from collections import defaultdict from datetime import datetime from flask.ext.sqlalchemy import SQLAlchemy, BaseQuery from flask import g from sqlalchemy import orm db = SQLAlchemy() # define models class Project(db.Model): _to_serialize = ("id", "name", "password", "contact_email", "members", "active_members", "balance") id = db.Column(db.String(64), primary_key=True) name = db.Column(db.UnicodeText) password = db.Column(db.String(128)) contact_email = db.Column(db.String(128)) members = db.relationship("Person", backref="project") @property def active_members(self): return [m for m in self.members if m.activated] @property def balance(self): balances, should_pay, should_receive = (defaultdict(int) for time in (1, 2, 3)) # for each person for person in self.members: # get the list of bills he has to pay bills = Bill.query.filter(Bill.owers.contains(person)) for bill in bills.all(): if person != bill.payer: share = bill.pay_each() * person.weight should_pay[person] += share should_receive[bill.payer] += share for person in self.members: balance = should_receive[person] - should_pay[person] balances[person.id] = balance return balances @property def uses_weights(self): return len([i for i in self.members if i.weight != 1]) > 0 def get_transactions_to_settle_bill(self): """Return a list of transactions that could be made to settle the bill""" #cache value for better performance balance = self.balance credits, debts, transactions = [],[],[] # Create lists of credits and debts for person in self.members: if round(balance[person.id], 2) > 0: credits.append({"person": person, "balance": balance[person.id]}) elif round(balance[person.id], 2) < 0: debts.append({"person": person, "balance": -balance[person.id]}) # Try and find exact matches for credit in credits: match = self.exactmatch(round(credit["balance"], 2), debts) if match: for m in match: transactions.append({"ower": m["person"], "receiver": credit["person"], "amount": m["balance"]}) debts.remove(m) credits.remove(credit) # Split any remaining debts & credits while credits and debts: if credits[0]["balance"] > debts[0]["balance"]: transactions.append({"ower": debts[0]["person"], "receiver": credits[0]["person"], "amount": debts[0]["balance"]}) credits[0]["balance"] = credits[0]["balance"] - debts[0]["balance"] del debts[0] else: transactions.append({"ower": debts[0]["person"], "receiver": credits[0]["person"], "amount": credits[0]["balance"]}) debts[0]["balance"] = debts[0]["balance"] - credits[0]["balance"] del credits[0] return transactions def exactmatch(self, credit, debts): """Recursively try and find subsets of 'debts' whose sum is equal to credit""" if not debts: return None if debts[0]["balance"] > credit: return self.exactmatch(credit, debts[1:]) elif debts[0]["balance"] == credit: return [debts[0]] else: match = self.exactmatch(credit-debts[0]["balance"], debts[1:]) if match: match.append(debts[0]) else: match = self.exactmatch(credit, debts[1:]) return match def has_bills(self): """return if the project do have bills or not""" return self.get_bills().count() > 0 def get_bills(self): """Return the list of bills related to this project""" return Bill.query.join(Person, Project)\ .filter(Bill.payer_id == Person.id)\ .filter(Person.project_id == Project.id)\ .filter(Project.id == self.id)\ .order_by(Bill.date.desc()) def remove_member(self, member_id): """Remove a member from the project. If the member is not bound to a bill, then he is deleted, otherwise he is only deactivated. This method returns the status DELETED or DEACTIVATED regarding the changes made. """ try: person = Person.query.get(member_id, self) except orm.exc.NoResultFound: return None if not person.has_bills(): db.session.delete(person) db.session.commit() else: person.activated = False db.session.commit() return person def remove_project(self): db.session.delete(self) db.session.commit() def __repr__(self): return "" % self.name class Person(db.Model): class PersonQuery(BaseQuery): def get_by_name(self, name, project): return Person.query.filter(Person.name == name)\ .filter(Project.id == project.id).one() def get(self, id, project=None): if not project: project = g.project return Person.query.filter(Person.id == id)\ .filter(Project.id == project.id).one() query_class = PersonQuery _to_serialize = ("id", "name", "weight", "activated") id = db.Column(db.Integer, primary_key=True) project_id = db.Column(db.String(64), db.ForeignKey("project.id")) bills = db.relationship("Bill", backref="payer") name = db.Column(db.UnicodeText) weight = db.Column(db.Float, default=1) activated = db.Column(db.Boolean, default=True) def has_bills(self): """return if the user do have bills or not""" bills_as_ower_number = db.session.query(billowers)\ .filter(billowers.columns.get("person_id") == self.id)\ .count() return bills_as_ower_number != 0 or len(self.bills) != 0 def __str__(self): return self.name def __repr__(self): return "" % (self.name, self.project.name) # We need to manually define a join table for m2m relations billowers = db.Table('billowers', db.Column('bill_id', db.Integer, db.ForeignKey('bill.id')), db.Column('person_id', db.Integer, db.ForeignKey('person.id')), ) class Bill(db.Model): class BillQuery(BaseQuery): def get(self, project, id): try: return self.join(Person, Project)\ .filter(Bill.payer_id == Person.id)\ .filter(Person.project_id == Project.id)\ .filter(Project.id == project.id)\ .filter(Bill.id == id).one() except orm.exc.NoResultFound: return None def delete(self, project, id): bill = self.get(project, id) if bill: db.session.delete(bill) return bill query_class = BillQuery _to_serialize = ("id", "payer_id", "owers", "amount", "date", "what") id = db.Column(db.Integer, primary_key=True) payer_id = db.Column(db.Integer, db.ForeignKey("person.id")) owers = db.relationship(Person, secondary=billowers) amount = db.Column(db.Float) date = db.Column(db.Date, default=datetime.now) what = db.Column(db.UnicodeText) archive = db.Column(db.Integer, db.ForeignKey("archive.id")) def pay_each(self): """Compute what each share has to pay""" if self.owers: # FIXME: SQL might dot that more efficiently return self.amount / sum(i.weight for i in self.owers) else: return 0 def __repr__(self): return "" % (self.amount, self.payer, ", ".join([o.name for o in self.owers])) class Archive(db.Model): id = db.Column(db.Integer, primary_key=True) project_id = db.Column(db.String(64), db.ForeignKey("project.id")) name = db.Column(db.UnicodeText) @property def start_date(self): pass @property def end_date(self): pass def __repr__(self): return ""