Proper complete implementation of cash basis based on FIFO

ledger_pyreport/__init__.py

@@ -45,7 +45,7 @@ def trial():
 		# Get trial balance
 		l = ledger.raw_transactions_at_date(date)
 		if cash:
-			l = accounting.cash_basis(l, report_currency)
+			l = accounting.ledger_to_cash(l, report_currency)
 		trial_balance = accounting.trial_balance(l, date, pstart)
 		
 		trial_balance = accounting.add_unrealized_gains(trial_balance, report_currency)
@@ -69,7 +69,7 @@ def trial():
 		
 		l = ledger.raw_transactions_at_date(date)
 		if cash:
-			l = accounting.cash_basis(l, report_currency)
+			l = accounting.ledger_to_cash(l, report_currency)
 		trial_balances = [accounting.add_unrealized_gains(accounting.trial_balance(l, d, p), report_currency) for d, p in zip(dates, pstarts)]
 		
 		# Delete accounts with always zero balances
@@ -93,7 +93,7 @@ def balance():
 	report_currency = Currency(*config['report_currency'])
 	l = ledger.raw_transactions_at_date(date)
 	if cash:
-		l = accounting.cash_basis(l, report_currency)
+		l = accounting.ledger_to_cash(l, report_currency)
 	balance_sheets = [accounting.balance_sheet(accounting.add_unrealized_gains(accounting.trial_balance(l, d, p), report_currency)) for d, p in zip(dates, pstarts)]
 	
 	# Delete accounts with always zero balances
@@ -125,7 +125,7 @@ def pandl():
 	report_currency = Currency(*config['report_currency'])
 	l = ledger.raw_transactions_at_date(date_end)
 	if cash:
-		l = accounting.cash_basis(l, report_currency)
+		l = accounting.ledger_to_cash(l, report_currency)
 	pandls = [accounting.trial_balance(l, de, db) for de, db in zip(dates_end, dates_beg)]
 	
 	# Delete accounts with always zero balances
@@ -148,7 +148,7 @@ def transactions():
 	# General ledger
 	l = ledger.raw_transactions_at_date(date)
 	if cash:
-		l = accounting.cash_basis(l, report_currency)
+		l = accounting.ledger_to_cash(l, report_currency)
 	
 	# Unrealized gains
 	l = accounting.add_unrealized_gains(accounting.trial_balance(l, date, pstart), report_currency).ledger
@@ -159,7 +159,7 @@ def transactions():
 		total_dr = sum((p.amount for t in transactions for p in t.postings if p.amount > 0), Balance()).exchange(report_currency, True)
 		total_cr = sum((p.amount for t in transactions for p in t.postings if p.amount < 0), Balance()).exchange(report_currency, True)
 		
-		return flask.render_template('transactions.html', date=date, pstart=pstart, account=None, ledger=l, transactions=transactions, total_dr=total_dr, total_cr=total_cr, report_currency=report_currency, cash=cash)
+		return flask.render_template('transactions.html', date=date, pstart=pstart, period=describe_period(date, pstart), account=None, ledger=l, transactions=transactions, total_dr=total_dr, total_cr=total_cr, report_currency=report_currency, cash=cash)
 	else:
 		account = l.get_account(account)
 		transactions = [t for t in l.transactions if t.date <= date and t.date >= pstart and any(p.account == account for p in t.postings)]
@@ -169,6 +169,8 @@ def transactions():
 		
 		return flask.render_template('transactions.html', date=date, pstart=pstart, period=describe_period(date, pstart), account=account, ledger=l, transactions=transactions, opening_balance=opening_balance, closing_balance=closing_balance, report_currency=report_currency, cash=cash, timedelta=timedelta)
 
