Refactor the Reason struct and how tags for lookups are generated (#2087)

## Description

Solidify the interface between BackupOp and KopiaWrapper by making Reason the de facto way to pass/generate tags for things. The Reason struct now includes a function to generate tags for that instance. KopiaWrapper also now hides the fact that it prefixes tags from other components

## Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No 

## Type of change

- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Test
- [ ] 💻 CI/Deployment
- [x] 🧹 Tech Debt/Cleanup

## Issue(s)

* #1916 

## Test Plan

- [ ] 💪 Manual
- [x] ⚡ Unit test
- [x] 💚 E2E

src/internal/kopia/snapshot_manager.go

@@ -32,6 +32,13 @@ type Reason struct {
 	Category      path.CategoryType
 }
 
+func (r Reason) TagKeys() []string {
+	return []string{
+		r.ResourceOwner,
+		serviceCatString(r.Service, r.Category),
+	}
+}
+
 type ManifestEntry struct {
 	*snapshot.Manifest
 	// Reason contains the ResourceOwners and Service/Categories that caused this
@@ -44,6 +51,13 @@ type ManifestEntry struct {
 	Reasons []Reason
 }
 
+func (me ManifestEntry) GetTag(key string) (string, bool) {
+	k, _ := makeTagKV(key)
+	v, ok := me.Tags[k]
+
+	return v, ok
+}
+
 type snapshotManager interface {
 	FindManifests(
 		ctx context.Context,
@@ -68,6 +82,10 @@ func MakeServiceCat(s path.ServiceType, c path.CategoryType) (string, ServiceCat
 	return serviceCatString(s, c), ServiceCat{s, c}
 }
 
+// TODO(ashmrtn): Remove in a future PR.
+//
+//nolint:unused
+//lint:ignore U1000 will be removed in future PR.
 func serviceCatTag(p path.Path) string {
 	return serviceCatString(p.Service(), p.Category())
 }
@@ -82,7 +100,7 @@ func serviceCatString(s path.ServiceType, c path.CategoryType) string {
 // Returns the normalized Key plus a default value.  If you're embedding a
 // key-only tag, the returned default value msut be used instead of an
 // empty string.
-func MakeTagKV(k string) (string, string) {
+func makeTagKV(k string) (string, string) {
 	return userTagPrefix + k, defaultTagValue
 }
 
@@ -101,12 +119,12 @@ func tagsFromStrings(oc *OwnersCats) map[string]string {
 	res := make(map[string]string, len(oc.ServiceCats)+len(oc.ResourceOwners))
 
 	for k := range oc.ServiceCats {
-		tk, tv := MakeTagKV(k)
+		tk, tv := makeTagKV(k)
 		res[tk] = tv
 	}
 
 	for k := range oc.ResourceOwners {
-		tk, tv := MakeTagKV(k)
+		tk, tv := makeTagKV(k)
 		res[tk] = tv
 	}
 
@@ -195,14 +213,14 @@ func fetchPrevManifests(
 	reason Reason,
 	tags map[string]string,
 ) ([]*ManifestEntry, error) {
-	tags = normalizeTagKVs(tags)
-	serviceCatKey, _ := MakeServiceCat(reason.Service, reason.Category)
-	allTags := normalizeTagKVs(map[string]string{
-		serviceCatKey:        "",
-		reason.ResourceOwner: "",
-	})
+	allTags := map[string]string{}
+
+	for _, k := range reason.TagKeys() {
+		allTags[k] = ""
+	}
 
 	maps.Copy(allTags, tags)
+	allTags = normalizeTagKVs(allTags)
 
 	metas, err := sm.FindManifests(ctx, allTags)
 	if err != nil {
@@ -335,7 +353,7 @@ func normalizeTagKVs(tags map[string]string) map[string]string {
 	t2 := make(map[string]string, len(tags))
 
 	for k, v := range tags {
-		mk, mv := MakeTagKV(k)
+		mk, mv := makeTagKV(k)
 
 		if len(v) == 0 {
 			v = mv

src/internal/kopia/snapshot_manager_test.go

@@ -29,16 +29,9 @@ var (
 	testID2 = manifest.ID("snap2")
 	testID3 = manifest.ID("snap3")
 
