split duplicate grouping and hash helpers

internal/service/duplicate_groups.go

@@ -0,0 +1,93 @@
+// Package service — duplicate grouping helpers.
+package service
+
+import (
+	"context"
+	"fmt"
+	"sort"
+
+	"go.uber.org/zap"
+
+	"github.com/ShukeBta/MediaStationGo/internal/model"
+)
+
+func (d *DuplicateService) markDuplicateGroup(ctx context.Context, rep *Report, key string, group []model.Media, markedIDs map[string]struct{}) {
+	primary := pickPrimary(group)
+	dupes := make([]model.Media, 0, len(group)-1)
+	for _, m := range group {
+		if m.ID == primary.ID || m.DuplicateOf == primary.ID {
+			continue
+		}
+		if _, ok := markedIDs[m.ID]; ok {
+			continue
+		}
+		dupes = append(dupes, m)
+		if err := d.repo.DB.WithContext(ctx).
+			Model(&model.Media{}).
+			Where("id = ?", m.ID).
+			Updates(map[string]any{
+				"is_duplicate": true,
+				"duplicate_of": primary.ID,
+			}).Error; err != nil {
+			d.log.Warn("dup mark failed", zap.Error(err))
+			continue
+		}
+		markedIDs[m.ID] = struct{}{}
+		rep.ItemsMarked++
+	}
+	if len(dupes) == 0 {
+		return
+	}
+	rep.Groups = append(rep.Groups, Group{
+		Hash:       key,
+		Primary:    primary,
+		Duplicates: dupes,
+	})
+}
+
+func groupByExternalIdentity(rows []model.Media) map[string][]model.Media {
+	groups := map[string][]model.Media{}
+	for _, row := range rows {
+		key := mediaExternalIdentityKey(row)
+		if key == "" {
+			continue
+		}
+		groups[key] = append(groups[key], row)
+	}
+	return groups
+}
+
+func mediaExternalIdentityKey(row model.Media) string {
+	var key string
+	switch {
+	case row.TMDbID > 0:
+		key = fmt.Sprintf("tmdb:%d", row.TMDbID)
+	case row.BangumiID > 0:
+		key = fmt.Sprintf("bangumi:%d", row.BangumiID)
+	case row.DoubanID != "":
+		key = "douban:" + row.DoubanID
+	case row.TheTVDBID != "":
+		key = "thetvdb:" + row.TheTVDBID
+	default:
+		return ""
+	}
+	if row.SeasonNum > 0 || row.EpisodeNum > 0 {
+		key += fmt.Sprintf(":s%d:e%d", row.SeasonNum, row.EpisodeNum)
+	}
+	return key
+}
+
+// pickPrimary picks the "best" media row to keep: prefer scraped > size > id.
+func pickPrimary(group []model.Media) model.Media {
+	sort.SliceStable(group, func(i, j int) bool {
+		ai, aj := group[i].ScrapeStatus == "matched", group[j].ScrapeStatus == "matched"
+		if ai != aj {
+			return ai
+		}
+		if group[i].SizeBytes != group[j].SizeBytes {
+			return group[i].SizeBytes > group[j].SizeBytes
+		}
+		return group[i].ID < group[j].ID
+	})
+	return group[0]
+}