new backend pagination approach (#49)

* new backend pagination approach

* prettier

backend/api/v1/schemas/artist.py

@@ -15,9 +15,16 @@ class ArtistReleases(AppStruct):
     albums: list[ReleaseItem] = []
     singles: list[ReleaseItem] = []
     eps: list[ReleaseItem] = []
-    total_count: int = 0
+
+    offset: int = 0
+    limit: int = 50
+    returned_count: int = 0
+
+    next_offset: int | None = None
     has_more: bool = False
 
+    source_total_count: int | None = None
+
 
 class LastFmSimilarArtistSchema(AppStruct):
     name: str

backend/services/artist_service.py

@@ -543,46 +543,126 @@ class ArtistService:
             included_primary_types = set(t.lower() for t in prefs.primary_types)
             included_secondary_types = set(t.lower() for t in prefs.secondary_types)
 
-            if in_library and offset == 0:
-                lidarr_albums = await self._lidarr_repo.get_artist_albums(artist_id)
-                albums, singles, eps = self._categorize_lidarr_albums(lidarr_albums, album_mbids, requested_mbids=requested_mbids)
-
-                total_count = len(albums) + len(singles) + len(eps)
-
+            if in_library:
+                if offset == 0:
+                    lidarr_albums = await self._lidarr_repo.get_artist_albums(artist_id)
+                    albums, singles, eps = self._categorize_lidarr_albums(lidarr_albums, album_mbids, requested_mbids=requested_mbids)
+                    total_count = len(albums) + len(singles) + len(eps)
+                    return ArtistReleases(
+                        albums=albums,
+                        singles=singles,
+                        eps=eps,
+                        offset=0,
+                        limit=limit,
+                        returned_count=total_count,
+                        next_offset=None,
+                        has_more=False,
+                        source_total_count=None,
+                    )
                 return ArtistReleases(
-                    albums=albums,
-                    singles=singles,
-                    eps=eps,
-                    total_count=total_count,
-                    has_more=False
+                    albums=[], singles=[], eps=[],
+                    offset=offset, limit=limit, returned_count=0,
+                    next_offset=None, has_more=False, source_total_count=None,
                 )
 
-            release_groups, total_count = await self._mb_repo.get_artist_release_groups(
-                artist_id, offset, limit
-            )
-
-            temp_artist = {"release-group-list": release_groups}
-
-            albums, singles, eps = categorize_release_groups(
-                temp_artist,
-                album_mbids,
-                included_primary_types,
-                included_secondary_types,
-                requested_mbids
-            )
-            
-            has_more = (offset + len(release_groups)) < total_count
-            
-            return ArtistReleases(
-                albums=albums,
-                singles=singles,
-                eps=eps,
-                total_count=total_count,
-                has_more=has_more
+            return await self._filter_aware_release_page(
+                artist_id, offset, limit, album_mbids, requested_mbids,
+                included_primary_types, included_secondary_types,
             )
         except Exception as e:  # noqa: BLE001
             logger.error(f"Error fetching releases for artist {artist_id} at offset {offset}: {e}")
-            return ArtistReleases(albums=[], singles=[], eps=[], total_count=0, has_more=False)
+            return ArtistReleases(
+                albums=[], singles=[], eps=[],
+                offset=offset, limit=limit, returned_count=0,
+                next_offset=None, has_more=False, source_total_count=None,
+            )
+
+    async def _filter_aware_release_page(
+        self,
+        artist_id: str,
+        offset: int,
+        limit: int,
+        album_mbids: set[str],
+        requested_mbids: set[str],
+        included_primary_types: set[str],
+        included_secondary_types: set[str],
+    ) -> ArtistReleases:
+        if not included_primary_types:
+            return ArtistReleases(
+                albums=[], singles=[], eps=[],
+                offset=offset, limit=limit, returned_count=0,
+                next_offset=None, has_more=False, source_total_count=None,
+            )
+
+        _SCAN_BATCH = 100
+        _MAX_SCAN_BATCHES = 20
+        seen_mbids: set[str] = set()
+        all_albums: list[ReleaseItem] = []
+        all_singles: list[ReleaseItem] = []
+        all_eps: list[ReleaseItem] = []
+
+        raw_offset = offset
+        source_total: int | None = None
+        batches_scanned = 0
+
+        while batches_scanned < _MAX_SCAN_BATCHES:
+            release_groups, mb_total = await self._mb_repo.get_artist_release_groups(
+                artist_id, raw_offset, _SCAN_BATCH
+            )
+            if source_total is None:
+                source_total = mb_total
+
+            if not release_groups:
+                break
+
+            temp_artist = {"release-group-list": release_groups}
+            page_albums, page_singles, page_eps = categorize_release_groups(
+                temp_artist, album_mbids, included_primary_types,
+                included_secondary_types, requested_mbids,
+            )
+
+            for item in page_albums:
+                if item.id and item.id not in seen_mbids:
+                    seen_mbids.add(item.id)
+                    all_albums.append(item)
+            for item in page_singles:
+                if item.id and item.id not in seen_mbids:
+                    seen_mbids.add(item.id)
+                    all_singles.append(item)
+            for item in page_eps:
+                if item.id and item.id not in seen_mbids:
+                    seen_mbids.add(item.id)
+                    all_eps.append(item)
+
+            raw_offset += len(release_groups)
+            batches_scanned += 1
+
+            total_collected = len(all_albums) + len(all_singles) + len(all_eps)
+            if total_collected >= limit:
+                break
+            if raw_offset >= mb_total:
+                break
+
+        for lst in (all_albums, all_singles, all_eps):
+            lst.sort(key=lambda x: (x.year is None, -(x.year or 0)))
+
+        returned_count = len(all_albums) + len(all_singles) + len(all_eps)
+
+        has_more = raw_offset < (source_total or 0)
+
+        next_offset = raw_offset if has_more else None
+
+        return ArtistReleases(
+            albums=all_albums,
+            singles=all_singles,
+            eps=all_eps,
+            offset=offset,
+            limit=limit,
+            returned_count=returned_count,
+            next_offset=next_offset,
+            has_more=has_more,
+            source_total_count=source_total,
+        )
     
