Add NIP-42 authentication to relay discovery (#10)

* Add NIP-42 authentication to relay discovery

* Move discovery tests into tests directory

tests/test_nostr_relay_discovery.py

@@ -0,0 +1,121 @@
+import asyncio
+import hashlib
+import json
+import unittest
+from unittest.mock import patch
+
+from coincurve import PublicKeyXOnly
+
+from nostr_relay_discovery import NostrRelayDiscovery
+
+
+class FakeWebSocket:
+    def __init__(self, messages):
+        self.messages = iter(messages)
+        self.sent = []
+
+    async def recv(self):
+        return next(self.messages)
+
+    async def send(self, message):
+        self.sent.append(json.loads(message))
+
+
+class Nip42Tests(unittest.TestCase):
+    def setUp(self):
+        self.discovery = NostrRelayDiscovery(
+            "wss://relay.example.com",
+            private_key="01".zfill(64),
+        )
+
+    def test_build_auth_event_is_valid_schnorr_event(self):
+        with patch("nostr_relay_discovery.time.time", return_value=1_700_000_000):
+            event = self.discovery.build_auth_event(
+                "wss://relay.example.com", "challenge"
+            )
+
+        serialized = json.dumps(
+            [
+                0,
+                event["pubkey"],
+                event["created_at"],
+                event["kind"],
+                event["tags"],
+                event["content"],
+            ],
+            separators=(",", ":"),
+            ensure_ascii=False,
+        ).encode()
+        event_id = hashlib.sha256(serialized).digest()
+
+        self.assertEqual(event["id"], event_id.hex())
+        self.assertTrue(
+            PublicKeyXOnly(bytes.fromhex(event["pubkey"])).verify(
+                bytes.fromhex(event["sig"]), event_id
+            )
+        )
+
+    def test_receive_with_auth_returns_subscription_response(self):
+        async def run_test():
+            auth_event = self.discovery.build_auth_event(
+                "wss://relay.example.com", "challenge"
+            )
+            websocket = FakeWebSocket(
+                [
+                    json.dumps(["AUTH", "challenge"]),
+                    json.dumps(
+                        ["CLOSED", "subscription", "auth-required: authenticate"]
+                    ),
+                    json.dumps(["OK", auth_event["id"], True, ""]),
+                    json.dumps(["EOSE", "subscription"]),
+                ]
+            )
+
+            with patch.object(
+                self.discovery, "build_auth_event", return_value=auth_event
+            ):
+                response = await self.discovery.receive_with_auth(
+                    websocket,
+                    "wss://relay.example.com",
+                    5,
+                    ["REQ", "subscription", {"kinds": [1]}],
+                )
+
+            self.assertEqual(response, ["EOSE", "subscription"])
+            self.assertEqual(
+                websocket.sent,
+                [
+                    ["AUTH", auth_event],
+                    ["REQ", "subscription", {"kinds": [1]}],
+                ],
+            )
+
+        asyncio.run(run_test())
+
+    def test_receive_with_auth_reports_rejection(self):
+        async def run_test():
+            auth_event = self.discovery.build_auth_event(
+                "wss://relay.example.com", "challenge"
+            )
+            websocket = FakeWebSocket(
+                [
+                    json.dumps(["AUTH", "challenge"]),
+                    json.dumps(
+                        ["OK", auth_event["id"], False, "restricted: not a member"]
+                    ),
+                ]
+            )
+
+            with patch.object(
+                self.discovery, "build_auth_event", return_value=auth_event
+            ):
+                with self.assertRaisesRegex(PermissionError, "not a member"):
+                    await self.discovery.receive_with_auth(
+                        websocket, "wss://relay.example.com", 5
+                    )
+
+        asyncio.run(run_test())
+
+
+if __name__ == "__main__":
+    unittest.main()