DrCr/austax/__init__.py

#   DrCr: Web-based double-entry bookkeeping framework
#   Copyright (C) 2022–2023  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/>.

from flask import render_template

from drcr.models import AccountConfiguration, Amount, Posting, Transaction, TrialBalancer
from drcr.database import db
import drcr.plugins
from drcr.plugins import render_plugin_template
from drcr.webapp import app

from .models import CGTAsset
from .reports import eofy_date, tax_summary_report

def plugin_init():
	drcr.plugins.advanced_reports.append(('/tax/cgt-assets', 'CGT assets'))
	drcr.plugins.advanced_reports.append(('/tax/summary', 'Tax summary'))
	
	drcr.plugins.account_kinds.append(('austax.income1', 'Salary or wages (1)'))
	drcr.plugins.account_kinds.append(('austax.income5', 'Australian Government allowances and payments (5)'))
	drcr.plugins.account_kinds.append(('austax.income10', 'Gross interest (10)'))
	drcr.plugins.account_kinds.append(('austax.d4', 'Work-related self-education expenses (D4)'))
	drcr.plugins.account_kinds.append(('austax.d5', 'Other work-related expenses (D5)'))
	drcr.plugins.account_kinds.append(('austax.paygw', 'PAYG withheld amounts'))
	drcr.plugins.account_kinds.append(('austax.cgtasset', 'CGT asset'))
	
	drcr.plugins.transaction_providers.append(make_tax_transactions)

@app.route('/tax/cgt-assets')
def cgt_assets():
	# Find all CGT asset accounts
	cgt_accounts = []
	account_configurations = AccountConfiguration.get_all_kinds()
	for account_name, kinds in account_configurations.items():
		if 'austax.cgtasset' in kinds:
			cgt_accounts.append(account_name)
	
	# Get all postings to CGT asset accounts
	cgt_postings = db.session.scalars(
		db.select(Posting)
		.where(Posting.account.in_(cgt_accounts))
		.join(Posting.transaction)
		.order_by(Transaction.dt)
	).all()
	
	# Process postings to determine final balances
	assets = []
	
	for posting in cgt_postings:
		if posting.quantity >= 0:
			assets.append(CGTAsset(posting.quantity, posting.commodity, posting.account, posting.transaction.dt))
		elif posting.quantity < 0:
			asset = next((a for a in assets if a.commodity == posting.commodity and a.account == posting.account), None)
			
			if asset is None:
				raise Exception('Attempted credit {} without preceding debit balance'.quantity(posting.amount()))
			if asset.quantity + posting.quantity < 0:
				raise Exception('Attempted credit {} with insufficient debit balance {}'.quantity(posting.amount(), asset.amount()))
			
			if asset.quantity + posting.quantity != 0:
				raise NotImplementedError('Partial disposal of CGT asset not implemented')
			
			asset.disposal_date = posting.transaction.dt
			
			# Calculate disposal value by searching for matching asset postings
			asset.disposal_value = Amount(0, '$')
			for other_posting in posting.transaction.postings:
				if posting != other_posting and 'drcr.asset' in account_configurations.get(other_posting.account, []):
					asset.disposal_value.quantity += other_posting.amount().as_cost().quantity
	
	return render_plugin_template('austax', 'cgt_assets.html', assets=assets)

@app.route('/tax/summary')
def tax_summary():
	report = tax_summary_report()
	return render_template('report.html', report=report)

def make_tax_transactions():
	report = tax_summary_report()
	tax_amount = report.by_id('total_tax').amount
	
	# Get EOFY date
	dt = eofy_date()
	
	# Estimated tax payable
	transactions = [Transaction(
		dt=dt,
		description='Estimated income tax',
		postings=[
			Posting(account='Income Tax', quantity=tax_amount.quantity, commodity='$'),
			Posting(account='Income Tax Control', quantity=-tax_amount.quantity, commodity='$')
		]
	)]
	
	# Mandatory study loan repayment
	loan_repayment = report.by_id('loan_repayment').amount
	if loan_repayment.quantity != 0:
		transactions.append(Transaction(
			dt=dt,
			description='Mandatory study loan repayment payable',
			postings=[
				Posting(account='HELP', quantity=loan_repayment.quantity, commodity='$'),  # FIXME: Correct account
				Posting(account='Income Tax Control', quantity=-loan_repayment.quantity, commodity='$')
			]
		))
	
	# Get trial balance
	balancer = TrialBalancer()
	balancer.apply_transactions(db.session.scalars(db.select(Transaction).options(db.selectinload(Transaction.postings))).all())
	
	accounts = dict(sorted(balancer.accounts.items()))
	
	# Get account configurations
	account_configurations = AccountConfiguration.get_all_kinds()
	
	# PAYG withholding
	for account_name, kinds in account_configurations.items():
		if 'austax.paygw' in kinds:
			if accounts[account_name].quantity != 0:
				# Transfer balance to Income Tax Control
				transactions.append(Transaction(
					dt=dt,
					description='PAYG withheld amounts',
					postings=[
						Posting(account='Income Tax Control', quantity=accounts[account_name].quantity, commodity='$'),
						Posting(account=account_name, quantity=-accounts[account_name].quantity, commodity='$')
					]
				))
	
	return transactions