From 8ed1a52c250bedd870b9f97b5c897f7b7690e285 Mon Sep 17 00:00:00 2001
From: Sam Cooke <sam@mixcloud.com>
Date: Tue, 13 Feb 2018 11:39:06 +0000
Subject: [PATCH] Adding support for LAST

---
 tinyquery/evaluator_test.py | 16 ++++++++++++++++
 tinyquery/runtime.py        | 21 ++++++++++++++++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/tinyquery/evaluator_test.py b/tinyquery/evaluator_test.py
index 61d2c2c..d49fe7b 100644
--- a/tinyquery/evaluator_test.py
+++ b/tinyquery/evaluator_test.py
@@ -1270,6 +1270,22 @@ def test_first(self):
             ])
         )
 
+    def test_last(self):
+        # Test over the equivalent of a GROUP BY
+        self.assert_query_result(
+            'SELECT LAST(val1) FROM test_table',
+            self.make_context([
+                ('f0_', tq_types.INT, [2])
+            ])
+        )
+        # Test over something repeated
+        self.assert_query_result(
+            'SELECT LAST(QUANTILES(val1, 3)) FROM test_table',
+            self.make_context([
+                ('f0_', tq_types.INT, [8])
+            ])
+        )
+
         # TODO(colin): test behavior on empty list in both cases
 
     def test_left(self):
diff --git a/tinyquery/runtime.py b/tinyquery/runtime.py
index 12d0eab..2c33266 100644
--- a/tinyquery/runtime.py
+++ b/tinyquery/runtime.py
@@ -558,6 +558,24 @@ def _evaluate(self, num_rows, column):
                               values=values)
 
 
+class LastFunction(AggregateFunction):
+    def check_types(self, rep_list_type):
+        return rep_list_type
+
+    def _evaluate(self, num_rows, column):
+        values = []
+        if len(column.values) == 0:
+            values = [None]
+
+        if column.mode == tq_modes.REPEATED:
+            values = [repeated_row[-1] if len(repeated_row) > 0 else None
+                      for repeated_row in column.values]
+        else:
+            values = [column.values[-1]]
+        return context.Column(type=column.type, mode=tq_modes.NULLABLE,
+                              values=values)
+
+
 class NoArgFunction(ScalarFunction):
     def __init__(self, func, return_type=tq_types.INT):
         self.func = func
@@ -1304,7 +1322,8 @@ def _evaluate(self, num_rows, json_expressions, json_paths):
     'count_distinct': CountDistinctFunction(),
     'stddev_samp': StddevSampFunction(),
     'quantiles': QuantilesFunction(),
-    'first': FirstFunction()
+    'first': FirstFunction(),
+    'last': LastFunction(),
 }