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

test/media_library_http_test.go

@@ -943,7 +943,7 @@ func TestMediaMerging(t *testing.T) {
 
 	t.Run("A duplicated id reaching the use case is refused before anything is read", func(t *testing.T) {
 		env := newEnv(t)
-		uc := useCases.NewMergeMediaUseCase(env.images, env.articles, env.storage, newMockVariantFileRepo(), discardRecorder, plainSites(), plainAuthors(), newMockContentTypeRepo(), newMockEntryRepo())
+		uc := newTestMergeMedia(env.images, env.articles, env.storage, newMockVariantFileRepo(), discardRecorder, plainSites(), plainAuthors(), newMockContentTypeRepo(), newMockEntryRepo())
 
 		_, err := uc.Merge(testCtx, 2, []uint32{3, 3})
 
@@ -971,18 +971,18 @@ func TestMediaMerging(t *testing.T) {
 		expectIds(t, env.imageIds(), []uint32{1, 2, 3, 6})
 	})
 
-	t.Run("A failure deleting a copy after the rewrite is 500 and the bodies stay switched", func(t *testing.T) {
+	t.Run("A failure deleting a copy after the rewrite is 500 and the bodies are rolled back", func(t *testing.T) {
 		env := newEnv(t)
 		env.images.failDeleteFor = map[uint32]error{3: errRepositoryFailure}
-		keep := env.urlOf(2)
+		bodiesBefore := env.bodies()
 
 		rec := env.send(t, http.MethodPost, "/v1/media/merge", `{"keep_id": 2, "merge_ids": [3]}`, mediaVerifiedUserId)
 
 		if rec.Code != http.StatusInternalServerError {
 			t.Fatalf("expected status 500, got %d", rec.Code)
 		}
-		if !strings.Contains(env.articles.articles[1].Body, keep) || strings.Contains(env.articles.articles[1].Body, env.urlOf(3)) {
-			t.Errorf("expected article 1 to use image 2's url, got %q", env.articles.articles[1].Body)
+		if !reflect.DeepEqual(env.bodies(), bodiesBefore) {
+			t.Errorf("expected every body back to its original text, got %v", env.bodies())
 		}
 		if _, ok := env.images.images[3]; !ok {
 			t.Errorf("expected image 3 to still exist")
@@ -1038,7 +1038,7 @@ func TestMediaSentinels(t *testing.T) {
 		env.seedImage(2, "b.png", 1, "image/png", 1, 1, hashB, 1)
 		env.seedImage(3, "c.png", 1, "image/png", 1, 1, "", 1)
 		env.seedImage(4, "d.png", 1, "image/png", 1, 1, "", 1)
-		uc := useCases.NewMergeMediaUseCase(env.images, env.articles, env.storage, newMockVariantFileRepo(), discardRecorder, plainSites(), plainAuthors(), newMockContentTypeRepo(), newMockEntryRepo())
+		uc := newTestMergeMedia(env.images, env.articles, env.storage, newMockVariantFileRepo(), discardRecorder, plainSites(), plainAuthors(), newMockContentTypeRepo(), newMockEntryRepo())
 
 		if _, err := uc.Merge(testCtx, 1, []uint32{9999}); !errors.Is(err, domainImage.ErrMergeCopyMissing) {
 			t.Errorf("expected ErrMergeCopyMissing, got %v", err)