#!/usr/bin/env python3

"""accrual-report - Status reports for accruals

accrual-report checks accruals (postings under Assets:Receivable and

Liabilities:Payable) for errors and metadata consistency, and reports any

problems on stderr. Then it writes a report about the status of those

accruals.

If you run it with no arguments, it will generate an aging report in ODS format

in the current directory.

Otherwise, the typical way to run it is to pass an RT ticket number or

invoice link as an argument, to report about accruals that match those

criteria::

    # Report all accruals associated with RT#1230:

    accrual-report 1230

    # Report all accruals with the invoice link rt:45/670.

    accrual-report 45/670

    # Report all accruals with the invoice link Invoice980.pdf.

    accrual-report Invoice980.pdf

By default, to stay fast, accrual-report only looks for postings from the

beginning of the last fiscal year. You can search further back in history

by passing the ``--since`` argument. The argument can be a fiscal year, or

a negative number of how many years back to search::

    # Search for accruals since 2016

    accrual-report --since 2016 [search terms …]

    # Search for accruals from the beginning of three fiscal years ago

    accrual-report --since -3 [search terms …]

If you want to further limit what accruals are reported, you can match on

other metadata by passing additional arguments in ``name=value`` format.

You can pass any number of search terms. For example::

    # Report accruals associated with RT#1230 and Jane Doe

    accrual-report 1230 entity=Doe-Jane

accrual-report will automatically decide what kind of report to generate

from the search terms you provide and the results they return. If you pass

no search terms, it generates an aging report. If your search terms match a

single outstanding payable, it writes an outgoing approval report.

Otherwise, it writes a basic balance report. You can specify what report

type you want with the ``--report-type`` option::

    # Write an outgoing approval report for all outstanding accruals for

    # Jane Doe, even if there's more than one

    accrual-report --report-type outgoing entity=Doe-Jane

    # Write an aging report for a specific project

    accrual-report --report-type aging project=ProjectName

"""

# 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 logging

import operator

import re

import sys

import urllib.parse as urlparse

from pathlib import Path

from typing import (

    cast,

    Any,

    BinaryIO,

    Callable,

    Dict,

    Iterable,

    Iterator,

    FrozenSet,

    List,

    Mapping,

    NamedTuple,

    Optional,

    Sequence,

    Set,

    TextIO,

    Tuple,

    TypeVar,

    Union,

)

from ..beancount_types import (

    Entries,

    Error,

    Errors,

    MetaKey,

    MetaValue,

    Transaction,

)

import odf.style  # type:ignore[import]

import odf.table  # type:ignore[import]

import rt

from beancount.parser import printer as bc_printer

from . import core

from .. import cliutil

from .. import config as configmod

from .. import data

from .. import filters

from .. import rtutil

PROGNAME = 'accrual-report'

STANDARD_PATH = Path('-')

CompoundAmount = TypeVar('CompoundAmount', data.Amount, core.Balance)

PostGroups = Mapping[Optional[MetaValue], 'AccrualPostings']

RTObject = Mapping[str, str]

logger = logging.getLogger('conservancy_beancount.reports.accrual')

class Sentinel:

    pass

class Account(NamedTuple):

    name: str

    aging_thresholds: Sequence[int]

class AccrualAccount(enum.Enum):

    # Note the aging report uses the same order accounts are defined here.

    # See AgingODS.start_spreadsheet().

    @classmethod

    def account_names(cls) -> Iterator[str]:

        return (acct.value.name for acct in cls)

    @classmethod

    def by_account(cls, name: data.Account) -> 'AccrualAccount':

        for account in cls:

            if name.is_under(account.value.name):

                return account

        raise ValueError(f"unrecognized account {name!r}")

    @classmethod

    def classify(cls, related: core.RelatedPostings) -> 'AccrualAccount':

        for account in cls:

            account_name = account.value.name

            if all(post.account.is_under(account_name) for post in related):

                return account

        raise ValueError("unrecognized account set in related postings")

class AccrualPostings(core.RelatedPostings):

    def _meta_getter(key: MetaKey) -> Callable[[data.Posting], MetaValue]:  # type:ignore[misc]

        def meta_getter(post: data.Posting) -> MetaValue:

            return post.meta.get(key)

        return meta_getter

    _FIELDS: Dict[str, Callable[[data.Posting], MetaValue]] = {

        'account': operator.attrgetter('account'),

        'contract': _meta_getter('contract'),

        'invoice': _meta_getter('invoice'),

        'purchase_order': _meta_getter('purchase-order'),

    }

    INCONSISTENT = Sentinel()