     async def _fetch_artist_data(
         self,

backend/tests/routes/test_artist_releases_route.py

@@ -26,8 +26,12 @@ def mock_artist_service():
             albums=[ReleaseItem(id="rg-2", title="Album Two", type="Album", year=2023)],
             singles=[],
             eps=[],
-            total_count=120,
+            offset=0,
+            limit=50,
+            returned_count=1,
+            next_offset=100,
             has_more=True,
+            source_total_count=120,
         )
     )
     mock.get_artist_info_basic = AsyncMock()
@@ -61,13 +65,17 @@ class TestGetArtistReleasesRoute:
         assert response.status_code == 200
         mock_artist_service.get_artist_releases.assert_awaited_once_with(VALID_MBID, 50, 50)
 
-    def test_has_more_flag_propagated(self, client):
+    def test_new_pagination_fields_propagated(self, client):
         response = client.get(f"/api/v1/artists/{VALID_MBID}/releases?offset=0&limit=50")
         body = response.json()
 
         assert response.status_code == 200
         assert body["has_more"] is True
-        assert body["total_count"] == 120
+        assert body["offset"] == 0
+        assert body["limit"] == 50
+        assert body["returned_count"] == 1
+        assert body["next_offset"] == 100
+        assert body["source_total_count"] == 120
 
     def test_default_params(self, client, mock_artist_service):
         response = client.get(f"/api/v1/artists/{VALID_MBID}/releases")

