small paths code rearrangement (#4007)

small cleanup in paths, primarily splitting files
so that file contents are more clearly owned, which should be a little better for readability and code placement.

Also renames `ServicePrefix` to `BuildPrefix` in
anticipation of multi-service prefixes.

no logic changes, just movement/renaming.

---

#### 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/kopia/base_finder.go

@@ -70,7 +70,7 @@ func (r reason) Category() path.CategoryType {
 }
 
 func (r reason) SubtreePath() (path.Path, error) {
-	p, err := path.ServicePrefix(
+	p, err := path.BuildPrefix(
 		r.Tenant(),
 		r.ProtectedResource(),
 		r.Service(),

src/internal/kopia/upload_test.go

@@ -2865,16 +2865,16 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeSelectsMigrateSubt
 		migratedUser = "user_migrate"
 	)
 
-	oldPrefixPathEmail, err := path.ServicePrefix(testTenant, testUser, path.ExchangeService, path.EmailCategory)
+	oldPrefixPathEmail, err := path.BuildPrefix(testTenant, testUser, path.ExchangeService, path.EmailCategory)
 	require.NoError(t, err, clues.ToCore(err))
 
-	newPrefixPathEmail, err := path.ServicePrefix(testTenant, migratedUser, path.ExchangeService, path.EmailCategory)
+	newPrefixPathEmail, err := path.BuildPrefix(testTenant, migratedUser, path.ExchangeService, path.EmailCategory)
 	require.NoError(t, err, clues.ToCore(err))
 
-	oldPrefixPathCont, err := path.ServicePrefix(testTenant, testUser, path.ExchangeService, path.ContactsCategory)
+	oldPrefixPathCont, err := path.BuildPrefix(testTenant, testUser, path.ExchangeService, path.ContactsCategory)
 	require.NoError(t, err, clues.ToCore(err))
 
-	newPrefixPathCont, err := path.ServicePrefix(testTenant, migratedUser, path.ExchangeService, path.ContactsCategory)
+	newPrefixPathCont, err := path.BuildPrefix(testTenant, migratedUser, path.ExchangeService, path.ContactsCategory)
 	require.NoError(t, err, clues.ToCore(err))
 
 	var (

src/internal/m365/graph/collections.go

@@ -79,7 +79,7 @@ func BaseCollections(
 	for cat := range categories {
 		ictx := clues.Add(ctx, "base_service", service, "base_category", cat)
 
-		full, err := path.ServicePrefix(tenant, rOwner, service, cat)
+		full, err := path.BuildPrefix(tenant, rOwner, service, cat)
 		if err != nil {
 			// Shouldn't happen.
 			err = clues.Wrap(err, "making path").WithClues(ictx)

src/internal/m365/graph/collections_test.go

@@ -24,10 +24,10 @@ func (suite *CollectionsUnitSuite) TestNewPrefixCollection() {
 	serv := path.OneDriveService
 	cat := path.FilesCategory
 
-	p1, err := path.ServicePrefix("t", "ro1", serv, cat)
+	p1, err := path.BuildPrefix("t", "ro1", serv, cat)
 	require.NoError(t, err, clues.ToCore(err))
 
-	p2, err := path.ServicePrefix("t", "ro2", serv, cat)
+	p2, err := path.BuildPrefix("t", "ro2", serv, cat)
 	require.NoError(t, err, clues.ToCore(err))
 
 	items, err := path.Build("t", "ro", serv, cat, true, "fld", "itm")

src/internal/m365/service/onedrive/backup.go

@@ -109,7 +109,7 @@ func migrationCollections(
 
 	// unlike exchange, which enumerates all folders on every
 	// backup, onedrive needs to force the owner PN -> ID migration
-	mc, err := path.ServicePrefix(
+	mc, err := path.BuildPrefix(
 		tenant,
 		bpc.ProtectedResource.ID(),
 		path.OneDriveService,
@@ -118,7 +118,7 @@ func migrationCollections(
 		return nil, clues.Wrap(err, "creating user id migration path")
 	}
 
