move selectorsToReason into selectors (#4006)

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

- [x] ⛔ No

#### Type of change

- [x] 🧹 Tech Debt/Cleanup

#### Issue(s)

* #3993

#### Test Plan

- [x] ⚡ Unit test
- [x] 💚 E2E

src/internal/operations/backup.go

@@ -326,11 +326,17 @@ func (op *BackupOperation) do(
 	detailsStore streamstore.Streamer,
 	backupID model.StableID,
 ) (*details.Builder, error) {
-	var (
-		reasons           = selectorToReasons(op.account.ID(), op.Selectors, false)
-		fallbackReasons   = makeFallbackReasons(op.account.ID(), op.Selectors)
-		lastBackupVersion = version.NoBackup
-	)
+	lastBackupVersion := version.NoBackup
+
+	reasons, err := op.Selectors.Reasons(op.account.ID(), false)
+	if err != nil {
+		return nil, clues.Wrap(err, "getting reasons")
+	}
+
+	fallbackReasons, err := makeFallbackReasons(op.account.ID(), op.Selectors)
+	if err != nil {
+		return nil, clues.Wrap(err, "getting fallback reasons")
+	}
 
 	logger.Ctx(ctx).With(
 		"control_options", op.Options,
@@ -424,13 +430,14 @@ func (op *BackupOperation) do(
 	return deets, nil
 }
 
-func makeFallbackReasons(tenant string, sel selectors.Selector) []identity.Reasoner {
+func makeFallbackReasons(tenant string, sel selectors.Selector) ([]identity.Reasoner, error) {
 	if sel.PathService() != path.SharePointService &&
 		sel.DiscreteOwner != sel.DiscreteOwnerName {
-		return selectorToReasons(tenant, sel, true)
+		return sel.Reasons(tenant, true)
 	}
 
-	return nil
+	// return nil for fallback reasons since a nil value will no-op.
+	return nil, nil
 }
 
 // checker to see if conditions are correct for incremental backup behavior such as
@@ -472,35 +479,6 @@ func produceBackupDataCollections(
 // Consumer funcs
 // ---------------------------------------------------------------------------
 
-func selectorToReasons(
-	tenant string,
-	sel selectors.Selector,
-	useOwnerNameForID bool,
-) []identity.Reasoner {
-	service := sel.PathService()
-	reasons := []identity.Reasoner{}
-
-	pcs, err := sel.PathCategories()
-	if err != nil {
-		// This is technically safe, it's just that the resulting backup won't be
-		// usable as a base for future incremental backups.
-		return nil
-	}
-
-	owner := sel.DiscreteOwner
-	if useOwnerNameForID {
-		owner = sel.DiscreteOwnerName
-	}
-
-	for _, sl := range [][]path.CategoryType{pcs.Includes, pcs.Filters} {
-		for _, cat := range sl {
-			reasons = append(reasons, kopia.NewReason(tenant, owner, service, cat))
-		}
-	}
-
-	return reasons
-}
-
 // calls kopia to backup the collections of data
 func consumeBackupCollections(
 	ctx context.Context,

src/pkg/selectors/exchange.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/alcionai/corso/src/internal/common/dttm"
 	"github.com/alcionai/corso/src/pkg/backup/details"
+	"github.com/alcionai/corso/src/pkg/backup/identity"
 	"github.com/alcionai/corso/src/pkg/fault"
 	"github.com/alcionai/corso/src/pkg/filters"
 	"github.com/alcionai/corso/src/pkg/path"
@@ -43,6 +44,7 @@ type (
 var (
 	_ Reducer        = &ExchangeRestore{}
 	_ pathCategorier = &ExchangeRestore{}
+	_ reasoner       = &ExchangeRestore{}
 )
 
 // NewExchange produces a new Selector with the service set to ServiceExchange.
@@ -122,6 +124,13 @@ func (s exchange) PathCategories() selectorPathCategories {
 	}
 }
 
+// Reasons returns a deduplicated set of the backup reasons produced
+// using the selector's discrete owner and each scopes' service and
+// category types.
+func (s exchange) Reasons(tenantID string, useOwnerNameForID bool) []identity.Reasoner {
+	return reasonsFor(s, tenantID, useOwnerNameForID)
+}
+
 // ---------------------------------------------------------------------------
 // Stringers and Concealers
 // ---------------------------------------------------------------------------

src/pkg/selectors/groups.go

@@ -7,6 +7,7 @@ import (
 	"github.com/alcionai/clues"
 