backend/tests/services/test_artist_release_pagination.py

@@ -0,0 +1,313 @@
+"""Service-level tests for filter-aware artist release pagination."""
+import os
+import tempfile
+
+os.environ.setdefault("ROOT_APP_DIR", tempfile.mkdtemp())
+
+import pytest
+from unittest.mock import AsyncMock, MagicMock
+
+from services.artist_service import ArtistService
+
+
+ARTIST_MBID = "f4a31f0a-51dd-4fa7-986d-3095c40c5ed9"
+
+
+def _make_release_group(rg_id: str, title: str, primary_type: str, date: str = "2020-01-01") -> dict:
+    return {
+        "id": rg_id,
+        "title": title,
+        "primary-type": primary_type,
+        "secondary-types": [],
+        "first-release-date": date,
+    }
+
+
+def _make_prefs(primary_types: list[str] | None = None, secondary_types: list[str] | None = None) -> MagicMock:
+    p = MagicMock()
+    p.get_preferences.return_value = MagicMock(
+        primary_types=primary_types if primary_types is not None else ["Album", "Single", "EP"],
+        secondary_types=secondary_types if secondary_types is not None else ["Studio", "Live", "Compilation"],
+    )
+    p.get_advanced_settings.return_value = MagicMock(
+        cache_ttl_artist_library=21600,
+        cache_ttl_artist_non_library=3600,
+    )
+    return p
+
+
+def _make_service(
+    *,
+    mb_release_pages: list[tuple[list[dict], int]] | None = None,
+    lidarr_artist: dict | None = None,
+    prefs: MagicMock | None = None,
+) -> ArtistService:
+    mb_repo = AsyncMock()
+    if mb_release_pages is not None:
+        mb_repo.get_artist_release_groups = AsyncMock(side_effect=mb_release_pages)
+    else:
+        mb_repo.get_artist_release_groups = AsyncMock(return_value=([], 0))
+
+    lidarr_repo = MagicMock()
+    lidarr_repo.is_configured.return_value = False
+    lidarr_repo.get_artist_details = AsyncMock(return_value=lidarr_artist)
+    lidarr_repo.get_library_mbids = AsyncMock(return_value=set())
+    lidarr_repo.get_requested_mbids = AsyncMock(return_value=set())
+    lidarr_repo.get_artist_mbids = AsyncMock(return_value=set())
+
+    wikidata_repo = AsyncMock()
+
+    memory_cache = AsyncMock()
+    memory_cache.get = AsyncMock(return_value=None)
+    memory_cache.set = AsyncMock()
+
+    disk_cache = AsyncMock()
+    disk_cache.get_artist = AsyncMock(return_value=None)
+    disk_cache.set_artist = AsyncMock()
+
+    return ArtistService(
+        mb_repo=mb_repo,
+        lidarr_repo=lidarr_repo,
+        wikidata_repo=wikidata_repo,
+        preferences_service=prefs or _make_prefs(),
+        memory_cache=memory_cache,
+        disk_cache=disk_cache,
+    )
+
+
+class TestFilterAwarePagination:
+    @pytest.mark.asyncio
+    async def test_single_page_fits_filter(self):
+        rg1 = _make_release_group("rg-1", "Album A", "Album")
+        rg2 = _make_release_group("rg-2", "Single B", "Single")
+        svc = _make_service(mb_release_pages=[([rg1, rg2], 2)])
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert len(result.albums) == 1
+        assert result.albums[0].title == "Album A"
+        assert len(result.singles) == 1
+        assert result.singles[0].title == "Single B"
+        assert result.has_more is False
+        assert result.next_offset is None
+        assert result.returned_count == 2
+        assert result.source_total_count == 2
+
+    @pytest.mark.asyncio
+    async def test_sparse_filter_scans_multiple_batches(self):
+        batch1 = [_make_release_group(f"rg-{i}", f"Broadcast {i}", "Broadcast") for i in range(5)]
+        batch2 = [_make_release_group("rg-album", "Real Album", "Album")]
+        svc = _make_service(
+            mb_release_pages=[
+                (batch1, 6),
+                (batch2, 6),
+            ]
+        )
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert result.albums[0].title == "Real Album"
+        assert result.returned_count == 1
+        assert result.source_total_count == 6
+
+    @pytest.mark.asyncio
+    async def test_has_more_true_when_unscanned_raw_data_remains(self):
+        rgs = [_make_release_group("rg-1", "Album 1", "Album")]
+        svc = _make_service(mb_release_pages=[(rgs, 200), ([], 200), ([], 200)])
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert result.has_more is True
+        assert result.next_offset is not None
+        assert result.returned_count == 1
+
+    @pytest.mark.asyncio
+    async def test_next_offset_is_scan_position(self):
+        batch1 = [_make_release_group(f"rg-{i}", f"Album {i}", "Album") for i in range(100)]
+        svc = _make_service(mb_release_pages=[(batch1, 200)])
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=10)
+
+        assert result.has_more is True
+        assert result.next_offset == 100
+
+    @pytest.mark.asyncio
+    async def test_no_duplicates_within_scan(self):
+        batch1 = [_make_release_group(f"rg-{i}", f"Album {i}", "Album") for i in range(5)]
+        batch2 = [_make_release_group(f"rg-{i}", f"Album {i}", "Album") for i in range(3, 8)]
+        svc = _make_service(
+            mb_release_pages=[
+                (batch1, 8),
+                (batch2, 8),
+            ]
+        )
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        all_ids = [r.id for r in result.albums]
+        assert len(all_ids) == len(set(all_ids))
+
+    @pytest.mark.asyncio
+    async def test_no_drops_across_sequential_pages(self):
+        rgs = [_make_release_group(f"rg-{i}", f"Album {i}", "Album") for i in range(10)]
+        svc = _make_service(mb_release_pages=[(rgs, 10)])
+
+        page1 = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=3)
+        assert page1.returned_count == 10
+        assert page1.has_more is False
+        assert page1.next_offset is None
