Run download jobs and deliver books to CWA

Jobs download new chapters, recheck chapters, replace the book, update
metadata or rebuild from stored chapters. Locked metadata fields keep
their values. A scheduler queues updates. An update finds the library
book of a story through CWA, and fails with an error if it cannot, so
that it never makes a duplicate book.

tests/test_metadata.py

@@ -0,0 +1,74 @@
+import pytest
+
+from bindery import orchestrator as backend
+
+SITE = {
+    "title": "Site Title",
+    "authors": ["Writer"],
+    "comments": "<p>New blurb</p>",
+    "tags": ["Fantasy", "Completed"],
+    "series": "Saga",
+    "series_index": 2.0,
+    "pubdate": "2020-01-01T00:00:00",
+    "languages": "en",
+}
+
+
+def story(**extra):
+    base = {"locked_fields": ["title"], "pinned": {}, "site_values": {}}
+    base.update(extra)
+    return base
+
+
+def test_first_download_keeps_site_value():
+    assert backend._resolve_metadata(story(), SITE, []) == {"title": "Site Title"}
+
+
+def test_locked_field_keeps_its_value():
+    assert backend._resolve_metadata(story(pinned={"title": "Old"}), SITE, []) == {"title": "Old"}
+
+
+def test_forced_field_takes_site_value_and_stays_locked():
+    s = story(pinned={"title": "Old"})
+    assert backend._resolve_metadata(s, SITE, ["title"]) == {"title": "Site Title"}
+
+
+def test_edited_unlocked_field_stays_until_the_site_changes_it():
+    s = story(pinned={"title": "Old", "tags": ["mine"]}, site_values=SITE)
+    assert backend._resolve_metadata(s, SITE, []) == {"title": "Old", "tags": ["mine"]}
+    changed = {**SITE, "tags": ["Fantasy", "Completed", "LitRPG"]}
+    assert backend._resolve_metadata(s, changed, []) == {"title": "Old"}
+    # A change to another field keeps the edit.
+    assert backend._resolve_metadata(s, {**SITE, "comments": "<p>x</p>"}, []) == {"title": "Old", "tags": ["mine"]}
+
+
+def test_forced_update_replaces_an_edited_unlocked_field():
+    s = story(pinned={"tags": ["mine"]}, site_values=SITE)
+    assert backend._resolve_metadata(s, SITE, ["tags"]) == {"title": "Site Title"}
+
+
+def test_edit_before_the_first_site_values_stays():
+    s = story(pinned={"tags": ["mine"]})
+    assert backend._resolve_metadata(s, SITE, []) == {"title": "Site Title", "tags": ["mine"]}
+
+
+def test_edited_values_are_checked_and_normalized():
+    assert backend._edited_value("authors", "A & B ") == ["A", "B"]
+    assert backend._edited_value("tags", "x, y,,") == ["x", "y"]
+    assert backend._edited_value("series", "Saga [2]") == ["Saga", 2.0]
+    assert backend._edited_value("series", ["Saga", "3"]) == ["Saga", 3.0]
+    assert backend._edited_value("series", "") == ["", None]
+    assert backend._edited_value("pubdate", "2024-01-31") == "2024-01-31"
+    assert backend._edited_value("title", " New ") == "New"
+    for field, value in (("title", " "), ("authors", "&"), ("pubdate", "soon")):
+        with pytest.raises(ValueError):
+            backend._edited_value(field, value)
+
+
+def test_series_keeps_name_and_index():
+    s = story(locked_fields=["series"])
+    assert backend._resolve_metadata(s, SITE, []) == {"series": ["Saga", 2.0]}
+
+
+def test_resolve_without_site_values_does_not_fail():
+    assert backend._resolve_metadata(story(pinned={"title": "Old"}), {}, []) == {"title": "Old"}