From 91c720eceea4ab48d386e17b4a9bc2fe9b3f847f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Sa=C5=82aban?= <michal@salaban.info>
Date: Fri, 19 Oct 2018 01:26:15 +0200
Subject: [PATCH] Sort payments by height (descending) and mempool on top

---
 monero/transaction.py     | 36 +++++++++++++++++++++++++++++++++++-
 tests/test_transaction.py | 24 +++++++++++++++++++++++-
 2 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/monero/transaction.py b/monero/transaction.py
index 4457c8a..20e9bcf 100644
--- a/monero/transaction.py
+++ b/monero/transaction.py
@@ -112,6 +112,38 @@ class PaymentManager(object):
         return fetch(self.account_idx, PaymentFilter(**filterparams))
 
 
+class _ByHeight(object):
+    """A helper class used as key in sorting of payments by height.
+    Mempool goes on top, blockchain payments are ordered with descending block numbers.
+
+    **WARNING:** Integer sorting is reversed here.
+    """
+    def __init__(self, pmt):
+        self.pmt = pmt
+    def _cmp(self, other):
+        sh = self.pmt.transaction.height
+        oh = other.pmt.transaction.height
+        if sh is oh is None:
+            return 0
+        if sh is None:
+            return 1
+        if oh is None:
+            return -1
+        return (sh > oh) - (sh < oh)
+    def __lt__(self, other):
+        return self._cmp(other) > 0
+    def __le__(self, other):
+        return self._cmp(other) >= 0
+    def __eq__(self, other):
+        return self._cmp(other) == 0
+    def __ge__(self, other):
+        return self._cmp(other) <= 0
+    def __gt__(self, other):
+        return self._cmp(other) < 0
+    def __ne__(self, other):
+        return self._cmp(other) != 0
+
+
 class PaymentFilter(object):
     """
     A helper class that filters payments retrieved by the backend.
@@ -176,4 +208,6 @@ class PaymentFilter(object):
         return True
 
     def filter(self, payments):
-        return filter(self.check, payments)
+        return sorted(
+            filter(self.check, payments),
+            key=_ByHeight)
diff --git a/tests/test_transaction.py b/tests/test_transaction.py
index d83c2d6..35cc2d9 100644
--- a/tests/test_transaction.py
+++ b/tests/test_transaction.py
@@ -1,10 +1,12 @@
 from datetime import datetime
 from decimal import Decimal
+from operator import attrgetter
+import random
 import unittest
 
 from monero.address import address
 from monero.numbers import PaymentID
-from monero.transaction import IncomingPayment, OutgoingPayment, Transaction
+from monero.transaction import IncomingPayment, OutgoingPayment, Transaction, _ByHeight
 
 class FiltersTestCase(unittest.TestCase):
     def setUp(self):
@@ -26,3 +28,23 @@ class FiltersTestCase(unittest.TestCase):
         self.assertIn(
             'a0b876ebcf7c1d499712d84cedec836f9d50b608bb22d6cb49fd2feae3ffed14',
             repr(self.pm1))
+
+
+class SortingTestCase(unittest.TestCase):
+    def test_sorting(self):
+        pmts = [
+            IncomingPayment(transaction=Transaction(height=10)),
+            IncomingPayment(transaction=Transaction(height=12)),
+            IncomingPayment(transaction=Transaction(height=13)),
+            IncomingPayment(transaction=Transaction(height=None)),
+            IncomingPayment(transaction=Transaction(height=100)),
+            IncomingPayment(transaction=Transaction(height=None)),
+            IncomingPayment(transaction=Transaction(height=1))
+        ]
+        for i in range(1680):    # 1/3 of possible permutations
+            sorted_pmts = sorted(pmts, key=_ByHeight)
+            self.assertEqual(
+                list(map(attrgetter('height'), map(attrgetter('transaction'), sorted_pmts))),
+                [None, None, 100, 13, 12, 10, 1])
+            random.shuffle(pmts)
+