Merge pull request #1650 from gittip/fix-exchanges-bug

Fix bug in record-an-exchange; #1633

docs/index.rst

@@ -19,6 +19,13 @@ blacklisted or whitelisted user.
     * blacklisted cannot do anything
 
 
+The exchanges table records movements of money into and out of Gittip. The
+``amount`` column shows a positive amount for payins and a negative amount for
+payouts. The ``fee`` column is always positive. For both payins and payouts,
+the ``amount`` does not include the ``fee`` (e.g., a $10 payin would result in
+an ``amount`` of ``9.41`` and a ``fee`` of ``0.59``, and a $100 payout with a
+2% fee would result in an ``amount`` of ``-98.04`` and a fee of ``1.96``).
+
 
 Contents
 --------

tests/test_record_an_exchange.py

@@ -99,3 +99,10 @@ def test_withdrawals_work(self):
         SQL = "SELECT balance FROM participants WHERE username='bob'"
         actual = self.db.one(SQL)
         assert actual == expected
+
+    def test_withdrawals_take_fee_out_of_balance(self):
+        self.make_participant('alice', claimed_time=utcnow(), is_admin=True)
+        self.make_participant('bob', claimed_time=utcnow(), balance=20)
+        self.record_an_exchange('-7', '1.13', 'noted', False)
+        SQL = "SELECT balance FROM participants WHERE username='bob'"
+        assert self.db.one(SQL) == Decimal('11.87')

www/%username/history/record-an-exchange.spt

@@ -31,8 +31,16 @@ with gittip.db.get_cursor() as cursor:
           "VALUES (%s, %s, %s, %s, %s)"
     cursor.execute(SQL, params)
 
+    if amount < 0:
+        # For payouts, we need to take the fee out of their Gittip balance.
+        balance_adjustment = amount - fee
+    else:
+        # For payins, we don't have to worry about the fee relative to their
+        # balance, because the amount is already less the fee.
+        balance_adjustment = amount
+
     SQL = "UPDATE participants SET balance = balance + %s WHERE username=%s"
-    cursor.execute(SQL, (amount, participant.username))
+    cursor.execute(SQL, (balance_adjustment, participant.username))
 
 request.redirect('/%s/history/' % participant.username)