BR-3276 Fix bearer token expiry calculation

src/m3ter/_client.py

@@ -5,7 +5,7 @@
 import os
 import base64
 from typing import TYPE_CHECKING, Any, Mapping
-from datetime import datetime
+from datetime import datetime, timedelta
 from typing_extensions import Self, override
 
 import httpx
@@ -1038,7 +1038,7 @@ def _prepare_options(
                 )
                 self.token = token.access_token
                 # expiry minus 5 minutes from effective refreshing
-                self.token_expiry = datetime.fromtimestamp(token.expires_in - 300)
+                self.token_expiry = datetime.now() + timedelta(seconds=token.expires_in - 300)
         return options
 
     def copy(

tests/test_client.py

@@ -10,6 +10,7 @@
 import inspect
 import dataclasses
 import tracemalloc
+from datetime import datetime, timedelta
 from typing import Any, Union, TypeVar, Callable, Iterable, Iterator, Optional, Coroutine, cast
 from unittest import mock
 from typing_extensions import Literal, AsyncIterator, override
@@ -127,6 +128,44 @@ def test_raw_response_for_binary(self, respx_mock: MockRouter, client: M3ter) ->
         assert isinstance(response, httpx.Response)
         assert response.json() == {"foo": "bar"}
 
+    @pytest.mark.respx(base_url=base_url)
+    def test_bearer_token_expiry_uses_expires_in_duration(self, respx_mock: MockRouter) -> None:
+        token_route = respx_mock.post("/oauth/token").mock(
+            return_value=httpx.Response(
+                200,
+                json={
+                    "access_token": "refreshed-token",
+                    "expires_in": 3600,
+                    "token_type": "bearer",
+                },
+            )
+        )
+        respx_mock.get("/foo").mock(return_value=httpx.Response(200, json={"foo": "bar"}))
+
+        with update_env(**{"M3TER_API_TOKEN": Omit()}):
+            client = M3ter(
+                base_url=base_url,
+                api_key=api_key,
+                api_secret=api_secret,
+                token=None,
+                org_id=org_id,
+                _strict_response_validation=True,
+            )
+
+        now = datetime.now()
+
+        response = client.get("/foo", cast_to=httpx.Response)
+        assert response.status_code == 200
+        assert client.token == "refreshed-token"
+        assert client.token_expiry is not None
+        assert client.token_expiry > now + timedelta(minutes=50)
+
+        response = client.get("/foo", cast_to=httpx.Response)
+        assert response.status_code == 200
+        assert token_route.call_count == 1
+
+        client.close()
+
     def test_copy(self, client: M3ter) -> None:
         copied = client.copy()
         assert id(copied) != id(client)