1 files changed, 70 insertions, 0 deletions

diff --git a/beancount_extras_kris7t/plugins/closing_balance.py b/beancount_extras_kris7t/plugins/closing_balance.py
new file mode 100644
index 0000000..a22e712
--- /dev/null
+++ b/beancount_extras_kris7t/plugins/closing_balance.py
@@ -0,0 +1,70 @@
+'''
+Plugin that closes an account by transferring its whole balance to another account.
+'''
+__copyright__ = 'Copyright (c) 2020  Kristóf Marussy <kristof@marussy.com>'
+__license__ = 'GNU GPLv2'
+
+from typing import Any, Dict, List, NamedTuple, Optional, Tuple
+
+from beancount.core.data import Balance, Close, Directive, Entries, Meta, Posting, Transaction
+from beancount.core.flags import FLAG_OKAY
+from beancount.core.number import ZERO
+
+__plugins__ = ('close_with_balance_assertions',)
+
+CLOSE_TO_META = 'close-to'
+CLOSING_META = 'closing'
+
+
+class ClosingBalanceError(NamedTuple):
+    source: Optional[Meta]
+    message: str
+    entry: Directive
+
+
+def close_with_balance_assertions(entries: Entries,
+                                  options_map: Dict[str, Any],
+                                  config_str: Optional[str] = None) -> \
+                                  Tuple[Entries, List[ClosingBalanceError]]:
+    new_entries: Entries = []
+    errors: List[ClosingBalanceError] = []
+    for entry in entries:
+        new_entries.append(entry)
+        if isinstance(entry, Balance) and CLOSE_TO_META in entry.meta:
+            close_to_account = entry.meta[CLOSE_TO_META]
+            if not isinstance(close_to_account, str):
+                errors.append(ClosingBalanceError(
+                    entry.meta,
+                    f'{CLOSE_TO_META} must be a string, got {close_to_account} instead',
+                    entry))
+                continue
+            if entry.tolerance is not None and entry.tolerance != ZERO:
+                errors.append(ClosingBalanceError(
+                    entry.meta,
+                    f'Closing an account requires {ZERO} tolerance, got {entry.tolerance} instead',
+                    entry))
+                continue
+            if entry.diff_amount is not None:
+                errors.append(ClosingBalanceError(
+                    entry.meta,
+                    f'Not closing {entry.account} with {entry.diff_amount} failed balance check',
+                    entry))
+                continue
+            new_meta = dict(entry.meta)
+            del new_meta[CLOSE_TO_META]
+            if entry.amount.number != ZERO:
+                new_entries.append(Transaction(
+                    new_meta,
+                    entry.date,
+                    FLAG_OKAY,
+                    None,
+                    f'Closing {entry.account}',
+                    set(),
+                    set(),
+                    [
+                        Posting(entry.account, -entry.amount, None, None, None,
+                                {CLOSING_META: True}),
+                        Posting(close_to_account, entry.amount, None, None, None, None)
+                    ]))
+            new_entries.append(Close(new_meta, entry.date, entry.account))
+    return new_entries, errors