-	mpc, err := path.ServicePrefix(
+	mpc, err := path.BuildPrefix(
 		tenant,
 		bpc.ProtectedResource.Name(),
 		path.OneDriveService,

src/internal/operations/pathtransformer/restore_path_transformer.go

@@ -42,7 +42,7 @@ func locationRef(
 
 func basicLocationPath(repoRef path.Path, locRef *path.Builder) (path.Path, error) {
 	if len(locRef.Elements()) == 0 {
-		res, err := path.ServicePrefix(
+		res, err := path.BuildPrefix(
 			repoRef.Tenant(),
 			repoRef.ResourceOwner(),
 			repoRef.Service(),

src/internal/operations/test/exchange_test.go

@@ -347,7 +347,7 @@ func testExchangeContinuousBackups(suite *ExchangeBackupIntgSuite, toggles contr
 		// },
 	}
 
-	rrPfx, err := path.ServicePrefix(acct.ID(), uidn.ID(), service, path.EmailCategory)
+	rrPfx, err := path.BuildPrefix(acct.ID(), uidn.ID(), service, path.EmailCategory)
 	require.NoError(t, err, clues.ToCore(err))
 
 	// strip the category from the prefix; we primarily want the tenant and resource owner.

src/internal/operations/test/onedrive_test.go

@@ -213,7 +213,7 @@ func runDriveIncrementalTest(
 		}
 	)
 
-	rrPfx, err := path.ServicePrefix(atid, roidn.ID(), service, category)
+	rrPfx, err := path.BuildPrefix(atid, roidn.ID(), service, category)
 	require.NoError(t, err, clues.ToCore(err))
 
 	// strip the category from the prefix; we primarily want the tenant and resource owner.

