From 573a73aa0123dc1aca3052bd30c80ae18a95e71c Mon Sep 17 00:00:00 2001
From: Cameron Rowshanbin <crowshan@thoughtworks.com>
Date: Wed, 10 Dec 2014 11:53:40 -0600
Subject: [PATCH] With @ethome, add filtering of instances by security group id

---
 moto/ec2/utils.py                | 13 ++++++++++++-
 tests/test_ec2/test_instances.py | 15 +++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/moto/ec2/utils.py b/moto/ec2/utils.py
index 6ff04821c..90cf607e7 100644
--- a/moto/ec2/utils.py
+++ b/moto/ec2/utils.py
@@ -324,16 +324,20 @@ filter_dict_attribute_mapping = {
     'state-reason-code': '_state_reason.code',
     'source-dest-check': 'source_dest_check',
     'vpc-id': 'vpc_id',
+    'group-id': 'security_groups',
+    'instance.group-id': 'security_groups'
 }
 
 
 def passes_filter_dict(instance, filter_dict):
     for filter_name, filter_values in filter_dict.items():
+          
         if filter_name in filter_dict_attribute_mapping:
             instance_attr = filter_dict_attribute_mapping[filter_name]
             instance_value = get_object_value(instance, instance_attr)
-            if instance_value not in filter_values:
+            if not instance_value_in_filter_values(instance_value, filter_values):
                 return False
+
         elif is_tag_filter(filter_name):
             if not tag_filter_matches(instance, filter_name, filter_values):
                 return False
@@ -343,6 +347,13 @@ def passes_filter_dict(instance, filter_dict):
                 filter_name)
     return True
 
+def instance_value_in_filter_values(instance_value, filter_values):
+    if isinstance(instance_value, list):
+        if not set(filter_values).intersection(set(instance_value)):
+            return False
+    elif instance_value not in filter_values: 
+            return False
+    return True
 
 def filter_reservations(reservations, filter_dict):
     result = []
diff --git a/tests/test_ec2/test_instances.py b/tests/test_ec2/test_instances.py
index a63f939b1..4036f1214 100644
--- a/tests/test_ec2/test_instances.py
+++ b/tests/test_ec2/test_instances.py
@@ -600,3 +600,18 @@ def test_describe_instance_status_with_non_running_instances():
 
     status3 = next((s for s in all_status if s.id == instance3.id), None)
     status3.state_name.should.equal('running')
+
+@mock_ec2
+def test_get_instance_by_security_group():
+    conn = boto.connect_ec2('the_key', 'the_secret')
+    
+    conn.run_instances('ami-1234abcd')
+    instance = conn.get_only_instances()[0]
+
+    security_group = conn.create_security_group('test', 'test')
+    conn.modify_instance_attribute(instance.id, "groupSet", [security_group.id])
+    
+    security_group_instances = security_group.instances()
+
+    assert len(security_group_instances) == 1
+    assert security_group_instances[0].id == instance.id