    __slots__ = (

        'accrual_type',

        'accrued_entities',

        'end_balance',

        'paid_entities',

        'account',

        'accounts',

        'contract',

        'contracts',

        'invoice',

        'invoices',

        'purchase_order',

        'purchase_orders',

    )

    def __init__(self,

                 source: Iterable[data.Posting]=(),

                 *,

                 _can_own: bool=False,

    ) -> None:

        super().__init__(source, _can_own=_can_own)

        # The following type declarations tell mypy about values set in the for

        # loop that are important enough to be referenced directly elsewhere.

        self.account: Union[data.Account, Sentinel]

        self.invoice: Union[MetaValue, Sentinel]

        for name, get_func in self._FIELDS.items():

            values = frozenset(get_func(post) for post in self)

            setattr(self, f'{name}s', values)

            if len(values) == 1:

                one_value = next(iter(values))

            else:

                one_value = self.INCONSISTENT

            setattr(self, name, one_value)

        if self.account is self.INCONSISTENT:

            self.accrual_type: Optional[AccrualAccount] = None

            self.end_balance = self.balance_at_cost()

            self.accrued_entities = self._collect_entities()

            self.paid_entities = self.accrued_entities

        else:

            self.accrual_type = AccrualAccount.classify(self)

            self.end_balance = norm_func(self.balance_at_cost())

            self.accrued_entities = self._collect_entities(

                lambda post: norm_func(post.units).number > 0,

            )

            self.paid_entities = self._collect_entities(

                lambda post: norm_func(post.units).number < 0,

            )

    def _collect_entities(self,

                          pred: Callable[[data.Posting], bool]=bool,

                          default: str='<empty>',

    ) -> FrozenSet[MetaValue]:

        return frozenset(

            post.meta.get('entity') or default

            for post in self if pred(post)

        )

    def entities(self) -> Iterator[MetaValue]:

        yield from self.accrued_entities

        yield from self.paid_entities.difference(self.accrued_entities)

    def make_consistent(self) -> Iterator[Tuple[MetaValue, 'AccrualPostings']]:

        account_ok = isinstance(self.account, str)

        if len(self.accrued_entities) == 1:

            entity = next(iter(self.accrued_entities))

        else:

            entity = None

        # `'/' in self.invoice` is just our heuristic to ensure that the

        # invoice metadata is "unique enough," and not just a placeholder

        # value like "FIXME". It can be refined if needed.

        invoice_ok = isinstance(self.invoice, str) and '/' in self.invoice

        if account_ok and entity is not None and invoice_ok:

            yield (self.invoice, self)

            return

        groups = collections.defaultdict(list)

        for post in self:

            post_invoice = self.invoice if invoice_ok else (

                post.meta.get('invoice') or 'BlankInvoice'

            )

            post_entity = entity if entity is not None else (

                post.meta.get('entity') or 'BlankEntity'

            )

            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 report_inconsistencies(self) -> Iterable[Error]:

        for field_name, get_func in self._FIELDS.items():

            if getattr(self, field_name) is self.INCONSISTENT:

                for post in self:

                    errmsg = 'inconsistent {} for invoice {}: {}'.format(

                        field_name.replace('_', '-'),

                        self.invoice or "<none>",

                        get_func(post),

                    )

                    yield Error(post.meta, errmsg, post.meta.txn)

        costs = collections.defaultdict(set)

        for post in self:

            costs[post.units.currency].add(post.cost)

        for code, currency_costs in costs.items():

            if len(currency_costs) > 1:

                for post in self:

                    if post.units.currency == code:

                        errmsg = 'inconsistent cost for invoice {}: {}'.format(

                            self.invoice or "<none>", post.cost,

                        )

                        yield Error(post.meta, errmsg, post.meta.txn)

    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:]

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',

        'Entity',

        'Invoice Amount',

        'Booked Amount',

        'Ticket',

        'Invoice',

    ]

    COL_COUNT = len(COLUMNS)

    def __init__(self,

                 rt_client: rt.Rt,

                 date: datetime.date,

                 logger: logging.Logger,

    ) -> None:

        super().__init__()

        self.rt_client = rt_client

        self.rt_wrapper = rtutil.RT(self.rt_client)

        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])

        acct_parts = key.split(':')

        self.use_sheet(acct_parts[1])

        self.add_row()

        self.add_row(self.string_cell(

            f"{' '.join(acct_parts[2:])} {acct_parts[1]} Aging Report"

            f" Accrued by {accrual_date.isoformat()} Unpaid by {self.date.isoformat()}",

            stylename=self.merge_styles(self.style_bold, self.style_centertext),

            numbercolumnsspanned=self.COL_COUNT,

        ))

        self.add_row()

