From e2c3399ed37b604c628b6e240329acb17d5626bb Mon Sep 17 00:00:00 2001
From: dennisvang <29799340+dennisvang@users.noreply.github.com>
Date: Fri, 9 Feb 2024 22:49:14 +0100
Subject: [PATCH] introduce MAX_SIZE_RATIO for decision patch vs full update

---
 src/tufup/client.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/tufup/client.py b/src/tufup/client.py
index abf41d4..d73cf25 100644
--- a/src/tufup/client.py
+++ b/src/tufup/client.py
@@ -19,6 +19,8 @@
 
 DEFAULT_EXTRACT_DIR = pathlib.Path(tempfile.gettempdir()) / 'tufup'
 SUFFIX_FAILED = '.failed'
+# do full update if patch-size/full-size > MAX_SIZE_RATIO
+MAX_SIZE_RATIO = 0.8
 
 
 class Client(tuf.ngclient.Updater):
@@ -208,7 +210,9 @@ def check_for_updates(
             # is not available, we must do a full update)
             self.new_targets = new_patches
             no_patches = total_patch_size == 0
-            patch_too_big = total_patch_size > self.new_archive_info.length
+            patch_too_big = (
+                total_patch_size / self.new_archive_info.length > MAX_SIZE_RATIO
+            )
             no_archive = not self.current_archive_local_path.exists()
             if not patch or no_patches or patch_too_big or no_archive or abort_patch:
                 # fall back on full update