 	"github.com/alcionai/corso/src/pkg/backup/details"
+	"github.com/alcionai/corso/src/pkg/backup/identity"
 	"github.com/alcionai/corso/src/pkg/fault"
 	"github.com/alcionai/corso/src/pkg/path"
 )
@@ -40,6 +41,7 @@ type (
 var (
 	_ Reducer        = &GroupsRestore{}
 	_ pathCategorier = &GroupsRestore{}
+	_ reasoner       = &GroupsRestore{}
 )
 
 // NewGroupsBackup produces a new Selector with the service set to ServiceGroups.
@@ -119,6 +121,13 @@ func (s groups) PathCategories() selectorPathCategories {
 	}
 }
 
+// Reasons returns a deduplicated set of the backup reasons produced
+// using the selector's discrete owner and each scopes' service and
+// category types.
+func (s groups) Reasons(tenantID string, useOwnerNameForID bool) []identity.Reasoner {
+	return reasonsFor(s, tenantID, useOwnerNameForID)
+}
+
 // ---------------------------------------------------------------------------
 // Stringers and Concealers
 // ---------------------------------------------------------------------------

src/pkg/selectors/helpers_test.go

@@ -167,6 +167,8 @@ func (s mockScope) PlainString() string         { return plainString(s) }
 // selectors
 // ---------------------------------------------------------------------------
 
+var _ servicerCategorizerProvider = &mockSel{}
+
 type mockSel struct {
 	Selector
 }
@@ -183,6 +185,14 @@ func stubSelector(resourceOwners []string) mockSel {
 	}
 }
 
+func (m mockSel) PathCategories() selectorPathCategories {
+	return selectorPathCategories{
+		Includes: []path.CategoryType{pathCatStub},
+		Excludes: []path.CategoryType{pathCatStub},
+		Filters:  []path.CategoryType{pathCatStub},
+	}
+}
+
 // ---------------------------------------------------------------------------
 // helper funcs
 // ---------------------------------------------------------------------------

src/pkg/selectors/onedrive.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/alcionai/corso/src/internal/common/dttm"
 	"github.com/alcionai/corso/src/pkg/backup/details"
+	"github.com/alcionai/corso/src/pkg/backup/identity"
 	"github.com/alcionai/corso/src/pkg/fault"
 	"github.com/alcionai/corso/src/pkg/filters"
 	"github.com/alcionai/corso/src/pkg/path"
@@ -42,6 +43,7 @@ type (
 var (
 	_ Reducer        = &OneDriveRestore{}
 	_ pathCategorier = &OneDriveRestore{}
+	_ reasoner       = &OneDriveRestore{}
 )
 
 // NewOneDriveBackup produces a new Selector with the service set to ServiceOneDrive.
@@ -121,6 +123,13 @@ func (s oneDrive) PathCategories() selectorPathCategories {
 	}
 }
 
+// Reasons returns a deduplicated set of the backup reasons produced
+// using the selector's discrete owner and each scopes' service and
+// category types.
+func (s oneDrive) Reasons(tenantID string, useOwnerNameForID bool) []identity.Reasoner {
+	return reasonsFor(s, tenantID, useOwnerNameForID)
+}
+
 // ---------------------------------------------------------------------------
 // Stringers and Concealers
 // ---------------------------------------------------------------------------

