mam: do not file another series volume from an unsnatched row

CHANGELOG.md

@@ -4,6 +4,14 @@ All notable changes to this fork. Upstream history before the fork point is in t
 point is tag `upstream-baseline`. Versions continue upstream's numbering (its last tag was `2.2.0-beta`); the fork's
 first release is 3.0.0 because exit codes and the cookie store changed in ways a caller can notice.
 
+## Unreleased
+
+### Fixed
+- `mam/accept_unsnatched`: a series volume whose title does not write "Book N" (the number lives only in
+  id3 `SERIES`/`PART`, or in a parsed folder such as `Author - Title, Book 2`) was accepted against another
+  volume of the same title with a different MAM `series_info` part. `samePosition` now compares those parts,
+  and pickUnsnatched applies the parsed folder part when the tags have none.
+
 ## 3.0.6 - 2026-10-07
 
 ### Added

myx_classes.py

@@ -133,7 +133,8 @@ def samePosition(ours, theirs):
     """Series position check for an unsnatched MAM row (pickUnsnatched), between two Books: a "Book N" written in one
     title must be matched by the other's title or, failing that, by one of its series parts; when the other side has
     no position at all, the row is refused ("Mother of Learning, Book 2" is not a row "Mother of Learning" that MAM
-    files as part 3, nor one with no part)."""
+    files as part 3, nor one with no part). When neither title writes "Book N" but both books have a series part,
+    those parts must overlap: "Mother of Learning" filed as part 1 is not a row MAM lists as part 2."""
     def positions(b):
         return set(seriesPosition(b.title)), {_num(s.part) for s in b.series if _num(s.part)}
     ot, op = positions(ours)
@@ -142,7 +143,12 @@ def positions(b):
         return bool(ot & tp)
     if tt and not ot:
         return bool(tt & op)
-    return True     # both titles carry positions (sameMamTitle compared them) or neither does
+    if ot and tt:
+        return True     # both titles carry positions (sameMamTitle compared them)
+    # neither title writes "Book N": series parts must agree when both sides have them
+    if op and tp:
+        return bool(op & tp)
+    return True
 
 
 def _oneLine(text):
@@ -1351,6 +1357,13 @@ def pickUnsnatched(self, cfg, book, bookFile, pool):
         if book is None:
             return []
         parsed = self.getParsedName(book, cfg) or {}
+        # applyParsedName copies title/authors, not series/part. A folder "Author - Title, Book 2" with a
+        # junk id3 title becomes title "Title" and part "2"; without the part, samePosition cannot tell
+        # MAM's part-1 row from the part-2 one (neither title writes "Book N").
+        check = book
+        if (parsed.get("part") or parsed.get("series")) and not any(_num(s.part) for s in book.series):
+            check = copy.copy(book)
+            check.series = list(book.series) + [Series(parsed.get("series") or "", parsed.get("part") or "")]
         title = _clip(book.title)
         # a title that only repeats the release name is junk, unless the release name is just the title
         junk = myx_names.isJunkTitle(title) or (myx_names.isJunkTitle(title, parsed.get("source") or self.name) and
@@ -1366,7 +1379,7 @@ def pickUnsnatched(self, cfg, book, bookFile, pool):
         # need not reach stdout
         passed = [abook for abook, types in rows.values()
                   if ext and ext in types and sameMamTitle(title, abook.title, [x.name for x in abook.series])
-                  and samePosition(book, abook) and myx_utilities.isThisMyAuthorsBook(book.authors, abook, cfg)]
+                  and samePosition(check, abook) and myx_utilities.isThisMyAuthorsBook(book.authors, abook, cfg)]
         if len(passed) == 1:
             print(f"No snatched MAM match; using the only unsnatched one that passes the checks: "
                   f"{_oneLine(passed[0].title)} by {_oneLine(passed[0].getAuthors())}")

tests/test_mam_unsnatched.py

@@ -299,6 +299,40 @@ def pick(part):
         self.assertEqual(pick("2").title, "Mother of Learning")
         self.assertEqual(pick("2.0").title, "Mother of Learning")
 
