"""test_reports_related_postings - Unit tests for RelatedPostings"""
# 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 itertools

from decimal import Decimal

import pytest

from . import testutil

from conservancy_beancount import data
from conservancy_beancount.reports import core

def date_seq(date=testutil.FY_MID_DATE, step=1):
    while True:
        yield date
        date = date + datetime.timedelta(days=step)

def accruals_and_payments(acct, src_acct, dst_acct, start_date, *amounts):
    dates = date_seq(start_date)
    for amt, currency in amounts:
        yield testutil.Transaction(date=next(dates), postings=[
            (acct, amt, currency),
            (dst_acct if amt < 0 else src_acct, -amt, currency),
        ])

@pytest.fixture
def credit_card_cycle():
    return list(accruals_and_payments(
        'Liabilities:CreditCard',
        'Assets:Checking',
        'Expenses:Other',
        datetime.date(2020, 4, 1),
        (-110, 'USD'),
        (110, 'USD'),
        (-120, 'USD'),
        (120, 'USD'),
    ))

@pytest.fixture
def two_accruals_three_payments():
    return list(accruals_and_payments(
        'Assets:Receivable:Accounts',
        'Income:Donations',
        'Assets:Checking',
        datetime.date(2020, 4, 10),
        (440, 'USD'),
        (-230, 'USD'),
        (550, 'EUR'),
        (-210, 'USD'),
        (-550, 'EUR'),
    ))

def test_balance_empty():
    balance = core.RelatedPostings().balance()
    assert not balance
    assert balance.is_zero()

def test_balance_credit_card(credit_card_cycle):
    related = core.RelatedPostings()
    assert related.balance() == testutil.balance_map()
    expected = Decimal()
    for txn in credit_card_cycle:
        post = txn.postings[0]
        expected += post.units.number
        related.add(post)
        assert related.balance() == testutil.balance_map(USD=expected)
    assert expected == 0

def check_iter_with_balance(entries):
    expect_posts = [txn.postings[0] for txn in entries]
    expect_balances = []
    balance_tally = collections.defaultdict(Decimal)
    related = core.RelatedPostings()
    for post in expect_posts:
        number, currency = post.units
        balance_tally[currency] += number
        expect_balances.append(testutil.balance_map(balance_tally.items()))
        related.add(post)
    for (post, balance), exp_post, exp_balance in zip(
            related.iter_with_balance(),
            expect_posts,
            expect_balances,
    ):
        assert post is exp_post
        assert balance == exp_balance
    assert post is expect_posts[-1]
    assert related.balance() == expect_balances[-1]

def test_iter_with_balance_empty():
    assert not list(core.RelatedPostings().iter_with_balance())

def test_iter_with_balance_credit_card(credit_card_cycle):
    check_iter_with_balance(credit_card_cycle)

def test_iter_with_balance_two_acccruals(two_accruals_three_payments):
    check_iter_with_balance(two_accruals_three_payments)