-	testMail           = path.ExchangeService.String() + path.EmailCategory.String()
-	testMailServiceCat = ServiceCat{
-		Service:  path.ExchangeService,
-		Category: path.EmailCategory,
-	}
-	testEvents           = path.ExchangeService.String() + path.EventsCategory.String()
-	testEventsServiceCat = ServiceCat{
-		Service:  path.ExchangeService,
-		Category: path.EventsCategory,
-	}
+	testMail   = path.ExchangeService.String() + path.EmailCategory.String()
+	testEvents = path.ExchangeService.String() + path.EventsCategory.String()
+
 	testUser1 = "user1"
 	testUser2 = "user2"
 	testUser3 = "user3"
@@ -115,7 +108,7 @@ func newManifestInfo(
 	structTags := make(map[string]struct{}, len(tags))
 
 	for _, t := range tags {
-		tk, _ := MakeTagKV(t)
+		tk, _ := makeTagKV(t)
 		structTags[tk] = struct{}{}
 	}
 

src/internal/kopia/wrapper.go

@@ -230,7 +230,7 @@ func (w Wrapper) makeSnapshotWithRoot(
 			man.Tags = map[string]string{}
 
 			for k, v := range addlTags {
-				mk, mv := MakeTagKV(k)
+				mk, mv := makeTagKV(k)
 
 				if len(v) == 0 {
 					v = mv

src/internal/kopia/wrapper_test.go

@@ -212,11 +212,25 @@ func (suite *KopiaIntegrationSuite) TestBackupCollections() {
 	tags := map[string]string{
 		"fnords":    "smarf",
 		"brunhilda": "",
+	}
 
-		suite.testPath1.ResourceOwner(): "",
-		suite.testPath2.ResourceOwner(): "",
-		serviceCatTag(suite.testPath1):  "",
-		serviceCatTag(suite.testPath2):  "",
+	reasons := []Reason{
+		{
+			ResourceOwner: suite.testPath1.ResourceOwner(),
+			Service:       suite.testPath1.Service(),
+			Category:      suite.testPath1.Category(),
+		},
+		{
+			ResourceOwner: suite.testPath2.ResourceOwner(),
+			Service:       suite.testPath2.Service(),
+			Category:      suite.testPath2.Category(),
+		},
+	}
+
+	for _, r := range reasons {
+		for _, k := range r.TagKeys() {
+			tags[k] = ""
+		}
 	}
 
 	expectedTags := map[string]string{}
@@ -305,9 +319,15 @@ func (suite *KopiaIntegrationSuite) TestRestoreAfterCompressionChange() {
 
 	w := &Wrapper{k}
 
-	tags := map[string]string{
-		testUser: "",
-		serviceCatString(path.ExchangeService, path.EmailCategory): "",
+	tags := map[string]string{}
+	reason := Reason{
+		ResourceOwner: testUser,
+		Service:       path.ExchangeService,
+		Category:      path.EmailCategory,
+	}
+
+	for _, k := range reason.TagKeys() {
+		tags[k] = ""
 	}
 
 	dc1 := mockconnector.NewMockExchangeCollection(suite.testPath1, 1)
@@ -353,9 +373,15 @@ func (suite *KopiaIntegrationSuite) TestRestoreAfterCompressionChange() {
 func (suite *KopiaIntegrationSuite) TestBackupCollections_ReaderError() {
 	t := suite.T()
 