+
+    @pytest.mark.asyncio
+    async def test_empty_result_set(self):
+        svc = _make_service(mb_release_pages=[([], 0)])
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert result.returned_count == 0
+        assert result.has_more is False
+        assert result.next_offset is None
+        assert result.source_total_count == 0
+
+    @pytest.mark.asyncio
+    async def test_lidarr_library_artist_single_page(self):
+        lidarr_albums = [
+            {"mbid": "rg-1", "title": "Lib Album", "album_type": "Album", "release_date": "2020-01-01", "year": 2020, "track_file_count": 5, "secondary_types": []},
+        ]
+        svc = _make_service(lidarr_artist={"monitored": True})
+
+        lidarr_repo = svc._lidarr_repo
+        lidarr_repo.get_artist_albums = AsyncMock(return_value=lidarr_albums)
+        lidarr_repo.get_library_mbids = AsyncMock(return_value={"rg-1"})
+        lidarr_repo.get_requested_mbids = AsyncMock(return_value=set())
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert result.returned_count == 1
+        assert result.has_more is False
+        assert result.next_offset is None
+
+    @pytest.mark.asyncio
+    async def test_lidarr_library_artist_offset_gt_zero_returns_empty(self):
+        svc = _make_service(lidarr_artist={"monitored": True})
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=50, limit=50)
+
+        assert result.returned_count == 0
+        assert result.has_more is False
+        assert result.next_offset is None
+
+    @pytest.mark.asyncio
+    async def test_offset_reflects_client_param(self):
+        rg = _make_release_group("rg-1", "Album 1", "Album")
+        svc = _make_service(mb_release_pages=[([rg], 1)])
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=200, limit=50)
+
+        assert result.offset == 200
+
+    @pytest.mark.asyncio
+    async def test_returned_count_across_categories(self):
+        rgs = [
+            _make_release_group("rg-a1", "Album 1", "Album"),
+            _make_release_group("rg-a2", "Album 2", "Album"),
+            _make_release_group("rg-s1", "Single 1", "Single"),
+            _make_release_group("rg-e1", "EP 1", "EP"),
+        ]
+        svc = _make_service(mb_release_pages=[(rgs, 4)])
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert result.returned_count == 4
+        assert len(result.albums) == 2
+        assert len(result.singles) == 1
+        assert len(result.eps) == 1
+
+    @pytest.mark.asyncio
+    async def test_limit_controls_scan_termination_all_items_returned(self):
+        rgs = [
+            _make_release_group("rg-a1", "Album 1", "Album"),
+            _make_release_group("rg-a2", "Album 2", "Album"),
+            _make_release_group("rg-a3", "Album 3", "Album"),
+            _make_release_group("rg-s1", "Single 1", "Single"),
+            _make_release_group("rg-e1", "EP 1", "EP"),
+        ]
+        svc = _make_service(mb_release_pages=[(rgs, 5)])
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=3)
+
+        assert result.returned_count == 5
+        assert len(result.albums) == 3
+        assert len(result.singles) == 1
+        assert len(result.eps) == 1
+        assert result.has_more is False
+
+    @pytest.mark.asyncio
+    async def test_exception_returns_empty_page(self):
+        svc = _make_service()
+        svc._lidarr_repo.get_artist_details = AsyncMock(side_effect=RuntimeError("boom"))
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert result.returned_count == 0
+        assert result.has_more is False
+        assert result.next_offset is None
+
+    @pytest.mark.asyncio
+    async def test_empty_filter_types_returns_immediately(self):
+        svc = _make_service(
+            prefs=_make_prefs(primary_types=[], secondary_types=[]),
+        )
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert result.returned_count == 0
+        assert result.has_more is False
+        assert result.next_offset is None
+        svc._mb_repo.get_artist_release_groups.assert_not_awaited()
+
+    @pytest.mark.asyncio
+    async def test_all_types_filtered_out_except_one(self):
+        batch = (
+            [_make_release_group(f"rg-b{i}", f"Broadcast {i}", "Broadcast") for i in range(5)]
+            + [_make_release_group("rg-album", "Found Album", "Album")]
+        )
+        svc = _make_service(
+            mb_release_pages=[
+                (batch, 6),
+            ]
+        )
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert result.returned_count == 1
+        assert result.albums[0].title == "Found Album"
+        assert result.source_total_count == 6
+        assert result.has_more is False
+
+    @pytest.mark.asyncio
+    async def test_global_sort_across_batches(self):
+        batch1 = [_make_release_group("rg-a", "Old Album", "Album", "2010-01-01")]
+        batch2 = [_make_release_group("rg-b", "New Album", "Album", "2020-01-01")]
+        svc = _make_service(
+            mb_release_pages=[
+                (batch1, 2),
+                (batch2, 2),
+            ]
+        )
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert len(result.albums) == 2
+        assert result.albums[0].title == "New Album"
+        assert result.albums[1].title == "Old Album"
+
+    @pytest.mark.asyncio
+    async def test_scan_batch_cap_stops_early(self):
+        batches = [([_make_release_group(f"rg-{i}", f"Album {i}", "Album")], 5000) for i in range(25)]
+        svc = _make_service(mb_release_pages=batches)
+
+        result = await svc.get_artist_releases(ARTIST_MBID, offset=0, limit=50)
+
+        assert result.has_more is True
+        assert result.next_offset is not None
+        assert result.next_offset == 20

