From d27d952d389ba0747ea54102672dd17f8cab8ae5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rn-Michael=20Miehe?= <jmm@yavook.de>
Date: Fri, 8 Sep 2023 15:30:52 +0000
Subject: [PATCH] async context manager for WebDAV.read_buffer

---
 api/advent22_api/core/webdav.py | 21 +++++++------
 api/asynccontextmanager.py      | 52 +++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 9 deletions(-)
 create mode 100644 api/asynccontextmanager.py

diff --git a/api/advent22_api/core/webdav.py b/api/advent22_api/core/webdav.py
index 0553312..66d1e20 100644
--- a/api/advent22_api/core/webdav.py
+++ b/api/advent22_api/core/webdav.py
@@ -1,7 +1,7 @@
 import re
-from contextlib import contextmanager
+from contextlib import asynccontextmanager
 from io import BytesIO, TextIOWrapper
-from typing import ContextManager, Iterator
+from typing import AsyncContextManager, AsyncIterator
 
 from cache import AsyncTTL
 from webdav3.client import Client as WebDAVclient
@@ -44,18 +44,21 @@ class WebDAV:
 
         return cls._webdav_client.check(path)
 
-    @AsyncTTL(time_to_live=SETTINGS.cache_ttl)
     @classmethod
-    async def read_buffer(cls, path: str) -> ContextManager[BytesIO]:
+    async def read_buffer(cls, path: str) -> AsyncContextManager[BytesIO]:
         """
         Datei aus Pfad `path` in einen `BytesIO` Puffer laden
         """
 
-        buffer = BytesIO()
-        cls._webdav_client.resource(path).write_to(buffer)
+        @AsyncTTL(time_to_live=SETTINGS.cache_ttl)
+        async def inner() -> BytesIO:
+            buffer = BytesIO()
+            cls._webdav_client.resource(path).write_to(buffer)
+            return buffer
 
-        @contextmanager
-        def ctx() -> Iterator[BytesIO]:
+        @asynccontextmanager
+        async def ctx() -> AsyncIterator[BytesIO]:
+            buffer = await inner()
             buffer.seek(0)
             yield buffer
 
@@ -68,7 +71,7 @@ class WebDAV:
         Datei aus Pfad `path` als string zurückgeben
         """
 
-        with await cls.read_buffer(path) as buffer:
+        async with await cls.read_buffer(path) as buffer:
             tio = TextIOWrapper(buffer, encoding=encoding)
             tio.seek(0)
 
diff --git a/api/asynccontextmanager.py b/api/asynccontextmanager.py
new file mode 100644
index 0000000..fba5832
--- /dev/null
+++ b/api/asynccontextmanager.py
@@ -0,0 +1,52 @@
+import asyncio
+import functools
+from contextlib import asynccontextmanager, contextmanager
+from io import BytesIO
+from typing import AsyncContextManager, AsyncIterator, ContextManager, Iterator
+
+
+def get_buf_sync() -> ContextManager[BytesIO]:
+    @functools.lru_cache
+    def inner() -> BytesIO:
+        with open(__file__, "rb") as file:
+            return BytesIO(file.readline())
+
+    @contextmanager
+    def ctx() -> Iterator[BytesIO]:
+        buf = inner()
+        buf.seek(0)
+        yield buf
+
+    return ctx()
+
+
+def main_sync() -> None:
+    for _ in range(2):
+        with get_buf_sync() as buffer:
+            print(buffer.read())
+
+
+async def get_buf_async() -> AsyncContextManager[BytesIO]:
+    @functools.lru_cache
+    async def inner() -> BytesIO:
+        with open(__file__, "rb") as file:
+            return BytesIO(file.readline())
+
+    @asynccontextmanager
+    async def ctx() -> AsyncIterator[BytesIO]:
+        buf = await inner()
+        buf.seek(0)
+        yield buf
+
+    return ctx()
+
+
+async def main_async() -> None:
+    for _ in range(2):
+        async with await get_buf_async() as buffer:
+            print(buffer.read())
+
+
+if __name__ == "__main__":
+    main_sync()
+    asyncio.run(main_async())