-	tags := map[string]string{
-		testUser: "",
-		serviceCatString(path.ExchangeService, path.EmailCategory): "",
+	tags := map[string]string{}
+	reason := Reason{
+		ResourceOwner: testUser,
+		Service:       path.ExchangeService,
+		Category:      path.EmailCategory,
+	}
+
+	for _, k := range reason.TagKeys() {
+		tags[k] = ""
 	}
 
 	collections := []data.Collection{
@@ -586,9 +612,15 @@ func (suite *KopiaSimpleRepoIntegrationSuite) SetupTest() {
 		collections = append(collections, collection)
 	}
 
-	tags := map[string]string{
-		testUser: "",
-		serviceCatString(path.ExchangeService, path.EmailCategory): "",
+	tags := map[string]string{}
+	reason := Reason{
+		ResourceOwner: testUser,
+		Service:       path.ExchangeService,
+		Category:      path.EmailCategory,
+	}
+
+	for _, k := range reason.TagKeys() {
+		tags[k] = ""
 	}
 
 	stats, deets, _, err := suite.w.BackupCollections(

src/internal/operations/backup.go

@@ -344,10 +344,8 @@ func produceManifestsAndMetadata(
 			continue
 		}
 
-		tk, _ := kopia.MakeTagKV(kopia.TagBackupID)
-
-		bID := man.Tags[tk]
-		if len(bID) == 0 {
+		bID, ok := man.GetTag(kopia.TagBackupID)
+		if !ok {
 			return nil, nil, false, errors.New("snapshot manifest missing backup ID")
 		}
 
@@ -502,12 +500,9 @@ func consumeBackupDataCollections(
 	}
 
 	for _, reason := range reasons {
-		tags[reason.ResourceOwner] = ""
-
-		// TODO(ashmrtn): Create a separate helper function to go from service/cat
-		// to a tag.
-		serviceCat, _ := kopia.MakeServiceCat(reason.Service, reason.Category)
-		tags[serviceCat] = ""
+		for _, k := range reason.TagKeys() {
+			tags[k] = ""
+		}
 	}
 
 	bases := make([]kopia.IncrementalBase, 0, len(mans))
@@ -568,8 +563,10 @@ func mergeDetails(
 			continue
 		}
 
-		k, _ := kopia.MakeTagKV(kopia.TagBackupID)
-		bID := man.Tags[k]
+		bID, ok := man.GetTag(kopia.TagBackupID)
+		if !ok {
+			return errors.Errorf("no backup ID in snapshot manifest with ID %s", man.ID)
+		}
 
 		_, baseDeets, err := getBackupAndDetailsFromID(
 			ctx,

src/internal/operations/backup_integration_test.go

@@ -191,8 +191,12 @@ func checkBackupIsInManifests(
 			require.NoError(t, err)
 
 			for _, man := range mans {
-				tk, _ := kopia.MakeTagKV(kopia.TagBackupID)
-				if man.Tags[tk] == string(bo.Results.BackupID) {
+				bID, ok := man.GetTag(kopia.TagBackupID)
+				if !assert.Truef(t, ok, "snapshot manifest %s missing backup ID tag", man.ID) {
+					continue
+				}
+
+				if bID == string(bo.Results.BackupID) {
 					found = true
 					break
 				}

src/internal/operations/backup_test.go

@@ -276,14 +276,20 @@ func makeDetailsEntry(
 	return res
 }
 
+// TODO(ashmrtn): This should belong to some code that lives in the kopia
+// package that is only compiled when running tests.
+func makeKopiaTagKey(k string) string {
+	return "tag:" + k
+}
+
 func makeManifest(t *testing.T, backupID model.StableID, incompleteReason string) *snapshot.Manifest {
 	t.Helper()
 
-	backupIDTagKey, _ := kopia.MakeTagKV(kopia.TagBackupID)
+	tagKey := makeKopiaTagKey(kopia.TagBackupID)
 
 	return &snapshot.Manifest{
 		Tags: map[string]string{
-			backupIDTagKey: string(backupID),
+			tagKey: string(backupID),
 		},
 		IncompleteReason: incompleteReason,
 	}