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

test/media_purge_scheduler_test.go

@@ -31,7 +31,7 @@ type schedulerEnv struct {
 func newSchedulerEnv(t *testing.T) *schedulerEnv {
 	t.Helper()
 	env := newPurgeEnv(t)
-	merge := useCases.NewMergeMediaUseCase(env.images, env.articles, env.storage, newMockVariantFileRepo(), discardRecorder, plainSites(), plainAuthors(), newMockContentTypeRepo(), newMockEntryRepo())
+	merge := newTestMergeMedia(env.images, env.articles, env.storage, newMockVariantFileRepo(), discardRecorder, plainSites(), plainAuthors(), newMockContentTypeRepo(), newMockEntryRepo())
 	now := func() time.Time { return env.clock }
 	runPurge := useCases.NewRunPurgeUseCase(env.images, env.articles, merge, env.purgeSettings, now, log.New(env.logs, "", 0), discardRecorder, plainSites(), plainAuthors())
 	return &schedulerEnv{
@@ -64,7 +64,7 @@ func (e *schedulerEnv) seedPlannedGroup() {
 
 func (e *schedulerEnv) tick(t *testing.T, at string) (bool, error) {
 	t.Helper()
-	_, ran, err := e.scheduler.Tick(*purgeTime(at))
+	_, ran, err := e.scheduler.Tick(testCtx, *purgeTime(at))
 	return ran, err
 }
 
@@ -294,7 +294,7 @@ func TestPurgeSchedulerReportsTheRunResult(t *testing.T) {
 		env.configureDue()
 		env.seedPlannedGroup()
 
-		result, ran, err := env.scheduler.Tick(*purgeTime(schedulerClock))
+		result, ran, err := env.scheduler.Tick(testCtx, *purgeTime(schedulerClock))
 
 		want := purge.RunResult{GroupsTotal: 1, GroupsPurged: 1, Merged: 1, ArticlesUpdated: 1}
 		if err != nil || !ran || result != want {
@@ -305,7 +305,7 @@ func TestPurgeSchedulerReportsTheRunResult(t *testing.T) {
 	t.Run("A Tick that is not due returns an empty result", func(t *testing.T) {
 		env := newSchedulerEnv(t)
 
-		result, ran, err := env.scheduler.Tick(*purgeTime(schedulerClock))
+		result, ran, err := env.scheduler.Tick(testCtx, *purgeTime(schedulerClock))
 
 		if err != nil || ran || result != (purge.RunResult{}) {
 			t.Errorf("unexpected %+v, %v, %v", result, ran, err)
@@ -466,7 +466,7 @@ func newSchedulerJobFake(results ...schedulerJobResult) *schedulerJobFake {
 	return &schedulerJobFake{results: results, entered: make(chan time.Time, 16)}
 }
 
-func (f *schedulerJobFake) Tick(now time.Time) (purge.RunResult, bool, error) {
+func (f *schedulerJobFake) Tick(_ context.Context, now time.Time) (purge.RunResult, bool, error) {
 	f.mu.Lock()
 	f.calls = append(f.calls, now)
 	var result schedulerJobResult