src/pkg/selectors/reasons.go

@@ -0,0 +1,91 @@
+package selectors
+
+import (
+	"golang.org/x/exp/maps"
+
+	"github.com/alcionai/corso/src/internal/common/idname"
+	"github.com/alcionai/corso/src/pkg/backup/identity"
+	"github.com/alcionai/corso/src/pkg/path"
+)
+
+// ---------------------------------------------------------------------------
+// reasoner interface compliance
+// ---------------------------------------------------------------------------
+
+var _ identity.Reasoner = &backupReason{}
+
+type backupReason struct {
+	category path.CategoryType
+	resource string
+	service  path.ServiceType
+	tenant   string
+}
+
+func (br backupReason) Tenant() string {
+	return br.tenant
+}
+
+func (br backupReason) ProtectedResource() string {
+	return br.resource
+}
+
+func (br backupReason) Service() path.ServiceType {
+	return br.service
+}
+
+func (br backupReason) Category() path.CategoryType {
+	return br.category
+}
+
+func (br backupReason) SubtreePath() (path.Path, error) {
+	return path.ServicePrefix(
+		br.tenant,
+		br.resource,
+		br.service,
+		br.category)
+}
+
+func (br backupReason) key() string {
+	return br.category.String() + br.resource + br.service.String() + br.tenant
+}
+
+// ---------------------------------------------------------------------------
+// common transformer
+// ---------------------------------------------------------------------------
+
+type servicerCategorizerProvider interface {
+	pathServicer
+	pathCategorier
+	idname.Provider
+}
+
+func reasonsFor(
+	sel servicerCategorizerProvider,
+	tenantID string,
+	useOwnerNameForID bool,
+) []identity.Reasoner {
+	service := sel.PathService()
+	reasons := map[string]identity.Reasoner{}
+
+	resource := sel.ID()
+	if useOwnerNameForID {
+		resource = sel.Name()
+	}
+
+	pc := sel.PathCategories()
+
+	for _, sl := range [][]path.CategoryType{pc.Includes, pc.Filters} {
+		for _, cat := range sl {
+			br := backupReason{
+				category: cat,
+				resource: resource,
+				service:  service,
+				tenant:   tenantID,
+			}
+
+			reasons[br.key()] = br
+		}
+	}
+
+	return maps.Values(reasons)
+}