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

        if key is None:

            return

        self.add_row()

        text_style = self.merge_styles(self.style_bold, self.style_endtext)

        text_span = self.COL_COUNT - 1

        for threshold, balance in zip(self.age_thresholds, self.age_balances):

            years, days = divmod(threshold, 365)

            years_text = f"{years} {'Year' if years == 1 else 'Years'}"

            days_text = f"{days} Days"

            if years and days:

                age_text = f"{years_text} {days_text}"

            elif years:

                age_text = years_text

            else:

                age_text = days_text

            self.add_row(

                self.string_cell(

                    f"Total Aged Over {age_text}: ",

                    stylename=text_style,

                    numbercolumnsspanned=text_span,

                ),

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

                self.balance_cell(balance),

            )

    def _link_seq(self, row: AccrualPostings, key: MetaKey) -> Iterator[Tuple[str, str]]:

        for href in row.all_meta_links(key):

            text: Optional[str] = None

            rt_ids = self.rt_wrapper.parse(href)

            if rt_ids is not None:

                ticket_id, attachment_id = rt_ids

                if attachment_id is None:

                    text = f'RT#{ticket_id}'

                href = self.rt_wrapper.url(ticket_id, attachment_id) or href

            else:

                # '..' pops the ODS filename off the link path. In other words,

                # make the link relative to the directory the ODS is in.

                href = f'../{href}'

            if text is None:

                href_path = Path(urlparse.urlparse(href).path)

                text = urlparse.unquote(href_path.name)

            yield (href, text)

    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:

        if raw_balance == row.end_balance:

            amount_cell = odf.table.TableCell()

        else:

            amount_cell = self.balance_cell(raw_balance)

        self.add_row(

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

            self.multiline_cell(row.entities()),

            amount_cell,

            self.balance_cell(row.end_balance),

            self.multilink_cell(self._link_seq(row, 'rt-id')),

            self.multilink_cell(self._link_seq(row, 'invoice')),

        )

class AgingReport(BaseReport):

    def __init__(self,

                 rt_client: rt.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_client, date, self.logger)

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

        rows = list(group for group in groups.values() if not group.is_zero())

        rows.sort(key=lambda related: (

            related.account,

            related[0].meta.date,

            min(related.entities()) if related.accrued_entities else '',

        ))

        self.ods.write(rows)

        self.ods.save_file(self.out_bin)

class BalanceReport(BaseReport):

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

        posts = posts.since_last_nonzero()

        date_s = posts[0].meta.date.strftime('%Y-%m-%d')

        if index:

            yield ""

        yield f"{posts.invoice}:"

        yield f"  {posts.balance_at_cost()} outstanding since {date_s}"

class OutgoingReport(BaseReport):

    def __init__(self, rt_client: rt.Rt, out_file: TextIO) -> None:

        super().__init__(out_file)

        self.rt_client = rt_client

        self.rt_wrapper = rtutil.RT(rt_client)

    def _primary_rt_id(self, posts: AccrualPostings) -> rtutil.TicketAttachmentIds:

        rt_ids: Set[str] = set()

        for post in posts:

            try:

                rt_ids.add(post.meta.get_links('rt-id')[0])

            except (IndexError, TypeError):

                pass

        rt_ids_count = len(rt_ids)

        if rt_ids_count != 1:

            raise ValueError(f"{rt_ids_count} rt-id links found")

        parsed = rtutil.RT.parse(rt_ids.pop())

        if parsed is None:

            raise ValueError("rt-id is not a valid RT reference")

        else:

            return parsed

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

        posts = posts.since_last_nonzero()

        try:

            ticket_id, _ = self._primary_rt_id(posts)

            ticket = self.rt_client.get_ticket(ticket_id)

            # Note we only use this when ticket is None.

            errmsg = f"ticket {ticket_id} not found"

        except (ValueError, rt.RtError) as error:

            ticket = None

            errmsg = error.args[0]

        if ticket is None:

            self.logger.error(

                "can't generate outgoings report for %s because no RT ticket available: %s",

                posts.invoice, errmsg,

            )

            return

        try:

            rt_requestor = self.rt_client.get_user(ticket['Requestors'][0])

        except (IndexError, rt.RtError):

            rt_requestor = None

        if rt_requestor is None:

            requestor = ''

            requestor_name = ''

        else:

            requestor_name = (

                rt_requestor.get('RealName')

                or ticket.get('CF.{payment-to}')

                or ''

