Add support for .well-known/social-relay document

Used in apps to provide subscription preferences, see: https://www.loomio.org/d/9vpoe0UR/public-post-federation#comment-730911

federation/hostmeta/generators.py

@@ -1,4 +1,5 @@
 from base64 import b64encode
+import json
 import os
 from string import Template
 from xrd import XRD, Link, Element
@@ -170,3 +171,48 @@ class DiasporaHCard(object):
             assert isinstance(value, str)
         assert len(required) == 0
         return self.template.substitute(self.kwargs)
+
+
+class SocialRelayWellKnown(object):
+    """A `.well-known/social-relay` document in JSON.
+
+    For apps wanting to announce their preferences towards relay applications.
+
+    See WIP spec: https://wiki.diasporafoundation.org/Relay_servers_for_public_posts
+
+    Schema:
+
+        {
+          "$schema": "http://json-schema.org/draft-04/schema#",
+          "id": "http://the-federation.info/social-relay/well-known-schema-v1.json",
+          "type": "object",
+          "properties": {
+            "subscribe": {
+              "type": "boolean"
+            },
+            "tags": {
+              "type": "array",
+              "items": {"type": "string"}
+            }
+          },
+          "required": [
+            "subscribe",
+            "tags"
+          ]
+        }
+
+    Args:
+        subscribe (bool)
+        tags (tuple, optional)
+
+    Returns:
+        JSON document (str)
+    """
+    def __init__(self, subscribe, tags=(), *args, **kwargs):
+        self.doc = {
+            "subscribe": subscribe,
+            "tags": list(tags),
+        }
+
+    def render(self):
+        return json.dumps(self.doc)

federation/tests/hostmeta/test_generators.py

@@ -1,7 +1,9 @@
+import json
+from jsonschema import validate, ValidationError
 import pytest
 
-from federation.hostmeta.generators import generate_host_meta, generate_legacy_webfinger, generate_hcard
-
+from federation.hostmeta.generators import generate_host_meta, generate_legacy_webfinger, generate_hcard, \
+    SocialRelayWellKnown
 
 DIASPORA_HOSTMETA = """<?xml version="1.0" encoding="UTF-8"?>
 <XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0">
@@ -87,3 +89,33 @@ class TestDiasporaHCardGenerator(object):
                 firstname="firstname",
                 username="username"
             )
+
+
+class TestSocialRelayWellKnownGenerator(object):
+
+    def test_valid_social_relay_well_known(self):
+        with open("federation/tests/schemas/social-relay-well-known") as f:
+            schema = json.load(f)
+        well_known = SocialRelayWellKnown(subscribe=True, tags=("foo", "bar"))
+        assert well_known.doc["subscribe"] == True
+        assert well_known.doc["tags"] == ["foo", "bar"]
+        validate(well_known.doc, schema)
+
+    def test_valid_social_relay_well_known_empty_tags(self):
+        with open("federation/tests/schemas/social-relay-well-known") as f:
+            schema = json.load(f)
+        well_known = SocialRelayWellKnown(subscribe=False)
+        assert well_known.doc["subscribe"] == False
+        assert well_known.doc["tags"] == []
+        validate(well_known.doc, schema)
+
+    def test_invalid_social_relay_well_known(self):
+        with open("federation/tests/schemas/social-relay-well-known") as f:
+            schema = json.load(f)
+        well_known_doc = {
+            "subscribe": "true",
+            "tags": "foo,bar",
+            "someotherstuff": True,
+        }
+        with pytest.raises(ValidationError):
+            validate(well_known_doc, schema)

federation/tests/schemas/social-relay-well-known

@@ -0,0 +1,18 @@
+{
+  "$schema": "http://json-schema.org/draft-04/schema#",
+  "id": "http://the-federation.info/social-relay/well-known-schema-v1.json",
+  "type": "object",
+  "properties": {
+    "subscribe": {
+      "type": "boolean"
+    },
+    "tags": {
+      "type": "array",
+      "items": {"type": "string"}
+    }
+  },
+  "required": [
+    "subscribe",
+    "tags"
+  ]
+}

setup.py

@@ -19,6 +19,7 @@ setup(
         "python-xrd==0.1",
     ],
     test_require=[
+        "jsonschema==2.5.1",
         "pytest==2.7.2",
     ],
     include_package_data=True,