src/pkg/selectors/reasons_test.go

@@ -0,0 +1,406 @@
+package selectors
+
+import (
+	"testing"
+
+	"github.com/alcionai/clues"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/alcionai/corso/src/internal/tester"
+	"github.com/alcionai/corso/src/pkg/path"
+)
+
+type ReasonsUnitSuite struct {
+	tester.Suite
+}
+
+func TestReasonsUnitSuite(t *testing.T) {
+	suite.Run(t, &ReasonsUnitSuite{Suite: tester.NewUnitSuite(t)})
+}
+
+func (suite *ReasonsUnitSuite) TestReasonsFor_thorough() {
+	var (
+		tenantID = "tid"
+		exchange = path.ExchangeService.String()
+		email    = path.EmailCategory.String()
+		contacts = path.ContactsCategory.String()
+	)
+
+	type expect struct {
+		tenant            string
+		resource          string
+		category          string
+		service           string
+		subtreePath       string
+		subtreePathHadErr bool
+	}
+
+	stpFor := func(resource, category, service string) string {
+		return path.Builder{}.Append(tenantID, service, resource, category).String()
+	}
+
+	table := []struct {
+		name    string
+		sel     func() ExchangeRestore
+		useName bool
+		expect  []expect
+	}{
+		{
+			name: "no scopes",
+			sel: func() ExchangeRestore {
+				return *NewExchangeRestore([]string{"timbo"})
+			},
+			expect: []expect{},
+		},
+		{
+			name: "use name",
+			sel: func() ExchangeRestore {
+				sel := NewExchangeRestore([]string{"timbo"})
+				sel.Include(sel.MailFolders(Any()))
+				plainSel := sel.SetDiscreteOwnerIDName("timbo", "timbubba")
+
+				sel, err := plainSel.ToExchangeRestore()
+				require.NoError(suite.T(), err, clues.ToCore(err))
+
+				return *sel
+			},
+			useName: true,
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "timbubba",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("timbubba", email, exchange),
+				},
+			},
+		},
+		{
+			name: "only includes",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"bubba"})
+				sel.Include(sel.MailFolders(Any()))
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "bubba",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("bubba", email, exchange),
+				},
+			},
+		},
+		{
+			name: "only filters",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"tachoma dhaume"})
+				sel.Filter(sel.MailFolders(Any()))
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "tachoma dhaume",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("tachoma dhaume", email, exchange),
+				},
+			},
+		},
+		{
+			name: "duplicate includes and filters",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"vyng vang zoombah"})
+				sel.Include(sel.MailFolders(Any()))
+				sel.Filter(sel.MailFolders(Any()))
+
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "vyng vang zoombah",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("vyng vang zoombah", email, exchange),
+				},
+			},
+		},
+		{
+			name: "duplicate includes",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"fat billie"})
+				sel.Include(sel.MailFolders(Any()), sel.MailFolders(Any()))
+
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "fat billie",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("fat billie", email, exchange),
+				},
+			},
+		},
+		{
+			name: "duplicate filters",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"seathane"})
+				sel.Filter(sel.MailFolders(Any()), sel.MailFolders(Any()))
+
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "seathane",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("seathane", email, exchange),
+				},
+			},
+		},
+		{
+			name: "no duplicates",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"perell"})
+				sel.Include(sel.MailFolders(Any()), sel.ContactFolders(Any()))
+
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "perell",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("perell", email, exchange),
+				},
+				{
+					tenant:      tenantID,
+					resource:    "perell",
+					category:    contacts,
+					service:     exchange,
+					subtreePath: stpFor("perell", contacts, exchange),
+				},
+			},
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			t := suite.T()
+
+			results := []expect{}
+			rs := reasonsFor(test.sel(), tenantID, test.useName)
+
+			for _, r := range rs {
+				stp, err := r.SubtreePath()
+
+				t.Log("stp err", err)
+
+				stpStr := ""
+				if stp != nil {
+					stpStr = stp.String()
+				}
+
+				results = append(results, expect{
+					tenant:            r.Tenant(),
+					resource:          r.ProtectedResource(),
+					service:           r.Service().String(),
+					category:          r.Category().String(),
+					subtreePath:       stpStr,
+					subtreePathHadErr: err != nil,
+				})
+			}
+
+			assert.ElementsMatch(t, test.expect, results)
+		})
+	}
+}
+
+func (suite *ReasonsUnitSuite) TestReasonsFor_serviceChecks() {
+	var (
+		tenantID = "tid"
+		exchange = path.ExchangeService.String()
+		email    = path.EmailCategory.String()
+		contacts = path.ContactsCategory.String()
+	)
+
+	type expect struct {
+		tenant            string
+		resource          string
+		category          string
+		service           string
+		subtreePath       string
+		subtreePathHadErr bool
+	}
+
+	stpFor := func(resource, category, service string) string {
+		return path.Builder{}.Append(tenantID, service, resource, category).String()
+	}
+
+	table := []struct {
+		name    string
+		sel     func() ExchangeRestore
+		useName bool
+		expect  []expect
+	}{
+		{
+			name: "no scopes",
+			sel: func() ExchangeRestore {
+				return *NewExchangeRestore([]string{"timbo"})
+			},
+			expect: []expect{},
+		},
+		{
+			name: "only includes",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"bubba"})
+				sel.Include(sel.MailFolders(Any()))
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "bubba",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("bubba", email, exchange),
+				},
+			},
+		},
+		{
+			name: "only filters",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"tachoma dhaume"})
+				sel.Filter(sel.MailFolders(Any()))
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "tachoma dhaume",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("tachoma dhaume", email, exchange),
+				},
+			},
+		},
+		{
+			name: "duplicate includes and filters",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"vyng vang zoombah"})
+				sel.Include(sel.MailFolders(Any()))
+				sel.Filter(sel.MailFolders(Any()))
+
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "vyng vang zoombah",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("vyng vang zoombah", email, exchange),
+				},
+			},
+		},
+		{
+			name: "duplicate includes",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"fat billie"})
+				sel.Include(sel.MailFolders(Any()), sel.MailFolders(Any()))
+
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "fat billie",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("fat billie", email, exchange),
+				},
+			},
+		},
+		{
+			name: "duplicate filters",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"seathane"})
+				sel.Filter(sel.MailFolders(Any()), sel.MailFolders(Any()))
+
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "seathane",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("seathane", email, exchange),
+				},
+			},
+		},
+		{
+			name: "no duplicates",
+			sel: func() ExchangeRestore {
+				sel := *NewExchangeRestore([]string{"perell"})
+				sel.Include(sel.MailFolders(Any()), sel.ContactFolders(Any()))
+
+				return sel
+			},
+			expect: []expect{
+				{
+					tenant:      tenantID,
+					resource:    "perell",
+					category:    email,
+					service:     exchange,
+					subtreePath: stpFor("perell", email, exchange),
+				},
+				{
+					tenant:      tenantID,
+					resource:    "perell",
+					category:    contacts,
+					service:     exchange,
+					subtreePath: stpFor("perell", contacts, exchange),
+				},
+			},
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			t := suite.T()
+
+			results := []expect{}
+			rs := reasonsFor(test.sel(), tenantID, test.useName)
+
+			for _, r := range rs {
+				stp, err := r.SubtreePath()
+
+				t.Log("stp err", err)
+
+				stpStr := ""
+				if stp != nil {
+					stpStr = stp.String()
+				}
+
+				results = append(results, expect{
+					tenant:            r.Tenant(),
+					resource:          r.ProtectedResource(),
+					service:           r.Service().String(),
+					category:          r.Category().String(),
+					subtreePath:       stpStr,
+					subtreePathHadErr: err != nil,
+				})
+			}
+
+			assert.ElementsMatch(t, test.expect, results)
+		})
+	}
+}