            )

            requestor = f'{requestor_name} <{rt_requestor["EmailAddress"]}>'.strip()

        balance_s = posts.end_balance.format(None)

        raw_balance = -posts.balance()

        if raw_balance != posts.end_balance:

            balance_s = f'{raw_balance} ({balance_s})'

        contract_links = posts.all_meta_links('contract')

        if contract_links:

            contract_s = ' , '.join(self.rt_wrapper.iter_urls(

                contract_links, missing_fmt='<BROKEN RT LINK: {}>',

            ))

        else:

            contract_s = "NO CONTRACT GOVERNS THIS TRANSACTION"

        projects = [v for v in posts.meta_values('project')

                    if isinstance(v, str)]

        yield "PAYMENT FOR APPROVAL:"

        yield f"REQUESTOR: {requestor}"

        yield f"TOTAL TO PAY: {balance_s}"

        yield f"AGREEMENT: {contract_s}"

        yield f"PAYMENT TO: {ticket.get('CF.{payment-to}') or requestor_name}"

        yield f"PAYMENT METHOD: {ticket.get('CF.{payment-method}', '')}"

        yield f"PROJECT: {', '.join(projects)}"

        yield "\nBEANCOUNT ENTRIES:\n"

        last_txn: Optional[Transaction] = None

        for post in posts:

            txn = post.meta.txn

            if txn is not last_txn:

                last_txn = txn

                txn = self.rt_wrapper.txn_with_urls(txn, '{}')

                yield bc_printer.format_entry(txn)

class ReportType(enum.Enum):

    AGING = AgingReport

    BALANCE = BalanceReport

    OUTGOING = OutgoingReport

    AGE = AGING

    BAL = BALANCE

    OUT = OUTGOING

    OUTGOINGS = OUTGOING

    @classmethod

    def by_name(cls, name: str) -> 'ReportType':

        try:

            return cls[name.upper()]

        except KeyError:

            raise ValueError(f"unknown report type {name!r}") from None

    @classmethod

    def default_for(cls, groups: PostGroups) -> 'ReportType':

        if len(groups) == 1 and all(

                group.accrual_type is AccrualAccount.PAYABLE

                and not group.is_paid()

                for group in groups.values()

        ):

            return cls.OUTGOING

        else:

            return cls.BALANCE

class ReturnFlag(enum.IntFlag):

    LOAD_ERRORS = 1

    CONSISTENCY_ERRORS = 2

    REPORT_ERRORS = 4

    NOTHING_TO_REPORT = 8

def filter_search(postings: Iterable[data.Posting],

                  search_terms: Iterable[cliutil.SearchTerm],

) -> Iterable[data.Posting]:

    accounts = tuple(AccrualAccount.account_names())

    postings = (post for post in postings if post.account.is_under(*accounts))

    for query in search_terms:

        postings = query.filter_postings(postings)

    return postings

def parse_arguments(arglist: Optional[Sequence[str]]=None) -> argparse.Namespace:

    parser = argparse.ArgumentParser(prog=PROGNAME)

    cliutil.add_version_argument(parser)

    parser.add_argument(

        '--report-type', '-t',

        metavar='NAME',

        type=ReportType.by_name,

        help="""The type of report to generate, one of `aging`, `balance`, or

`outgoing`. If not specified, the default is `aging` when no search terms are

given, `outgoing` for search terms that return a single outstanding payable,

and `balance` any other time.

""")

    parser.add_argument(

        '--since',

        metavar='YEAR',

"""core.py - Common data classes for reporting functionality"""

# 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 abc

import collections

import datetime

import itertools

import operator

import re

import babel.core  # type:ignore[import]

import babel.numbers  # type:ignore[import]

import odf.config  # type:ignore[import]

import odf.element  # type:ignore[import]

import odf.number  # type:ignore[import]

import odf.opendocument  # type:ignore[import]

import odf.style  # type:ignore[import]

import odf.table  # type:ignore[import]

import odf.text  # type:ignore[import]

from decimal import Decimal

from pathlib import Path

from beancount.core import amount as bc_amount

from .. import data

from typing import (

    cast,

    overload,

    Any,

    BinaryIO,

    Callable,

    DefaultDict,

    Dict,

    Generic,

    Iterable,

    Iterator,

    List,

    Mapping,

    MutableMapping,

    Optional,

    Sequence,

    Set,

    Tuple,

    Type,

    TypeVar,

    Union,

)

from ..beancount_types import (

    MetaKey,

    MetaValue,

)

DecimalCompat = data.DecimalCompat

BalanceType = TypeVar('BalanceType', bound='Balance')

ElementType = Callable[..., odf.element.Element]

LinkType = Union[str, Tuple[str, Optional[str]]]

RelatedType = TypeVar('RelatedType', bound='RelatedPostings')

RT = TypeVar('RT', bound=Sequence)

ST = TypeVar('ST')

class Balance(Mapping[str, data.Amount]):

    """A collection of amounts mapped by currency

    Each key is a Beancount currency string, and each value represents the

    balance in that currency.

