Diff stage: snapshot/live collection modes, to_add + to_update outputs

compute_diff is a pure function over matches + collection items: new
games land in to_add.csv (carrying a confident version when matching
produced one); owned version-less entries with version_auto/approved
matches produce additive to_update.csv rows keyed by collid, consuming
distinct collids when photos show two editions; entries that already
carry a version are never touched — disagreements are reported in the
summary. Unseen collection entries are listed informationally. Live API
mode activates when BGG_API_TOKEN + username exist; otherwise the two
hand-pulled snapshot XMLs (real 2018 collection, 79 unique copies after
collid dedupe) are used, and they double as parsing fixtures in tests.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_diff.py

@@ -0,0 +1,166 @@
+"""Diff-stage tests: pure compute_diff cases plus the real 2018 collection
+snapshots as parsing fixtures. No network anywhere."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from bggpipe.diff import compute_diff, load_snapshot_collection
+from bggpipe.models import CollectionItem
+
+FIXTURES = Path(__file__).parent / "fixtures"
+
+
+def _item(object_id, coll_id, name="Game", version_id=None, own=True):
+    return CollectionItem(
+        object_id=object_id,
+        coll_id=coll_id,
+        name=name,
+        subtype="boardgame",
+        own=own,
+        year=None,
+        version_id=version_id,
+    )
+
+
+def _match(
+    title, bgg_id="", status="auto", vstatus="version_unknown", vid="", vname=""
+):
+    return {
+        "title_raw": title,
+        "bgg_id": bgg_id,
+        "bgg_name": title.title(),
+        "year": "2000",
+        "type": "boardgame",
+        "match_status": status,
+        "version_id": vid,
+        "version_name": vname,
+        "version_status": vstatus,
+        "candidates_json": "[]",
+        "version_candidates_json": "[]",
+        "source_photos": "x.jpg",
+    }
+
+
+# -- snapshot loading ---------------------------------------------------
+
+
+def test_load_real_snapshots_merges_and_dedupes():
+    collection = load_snapshot_collection(FIXTURES)
+    # 79 base + 3 expansions, but all 3 expansion collids also appear in
+    # the base file -> 79 unique physical copies
+    assert len(collection) == 79
+    assert len({c.coll_id for c in collection}) == 79
+    by_id = {c.object_id: c for c in collection}
+    assert by_id[207830].name == "5-Minute Dungeon"
+    assert by_id[177].name == "Advanced Civilization"
+    # hand-entered in 2018: every entry is version-less (parsed, not assumed)
+    assert all(c.version_id is None for c in collection)
+
+
+# -- compute_diff -------------------------------------------------------
+
+
+def test_new_game_goes_to_add_with_version():
+    result = compute_diff(
+        [
+            _match(
+                "Cat Crimes",
+                "235096",
+                vstatus="version_auto",
+                vid="360982",
+                vname="ThinkFun edition",
+            )
+        ],
+        [_item(13, 1)],
+    )
+    (row,) = result.to_add
+    assert row["bgg_id"] == "235096"
+    assert row["version_id"] == "360982"
+    assert not result.to_update
+
+
+def test_owned_versionless_plus_confident_version_goes_to_update():
+    result = compute_diff(
+        [
+            _match(
+                "Britannia",
+                "240",
+                vstatus="version_auto",
+                vid="55555",
+                vname="AH English edition",
+            )
+        ],
+        [_item(240, 900001, name="Britannia")],
+    )
+    assert result.already_owned == ["Britannia"]
+    (row,) = result.to_update
+    assert row == {
+        "collid": "900001",
+        "bgg_id": "240",
+        "bgg_name": "Britannia",
+        "version_id": "55555",
+        "version_name": "AH English edition",
+    }
+    assert not result.to_add
+
+
+def test_owned_with_matching_version_is_just_owned():
+    result = compute_diff(
+        [_match("Wingspan", "266192", vstatus="version_auto", vid="465063")],
+        [_item(266192, 5, version_id=465063)],
+    )
+    assert result.already_owned == ["Wingspan"]
+    assert not result.to_update and not result.to_add
+
+
+def test_owned_with_different_version_reports_disagreement_untouched():
+    result = compute_diff(
+        [
+            _match(
+                "Wingspan",
+                "266192",
+                vstatus="version_auto",
+                vid="521212",
+                vname="fourth printing",
+            )
+        ],
+        [_item(266192, 5, version_id=465063)],
+    )
+    assert result.already_owned == ["Wingspan"]
+    assert not result.to_update  # additive only: never edit a set version
+    assert "fourth printing" in result.disagreements[0]
+
+
+def test_version_unknown_owned_by_bare_id():
+    result = compute_diff(
+        [_match("Catan", "13")],
+        [_item(13, 1, name="Catan")],
+    )
+    assert result.already_owned == ["Catan"]
+    assert not result.to_add and not result.to_update
+
+
+def test_two_photo_editions_consume_distinct_collids():
+    matches = [
+        _match("Cosmic A", "39", vstatus="version_auto", vid="111"),
+        _match("Cosmic B", "39", vstatus="version_auto", vid="222"),
+    ]
+    collection = [_item(39, 701), _item(39, 702)]
+    result = compute_diff(matches, collection)
+    assert {r["collid"] for r in result.to_update} == {"701", "702"}
+    assert {r["version_id"] for r in result.to_update} == {"111", "222"}
+
+
+def test_pending_rejected_and_unseen_are_reported():
+    matches = [
+        _match("Mystery Spine", status="ambiguous"),
+        _match("Junk", status="rejected"),
+        _match("Catan", "13"),
+    ]
+    collection = [_item(13, 1, name="Catan"), _item(9209, 2, name="Ticket to Ride")]
+    result = compute_diff(matches, collection)
+    assert result.pending == ["Mystery Spine"]
+    assert result.rejected == 1
+    assert [c.object_id for c in result.unseen] == [9209]  # informational
+    assert result.recognized == 1