Adding back can_read to converters

Signed-off-by: Denis Makogon <[email protected]>

Author: denismakogon

README.md

@@ -76,8 +76,63 @@ In this topic you'd find various example how to integrate an SDK with various HT
 
 ### Python requests
 
+One of popular framework is [0.2-force-improvements](http://docs.python-requests.org/en/master/).
 
 
+#### CloudEvent to request
+
+The code below shows how integrate both libraries in order to convert a CloudEvent into an HTTP request:
+
+```python
+def run_binary(event, url):
+    binary_headers, binary_data = http_marshaller.ToRequest(
+        event, converters.TypeBinary, json.dumps)
+
+    print("binary CloudEvent")
+    for k, v in binary_headers.items():
+        print("{0}: {1}\r\n".format(k, v))
+    print(binary_data.getvalue())
+    response = requests.post(url,
+                             headers=binary_headers,
+                             data=binary_data.getvalue())
+    response.raise_for_status()
+
+
+def run_structured(event, url):
+    structured_headers, structured_data = http_marshaller.ToRequest(
+        event, converters.TypeStructured, json.dumps
+    )
+    print("structured CloudEvent")
+    print(structured_data.getvalue())
+
+    response = requests.post(url,
+                             headers=structured_headers,
+                             data=structured_data.getvalue())
+    response.raise_for_status()
+
+```
+
+Complete example of turning a CloudEvent into a request you can find [here](samples/python-requests/cloudevent_to_request.py).
+
+#### Request to CloudEvent
+
+The code below shows how integrate both libraries in order to create a CloudEvent from an HTTP request:
+```python
+    response = requests.get(url)
+    response.raise_for_status()
+    headers = response.headers
+    data = io.BytesIO(response.content)
+    event = v02.Event()
+    http_marshaller = marshaller.NewDefaultHTTPMarshaller()
+    event = http_marshaller.FromRequest(
+        event, headers, data, json.load)
+
+```
+Complete example of turning a CloudEvent into a request you can find [here](samples/python-requests/request_to_cloudevent.py).
+
+
+## SDK versioning
+
 The goal of this package is to provide support for all released versions of CloudEvents, ideally while maintaining
 the same API. It will use semantic versioning with following rules:
 * MAJOR version increments when backwards incompatible changes is introduced.

cloudevents/sdk/converters/base.py

@@ -25,6 +25,9 @@ def read(self, event, headers: dict, body: typing.IO,
              data_unmarshaller: typing.Callable) -> base.BaseEvent:
         raise Exception("not implemented")
 
+    def can_read(self, content_type):
+        raise Exception("not implemented")
+
     def write(self, event: base.BaseEvent,
               data_marshaller: typing.Callable) -> (dict, typing.IO):
         raise Exception("not implemented")

cloudevents/sdk/converters/binary.py

@@ -25,6 +25,9 @@ class BinaryHTTPCloudEventConverter(base.Converter):
     TYPE = "binary"
     SUPPORTED_VERSIONS = [v02.Event, ]
 
+    def can_read(self, content_type):
+        return True
+
     def read(self,
              event: event_base.BaseEvent,
              headers: dict, body: typing.IO,

cloudevents/sdk/converters/structured.py

@@ -23,6 +23,9 @@ class JSONHTTPCloudEventConverter(base.Converter):
 
     TYPE = "structured"
 
+    def can_read(self, content_type):
+        return content_type == "application/cloudevents+json"
+
     def read(self, event: event_base.BaseEvent,
              headers: dict,
              body: typing.IO,

cloudevents/sdk/exceptions.py

@@ -31,3 +31,10 @@ class NoSuchConverter(Exception):
     def __init__(self, converter_type):
         super().__init__(
             "No such converter {0}".format(converter_type))
+
+
+class UnsupportedEventConverter(Exception):
+    def __init__(self, content_type):
+        super().__init__(
+            "Unable to identify valid event converter "
+            "for content-type: '{0}'".format(content_type))

cloudevents/sdk/marshaller.py

@@ -55,8 +55,14 @@ def FromRequest(self, event: event_base.BaseEvent,
         :return: a CloudEvent
         :rtype: event_base.BaseEvent
         """
+        content_type = headers.get(
+            "content-type", headers.get("Content-Type"))
+
         for _, cnvrtr in self.__converters.items():
-            return cnvrtr.read(event, headers, body, data_unmarshaller)
+            if cnvrtr.can_read(content_type):
+                return cnvrtr.read(event, headers, body, data_unmarshaller)
+
+        raise exceptions.UnsupportedEventConverter(content_type)
 
     def ToRequest(self, event: event_base.BaseEvent,
                   converter_type: str,

cloudevents/tests/test_event_from_request_converter.py

@@ -58,7 +58,6 @@ def test_structured_converter_upstream():
     assert event.Get("id") == (data.ce_id, True)
 
 
-# todo: clarify whether spec 0.1 doesn't support binary format
 def test_binary_converter_v01():
     m = marshaller.NewHTTPMarshaller(
         [
@@ -69,7 +68,20 @@ def test_binary_converter_v01():
     pytest.raises(
         exceptions.UnsupportedEvent,
         m.FromRequest,
-        v01.Event, None, None, None)
+        v01.Event, {}, None, None)
+
+
+def test_unsupported_converter_v01():
+    m = marshaller.NewHTTPMarshaller(
+        [
+            structured.NewJSONHTTPCloudEventConverter()
+        ]
+    )
+
+    pytest.raises(
+        exceptions.UnsupportedEventConverter,
+        m.FromRequest,
+        v01.Event, {}, None, None)
 
 
 def test_structured_converter_v01():

samples/with_requests.py …python-requests/cloudevent_to_request.pysamples/with_requests.py renamed to samples/python-requests/cloudevent_to_request.py samples/with_requests.py renamed to samples/python-requests/cloudevent_to_request.py

@@ -0,0 +1,41 @@
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import json
+import io
+import requests
+import sys
+
+from cloudevents.sdk import marshaller
+
+from cloudevents.sdk.event import v02
+
+
+if __name__ == "__main__":
+
+    if len(sys.argv) < 2:
+        sys.exit("Usage: python with_requests.py "
+                 "<CloudEvent source URL>")
+
+    url = sys.argv[1]
+    response = requests.get(url)
+    response.raise_for_status()
+    headers = response.headers
+    data = io.BytesIO(response.content)
+    event = v02.Event()
+    http_marshaller = marshaller.NewDefaultHTTPMarshaller()
+    event = http_marshaller.FromRequest(
+        event, headers, data, json.load)
+
+    print(json.dumps(event.Properties()))