_last_nonzero()

            else:

                # Filter out new accruals after the report date.

                # e.g., cover the case that the same invoices has multiple

                # postings over time, and we don't want to report too-recent

                # ones.

                cutoff_date = self.ods.date - datetime.timedelta(

                    days=group.accrual_type.value.aging_thresholds[-1],

                )

                group = AccrualPostings(

                    post for post in group.since_last_nonzero()

                    if post.meta.date <= cutoff_date

                    or group.accrual_type.normalize_amount(post.units.number) < 0

                )

            if group and not group.is_zero():

                rows.append(group)

        rows.sort(key=lambda related: (

            related.account,

            related[0].meta.date,

            ('\0'.join(related.entities())

             if related.entity is related.INCONSISTENT

             else related.entity),

        ))

        self.ods.write(rows)

        self.ods.save_file(self.out_bin)

    'link1  link2',

    ' link1  link2   link3    ',

])

def test_get_links(value):

    meta = data.Metadata({'key': value})

    assert list(meta.get_links('key')) == value.split()

def test_get_links_missing():

    meta = data.Metadata({})

    assert not meta.get_links('key')

@pytest.mark.parametrize('value', testutil.NON_STRING_METADATA_VALUES)

def test_get_links_bad_type(value):

    meta = data.Metadata({'key': value})

    with pytest.raises(TypeError):

        meta.get_links('key')

def test_first_link_from_txn(simple_txn):

    meta = data.PostingMeta(simple_txn, 0)

    assert meta.first_link('note') == 'txn'

def test_first_link_from_post_override(simple_txn):

    meta = data.PostingMeta(simple_txn, 1)

    assert meta.first_link('note') == 'donation'

def test_first_link_is_only_link(simple_txn):

    meta = data.PostingMeta(simple_txn, 1)

    assert meta.first_link('extra') == 'Extra'

def test_first_link_nonexistent_metadata(simple_txn):

    meta = data.PostingMeta(simple_txn, 1)

    assert meta.first_link('Nonexistent') is None

def test_first_link_nonexistent_default(simple_txn):

    meta = data.PostingMeta(simple_txn, 1)

    assert meta.first_link('Nonexistent', 'missing') == 'missing'

@pytest.mark.parametrize('meta_value', testutil.NON_STRING_METADATA_VALUES)

def test_first_link_bad_type_metadata(simple_txn, meta_value):

    simple_txn.meta['badmeta'] = meta_value

    meta = data.PostingMeta(simple_txn, 1)

    assert meta.first_link('badmeta') is None

@pytest.mark.parametrize('meta_value', testutil.NON_STRING_METADATA_VALUES)

def test_first_link_bad_type_default(simple_txn, meta_value):

    simple_txn.meta['badmeta'] = meta_value

    meta = data.PostingMeta(simple_txn, 1)

    assert meta.first_link('badmeta', '_') == '_'