src/pkg/path/builder.go

@@ -0,0 +1,379 @@
+package path
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"fmt"
+
+	"github.com/alcionai/clues"
+)
+
+// interface compliance required for handling PII
+var (
+	_ clues.Concealer = &Builder{}
+	_ fmt.Stringer    = &Builder{}
+)
+
+// Builder is a simple path representation that only tracks path elements. It
+// can join, escape, and unescape elements. Higher-level packages are expected
+// to wrap this struct to build resource-specific contexts (e.x. an
+// ExchangeMailPath).
+// Resource-specific paths allow access to more information like segments in the
+// path. Builders that are turned into resource paths later on do not need to
+// manually add prefixes for items that normally appear in the data layer (ex.
+// tenant ID, service, user ID, etc).
+type Builder struct {
+	// Unescaped version of elements.
+	elements Elements
+}
+
+// Append creates a copy of this Builder and adds the given elements them to the
+// end of the new Builder. Elements are added in the order they are passed.
+func (pb Builder) Append(elements ...string) *Builder {
+	res := &Builder{elements: make([]string, len(pb.elements))}
+	copy(res.elements, pb.elements)
+
+	// Unescaped elements can't fail validation.
+	//nolint:errcheck
+	res.appendElements(false, elements)
+
+	return res
+}
+
+func (pb *Builder) appendElements(escaped bool, elements []string) error {
+	for _, e := range elements {
+		if len(e) == 0 {
+			continue
+		}
+
+		tmp := e
+
+		if escaped {
+			tmp = TrimTrailingSlash(tmp)
+			// If tmp was just the path separator then it will be empty now.
+			if len(tmp) == 0 {
+				continue
+			}
+
+			if err := validateEscapedElement(tmp); err != nil {
+				return err
+			}
+
+			tmp = unescape(tmp)
+		}
+
+		pb.elements = append(pb.elements, tmp)
+	}
+
+	return nil
+}
+
+// UnescapeAndAppend creates a copy of this Builder and adds one or more already
+// escaped path elements to the end of the new Builder. Elements are added in
+// the order they are passed.
+func (pb Builder) UnescapeAndAppend(elements ...string) (*Builder, error) {
+	res := &Builder{elements: make([]string, 0, len(pb.elements))}
+	copy(res.elements, pb.elements)
+
+	if err := res.appendElements(true, elements); err != nil {
+		return nil, err
+	}
+
+	return res, nil
+}
+
+// SplitUnescapeAppend takes in an escaped string representing a directory
+// path, splits the string, and appends it to the current builder.
+func (pb Builder) SplitUnescapeAppend(s string) (*Builder, error) {
+	elems := Split(TrimTrailingSlash(s))
+
+	return pb.UnescapeAndAppend(elems...)
+}
+
+func (pb Builder) PopFront() *Builder {
+	if len(pb.elements) <= 1 {
+		return &Builder{}
+	}
+
+	elements := make([]string, len(pb.elements)-1)
+	copy(elements, pb.elements[1:])
+
+	return &Builder{
+		elements: elements,
+	}
+}
+
+// Dir removes the last element from the builder.
+func (pb Builder) Dir() *Builder {
+	if len(pb.elements) <= 1 {
+		return &Builder{}
+	}
+
+	return &Builder{
+		// Safe to use the same elements because Builders are immutable.
+		elements: pb.elements[:len(pb.elements)-1],
+	}
+}
+
+// HeadElem returns the first element in the Builder.
+func (pb Builder) HeadElem() string {
+	if len(pb.elements) == 0 {
+		return ""
+	}
+
+	return pb.elements[0]
+}
+
+// LastElem returns the last element in the Builder.
+func (pb Builder) LastElem() string {
+	if len(pb.elements) == 0 {
+		return ""
+	}
+
+	return pb.elements[len(pb.elements)-1]
+}
+
+// UpdateParent updates leading elements matching prev to be cur and returns
+// true if it was updated. If prev is not a prefix of this Builder changes
+// nothing and returns false. If either prev or cur is nil does nothing and
+// returns false.
+func (pb *Builder) UpdateParent(prev, cur *Builder) bool {
+	if prev == cur || prev == nil || cur == nil || len(prev.Elements()) > len(pb.Elements()) {
+		return false
+	}
+
+	parent := true
+
+	for i, e := range prev.Elements() {
+		if pb.elements[i] != e {
+			parent = false
+			break
+		}
+	}
+
+	if !parent {
+		return false
+	}
+
+	pb.elements = append(cur.Elements(), pb.elements[len(prev.Elements()):]...)
+
+	return true
+}
+
+// ShortRef produces a truncated hash of the builder that
+// acts as a unique identifier.
+func (pb Builder) ShortRef() string {
+	if len(pb.elements) == 0 {
+		return ""
+	}
+
+	data := bytes.Buffer{}
+
+	for _, element := range pb.elements {
+		data.WriteString(element)
+	}
+
+	sum := sha256.Sum256(data.Bytes())
+
+	// Some conversions to get the right number of characters in the output. This
+	// outputs hex, so we need to take the target number of characters and do the
+	// equivalent of (shortRefCharacters * 4) / 8. This is
+	// <number of bits represented> / <bits per byte> which gets us how many bytes
+	// to give to our format command.
+	numBytes := shortRefCharacters / 2
+
+	return fmt.Sprintf("%x", sum[:numBytes])
+}
+
+// Elements returns all the elements in the path. This is a temporary function
+// and will likely be updated to handle encoded elements instead of clear-text
