'''
Plugin that splits off postings into a new transaction to simulate settlement dates.
'''
__copyright__ = 'Copyright (c) 2020  Kristóf Marussy <kristof@marussy.com>'
__license__ = 'GNU GPLv2'

from collections import defaultdict
import datetime as dt
from typing import Any, Dict, List, NamedTuple, Optional, Tuple, Union

from beancount.core import amount, convert
from beancount.core.amount import Amount
from beancount.core.data import Cost, CostSpec, Directive, Entries, Meta, Posting, Open, \
    Transaction
from beancount.core.inventory import Inventory
from beancount.core.number import ZERO

__plugins__ = ('split_entries_via_transfer_accounts',)

TRANSFER_ACCOUNT_META = 'transfer-account'
TRANSFER_DATE_META = 'transfer-date'
TRANSFER_CONVERTED_META = 'transfer-converted'
TRANSFER_CONVERTED_DEFAULT = True


class TransferAccountError(NamedTuple):
    source: Optional[Meta]
    message: str
    entry: Directive


class _OutgoingTransfer(NamedTuple):
    accout: str
    currency: str
    cost: Optional[Union[Cost, CostSpec]]
    price: Optional[Amount]


class _IncomingTransfer(NamedTuple):
    account: str
    date: dt.date


class _IncomingPostings(NamedTuple):
    postings: List[Posting]
    inventroy: Inventory


class _Splitter:
    _entry: Transaction
    _processed_entries: Entries
    _errors: List[TransferAccountError]
    _default_converted: Dict[str, bool]
    _processed_postings: List[Posting]
    _amounts_to_transfer: Dict[_OutgoingTransfer, Amount]
    _new_transactions: Dict[_IncomingTransfer, _IncomingPostings]

    def __init__(
            self,
            entry: Transaction,
            processed_entries: Entries,
            errors: List[TransferAccountError],
            default_converted: Dict[str, bool]):
        self._entry = entry
        self._processed_entries = processed_entries
        self._errors = errors
        self._default_converted = default_converted
        self._processed_postings = []
        self._amounts_to_transfer = {}
        self._new_transactions = defaultdict(lambda: _IncomingPostings([], Inventory()))

    def split(self) -> None:
        for posting in self._entry.postings:
            self._split_posting(posting)
        if not self._amounts_to_transfer:
            self._processed_entries.append(self._entry)
            return
        for (account, _, cost, price), units in self._amounts_to_transfer.items():
            if units.number != ZERO:
                self._processed_postings.append(Posting(account, units, cost, price, None, None))
        self._processed_entries.append(self._entry._replace(postings=self._processed_postings))
        for (account, date), (postings, inv) in self._new_transactions.items():
            for (units, cost) in inv:
                postings.append(Posting(account, -units, cost, None, None, None))
            self._processed_entries.append(self._entry._replace(date=date, postings=postings))

    def _split_posting(self, posting: Posting) -> None:
        if not posting.meta:
            self._processed_postings.append(posting)
            return
        transfer_account = posting.meta.pop(TRANSFER_ACCOUNT_META, None)
        transfer_date = posting.meta.pop(TRANSFER_DATE_META, None)
        transfer_converted = posting.meta.pop(TRANSFER_CONVERTED_META, None)
        if transfer_account is None:
            if transfer_date is not None:
                self._report_error(
                    f'{TRANSFER_DATE_META} was set but {TRANSFER_ACCOUNT_META} was not')
            if transfer_converted is not None:
                self._report_error(
                    f'{TRANSFER_CONVERTED_META} was set but {TRANSFER_ACCOUNT_META} was not')
            self._processed_postings.append(posting)
            return
        if not isinstance(transfer_account, str):
            self._report_error(
                f'{TRANSFER_ACCOUNT_META} must be a string, got {transfer_account} instead')
            self._processed_postings.append(posting)
            return
        if transfer_date is None:
            transfer_date = self._entry.date
        elif not isinstance(transfer_date, dt.date):
            self._report_error(
                f'{TRANSFER_DATE_META} must be a date, got {transfer_date} instead')
            transfer_date = self._entry.date
        transfer_converted_default = self._default_converted.get(
            transfer_account, TRANSFER_CONVERTED_DEFAULT)
        if transfer_converted is None:
            transfer_converted = transfer_converted_default
        elif not isinstance(transfer_converted, bool):
            self._report_error(
                f'{TRANSFER_CONVERTED_META} must be a Boolean, got {transfer_converted} instead')
            transfer_converted = transfer_converted_default
        elif posting.price is None and posting.cost is None:
            self._report_error(
                f'{TRANSFER_CONVERTED_META} was set, but there is no conversion')
        assert posting.units
        self._split_posting_with_options(
            posting, transfer_account, transfer_date, transfer_converted)

    def _split_posting_with_options(
            self,
            posting: Posting,
            transfer_account: str,
            transfer_date: dt.date,
            transfer_converted: bool) -> None:
        incoming = _IncomingTransfer(transfer_account, transfer_date)
        incoming_postings, inv = self._new_transactions[incoming]
        converted_amount = convert.get_weight(posting)
        if transfer_converted:
            outgoing = _OutgoingTransfer(
                transfer_account, posting.units.currency, posting.cost, posting.price)
            self._accumulate_outgoing(outgoing, posting.units)
            incoming_postings.append(posting._replace(price=None))
            inv.add_amount(posting.units, posting.cost)
        else:
            outgoing = _OutgoingTransfer(transfer_account, converted_amount.currency, None, None)
            self._accumulate_outgoing(outgoing, converted_amount)
            incoming_postings.append(posting)
            inv.add_amount(converted_amount)

    def _accumulate_outgoing(self, outgoing: _OutgoingTransfer, units: Amount) -> None:
        current_amount = self._amounts_to_transfer.get(outgoing, None)
        if current_amount:
            self._amounts_to_transfer[outgoing] = amount.add(current_amount, units)
        else:
            self._amounts_to_transfer[outgoing] = units

    def _report_error(self, message: str) -> None:
        self._errors.append(TransferAccountError(self._entry.meta, message, self._entry))


def split_entries_via_transfer_accounts(
        entries: Entries,
        options_map: Dict[str, Any],
        config_str: Optional[str] = None) -> Tuple[Entries, List[TransferAccountError]]:
    default_converted: Dict[str, bool] = {}
    errors: List[TransferAccountError] = []
    for entry in entries:
        if isinstance(entry, Open):
            if not entry.meta:
                continue
            transfer_converted = entry.meta.get(TRANSFER_CONVERTED_META, None)
            if transfer_converted is None:
                continue
            if not isinstance(transfer_converted, bool):
                errors.append(TransferAccountError(
                    entry.meta,
                    f'{TRANSFER_CONVERTED_META} must be a Boolean,' +
                    f' got {transfer_converted} instead',
                    entry))
            default_converted[entry.account] = transfer_converted
    processed_entries: Entries = []
    for entry in entries:
        if isinstance(entry, Transaction):
            splitter = _Splitter(entry, processed_entries, errors, default_converted)
            splitter.split()
        else:
            processed_entries.append(entry)
    return processed_entries, errors