Add ec2 filtering by instance state

moto/ec2/utils.py

@@ -1,4 +1,5 @@
 import random
+import re
 
 
 def random_id(prefix=''):
@@ -53,7 +54,7 @@ def resource_ids_from_querystring(querystring_dict):
     prefix = 'ResourceId'
     response_values = {}
     for key, value in querystring_dict.iteritems():
-        if prefix in key:
+        if key.startswith(prefix):
             resource_index = key.replace(prefix + ".", "")
             tag_key = querystring_dict.get("Tag.{}.Key".format(resource_index))[0]
 
@@ -65,3 +66,42 @@ def resource_ids_from_querystring(querystring_dict):
             response_values[value[0]] = (tag_key, tag_value)
 
     return response_values
+
+
+def filters_from_querystring(querystring_dict):
+    response_values = {}
+    for key, value in querystring_dict.iteritems():
+        match = re.search("Filter.(\d).Name", key)
+        if match:
+            filter_index = match.groups()[0]
+            value_prefix = "Filter.{}.Value".format(filter_index)
+            filter_values = [filter_value[0] for filter_key, filter_value in querystring_dict.iteritems() if filter_key.startswith(value_prefix)]
+            response_values[value[0]] = filter_values
+    return response_values
+
+
+filter_dict_attribute_mapping = {
+    'instance-state-name': 'state'
+}
+
+
+def passes_filter_dict(instance, filter_dict):
+    for filter_name, filter_values in filter_dict.iteritems():
+        if filter_name in filter_dict_attribute_mapping:
+            instance_attr = filter_dict_attribute_mapping[filter_name]
+        else:
+            raise NotImplementedError("Filter dicts have not been implemented in Moto for '%s' yet. Feel free to open an issue at https://github.com/spulec/moto/issues", filter_name)
+        instance_value = getattr(instance, instance_attr)
+        if instance_value not in filter_values:
+            return False
+    return True
+
+
+def filter_reservations(reservations, filter_dict):
+    for reservation in reservations:
+        new_instances = []
+        for instance in reservation.instances:
+            if passes_filter_dict(instance, filter_dict):
+                new_instances.append(instance)
+        reservation.instances = new_instances
+    return reservations