fix library preview series counts

internal/service/media_series.go

@@ -5,6 +5,7 @@ import (
 	"regexp"
 	"sort"
 	"strings"
+	"time"
 
 	"github.com/ShukeBta/MediaStationGo/internal/model"
 )
@@ -16,6 +17,11 @@ type SeriesCard struct {
 	Count     int         `json:"count"`
 }
 
+type seriesCardGroup struct {
+	card   SeriesCard
+	latest time.Time
+}
+
 func (s *MediaService) ListLibrarySeriesCards(ctx context.Context, libraryID string, visibility MediaVisibility) ([]SeriesCard, int64, error) {
 	rows, _, err := s.listAllMediaVisible(ctx, libraryID, visibility)
 	if err != nil {
@@ -73,7 +79,7 @@ func groupMediaSeriesCards(items []model.Media) []SeriesCard {
 	if len(items) == 0 {
 		return nil
 	}
-	cards := make([]SeriesCard, 0)
+	groups := make([]seriesCardGroup, 0)
 	byKey := make(map[string]int, len(items))
 	for _, item := range items {
 		key := mediaSeriesKey(item)
@@ -81,7 +87,11 @@ func groupMediaSeriesCards(items []model.Media) []SeriesCard {
 			continue
 		}
 		if idx, ok := byKey[key]; ok {
-			card := &cards[idx]
+			group := &groups[idx]
+			if latest := seriesMediaTime(item); latest.After(group.latest) {
+				group.latest = latest
+			}
+			card := &group.card
 			card.Count++
 			if betterSeriesLinkMedia(item, card.LinkMedia) {
 				card.LinkMedia = item
@@ -99,12 +109,29 @@ func groupMediaSeriesCards(items []model.Media) []SeriesCard {
 			}
 			continue
 		}
-		byKey[key] = len(cards)
-		cards = append(cards, SeriesCard{Key: key, Rep: item, LinkMedia: item, Count: 1})
+		byKey[key] = len(groups)
+		groups = append(groups, seriesCardGroup{
+			card:   SeriesCard{Key: key, Rep: item, LinkMedia: item, Count: 1},
+			latest: seriesMediaTime(item),
+		})
+	}
+	sort.SliceStable(groups, func(i, j int) bool {
+		return groups[i].latest.After(groups[j].latest)
+	})
+	cards := make([]SeriesCard, 0, len(groups))
+	for _, group := range groups {
+		cards = append(cards, group.card)
 	}
 	return cards
 }
 
+func seriesMediaTime(media model.Media) time.Time {
+	if media.UpdatedAt.After(media.CreatedAt) {
+		return media.UpdatedAt
+	}
+	return media.CreatedAt
+}
+
 func betterSeriesLinkMedia(candidate, current model.Media) bool {
 	candidateScore := librarySpecificityScore(candidate)
 	currentScore := librarySpecificityScore(current)

internal/service/media_series_test.go

@@ -2,6 +2,7 @@ package service
 
 import (
 	"testing"
+	"time"
 
 	"github.com/ShukeBta/MediaStationGo/internal/model"
 )
@@ -28,6 +29,45 @@ func TestMediaSeriesKeyCollapsesNestedSpecialFolders(t *testing.T) {
 	}
 }
 
+func TestGroupMediaSeriesCardsSortsByLatestEpisodeTime(t *testing.T) {
+	now := time.Date(2026, 7, 2, 12, 0, 0, 0, time.UTC)
+	newerFirstEpisode := model.Media{
+		Base:       model.Base{CreatedAt: now.Add(-72 * time.Hour), UpdatedAt: now.Add(-72 * time.Hour)},
+		LibraryID:  "lib-tv",
+		Title:      "更新合集",
+		Path:       `F:\media\电视剧\国产剧\更新合集\Season 01\更新合集.S01E01.mkv`,
+		SeasonNum:  1,
+		EpisodeNum: 1,
+	}
+	newerLatestEpisode := model.Media{
+		Base:       model.Base{CreatedAt: now, UpdatedAt: now},
+		LibraryID:  "lib-tv",
+		Title:      "更新合集",
+		Path:       `F:\media\电视剧\国产剧\更新合集\Season 01\更新合集.S01E02.mkv`,
+		SeasonNum:  1,
+		EpisodeNum: 2,
+	}
+	olderSeries := model.Media{
+		Base:       model.Base{CreatedAt: now.Add(-24 * time.Hour), UpdatedAt: now.Add(-24 * time.Hour)},
+		LibraryID:  "lib-tv",
+		Title:      "较早合集",
+		Path:       `F:\media\电视剧\国产剧\较早合集\Season 01\较早合集.S01E01.mkv`,
+		SeasonNum:  1,
+		EpisodeNum: 1,
+	}
+
+	cards := groupMediaSeriesCards([]model.Media{olderSeries, newerFirstEpisode, newerLatestEpisode})
+	if len(cards) != 2 {
+		t.Fatalf("cards=%#v, want two series cards", cards)
+	}
+	if cards[0].Key != mediaSeriesKey(newerFirstEpisode) {
+		t.Fatalf("first card key=%q, want latest series key=%q", cards[0].Key, mediaSeriesKey(newerFirstEpisode))
+	}
+	if cards[0].Count != 2 {
+		t.Fatalf("latest series count=%d, want 2", cards[0].Count)
+	}
+}
+
 func TestMediaSeriesKeyCollapsesSpecialTitleSuffix(t *testing.T) {
 	main := model.Media{
 		LibraryID:  "lib-tv",