+# Template filters
+
 @app.template_filter('a')
 def filter_amount(amt):
 	if amt.amount < 0.005 and amt.amount >= -0.005:
@@ -186,3 +188,41 @@ def filter_amount_positive(amt):
 @app.template_filter('bb')
 def filter_balance_positive(balance):
 	return flask.Markup('<br>'.join(filter_amount_positive(a) for a in balance.amounts))
+
+# Debug views
+
+@app.route('/debug/noncash_transactions')
+def debug_noncash_transactions():
+	date = datetime.strptime(flask.request.args['date'], '%Y-%m-%d')
+	pstart = datetime.strptime(flask.request.args['pstart'], '%Y-%m-%d')
+	account = flask.request.args.get('account')
+	
+	report_currency = Currency(*config['report_currency'])
+	
+	l = ledger.raw_transactions_at_date(date)
+	account = l.get_account(account)
+	
+	transactions = [t for t in l.transactions if any(p.account == account for p in t.postings)]
+	
+	accounting.account_to_cash(account, report_currency)
+	
+	return flask.render_template('debug_noncash_transactions.html', date=date, pstart=pstart, period=describe_period(date, pstart), account=account, ledger=l, transactions=transactions, report_currency=report_currency)
+
+@app.route('/debug/imbalances')
+def debug_imbalances():
+	date = datetime.strptime(flask.request.args['date'], '%Y-%m-%d')
+	pstart = datetime.strptime(flask.request.args['pstart'], '%Y-%m-%d')
+	cash = flask.request.args.get('cash', False)
+	
+	report_currency = Currency(*config['report_currency'])
+	
+	l = ledger.raw_transactions_at_date(date)
+	if cash:
+		l = accounting.ledger_to_cash(l, report_currency)
+	
+	transactions = [t for t in l.transactions if t.date <= date and t.date >= pstart and abs(sum((p.amount for p in t.postings), Balance()).exchange(report_currency, True).amount) > 0.005]
+	
+	total_dr = sum((p.amount for t in transactions for p in t.postings if p.amount > 0), Balance()).exchange(report_currency, True)
+	total_cr = sum((p.amount for t in transactions for p in t.postings if p.amount < 0), Balance()).exchange(report_currency, True)
+	
+	return flask.render_template('transactions.html', date=date, pstart=pstart, period=describe_period(date, pstart), account=None, ledger=l, transactions=transactions, total_dr=total_dr, total_cr=total_cr, report_currency=report_currency, cash=cash)

ledger_pyreport/accounting.py

@@ -16,6 +16,7 @@
 
 import csv
 from decimal import Decimal
+import math
 
 from .model import *
 
@@ -65,27 +66,64 @@ def balance_sheet(tb):
 	
 	return tb
 
-# Adjust (in place) a ledger to convert accounting to a cash basis
+def account_to_cash(account, currency):
-def cash_basis(ledger, currency):
+	# Apply FIFO methodology to match postings
-	for transaction in ledger.transactions:
+	balance = [] # list of [posting, amount to balance, amount remaining, balancing list of [posting, amount balanced]]
-		non_cash_postings = [p for p in transaction.postings if not (p.account.is_cash or p.account.is_income or p.account.is_expense or p.account.is_equity)]
 	
