Fixhancement: improve text thumbnail generation for large files (#10483)

src/paperless_text/tests/test_parser.py

@@ -1,3 +1,4 @@
+import tempfile
 from pathlib import Path
 
 from paperless_text.parsers import TextDocumentParser
@@ -35,3 +36,26 @@ class TestTextParser:
 
         assert text_parser.get_text() == "Pantothens<EFBFBD>ure\n"
         assert text_parser.get_archive_path() is None
+
+    def test_thumbnail_large_file(self, text_parser: TextDocumentParser):
+        """
+        GIVEN:
+            - A very large text file (>50MB)
+        WHEN:
+            - A thumbnail is requested
+        THEN:
+            - A thumbnail is created without reading the entire file into memory
+        """
+        with tempfile.NamedTemporaryFile(
+            delete=False,
+            mode="w",
+            encoding="utf-8",
+            suffix=".txt",
+        ) as tmp:
+            tmp.write("A" * (51 * 1024 * 1024))  # 51 MB of 'A'
+            large_file = Path(tmp.name)
+
+            thumb = text_parser.get_thumbnail(large_file, "text/plain")
+            assert thumb.exists()
+            assert thumb.is_file()
+            large_file.unlink()