Added support for all Redis versions (>=1.0.0) (#5)

Previously support was provided for Redis>=6.2.0

Reviewed-on: #5
Co-authored-by: Ivan Golikov <root@ivnglkv.me>
Co-committed-by: Ivan Golikov <root@ivnglkv.me>

pssecret_server/utils.py

@@ -1,7 +1,10 @@
+from functools import lru_cache
 from uuid import uuid4
 
 from cryptography.fernet import Fernet
 from redis.asyncio import Redis
+from redis.exceptions import ResponseError
+from redis.typing import ResponseT
 
 from pssecret_server.models import Secret
 
@@ -30,3 +33,35 @@ async def save_secret(data: Secret, redis: Redis) -> str:
     await redis.setex(new_key, 60 * 60 * 24, data.data)
 
     return new_key
+
+
+@lru_cache
+async def _is_getdel_available(redis: Redis) -> bool:
+    """Checks the availability of GETDEL command on the Redis server instance
+
+    GETDEL is not available in Redis prior to version 6.2
+    """
+    try:
+        await redis.getdel("test:getdel:availability")
+    except ResponseError:
+        return False
+
+    return True
+
+
+async def getdel(redis: Redis, key: str) -> ResponseT:
+    """Gets the value of key and deletes the key
+
+    Depending on the capabilities of Redis server this function
+    will either call GETDEL command, either first call GETSET with empty string
+    and DEL right after that.
+    """
+    result: ResponseT
+
+    if await _is_getdel_available(redis):
+        result = await redis.getdel(key)
+    else:
+        result = await redis.getset(key, "")
+        await redis.delete(key)
+
+    return result