DrCr/drcr/statements/models.py

#   DrCr: Web-based double-entry bookkeeping framework
#   Copyright (C) 2022  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 sqlalchemy import Column, DateTime, ForeignKey, Integer, String
from sqlalchemy.orm import relationship

from ..database import Base, db_session
from ..models import Amount, Posting, Transaction

class StatementLine(Base):
	__tablename__ = 'statement_lines'
	
	id = Column(Integer, primary_key=True)
	
	source_account = Column(String)
	dt = Column(DateTime)
	description = Column(String)
	quantity = Column(Integer)
	balance = Column(Integer)
	commodity = Column(String)
	
	postings = relationship('StatementLinePosting', back_populates='statement_line')
	
	def amount(self):
		return Amount(self.quantity, self.commodity)
	
	def into_transaction(self):
		if len(self.postings) > 0:
			# Will already be accounted for in a StatementLineTransaction
			#return None
			raise Exception('Should not call into_transaction on a StatementLine with associated StatementLinePosting')
		
		# Not classified
		unclassified_name = 'Unclassified Statement Line Debits' if -self.quantity >= 0 else 'Unclassified Statement Line Credits'
		
		return Transaction(
			dt=self.dt,
			description=self.description,
			postings=[
				Posting(account=self.source_account, quantity=self.quantity, commodity=self.commodity),
				Posting(account=unclassified_name, quantity=-self.quantity, commodity=self.commodity)
			]
		)
	
	def is_complex(self):
		if len(self.postings) > 1:
			return True
		
		if any(len(p.transaction.postings) > 2 for p in self.postings):
			return True
		
		return False
	
	def delete_postings(self):
		"""Delete existing StatementLineTransactions with postings for this StatementLine"""
		
		for posting in self.postings:
			# TODO: Will be wonky if transaction covers multiple StatementLines
			db_session.delete(posting.transaction)

class StatementLineTransaction(Base, Transaction):
	__tablename__ = 'statement_line_transactions'
	
	id = Column(Integer, primary_key=True)
	
	dt = Column(DateTime)
	description = Column(String)
	
	postings = relationship('StatementLinePosting', back_populates='transaction', cascade='all, delete')
	
	def charge_account(self, source_account):
		if len(self.postings) > 2:
			raise Exception('Cannot call charge_account on StatementLineTransaction with more than 2 postings')
		
		for posting in self.postings:
			if posting.account != source_account:
				return posting.account

class StatementLinePosting(Base, Posting):
	__tablename__ = 'statement_line_postings'
	
	id = Column(Integer, primary_key=True)
	transaction_id = Column(Integer, ForeignKey('statement_line_transactions.id'))
	line_id = Column(Integer, ForeignKey('statement_lines.id'))
	
	description = Column(String)
	account = Column(String)
	quantity = Column(Integer)
	commodity = Column(String)
	
	transaction = relationship('StatementLineTransaction', back_populates='postings')
	statement_line = relationship('StatementLine', back_populates='postings')
	
	def amount(self):
		return Amount(self.quantity, self.commodity)