src/pkg/selectors/selectors.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/alcionai/corso/src/internal/common/idname"
 	"github.com/alcionai/corso/src/pkg/backup/details"
+	"github.com/alcionai/corso/src/pkg/backup/identity"
 	"github.com/alcionai/corso/src/pkg/fault"
 	"github.com/alcionai/corso/src/pkg/filters"
 	"github.com/alcionai/corso/src/pkg/path"
@@ -87,6 +88,14 @@ type pathCategorier interface {
 	PathCategories() selectorPathCategories
 }
 
+type pathServicer interface {
+	PathService() path.ServiceType
+}
+
+type reasoner interface {
+	Reasons(tenantID string, useOwnerNameForID bool) []identity.Reasoner
+}
+
 // ---------------------------------------------------------------------------
 // Selector
 // ---------------------------------------------------------------------------
@@ -273,7 +282,7 @@ func (s Selector) Reduce(
 	return r.Reduce(ctx, deets, errs), nil
 }
 
-// returns the sets of path categories identified in each scope set.
+// PathCategories returns the sets of path categories identified in each scope set.
 func (s Selector) PathCategories() (selectorPathCategories, error) {
 	ro, err := selectorAsIface[pathCategorier](s)
 	if err != nil {
@@ -283,6 +292,18 @@ func (s Selector) PathCategories() (selectorPathCategories, error) {
 	return ro.PathCategories(), nil
 }
 
+// Reasons returns a deduplicated set of the backup reasons produced
+// using the selector's discrete owner and each scopes' service and
+// category types.
+func (s Selector) Reasons(tenantID string, useOwnerNameForID bool) ([]identity.Reasoner, error) {
+	ro, err := selectorAsIface[reasoner](s)
+	if err != nil {
+		return nil, err
+	}
+
+	return ro.Reasons(tenantID, useOwnerNameForID), nil
+}
+
 // transformer for arbitrary selector interfaces
 func selectorAsIface[T any](s Selector) (T, error) {
 	var (

src/pkg/selectors/sharepoint.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/alcionai/corso/src/internal/common/dttm"
 	"github.com/alcionai/corso/src/pkg/backup/details"
+	"github.com/alcionai/corso/src/pkg/backup/identity"
 	"github.com/alcionai/corso/src/pkg/fault"
 	"github.com/alcionai/corso/src/pkg/filters"
 	"github.com/alcionai/corso/src/pkg/path"
@@ -42,6 +43,7 @@ type (
 var (
 	_ Reducer        = &SharePointRestore{}
 	_ pathCategorier = &SharePointRestore{}
+	_ reasoner       = &SharePointRestore{}
 )
 
 // NewSharePointBackup produces a new Selector with the service set to ServiceSharePoint.
@@ -121,6 +123,13 @@ func (s sharePoint) PathCategories() selectorPathCategories {
 	}
 }
 
+// Reasons returns a deduplicated set of the backup reasons produced
+// using the selector's discrete owner and each scopes' service and
+// category types.
+func (s sharePoint) Reasons(tenantID string, useOwnerNameForID bool) []identity.Reasoner {
+	return reasonsFor(s, tenantID, useOwnerNameForID)
+}
+
 // ---------------------------------------------------------------------------
 // Stringers and Concealers
 // ---------------------------------------------------------------------------