+// elements in the future.
+func (pb Builder) Elements() Elements {
+	return append(Elements{}, pb.elements...)
+}
+
+// withPrefix creates a Builder prefixed with the parameter values, and
+// concatenated with the current builder elements.
+func (pb Builder) withPrefix(elements ...string) *Builder {
+	res := Builder{}.Append(elements...)
+	res.elements = append(res.elements, pb.elements...)
+
+	return res
+}
+
+// verifyPrefix ensures that the tenant and resourceOwner are valid
+// values, and that the builder has some directory structure.
+func (pb Builder) verifyPrefix(tenant, resourceOwner string) error {
+	if err := verifyInputValues(tenant, resourceOwner); err != nil {
+		return err
+	}
+
+	if len(pb.elements) == 0 {
+		return clues.New("missing path beyond prefix")
+	}
+
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// Data Layer Path Transformers
+// ---------------------------------------------------------------------------
+
+func (pb Builder) ToStreamStorePath(
+	tenant, purpose string,
+	service ServiceType,
+	isItem bool,
+) (Path, error) {
+	if err := verifyInputValues(tenant, purpose); err != nil {
+		return nil, err
+	}
+
+	if isItem && len(pb.elements) == 0 {
+		return nil, clues.New("missing path beyond prefix")
+	}
+
+	metadataService := UnknownService
+
+	switch service {
+	case ExchangeService:
+		metadataService = ExchangeMetadataService
+	case OneDriveService:
+		metadataService = OneDriveMetadataService
+	case SharePointService:
+		metadataService = SharePointMetadataService
+	}
+
+	return &dataLayerResourcePath{
+		Builder: *pb.withPrefix(
+			tenant,
+			metadataService.String(),
+			purpose,
+			DetailsCategory.String()),
+		service:  metadataService,
+		category: DetailsCategory,
+		hasItem:  isItem,
+	}, nil
+}
+
+func (pb Builder) ToServiceCategoryMetadataPath(
+	tenant, user string,
+	service ServiceType,
+	category CategoryType,
+	isItem bool,
+) (Path, error) {
+	if err := ValidateServiceAndCategory(service, category); err != nil {
+		return nil, err
+	}
+
+	if err := verifyInputValues(tenant, user); err != nil {
+		return nil, err
+	}
+
+	if isItem && len(pb.elements) == 0 {
+		return nil, clues.New("missing path beyond prefix")
+	}
+
+	metadataService := UnknownService
+
+	switch service {
+	case ExchangeService:
+		metadataService = ExchangeMetadataService
+	case OneDriveService:
+		metadataService = OneDriveMetadataService
+	case SharePointService:
+		metadataService = SharePointMetadataService
+	}
+
+	return &dataLayerResourcePath{
+		Builder: *pb.withPrefix(
+			tenant,
+			metadataService.String(),
+			user,
+			category.String(),
+		),
+		service:  metadataService,
+		category: category,
+		hasItem:  isItem,
+	}, nil
+}
+
+func (pb Builder) ToDataLayerPath(
+	tenant, user string,
+	service ServiceType,
+	category CategoryType,
+	isItem bool,
+) (Path, error) {
+	if err := ValidateServiceAndCategory(service, category); err != nil {
+		return nil, err
+	}
+
+	if err := pb.verifyPrefix(tenant, user); err != nil {
+		return nil, err
+	}
+
+	return &dataLayerResourcePath{
+		Builder: *pb.withPrefix(
+			tenant,
+			service.String(),
+			user,
+			category.String()),
+		service:  service,
+		category: category,
+		hasItem:  isItem,
+	}, nil
+}
+
+func (pb Builder) ToDataLayerExchangePathForCategory(
+	tenant, user string,
+	category CategoryType,
+	isItem bool,
+) (Path, error) {
+	return pb.ToDataLayerPath(tenant, user, ExchangeService, category, isItem)
+}
+
+func (pb Builder) ToDataLayerOneDrivePath(
+	tenant, user string,
+	isItem bool,
+) (Path, error) {
+	return pb.ToDataLayerPath(tenant, user, OneDriveService, FilesCategory, isItem)
+}
+
+func (pb Builder) ToDataLayerSharePointPath(
+	tenant, site string,
+	category CategoryType,
+	isItem bool,
+) (Path, error) {
+	return pb.ToDataLayerPath(tenant, site, SharePointService, category, isItem)
+}
+
+// ---------------------------------------------------------------------------
+// Stringers and PII Concealer Compliance
+// ---------------------------------------------------------------------------
+
+// Conceal produces a concealed representation of the builder, suitable for
+// logging, storing in errors, and other output.
+func (pb Builder) Conceal() string {
+	return pb.elements.Conceal()
+}
+
+// Format produces a concealed representation of the builder, even when
+// used within a PrintF, suitable for logging, storing in errors,
+// and other output.
+func (pb Builder) Format(fs fmt.State, _ rune) {
+	fmt.Fprint(fs, pb.Conceal())
+}
+
+// String returns a string that contains all path elements joined together.
+// Elements of the path that need escaping are escaped.
+// The result is not concealed, and is not suitable for logging or structured
+// errors.
+func (pb Builder) String() string {
+	return pb.elements.String()
+}
+
+// PlainString returns an unescaped, unmodified string of the builder.
+// The result is not concealed, and is not suitable for logging or structured
+// errors.
+func (pb Builder) PlainString() string {
+	return pb.elements.PlainString()
+}

