test: wishlist SQL pagination and category filter

Covers LIMIT/OFFSET paging, album/singles category filtering (including
EP/compilation/missing album_type edge cases), COUNT with and without
category, profile isolation, backward-compat no-args behavior for
existing callers, and date_added ordering.

tests/test_wishlist_pagination.py

@@ -0,0 +1,131 @@
+"""Unit tests for SQL-level wishlist pagination and category filtering.
+
+Fix 1.4: the API endpoint previously loaded the entire wishlist, filtered
+by category in Python, then sliced for the requested page. Pagination and
+category filtering are now pushed to SQL via LIMIT/OFFSET and json_extract.
+"""
+
+import json
+
+import pytest
+
+from database.music_database import MusicDatabase
+
+
+@pytest.fixture
+def db(tmp_path):
+    return MusicDatabase(str(tmp_path / "music.db"))
+
+
+def _insert(db, spotify_track_id, name, album_type, profile_id=1, date_added=None):
+    spotify_data = {
+        "id": spotify_track_id,
+        "name": name,
+        "artists": [{"name": "Test Artist"}],
+        "album": {"name": f"Album for {name}", "album_type": album_type, "images": []},
+    }
+    date_added = date_added or f"2026-01-{len(spotify_track_id):02d}T00:00:00"
+    with db._get_connection() as conn:
+        conn.execute(
+            """INSERT INTO wishlist_tracks
+               (spotify_track_id, spotify_data, failure_reason, retry_count,
+                date_added, source_type, source_info, profile_id)
+               VALUES (?, ?, '', 0, ?, 'test', '{}', ?)""",
+            (spotify_track_id, json.dumps(spotify_data), date_added, profile_id),
+        )
+        conn.commit()
+
+
+def test_pagination_limit_offset(db):
+    for i in range(5):
+        _insert(db, f"t{i}", f"Track {i}", "album", date_added=f"2026-01-0{i+1}T00:00:00")
+
+    page1 = db.get_wishlist_tracks(limit=2, offset=0)
+    page2 = db.get_wishlist_tracks(limit=2, offset=2)
+    page3 = db.get_wishlist_tracks(limit=2, offset=4)
+
+    assert [t["spotify_track_id"] for t in page1] == ["t0", "t1"]
+    assert [t["spotify_track_id"] for t in page2] == ["t2", "t3"]
+    assert [t["spotify_track_id"] for t in page3] == ["t4"]
+
+
+def test_category_filter_albums(db):
+    _insert(db, "a1", "Album Track 1", "album", date_added="2026-01-01T00:00:00")
+    _insert(db, "s1", "Single 1", "single", date_added="2026-01-02T00:00:00")
+    _insert(db, "a2", "Album Track 2", "album", date_added="2026-01-03T00:00:00")
+    _insert(db, "e1", "EP Track", "ep", date_added="2026-01-04T00:00:00")
+
+    albums = db.get_wishlist_tracks(category="albums")
+    assert sorted(t["spotify_track_id"] for t in albums) == ["a1", "a2"]
+
+
+def test_category_filter_singles_includes_non_album_types(db):
+    _insert(db, "a1", "Album", "album", date_added="2026-01-01T00:00:00")
+    _insert(db, "s1", "Single", "single", date_added="2026-01-02T00:00:00")
+    _insert(db, "e1", "EP", "ep", date_added="2026-01-03T00:00:00")
+    _insert(db, "c1", "Compilation", "compilation", date_added="2026-01-04T00:00:00")
+
+    singles = db.get_wishlist_tracks(category="singles")
+    assert sorted(t["spotify_track_id"] for t in singles) == ["c1", "e1", "s1"]
+
+
+def test_category_filter_singles_includes_missing_album_type(db):
+    # Manually insert a row whose album has no album_type (malformed)
+    with db._get_connection() as conn:
+        conn.execute(
+            """INSERT INTO wishlist_tracks
+               (spotify_track_id, spotify_data, failure_reason, retry_count,
+                date_added, source_type, source_info, profile_id)
+               VALUES ('x1', ?, '', 0, '2026-01-01', 'test', '{}', 1)""",
+            (json.dumps({"id": "x1", "name": "X", "album": {"name": "A"}}),),
+        )
+        conn.commit()
+
+    singles = db.get_wishlist_tracks(category="singles")
+    assert [t["spotify_track_id"] for t in singles] == ["x1"]
+
+
+def test_get_wishlist_count_no_filter(db):
+    for i in range(7):
+        _insert(db, f"t{i}", f"Track {i}", "album", date_added=f"2026-01-0{i+1}T00:00:00")
+
+    assert db.get_wishlist_count() == 7
+
+
+def test_get_wishlist_count_with_category_filter(db):
+    _insert(db, "a1", "A1", "album", date_added="2026-01-01T00:00:00")
+    _insert(db, "a2", "A2", "album", date_added="2026-01-02T00:00:00")
+    _insert(db, "s1", "S1", "single", date_added="2026-01-03T00:00:00")
+
+    assert db.get_wishlist_count(category="albums") == 2
+    assert db.get_wishlist_count(category="singles") == 1
+    assert db.get_wishlist_count() == 3
+
+
+def test_profile_isolation(db):
+    _insert(db, "p1-a", "A", "album", profile_id=1, date_added="2026-01-01T00:00:00")
+    _insert(db, "p1-b", "B", "album", profile_id=1, date_added="2026-01-02T00:00:00")
+    _insert(db, "p2-a", "C", "album", profile_id=2, date_added="2026-01-03T00:00:00")
+
+    assert db.get_wishlist_count(profile_id=1) == 2
+    assert db.get_wishlist_count(profile_id=2) == 1
+
+    p1 = db.get_wishlist_tracks(profile_id=1)
+    assert sorted(t["spotify_track_id"] for t in p1) == ["p1-a", "p1-b"]
+
+
+def test_backward_compat_no_args_returns_all(db):
+    """Existing callers (wishlist_service) pass no limit/offset — must still work."""
+    for i in range(3):
+        _insert(db, f"t{i}", f"Track {i}", "album", date_added=f"2026-01-0{i+1}T00:00:00")
+
+    rows = db.get_wishlist_tracks()
+    assert len(rows) == 3
+
+
+def test_ordering_by_date_added(db):
+    _insert(db, "newer", "Newer", "album", date_added="2026-02-01T00:00:00")
+    _insert(db, "older", "Older", "album", date_added="2026-01-01T00:00:00")
+
+    rows = db.get_wishlist_tracks()
+    assert [r["spotify_track_id"] for r in rows] == ["older", "newer"]