-		if non_cash_postings:
+	for transaction in account.ledger.transactions[:]:
-			# We have liabilities or non-cash assets which need to be excluded
+		if any(p.account == account for p in transaction.postings):
-			
+			for posting in transaction.postings[:]:
-			cash_postings = [p for p in transaction.postings if p.account.is_income or p.account.is_expense or p.account.is_equity]
+				if posting.account == account:
-			cash_total = sum((p.amount for p in cash_postings), Balance()).exchange(currency, True).amount
+					#transaction.postings.remove(posting)
-			
+					pass
-			if cash_postings:
-				for posting in non_cash_postings:
-					posting_amount = posting.amount.exchange(currency, True).amount
-					for posting_xfer in cash_postings:
-						posting_xfer_amount = posting_xfer.amount.exchange(currency, True).amount
-						transaction.postings.append(Posting(transaction, posting_xfer.account, Amount(posting_amount * posting_xfer_amount / cash_total, currency)))
-					
-					transaction.postings.remove(posting)
 				else:
-				for posting in non_cash_postings:
+					# Try to balance postings
-					posting.account = ledger.get_account(config['cash_other_income'])
+					amount_to_balance = posting.amount.exchange(currency, True).amount
+					
+					while amount_to_balance != 0:
+						balancing_posting = next((b for b in balance if b[2] != 0 and math.copysign(1, b[2]) != math.copysign(1, amount_to_balance)), None)
+						if balancing_posting is None:
+							break
+						
+						if abs(balancing_posting[2]) >= abs(amount_to_balance):
+							balancing_posting[3].append([posting, amount_to_balance])
+							balancing_posting[2] += amount_to_balance
+							amount_to_balance = Decimal(0)
+							break
+						else:
+							balancing_posting[3].append([posting, -balancing_posting[2]])
+							amount_to_balance += balancing_posting[2]
+							balancing_posting[2] = Decimal(0)
+					
+					if amount_to_balance != 0:
+						# New unbalanced remainder
+						balance.append([posting, amount_to_balance, amount_to_balance, []])
+			
+			transaction.postings = []
+	
+	# Finalise balanced postings
+	for orig_posting, amount_to_balance, amount_remaining, balancing_postings in balance:
+		posting = Posting(orig_posting.transaction, orig_posting.account, Amount(amount_to_balance, currency))
+		posting.transaction.postings.append(posting)
+		
+		for balancing_posting, amount_balanced in balancing_postings:
+			posting.transaction.postings.append(Posting(posting.transaction, balancing_posting.account, Amount(amount_balanced, currency)))
+			
+			if balancing_posting in balancing_posting.transaction.postings:
+				balancing_posting.transaction.postings.remove(balancing_posting)
+		
+		if amount_remaining != 0:
+			if account.is_asset:
+				# Cash - charge any unbalanced remainder to Other Income
+				posting.transaction.postings.append(Posting(posting.transaction, account.ledger.get_account(config['cash_other_income']), Amount(-amount_remaining, currency)))
+			else:
+				# Liabilities, etc. - discard any unbalanced remainder
+				posting.amount.amount -= amount_remaining
+
+# Adjust (in place) a ledger to convert accounting to a cash basis
+def ledger_to_cash(ledger, currency):
+	for account in list(ledger.accounts.values()):
+		if not (account.is_cash or account.is_income or account.is_expense or account.is_equity):
+			account_to_cash(account, currency)
 	
 	return ledger

ledger_pyreport/jinja2/debug_noncash_transactions.html

@@ -0,0 +1,50 @@
+{#
+    ledger-pyreport
+    Copyright © 2020  Lee Yingtong Li (RunasSudo)
+ 
+    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/>.
+#}
+
+{% extends 'base_report.html' %}
+
+{% block title %}Account Transactions as at {{ date.strftime('%d %B %Y') }}{% endblock %}
+
+{% block report %}
+	<h1>Account Transactions</h1>
+	<h2 style="margin-bottom: 0;">For {{ account.name }}</h2>
+	<h2>For the {{ period }}</h2>
+	
+	<table class="ledger">
+		<tr>
+			<th style="width: 5em;">Date</th>
+			<th>Description</th>
+			<th style="max-width: 8em;">Account</th>
+			<th class="h1" style="text-align: right; width: 5em;">Dr</th>
+			<th class="h1" style="text-align: right; width: 5em;">Cr</th>
+		</tr>
+		
+		{% for transaction in transactions %}
+			{% for posting in transaction.postings %}
+				{% set amount = posting.exchange(report_currency, transaction.date) %}
+				<tr>
+					<td>{% if loop.first %}{{ transaction.date.strftime('%Y-%m-%d') }}{% endif %}</td>
+					<td>{% if loop.first %}{{ transaction.description }}{% endif %}</td>
+					<td>{{ (posting.account.name|e).__str__().replace(':', ':<wbr>')|safe }}</td>
+					<td style="text-align: right;">{% if amount > 0 %}<span title="{{ posting.amount.tostr(False) }}">{{ amount|b }}</span>{% endif %}</td>
+					<td style="text-align: right;">{% if amount < 0 %}<span title="{{ (-posting.amount).tostr(False) }}">{{ -amount|b }}</span>{% endif %}</td>
+				</tr>
+			{% endfor %}
+		{% endfor %}
+	</table>
+{% endblock %}