src/pkg/path/builder_test.go

@@ -0,0 +1,369 @@
+package path
+
+import (
+	"fmt"
+	"strings"
+	"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"
+)
+
+type BuilderUnitSuite struct {
+	tester.Suite
+}
+
+func TestBuilderUnitSuite(t *testing.T) {
+	suite.Run(t, &BuilderUnitSuite{Suite: tester.NewUnitSuite(t)})
+}
+
+// set the clues hashing to mask for the span of this suite
+func (suite *BuilderUnitSuite) SetupSuite() {
+	clues.SetHasher(clues.HashCfg{HashAlg: clues.Flatmask})
+}
+
+// revert clues hashing to plaintext for all other tests
+func (suite *BuilderUnitSuite) TeardownSuite() {
+	clues.SetHasher(clues.NoHash())
+}
+
+func (suite *BuilderUnitSuite) TestAppend() {
+	table := append(append([]testData{}, genericCases...), basicUnescapedInputs...)
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			t := suite.T()
+
+			p := Builder{}.Append(test.input...)
+			assert.Equal(t, test.expectedString, p.String())
+		})
+	}
+}
+
+func (suite *BuilderUnitSuite) TestAppendItem() {
+	t := suite.T()
+
+	p, err := Build("t", "ro", ExchangeService, EmailCategory, false, "foo", "bar")
+	require.NoError(t, err, clues.ToCore(err))
+
+	pb := p.ToBuilder()
+	assert.Equal(t, pb.String(), p.String())
+
+	pb = pb.Append("qux")
+
+	p, err = p.AppendItem("qux")
+
+	require.NoError(t, err, clues.ToCore(err))
+	assert.Equal(t, pb.String(), p.String())
+
+	_, err = p.AppendItem("fnords")
+	require.Error(t, err, clues.ToCore(err))
+}
+
+func (suite *BuilderUnitSuite) TestUnescapeAndAppend() {
+	table := append(append([]testData{}, genericCases...), basicEscapedInputs...)
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			t := suite.T()
+
+			p, err := Builder{}.UnescapeAndAppend(test.input...)
+			require.NoError(t, err, clues.ToCore(err))
+
+			assert.Equal(t, test.expectedString, p.String())
+		})
+	}
+}
+
+func (suite *BuilderUnitSuite) TestEscapedFailure() {
+	target := "i_s"
+
+	for c := range charactersToEscape {
+		suite.Run(fmt.Sprintf("Unescaped-%c", c), func() {
+			tmp := strings.ReplaceAll(target, "_", string(c))
+
+			_, err := Builder{}.UnescapeAndAppend("this", tmp, "path")
+			assert.Errorf(suite.T(), err, "path with unescaped %s did not error", string(c))
+		})
+	}
+}
+
+func (suite *BuilderUnitSuite) TestBadEscapeSequenceErrors() {
+	target := `i\_s/a`
+	notEscapes := []rune{'a', 'b', '#', '%'}
+
+	for _, c := range notEscapes {
+		suite.Run(fmt.Sprintf("Escaped-%c", c), func() {
+			tmp := strings.ReplaceAll(target, "_", string(c))
+
+			_, err := Builder{}.UnescapeAndAppend("this", tmp, "path")
+			assert.Errorf(
+				suite.T(),
+				err,
+				"path with bad escape sequence %c%c did not error",
+				escapeCharacter,
+				c)
+		})
+	}
+}
+
+func (suite *BuilderUnitSuite) TestTrailingEscapeChar() {
+	base := []string{"this", "is", "a", "path"}
+
+	for i := 0; i < len(base); i++ {
+		suite.Run(fmt.Sprintf("Element%v", i), func() {
+			path := make([]string, len(base))
+			copy(path, base)
+			path[i] = path[i] + string(escapeCharacter)
+
+			_, err := Builder{}.UnescapeAndAppend(path...)
+			assert.Error(
+				suite.T(),
+				err,
+				"path with trailing escape character did not error")
+		})
+	}
+}
+
+func (suite *BuilderUnitSuite) TestElements() {
+	table := []struct {
+		name     string
+		input    []string
+		output   []string
+		pathFunc func(elements []string) (*Builder, error)
+	}{
+		{
+			name:   "SimpleEscapedPath",
+			input:  []string{"this", "is", "a", "path"},
+			output: []string{"this", "is", "a", "path"},
+			pathFunc: func(elements []string) (*Builder, error) {
+				return Builder{}.UnescapeAndAppend(elements...)
+			},
+		},
+		{
+			name:   "SimpleUnescapedPath",
+			input:  []string{"this", "is", "a", "path"},
+			output: []string{"this", "is", "a", "path"},
+			pathFunc: func(elements []string) (*Builder, error) {
+				return Builder{}.Append(elements...), nil
+			},
+		},
+		{
+			name:   "EscapedPath",
+			input:  []string{"this", `is\/`, "a", "path"},
+			output: []string{"this", "is/", "a", "path"},
+			pathFunc: func(elements []string) (*Builder, error) {
+				return Builder{}.UnescapeAndAppend(elements...)
+			},
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			t := suite.T()
+
+			p, err := test.pathFunc(test.input)
+			require.NoError(t, err, clues.ToCore(err))
+
+			assert.Equal(t, Elements(test.output), p.Elements())
+		})
+	}
+}
+
+func (suite *BuilderUnitSuite) TestPopFront() {
+	table := []struct {
+		name           string
+		base           *Builder
+		expectedString string
+	}{
+		{
+			name:           "Empty",
+			base:           &Builder{},
+			expectedString: "",
+		},
+		{
+			name:           "OneElement",
+			base:           Builder{}.Append("something"),
+			expectedString: "",
+		},
+		{
+			name:           "TwoElements",
