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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:
should_pay[person] += bill.pay_each()
should_receive[bill.payer] += bill.pay_each()
for person in self.members:
balance = should_receive[person] - should_pay[person]
balances[person.id] = balance
return balances
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 balance[person.id] > 0:
credits.append({"person": person, "balance": balance[person.id]})
elif balance[person.id] < 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 "<Project %s>" % 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", "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)
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 "<Person %s for project %s>" % (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 person has to pay"""
if self.owers:
return self.amount / len(self.owers)
else:
return 0
def __repr__(self):
return "<Bill of %s from %s for %s>" % (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 "<Archive>"
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