memory (cache): add persistent cache entries:

`max_age` can now be `C.MAX_AGE_PERSISTENT` to keep a cache entry indefinitely: its `eol`
is then `None` and no expiration check is done.

libervia/backend/core/constants.py

@@ -525,6 +525,7 @@ class Const:
     IGNORE = "ignore"
     NO_LIMIT = -1  # used in bridge when a integer value is expected
     DEFAULT_MAX_AGE = 1209600  # default max age of cached files, in seconds
+    MAX_AGE_PERSISTENT = -1  # keep a cache entry indefinitely
     STANZA_NAMES = ("iq", "message", "presence")
 
     # Stream Hooks

libervia/backend/memory/cache.py

@@ -22,7 +22,7 @@ from pathlib import Path
 import time
 from typing import Any
 
-from pydantic import BaseModel, ValidationError
+from pydantic import BaseModel, Field, ValidationError
 
 from libervia.backend import G
 from libervia.backend.core import exceptions
@@ -42,7 +42,9 @@ class CacheMetadata(BaseModel):
     uid: str
     filename: str
     creation: int
-    eol: int
+    eol: int | None = Field(
+        default=None, description="End of life. If None, entry is kept indefinitely"
+    )
     max_age: int = C.DEFAULT_MAX_AGE
     original_filename: str | None = None
     mime_type: str | None = None
@@ -95,7 +97,7 @@ class Cache:
                         f"and will be deleted: {cache_data_file!r}."
                     )
                     to_delete.add(cache_data_file)
-                elif cache_data.eol < now:
+                elif cache_data.eol is not None and cache_data.eol < now:
                     log.debug(
                         f"Purging expired cache file {cache_data_file} (expired for "
                         f"{int(time.time() - cache_data.eol)}s)"
@@ -156,7 +158,7 @@ class Cache:
             log.warning(f"Invalid encoding, this is not a cache metadata file.")
             return None
 
-        if cache_data.eol < time.time():
+        if cache_data.eol is not None and cache_data.eol < time.time():
             log.debug(
                 "removing expired cache (expired for {}s)".format(
                     time.time() - cache_data.eol
@@ -164,7 +166,7 @@ class Cache:
             )
             return None
 
-        if update_eol:
+        if update_eol and cache_data.eol is not None:
             now = int(time.time())
             cache_data.last_access = now
             cache_data.eol = now + cache_data.max_age
@@ -236,6 +238,7 @@ class Cache:
             the cache metadata will have an "eol" (end of life)
             None to use default value
             0 to ignore cache (file will be re-downloaded on each access)
+            C.MAX_AGE_PERSISTENT to keep the entry in cache indefinitely
         @param original_filename: if not None, will be used to retrieve file extension and
             guess mime type, and stored in "original_filename"
         @return: file object opened in write mode
@@ -266,7 +269,7 @@ class Cache:
             original_filename=original_filename,
             filename=filename,
             creation=now,
-            eol=now + max_age,
+            eol=None if max_age == C.MAX_AGE_PERSISTENT else now + max_age,
         )
 
         cache_metadata_file = self.get_path(f"{uid}{CACHE_METADATA_EXT}")

libervia/backend/plugins/plugin_xep_0231.py

@@ -194,7 +194,8 @@ class XEP_0231(object):
         )
         data_elt["cid"] = cid
         data_elt["type"] = metadata["mime_type"]
-        data_elt["max-age"] = str(int(max(0, metadata["eol"] - time.time())))
+        if metadata["eol"] is not None:
+            data_elt["max-age"] = str(int(max(0, metadata["eol"] - time.time())))
         client.send(result_elt)
 
     def _get_file(self, peer_jid_s, cid, profile):