From 7ba2c42d84ee48403376047fdca2af2d48e7c010 Mon Sep 17 00:00:00 2001
From: quettabit <27509167+quettabit@users.noreply.github.com>
Date: Wed, 3 Jun 2026 15:03:56 -0700
Subject: [PATCH] wip

---
 src/s2_sdk/_s2s/_append_session.py | 90 +++++++++++++++++++++++++++---
 1 file changed, 81 insertions(+), 9 deletions(-)

diff --git a/src/s2_sdk/_s2s/_append_session.py b/src/s2_sdk/_s2s/_append_session.py
index e2d6e03..b765dfb 100644
--- a/src/s2_sdk/_s2s/_append_session.py
+++ b/src/s2_sdk/_s2s/_append_session.py
@@ -1,8 +1,9 @@
 import asyncio
 import logging
 from collections import deque
-from collections.abc import AsyncGenerator, AsyncIterable
-from typing import NamedTuple
+from collections.abc import AsyncGenerator, AsyncIterable, AsyncIterator
+from dataclasses import dataclass
+from typing import Any
 
 import s2_sdk._generated.s2.v1.s2_pb2 as pb
 from s2_sdk._client import HttpClient
@@ -32,9 +33,11 @@
 _QUEUE_MAX_SIZE = 100
 
 
-class _InflightInput(NamedTuple):
+@dataclass(slots=True)
+class _InflightInput:
     num_records: int
     encoded: bytes
+    ack_deadline: float | None = None
 
 
 async def run_append_session(
@@ -149,11 +152,22 @@ async def _run_attempt(
     if encryption_key is not None:
         headers[_S2_ENCRYPTION_KEY_HEADER] = encryption_key
 
+    ack_deadline_updated = asyncio.Event()
+    for resend_inp in pending_resend:
+        resend_inp.ack_deadline = None
+
     async with client.streaming_request(
         "POST",
         _stream_records_path(stream_name),
         headers=headers,
-        content=_body_gen(inflight_inputs, input_queue, pending_resend, compression),
+        content=_body_gen(
+            inflight_inputs,
+            input_queue,
+            pending_resend,
+            compression,
+            ack_deadline_updated,
+            ack_timeout,
+        ),
         frame_signal=frame_signal,
     ) as response:
         if response.status_code != 200:
@@ -166,13 +180,14 @@ async def _run_attempt(
         messages = read_messages(response.aiter_bytes())
         while True:
             try:
-                msg_body = await asyncio.wait_for(
-                    messages.__anext__(), timeout=ack_timeout
+                msg_body = await _next_message(
+                    messages,
+                    inflight_inputs,
+                    ack_deadline_updated,
+                    ack_timeout,
                 )
             except StopAsyncIteration:
                 break
-            except asyncio.TimeoutError:
-                raise ReadTimeoutError("Append session ack timeout")
 
             if attempt.value > 0:
                 attempt.value = 0
@@ -185,6 +200,8 @@ async def _run_attempt(
                 raise S2ClientError("Invalid ack: not monotonically increasing")
             prev_ack_end = ack.end.seq_num
 
+            if not inflight_inputs:
+                raise S2ClientError("Invalid ack: no inflight append")
             num_records_sent = inflight_inputs.popleft().num_records
             num_records_ackd = ack.end.seq_num - ack.start.seq_num
             if num_records_sent != num_records_ackd:
@@ -203,11 +220,53 @@ async def _run_attempt(
                     frame_signal.reset()
 
 
+async def _next_message(
+    messages: AsyncIterator[bytes],
+    inflight_inputs: deque[_InflightInput],
+    ack_deadline_updated: asyncio.Event,
+    ack_timeout: float | None,
+) -> bytes:
+    if ack_timeout is None:
+        return await messages.__anext__()
+
+    pending_message: asyncio.Future[Any] | None = None
+    try:
+        while True:
+            deadline = inflight_inputs[0].ack_deadline if inflight_inputs else None
+            if deadline is not None:
+                try:
+                    async with asyncio.timeout_at(deadline):
+                        if pending_message is not None:
+                            return await pending_message
+                        return await messages.__anext__()
+                except TimeoutError:
+                    raise ReadTimeoutError("Append session ack timeout") from None
+
+            if pending_message is None:
+                pending_message = asyncio.ensure_future(messages.__anext__())
+            deadline_update = asyncio.create_task(ack_deadline_updated.wait())
+            done, _ = await asyncio.wait(
+                {pending_message, deadline_update},
+                return_when=asyncio.FIRST_COMPLETED,
+            )
+            if deadline_update not in done:
+                deadline_update.cancel()
+
+            if pending_message in done:
+                return pending_message.result()
+            ack_deadline_updated.clear()
+    finally:
+        if pending_message is not None and not pending_message.done():
+            pending_message.cancel()
+
+
 async def _body_gen(
     inflight_inputs: deque[_InflightInput],
     input_queue: asyncio.Queue[AppendInput | None],
     pending_resend: tuple[_InflightInput, ...],
     compression: Compression,
+    ack_deadline_updated: asyncio.Event | None = None,
+    ack_timeout: float | None = None,
 ) -> AsyncGenerator[bytes]:
     if pending_resend:
         logger.debug(
@@ -215,7 +274,13 @@ async def _body_gen(
             len(pending_resend),
             sum(len(inp.encoded) for inp in pending_resend),
         )
+    loop = asyncio.get_running_loop()
     for resend_inp in pending_resend:
+        resend_inp.ack_deadline = (
+            loop.time() + ack_timeout if ack_timeout is not None else None
+        )
+        if ack_deadline_updated is not None:
+            ack_deadline_updated.set()
         yield resend_inp.encoded
     if pending_resend:
         logger.debug("finished resending inflight appends")
@@ -226,9 +291,16 @@ async def _body_gen(
             await input_queue.put(None)
             return
         encoded = _encode_input(inp, compression)
+        ack_deadline = loop.time() + ack_timeout if ack_timeout is not None else None
         inflight_inputs.append(
-            _InflightInput(num_records=len(inp.records), encoded=encoded)
+            _InflightInput(
+                num_records=len(inp.records),
+                encoded=encoded,
+                ack_deadline=ack_deadline,
+            )
         )
+        if ack_deadline_updated is not None:
+            ack_deadline_updated.set()
         yield encoded