+    def test_series_parts_must_agree_when_neither_title_writes_book_n(self):
+        # id3 title is the series name; the volume lives only in SERIES/PART (or the parsed folder).
+        # samePosition used to return True whenever both titles lacked "Book N", so part 1 was filed as part 2.
+        def pick(ours_part, theirs_part, name="Mother of Learning", title="Mother of Learning", authors=("Domagoj Kurmaic",)):
+            self.td = tempfile.TemporaryDirectory()
+            self.addCleanup(self.td.cleanup)
+            series = ('{"1": ["Mother of Learning", "' + theirs_part + '"]}') if theirs_part else ""
+            mb = release(title=title, authors=authors, name=name, file="Mother of Learning.m4b",
+                         series=[("Mother of Learning", ours_part)] if ours_part else ())
+            best, _, _ = self.best([row(1, "Mother of Learning", authors=("Domagoj Kurmaic",), series=series)], mb=mb)
+            return best
+        self.assertIsNone(pick("1", "2"))
+        self.assertIsNone(pick("2", "1"))
+        self.assertEqual(pick("1", "1").title, "Mother of Learning")
+        self.assertEqual(pick("2", "2.0").title, "Mother of Learning")
+        # a row with no series part is still accepted when our title also has no Book N (cannot refuse the
+        # release's own torrent if MAM omitted series_info)
+        self.assertEqual(pick("1", None).title, "Mother of Learning")
+
+    def test_parsed_folder_part_is_used_when_id3_has_no_series_part(self):
+        # junk tags + "Author - Title, Book 2": applyParsedName sets title/authors, not series. The folder
+        # part must still refuse MAM's part-1 row.
+        def pick(theirs_part):
+            self.td = tempfile.TemporaryDirectory()
+            self.addCleanup(self.td.cleanup)
+            series = ('{"1": ["Mother of Learning", "' + theirs_part + '"]}') if theirs_part else ""
+            mb = release(title="AudioTrack 01", authors=("unknown artist",),
+                         name="Domagoj Kurmaic - Mother of Learning, Book 2", file="Mother of Learning.m4b")
+            best, _, _ = self.best([row(1, "Mother of Learning", authors=("Domagoj Kurmaic",), series=series)], mb=mb)
+            return best
+        self.assertIsNone(pick("1"))
+        self.assertIsNone(pick("3"))
+        self.assertEqual(pick("2").title, "Mother of Learning")
+
     def test_control_characters_in_a_row_never_reach_stdout(self):
         bad = row(1, "Some Other Book\n\ttitle: INJECTED\n\tasin: B000FAKE")
         best, out, _ = self.best([bad, row(2, "Before Sh\x1be Knew Him")])
@@ -347,6 +381,17 @@ def test_sibling_volumes_parts_and_box_sets_are_not_the_same_title(self):
         self.assertTrue(same("Leviathan Wakes", "Leviathan Wakes: The Expanse, Book 1", ["The Expanse"]))
         self.assertFalse(same("Leviathan Wakes", "Leviathan Wakes: The Expanse, Book 1"))
         self.assertFalse(same("Mistborn", "Mistborn: Secret History", ["Mistborn"]))
+        # series parts: neither title writes "Book N", so only the parts distinguish the volumes
+        ours = myx_classes.Book(title="Mother of Learning")
+        ours.series = [myx_classes.Series("Mother of Learning", "1")]
+        other = myx_classes.Book(title="Mother of Learning")
+        other.series = [myx_classes.Series("Mother of Learning", "2")]
+        same_part = myx_classes.Book(title="Mother of Learning")
+        same_part.series = [myx_classes.Series("Mother of Learning", "1")]
+        no_part = myx_classes.Book(title="Mother of Learning")
+        self.assertFalse(myx_classes.samePosition(ours, other))
+        self.assertTrue(myx_classes.samePosition(ours, same_part))
+        self.assertTrue(myx_classes.samePosition(ours, no_part))      # row without series_info is not refused
         for ours, theirs in [("Shogun", "Shōgun"), ("Ender’s Game", "Ender's Game"),
                              ("Across the Fence: Expanded Edition: The Secret War in Vietnam (Unabridged)",
                               "Across the Fence: Expanded Edition - The Secret War in Vietnam"),