test(downloads): validate author_title stem generation and cache fallbacks

tests/downloads/test_download_manager_cache_and_validation.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from pathlib import Path
+from typing import Any, cast
 
 import pytest
 
@@ -17,9 +18,11 @@ def _manager_with_cache_dir(tmp_path: Path) -> DownloadManager:
 
 
 def test_sanitize_filename_replaces_invalid_characters() -> None:
-    """Ensure filesystem-invalid symbols are replaced with underscores."""
+    """Ensure filename normalization uses ASCII words and dashes."""
     manager = DownloadManager.__new__(DownloadManager)
-    assert manager._sanitize_filename('a<>:"/\\|?*b') == "a_________b"
+    assert (
+        manager._sanitize_filename("Stephen King 11/22/63") == "Stephen-King-11-22-63"
+    )
 
 
 def test_validate_download_url_accepts_only_http_schemes() -> None:
@@ -35,8 +38,12 @@ def test_get_cached_path_and_remove_cached(
 ) -> None:
     """Ensure cache lookup and cache deletion work for valid files."""
     manager = _manager_with_cache_dir(tmp_path)
-    monkeypatch.setattr(manager, "_get_name_from_asin", lambda asin: "My Book")
-    cached_path = tmp_path / "My Book.aax"
+    monkeypatch.setattr(
+        manager,
+        "_get_filename_stems_from_asin",
+        lambda asin: ["Stephen-King_11-22-63", "11-22-63"],
+    )
+    cached_path = tmp_path / "Stephen-King_11-22-63.aax"
     cached_path.write_bytes(b"0" * MIN_FILE_SIZE)
     messages: list[str] = []
     assert manager.get_cached_path("ASIN123") == cached_path
@@ -51,7 +58,34 @@ def test_get_cached_path_ignores_small_files(
 ) -> None:
     """Ensure undersized files are not treated as valid cache entries."""
     manager = _manager_with_cache_dir(tmp_path)
-    monkeypatch.setattr(manager, "_get_name_from_asin", lambda asin: "My Book")
-    cached_path = tmp_path / "My Book.aax"
+    monkeypatch.setattr(
+        manager,
+        "_get_filename_stems_from_asin",
+        lambda asin: ["Stephen-King_11-22-63", "11-22-63"],
+    )
+    cached_path = tmp_path / "Stephen-King_11-22-63.aax"
     cached_path.write_bytes(b"0" * (MIN_FILE_SIZE - 1))
     assert manager.get_cached_path("ASIN123") is None
+
+
+def test_get_filename_stems_include_author_title_and_legacy_title() -> None:
+    """Ensure filename candidates include new author_title and legacy title names."""
+    manager = DownloadManager.__new__(DownloadManager)
+    manager.client = cast(
+        Any,
+        type(
+            "Client",
+            (),
+            {
+                "get": lambda self, path, **kwargs: {
+                    "product": {
+                        "title": "11/22/63",
+                        "authors": [{"name": "Stephen King"}],
+                    }
+                }
+            },
+        )(),
+    )
+    stems = manager._get_filename_stems_from_asin("B00TEST")
+    assert stems[0] == "Stephen-King_11-22-63"
+    assert "11-22-63" in stems