+			base:           Builder{}.Append("something", "else"),
+			expectedString: "else",
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			t := suite.T()
+
+			assert.Equal(t, test.expectedString, test.base.PopFront().String())
+		})
+	}
+}
+
+func (suite *BuilderUnitSuite) TestShortRef() {
+	table := []struct {
+		name          string
+		inputElements []string
+		expectedLen   int
+	}{
+		{
+			name:          "PopulatedPath",
+			inputElements: []string{"this", "is", "a", "path"},
+			expectedLen:   shortRefCharacters,
+		},
+		{
+			name:          "EmptyPath",
+			inputElements: nil,
+			expectedLen:   0,
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			pb := Builder{}.Append(test.inputElements...)
+			ref := pb.ShortRef()
+			assert.Len(suite.T(), ref, test.expectedLen)
+		})
+	}
+}
+
+func (suite *BuilderUnitSuite) TestShortRefIsStable() {
+	t := suite.T()
+	pb := Builder{}.Append("this", "is", "a", "path")
+	prevRef := pb.ShortRef()
+	assert.Len(t, prevRef, shortRefCharacters)
+
+	for i := 0; i < 5; i++ {
+		ref := pb.ShortRef()
+		assert.Len(t, ref, shortRefCharacters)
+		assert.Equal(t, prevRef, ref, "ShortRef changed between calls")
+
+		prevRef = ref
+	}
+}
+
+func (suite *BuilderUnitSuite) TestShortRefIsUnique() {
+	pb1 := Builder{}.Append("this", "is", "a", "path")
+	pb2 := pb1.Append("also")
+
+	require.NotEqual(suite.T(), pb1, pb2)
+	assert.NotEqual(suite.T(), pb1.ShortRef(), pb2.ShortRef())
+}
+
+// TestShortRefUniqueWithEscaping tests that two paths that output the same
+// unescaped string but different escaped strings have different shortrefs. This
+// situation can occur when one path has embedded path separators while the
+// other does not but contains the same characters.
+func (suite *BuilderUnitSuite) TestShortRefUniqueWithEscaping() {
+	pb1 := Builder{}.Append(`this`, `is`, `a`, `path`)
+	pb2 := Builder{}.Append(`this`, `is/a`, `path`)
+
+	require.NotEqual(suite.T(), pb1, pb2)
+	assert.NotEqual(suite.T(), pb1.ShortRef(), pb2.ShortRef())
+}
+
+func (suite *BuilderUnitSuite) TestFolder() {
+	table := []struct {
+		name         string
+		p            func(t *testing.T) Path
+		escape       bool
+		expectFolder string
+		expectSplit  []string
+	}{
+		{
+			name: "clean path",
+			p: func(t *testing.T) Path {
+				p, err := Builder{}.
+					Append("a", "b", "c").
+					ToDataLayerExchangePathForCategory("t", "u", EmailCategory, false)
+				require.NoError(t, err, clues.ToCore(err))
+
+				return p
+			},
+			expectFolder: "a/b/c",
+			expectSplit:  []string{"a", "b", "c"},
+		},
+		{
+			name: "clean path escaped",
+			p: func(t *testing.T) Path {
+				p, err := Builder{}.
+					Append("a", "b", "c").
+					ToDataLayerExchangePathForCategory("t", "u", EmailCategory, false)
+				require.NoError(t, err, clues.ToCore(err))
+
+				return p
+			},
+			escape:       true,
+			expectFolder: "a/b/c",
+			expectSplit:  []string{"a", "b", "c"},
+		},
+		{
+			name: "escapable path",
+			p: func(t *testing.T) Path {
+				p, err := Builder{}.
+					Append("a/", "b", "c").
+					ToDataLayerExchangePathForCategory("t", "u", EmailCategory, false)
+				require.NoError(t, err, clues.ToCore(err))
+
+				return p
+			},
+			expectFolder: "a//b/c",
+			expectSplit:  []string{"a", "b", "c"},
+		},
+		{
+			name: "escapable path escaped",
+			p: func(t *testing.T) Path {
+				p, err := Builder{}.
+					Append("a/", "b", "c").
+					ToDataLayerExchangePathForCategory("t", "u", EmailCategory, false)
+				require.NoError(t, err, clues.ToCore(err))
+
+				return p
+			},
+			escape:       true,
+			expectFolder: "a\\//b/c",
+			expectSplit:  []string{"a\\/", "b", "c"},
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			t := suite.T()
+
+			p := test.p(t)
+			result := p.Folder(test.escape)
+			assert.Equal(t, test.expectFolder, result)
+			assert.Equal(t, test.expectSplit, Split(result))
+		})
+	}
+}
+
+func (suite *BuilderUnitSuite) TestPIIHandling() {
+	p, err := Build("t", "ro", ExchangeService, EventsCategory, true, "dir", "item")
+	require.NoError(suite.T(), err)
+
+	table := []struct {
+		name        string
+		p           Path
+		expect      string
+		expectPlain string
+	}{
+		{
+			name:        "standard path",
+			p:           p,
+			expect:      "***/exchange/***/events/***/***",
+			expectPlain: "t/exchange/ro/events/dir/item",
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			t := suite.T()
+
+			assert.Equal(t, test.expect, test.p.Conceal(), "conceal")
+			assert.Equal(t, test.expectPlain, test.p.String(), "string")
+			assert.Equal(t, test.expect, fmt.Sprintf("%s", test.p), "fmt %%s")
+			assert.Equal(t, test.expect, fmt.Sprintf("%+v", test.p), "fmt %%+v")
+			assert.Equal(t, test.expectPlain, test.p.PlainString(), "plain")
+		})
+	}
+}

