reports: Add normalize_amount_func() function.

conservancy_beancount/reports/accrual.py

@@ -125,6 +125,7 @@ STANDARD_PATH = Path('-')
 CompoundAmount = TypeVar('CompoundAmount', data.Amount, core.Balance)
 PostGroups = Mapping[Optional[MetaValue], 'AccrualPostings']
 RTObject = Mapping[str, str]
+T = TypeVar('T')
 
 logger = logging.getLogger('conservancy_beancount.reports.accrual')
 
@@ -134,19 +135,14 @@ class Sentinel:
 
 class Account(NamedTuple):
     name: str
-    norm_func: Callable[[CompoundAmount], CompoundAmount]
     aging_thresholds: Sequence[int]
 
 
 class AccrualAccount(enum.Enum):
     # Note the aging report uses the same order accounts are defined here.
     # See AgingODS.start_spreadsheet().
-    RECEIVABLE = Account(
-        'Assets:Receivable', lambda bal: bal, [365, 120, 90, 60],
-    )
-    PAYABLE = Account(
-        'Liabilities:Payable', operator.neg, [365, 90, 60, 30],
-    )
+    RECEIVABLE = Account('Assets:Receivable', [365, 120, 90, 60])
+    PAYABLE = Account('Liabilities:Payable', [365, 90, 60, 30])
 
     @classmethod
     def account_names(cls) -> Iterator[str]:
@@ -167,6 +163,10 @@ class AccrualAccount(enum.Enum):
                 return account
         raise ValueError("unrecognized account set in related postings")
 
+    @property
+    def normalize_amount(self) -> Callable[[T], T]:
+        return core.normalize_amount_func(self.value.name)
+
 
 class AccrualPostings(core.RelatedPostings):
     def _meta_getter(key: MetaKey) -> Callable[[data.Posting], MetaValue]:  # type:ignore[misc]
@@ -221,8 +221,7 @@ class AccrualPostings(core.RelatedPostings):
             self.paid_entities = self.accrued_entities
         else:
             self.accrual_type = AccrualAccount.classify(self)
-            accrual_acct: Account = self.accrual_type.value
-            norm_func = accrual_acct.norm_func
+            norm_func = self.accrual_type.normalize_amount
             self.end_balance = norm_func(self.balance_at_cost())
             self.accrued_entities = self._collect_entities(
                 lambda post: norm_func(post.units).number > 0,
@@ -453,7 +452,7 @@ class AgingODS(core.BaseODS[AccrualPostings, Optional[data.Account]]):
                 return
         raw_balance = row.balance()
         if row.accrual_type is not None:
-            raw_balance = row.accrual_type.value.norm_func(raw_balance)
+            raw_balance = row.accrual_type.normalize_amount(raw_balance)
         if raw_balance == row.end_balance:
             amount_cell = odf.table.TableCell()
         else:

conservancy_beancount/reports/core.py

@@ -73,6 +73,7 @@ LinkType = Union[str, Tuple[str, Optional[str]]]
 RelatedType = TypeVar('RelatedType', bound='RelatedPostings')
 RT = TypeVar('RT', bound=Sequence)
 ST = TypeVar('ST')
+T = TypeVar('T')
 
 class Balance(Mapping[str, data.Amount]):
     """A collection of amounts mapped by currency
@@ -898,3 +899,21 @@ class BaseODS(BaseSpreadsheet[RT, ST], metaclass=abc.ABCMeta):
         with path.open(f'{mode}b') as out_file:
             out_file = cast(BinaryIO, out_file)
             self.save_file(out_file)
+
+
+def normalize_amount_func(account_name: str) -> Callable[[T], T]:
+    """Get a function to normalize amounts for reporting
+
+    Given an account name, return a function that can be used on "amounts"
+    under that account (including numbers, Amount objects, and Balance objects)
+    to normalize them for reporting. Right now that means make flipping the
+    sign for accounts where "normal" postings are negative.
+    """
+    if account_name.startswith(('Assets:', 'Expenses:')):
+        # We can't just return operator.pos because Beancount's Amount class
+        # doesn't implement __pos__.
+        return lambda amt: amt
+    elif account_name.startswith(('Equity:', 'Income:', 'Liabilities:')):
+        return operator.neg
+    else:
+        raise ValueError(f"unrecognized account name {account_name!r}")

tests/test_reports_core.py

@@ -0,0 +1,66 @@
+"""test_reports_core - Unit tests for basic reports functions"""
+# 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 pytest
+
+from decimal import Decimal
+
+from . import testutil
+
+from conservancy_beancount.reports import core
+
+AMOUNTS = [
+    2,
+    Decimal('4.40'),
+    testutil.Amount('6.60', 'CHF'),
+    core.Balance([testutil.Amount('8.80')]),
+]
+
+@pytest.mark.parametrize('acct_name', [
+    'Assets:Checking',
+    'Assets:Receivable:Accounts',
+    'Expenses:Other',
+    'Expenses:FilingFees',
+])
+def test_normalize_amount_func_pos(acct_name):
+    actual = core.normalize_amount_func(acct_name)
+    for amount in AMOUNTS:
+        assert actual(amount) == amount
+
+@pytest.mark.parametrize('acct_name', [
+    'Equity:Funds:Restricted',
+    'Equity:Realized:CurrencyConversion',
+    'Income:Donations',
+    'Income:Other',
+    'Liabilities:CreditCard',
+    'Liabilities:Payable:Accounts',
+])
+def test_normalize_amount_func_neg(acct_name):
+    actual = core.normalize_amount_func(acct_name)
+    for amount in AMOUNTS:
+        assert actual(amount) == -amount
+
+@pytest.mark.parametrize('acct_name', [
+    '',
+    'Assets',
+    'Equity',
+    'Expenses',
+    'Income',
+    'Liabilities',
+])
+def test_normalize_amount_func_bad_acct_name(acct_name):
+    with pytest.raises(ValueError):
+        core.normalize_amount_func(acct_name)