    """

    __slots__ = ('_currency_map', 'tolerance')

    TOLERANCE = Decimal('0.01')

    def __init__(self,

                 source: Iterable[data.Amount]=(),

                 tolerance: Optional[Decimal]=None,

    ) -> None:

        if tolerance is None:

            tolerance = self.TOLERANCE

        self._currency_map = {amount.currency: amount for amount in source}

        self.tolerance = tolerance

    def _add_amount(self,

                    currency_map: MutableMapping[str, data.Amount],

                    amount: data.Amount,

    ) -> None:

        code = amount.currency

        try:

            current_number = currency_map[code].number

        except KeyError:

            current_number = Decimal(0)

        currency_map[code] = data.Amount(current_number + amount.number, code)

    def _add_other(self,

                   currency_map: MutableMapping[str, data.Amount],

                   other: Union[data.Amount, 'Balance'],

    ) -> None:

        if isinstance(other, Balance):

            for amount in other.values():

                self._add_amount(currency_map, amount)

        else:

            self._add_amount(currency_map, other)

    def __repr__(self) -> str:

        values = [repr(amt) for amt in self.values()]

        return f"{type(self).__name__}({values!r})"

    def __str__(self) -> str:

        return self.format()

    def __abs__(self: BalanceType) -> BalanceType:

        return type(self)(bc_amount.abs(amt) for amt in self.values())

    def __add__(self: BalanceType, other: Union[data.Amount, 'Balance']) -> BalanceType:

        retval_map = self._currency_map.copy()

        self._add_other(retval_map, other)

        return type(self)(retval_map.values())

    def __eq__(self, other: Any) -> bool:

        if (self.is_zero()

            and isinstance(other, Balance)

            and other.is_zero()):

            return True

        else:

            return super().__eq__(other)

    def __neg__(self: BalanceType) -> BalanceType:

        return type(self)(-amt for amt in self.values())

    def __getitem__(self, key: str) -> data.Amount:

        return self._currency_map[key]

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

        return iter(self._currency_map)

    def __len__(self) -> int:

        return len(self._currency_map)

    def _all_amounts(self,

                     op_func: Callable[[DecimalCompat, DecimalCompat], bool],

                     operand: DecimalCompat,

    ) -> bool:

        return all(op_func(amt.number, operand) for amt in self.values())

    @staticmethod

    def within_tolerance(dec: DecimalCompat, tolerance: DecimalCompat) -> bool:

        dec = cast(Decimal, dec)

        return abs(dec) < tolerance

    def eq_zero(self) -> bool:

        """Returns true if all amounts in the balance == 0, within tolerance."""

        return self._all_amounts(self.within_tolerance, self.tolerance)

    is_zero = eq_zero

    def ge_zero(self) -> bool:

        """Returns true if all amounts in the balance >= 0, within tolerance."""

        op_func = operator.gt if self.tolerance else operator.ge

        return self._all_amounts(op_func, -self.tolerance)

    def le_zero(self) -> bool:

        """Returns true if all amounts in the balance <= 0, within tolerance."""

        op_func = operator.lt if self.tolerance else operator.le

        return self._all_amounts(op_func, self.tolerance)

    def format(self,

               fmt: Optional[str]='#,#00.00 ¤¤',

               sep: str=', ',

               empty: str="Zero balance",

    ) -> str:

        """Formats the balance as a string with the given parameters

        If the balance is zero, returns ``empty``. Otherwise, returns a string

        with each amount in the balance formatted as ``fmt``, separated by

        ``sep``.

        If you set ``fmt`` to None, amounts will be formatted according to the

        user's locale. The default format is Beancount's input format.

        """

        amounts = [amount for amount in self.values() if amount.number]

        if not amounts:

            return empty

        amounts.sort(key=lambda amt: abs(amt.number), reverse=True)

        return sep.join(

            babel.numbers.format_currency(amt.number, amt.currency, fmt)

            for amt in amounts

        )

class MutableBalance(Balance):

    __slots__ = ()

    def __iadd__(self: BalanceType, other: Union[data.Amount, Balance]) -> BalanceType:

        self._add_other(self._currency_map, other)

        return self

class RelatedPostings(Sequence[data.Posting]):

    """Collect and query related postings

    This class provides common functionality for collecting related postings

    and running queries on them: iterating over them, tallying their balance,

    etc.