src/pkg/path/category_type.go

@@ -0,0 +1,108 @@
+package path
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/alcionai/clues"
+)
+
+var ErrorUnknownCategory = clues.New("unknown category string")
+
+// CategoryType denotes what category of data the path corresponds to. The order
+// of the enums below can be changed, but the string representation of each enum
+// must remain the same or migration code needs to be added to handle changes to
+// the string format.
+type CategoryType int
+
+//go:generate stringer -type=CategoryType -linecomment
+const (
+	UnknownCategory   CategoryType = iota
+	EmailCategory                  // email
+	ContactsCategory               // contacts
+	EventsCategory                 // events
+	FilesCategory                  // files
+	ListsCategory                  // lists
+	LibrariesCategory              // libraries
+	PagesCategory                  // pages
+	DetailsCategory                // details
+)
+
+func ToCategoryType(category string) CategoryType {
+	cat := strings.ToLower(category)
+
+	switch cat {
+	case strings.ToLower(EmailCategory.String()):
+		return EmailCategory
+	case strings.ToLower(ContactsCategory.String()):
+		return ContactsCategory
+	case strings.ToLower(EventsCategory.String()):
+		return EventsCategory
+	case strings.ToLower(FilesCategory.String()):
+		return FilesCategory
+	case strings.ToLower(LibrariesCategory.String()):
+		return LibrariesCategory
+	case strings.ToLower(ListsCategory.String()):
+		return ListsCategory
+	case strings.ToLower(PagesCategory.String()):
+		return PagesCategory
+	case strings.ToLower(DetailsCategory.String()):
+		return DetailsCategory
+	default:
+		return UnknownCategory
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Service-Category pairings
+// ---------------------------------------------------------------------------
+
+// serviceCategories is a mapping of all valid service/category pairs for
+// non-metadata paths.
+var serviceCategories = map[ServiceType]map[CategoryType]struct{}{
+	ExchangeService: {
+		EmailCategory:    {},
+		ContactsCategory: {},
+		EventsCategory:   {},
+	},
+	OneDriveService: {
+		FilesCategory: {},
+	},
+	SharePointService: {
+		LibrariesCategory: {},
+		ListsCategory:     {},
+		PagesCategory:     {},
+	},
+}
+
+func validateServiceAndCategoryStrings(s, c string) (ServiceType, CategoryType, error) {
+	service := toServiceType(s)
+	if service == UnknownService {
+		return UnknownService, UnknownCategory, clues.Stack(ErrorUnknownService).With("service", fmt.Sprintf("%q", s))
+	}
+
+	category := ToCategoryType(c)
+	if category == UnknownCategory {
+		return UnknownService, UnknownCategory, clues.Stack(ErrorUnknownService).With("category", fmt.Sprintf("%q", c))
+	}
+
+	if err := ValidateServiceAndCategory(service, category); err != nil {
+		return UnknownService, UnknownCategory, err
+	}
+
+	return service, category, nil
+}
+
+func ValidateServiceAndCategory(service ServiceType, category CategoryType) error {
+	cats, ok := serviceCategories[service]
+	if !ok {
+		return clues.New("unsupported service").With("service", fmt.Sprintf("%q", service))
+	}
+
+	if _, ok := cats[category]; !ok {
+		return clues.New("unknown service/category combination").
+			With("service", fmt.Sprintf("%q", service), "category", fmt.Sprintf("%q", category))
+	}
+
+	return nil
+}

