"""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

from beancount.core import account as bc_account

from typing import (

    Iterable,

    Iterator,

    MutableMapping,

    Optional,

    Sequence,

)

from .beancount_types import (

    MetaKey,

    MetaValue,

    Posting as BasePosting,

    Transaction,

)

LINK_METADATA = frozenset([

    'approval',

    'check',

    'contract',

    'invoice',

    'purchase-order',

    'receipt',

    'statement',

])

class Account(str):

    """Account name string

    This is a string that names an account, like Accrued:AccountsPayable

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

    account name parsing and queries.

    """

    SEP = bc_account.sep

    def is_income(self) -> bool:

        return self.is_under('Income:', 'UnearnedIncome:') is not None

    def is_real_asset(self) -> bool:

        return bool(

            self.is_under('Assets:')

            and not self.is_under('Assets:PrepaidExpenses', 'Assets:PrepaidVacation')

        )

    def is_under(self, *acct_seq: str) -> Optional[str]:

        """Return a match if this account is "under" a part of the hierarchy

        Pass in any number of account name strings as arguments. If this

        account is under one of those strings in the account hierarchy, the

        first matching string will be returned. Otherwise, None is returned.

        You can use the return value of this method as a boolean if you don't

        care which account string is matched.

        An account is considered to be under itself:

          Account('Expenses:Tax').is_under('Expenses:Tax') # returns 'Expenses:Tax'

        To do a "strictly under" search, end your search strings with colons:

          Account('Expenses:Tax').is_under('Expenses:Tax:') # returns None

          Account('Expenses:Tax').is_under('Expenses:') # returns 'Expenses:'

        This method does check that all the account boundaries match:

          Account('Expenses:Tax').is_under('Exp') # returns None

        """

        for prefix in acct_seq:

            if self.startswith(prefix) and (

                prefix.endswith(self.SEP)

                or self == prefix

                or self[len(prefix)] == self.SEP

            ):

                return prefix

        return None

class Metadata(MutableMapping[MetaKey, MetaValue]):

    """Transaction or posting metadata

    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.

    """

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

        if self.post.meta is None:

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

            self.txn.postings[self.index] = self.post

            # mypy complains that self.post.meta could be None, but we know

            # from two lines up that it's not.

            self.meta = collections.ChainMap(self.post.meta, self.txn.meta)  # type:ignore[arg-type]

        else:

            super().__setitem__(key, value)

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

        if self.post.meta is None:

            raise KeyError(key)

        else:

            super().__delitem__(key)

class Posting(BasePosting):

    """Enhanced Posting objects

    This class is a subclass of Beancount's native Posting class where

    specific fields are replaced with enhanced versions:

    * The `account` field is an Account object

    * The `meta` field is a PostingMeta object

    """

    account: Account

    # mypy correctly complains that our MutableMapping is not compatible

    # with Beancount's meta type declaration of Optional[Dict]. IMO

    # Beancount's type declaration is a smidge too specific: I think its type

    # declaration should also use MutableMapping, because it would be very

    # unusual for code to specifically require a Dict over that.

    # If it did, this declaration would pass without issue.

    meta: Metadata  # type:ignore[assignment]

def iter_postings(txn: Transaction) -> Iterator[Posting]:

    """Yield an enhanced Posting object for every posting in the transaction"""

    for index, source in enumerate(txn.postings):

        yield Posting(

            Account(source.account),

            *source[1:5],

            # see rationale above about Posting.meta

            PostingMeta(txn, index, source), # type:ignore[arg-type]

        )

"""Mock Beancount objects for testing"""

# 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 beancount.core.amount as bc_amount

import beancount.core.data as bc_data

from decimal import Decimal

from pathlib import Path

from conservancy_beancount import rtutil

EXTREME_FUTURE_DATE = datetime.date(datetime.MAXYEAR, 12, 30)

FUTURE_DATE = datetime.date.today() + datetime.timedelta(days=365 * 99)

FY_START_DATE = datetime.date(2020, 3, 1)

FY_MID_DATE = datetime.date(2020, 9, 1)

PAST_DATE = datetime.date(2000, 1, 1)

TESTS_DIR = Path(__file__).parent

def check_post_meta(txn, *expected_meta, default=None):

    assert len(txn.postings) == len(expected_meta)

    for post, expected in zip(txn.postings, expected_meta):

        if not expected:

            assert not post.meta

        else:

            actual = None if post.meta is None else {

                key: post.meta.get(key, default) for key in expected

            }

            assert actual == expected

def combine_values(*value_seqs):

    return itertools.islice(

        zip(*(itertools.cycle(seq) for seq in value_seqs)),

    )

def parse_date(s, fmt='%Y-%m-%d'):

    return datetime.datetime.strptime(s, fmt).date()

def test_path(s):

    if s is None:

        return s

    s = Path(s)

    if not s.is_absolute():

        s = TESTS_DIR / s

    return s

def Amount(number, currency='USD'):

    return bc_amount.Amount(Decimal(number), currency)

def Posting(account, number,

            currency='USD', cost=None, price=None, flag=None,

            **meta):

    if not meta:

        meta = None

    return bc_data.Posting(

        account,

        bc_amount.Amount(Decimal(number), currency),

        cost,

        price,

        flag,

        meta,

    )

LINK_METADATA_STRINGS = {

    'Invoices/304321.pdf',

    'rt:123/456',

    'rt://ticket/234',

}

NON_LINK_METADATA_STRINGS = {

    '',

    ' ',

    '     ',

}

NON_STRING_METADATA_VALUES = [

    Decimal(5),

    FY_MID_DATE,

    Amount(50),

    Amount(500, None),

]

class Transaction:

    def __init__(self,

                 date=FY_MID_DATE, flag='*', payee=None,

                 narration='', tags=None, links=None, postings=None,

                 **meta):

        if isinstance(date, str):

            date = parse_date(date)

        self.date = date

        self.flag = flag

        self.payee = payee

        self.narration = narration

        self.tags = set(tags or '')

        self.links = set(links or '')

        self.postings = []

        self.meta = {