1 files changed, 20 insertions, 0 deletions
diff --git a/hooks/_common.py b/hooks/_common.py
index d4bf520..e82f7ed 100644
--- a/hooks/_common.py
+++ b/hooks/_common.py
@@ -16,6 +16,7 @@ the tools themselves.
 """
 
 import json
+import os
 import re
 import sys
 from typing import Optional
@@ -64,6 +65,25 @@ def respond_ask(reason: str, system_message: Optional[str] = None) -> None:
     print(json.dumps(output))
 
 
+def read_referenced_file(path: str, max_bytes: int = 1_000_000) -> Optional[str]:
+    """Read a local file referenced by -F/--file/--body-file so its text can be
+    attribution-scanned. Return the text, or None if it can't be safely read
+    (missing, not a regular file, larger than max_bytes, or not valid UTF-8).
+    None means 'could not inspect', never 'clean'."""
+    if not path:
+        return None
+    try:
+        expanded = os.path.expanduser(path)
+        if not os.path.isfile(expanded):
+            return None
+        if os.path.getsize(expanded) > max_bytes:
+            return None
+        with open(expanded, "r", encoding="utf-8", errors="strict") as fh:
+            return fh.read()
+    except (OSError, UnicodeDecodeError):
+        return None
+
+
 def scan_attribution(text: str) -> list[str]:
     """Return human-readable descriptions of any AI-attribution hits."""
     if not text: