added a 'My Share' column to lists of expenditures

[bluechips.git] / bluechips / model / expenditure.py

diff --git a/bluechips/model/expenditure.py b/bluechips/model/expenditure.py
index c093e75cdf3f8219120d4af080c3e7fc13369a84..296ecf04929aa2c3c66790d3f5a86a76cdcd88b9 100644 (file)
--- a/bluechips/model/expenditure.py
+++ b/bluechips/model/expenditure.py
@@ -1,6 +1,106 @@
+from bluechips.model.user import User
+from bluechips.model.split import Split
+from bluechips.model import meta
+from bluechips.model.types import Currency
+from decimal import Decimal
+from datetime import datetime
+import random
+
 class Expenditure(object):
+    def __init__(self, spender=None, amount=Currency(0), description=u"",
+                 date=None):
+        self.spender = spender
+        self.amount = amount
+        self.description = description
+        if self.date == None:
+            self.date = datetime.now()
+    
     def __repr__(self):
         return '<Expenditure: spender: %s spent: %s>' % (self.spender,
                                                          self.amount)
 
+    def even_split(self):
+        """
+        Split up an expenditure evenly among the resident users
+        """
+        
+        residents = meta.Session.query(User).filter(User.resident==True)
+        split_percentage = Decimal(100) / Decimal(residents.count())
+        self.split(dict((resident, split_percentage) for resident in residents))
+    
+    def update_split(self):
+        """
+        Re-split an expenditure using the same percentages as what is
+        currently in the database
+        """
+        
+        old_splits = meta.Session.query(Split).filter(Split.expenditure==self)
+        split_dict = dict((s.user, Decimal(int(s.share))) for s in old_splits)
+        self.split(split_dict)
+    
+    def split(self, split_dict):
+        """
+        Split up an expenditure.
+        
+        split_dict should be a dict mapping from bluechips.model:User
+        objects to a decimal:Decimal object representing the percentage
+        that user is responsible for.
+        
+        Percentages will be normalized to sum to 100%.
+        
+        If the split leaks or gains money due to rounding errors, the
+        pennies will be randomly distributed to one of the users.
+        
+        I mean, come on. You're already living together. Are you really
+        going to squabble over a few pennies?
+        """
+        
+        map(meta.Session.delete, meta.Session.query(Split).\
+                filter_by(expenditure_id=self.id))
+        
+        total = sum(split_dict.itervalues())
+        
+        for user, share in split_dict.items():
+            if share == 0:
+                del split_dict[user]
+            else:
+                split_dict[user] = share / total
+            
+        amounts_dict = dict()
+        
+        for user, share in split_dict.iteritems():
+            amounts_dict[user] = Currency(split_dict[user] * self.amount)
+        
+        difference = self.amount - sum(amounts_dict.itervalues())
+        
+        if difference > 0:
+            for i in xrange(difference):
+                winner = random.choice(amounts_dict.keys())
+                amounts_dict[winner] += Currency(1)
+        elif difference < 0:
+            for i in xrange(-difference):
+                winner = random.choice(amounts_dict.keys())
+                amounts_dict[winner] -= Currency(1)
+        
+        for user, share in amounts_dict.iteritems():
+            s = Split(self, user, share)
+            meta.Session.add(s)
+
+    def involves(self, user):
+        "Returns True if ``user`` is involved in this expenditure."
+        return (meta.Session.query(Split.id).\
+                filter(Split.expenditure == self).\
+                filter(Split.user == user).\
+                filter(Split.share != 0).first() is not None)
+
+    def share(self, user):
+        "Return the share corresponding to ``user``."
+        share = meta.Session.query(Split.share).\
+                filter(Split.expenditure == self).\
+                filter(Split.user == user).scalar()
+        if share is None:
+            return Currency(0)
+        else:
+            return share
+
 __all__ = ['Expenditure']