refac: atomic merge, lost-update race, RunPurge cost, duplicated walks

internal/infrastructure/useCases/RunPurge.go

@@ -36,7 +36,7 @@ func NewRunPurgeUseCase(imageRepository image.Repository, articleRepository arti
 }
 
 func (u *RunPurgeUseCase) Run(ctx context.Context, fingerprint *string) (purge.RunResult, error) {
-	result, err := u.Execute(fingerprint)
+	result, err := u.Execute(ctx, fingerprint)
 	event := audit.NewEvent(audit.ActionMediaPurge, audit.CategoryMedia)
 	if err != nil {
 		recordFailure(ctx, u.recorder, event, err)
@@ -55,7 +55,7 @@ func purgeParams(result purge.RunResult) map[string]any {
 	return params
 }
 
-func (u *RunPurgeUseCase) Execute(fingerprint *string) (purge.RunResult, error) {
+func (u *RunPurgeUseCase) Execute(ctx context.Context, fingerprint *string) (purge.RunResult, error) {
 	if !u.guard.TryLock() {
 		return purge.RunResult{}, purge.ErrPurgeBusy
 	}
@@ -69,7 +69,10 @@ func (u *RunPurgeUseCase) Execute(fingerprint *string) (purge.RunResult, error)
 		return purge.RunResult{}, purge.ErrPurgeConflict
 	}
 
-	result := u.mergeGroups(plan)
+	result, err := u.mergeGroups(ctx, plan)
+	if err != nil {
+		return purge.RunResult{}, err
+	}
 	if err := u.recordRun(result); err != nil {
 		u.logger.Printf("purge: could not record the run result: %v", err)
 		return purge.RunResult{}, err
@@ -77,11 +80,14 @@ func (u *RunPurgeUseCase) Execute(fingerprint *string) (purge.RunResult, error)
 	return result, nil
 }
 
-func (u *RunPurgeUseCase) mergeGroups(plan purgePlan) purge.RunResult {
+func (u *RunPurgeUseCase) mergeGroups(ctx context.Context, plan purgePlan) (purge.RunResult, error) {
 	result := purge.RunResult{GroupsTotal: len(plan.groups)}
 	updated := map[uint32]bool{}
 	for _, group := range plan.groups {
-		merged, err := u.merge.merge(group.kept.ID, slices.Clone(group.mergedIds))
+		if err := ctx.Err(); err != nil {
+			return purge.RunResult{}, err
+		}
+		merged, err := u.merge.merge(ctx, group.kept.ID, slices.Clone(group.mergedIds), plan.entries)
 		if err != nil {
 			result.FailedGroups++
 			continue
@@ -95,7 +101,7 @@ func (u *RunPurgeUseCase) mergeGroups(plan purgePlan) purge.RunResult {
 		}
 	}
 	result.ArticlesUpdated = len(updated)
-	return result
+	return result, nil
 }
 
 func (u *RunPurgeUseCase) recordRun(result purge.RunResult) error {