frontend/src/lib/queries/artist/ArtistQueries.svelte.ts

@@ -115,13 +115,14 @@ export const getArtistReleasesInfiniteQuery = (getArtistId: Getter<string>) =>
 			);
 			return response;
 		},
-		getNextPageParam: (lastPage, allPages) => {
-			const wasLastPageEmpty =
-				lastPage.albums.length === 0 && lastPage.singles.length === 0 && lastPage.eps.length === 0;
-			if (!lastPage.has_more || wasLastPageEmpty) {
+		getNextPageParam: (lastPage) => {
+			if (!lastPage.has_more) {
 				return undefined;
 			}
-			return allPages.length * BATCH_SIZE;
+			if (lastPage.next_offset != null) {
+				return lastPage.next_offset;
+			}
+			return undefined;
 		}
 	}));
 

frontend/src/lib/types.ts

@@ -162,8 +162,12 @@ export type ArtistReleases = {
 	albums: ReleaseGroup[];
 	singles: ReleaseGroup[];
 	eps: ReleaseGroup[];
-	total_count: number;
+	offset: number;
+	limit: number;
+	returned_count: number;
+	next_offset: number | null;
 	has_more: boolean;
+	source_total_count: number | null;
 };
 
 export type UserPreferences = {

frontend/src/routes/artist/[id]/+page.svelte

@@ -128,8 +128,6 @@
 		releasesQuery.data?.pages.flatMap((page) => [...page.albums, ...page.singles, ...page.eps])
 			.length || 0
 	);
-	// Total count is not reliable, since it contains items that are filtered out
-	const totalReleaseCount = $derived(releasesQuery.data?.pages[0].total_count || 0);
 
 	$effect(() => {
 		if (hasMoreReleases && !releasesQuery.isFetchingNextPage) {
@@ -340,8 +338,7 @@
 							<span class="font-semibold text-base" style="color: {colors.accent};"
 								>Loading releases...</span
 							>
-							<span class="text-sm text-base-content/70"
-								>Loaded {loadedReleaseCount} of {totalReleaseCount} potential releases</span
+							<span class="text-sm text-base-content/70">Loading {loadedReleaseCount} releases</span
 							>
 						</div>
 					</div>