src/pkg/path/drive.go

@@ -2,6 +2,7 @@ package path
 
 import "github.com/alcionai/clues"
 
+// TODO: Move this into m365/collection/drive
 // drivePath is used to represent path components
 // of an item within the drive i.e.
 // Given `drives/b!X_8Z2zuXpkKkXZsr7gThk9oJpuj0yXVGnK5_VjRRPK-q725SX_8ZQJgFDK8PlFxA/root:/Folder1/Folder2/file`

src/pkg/path/path.go

@@ -51,8 +51,6 @@
 package path
 
 import (
-	"bytes"
-	"crypto/sha256"
 	"fmt"
 	"strings"
 
@@ -122,12 +120,6 @@ type Path interface {
 	fmt.Stringer
 }
 
-// interface compliance required for handling PII
-var (
-	_ clues.Concealer = &Builder{}
-	_ fmt.Stringer    = &Builder{}
-)
-
 // RestorePaths denotes the location to find an item in kopia and the path of
 // the collection to place the item in for restore.
 type RestorePaths struct {
@@ -135,185 +127,26 @@ type RestorePaths struct {
 	RestorePath Path
 }
 
-// Builder is a simple path representation that only tracks path elements. It
-// can join, escape, and unescape elements. Higher-level packages are expected
-// to wrap this struct to build resource-specific contexts (e.x. an
-// ExchangeMailPath).
-// Resource-specific paths allow access to more information like segments in the
-// path. Builders that are turned into resource paths later on do not need to
-// manually add prefixes for items that normally appear in the data layer (ex.
-// tenant ID, service, user ID, etc).
-type Builder struct {
-	// Unescaped version of elements.
-	elements Elements
+// ---------------------------------------------------------------------------
+// Exported Helpers
+// ---------------------------------------------------------------------------
+
+func Build(
+	tenant, resourceOwner string,
+	service ServiceType,
+	category CategoryType,
+	hasItem bool,
+	elements ...string,
+) (Path, error) {
+	b := Builder{}.Append(elements...)
+
+	return b.ToDataLayerPath(
+		tenant, resourceOwner,
+		service, category,
+		hasItem)
 }
 
-// Append creates a copy of this Builder and adds the given elements them to the
-// end of the new Builder. Elements are added in the order they are passed.
-func (pb Builder) Append(elements ...string) *Builder {
-	res := &Builder{elements: make([]string, len(pb.elements))}
-	copy(res.elements, pb.elements)
-
-	// Unescaped elements can't fail validation.
-	//nolint:errcheck
-	res.appendElements(false, elements)
-
-	return res
-}
-
-func (pb *Builder) appendElements(escaped bool, elements []string) error {
-	for _, e := range elements {
-		if len(e) == 0 {
-			continue
-		}
-
-		tmp := e
-
-		if escaped {
-			tmp = TrimTrailingSlash(tmp)
-			// If tmp was just the path separator then it will be empty now.
-			if len(tmp) == 0 {
-				continue
-			}
-
-			if err := validateEscapedElement(tmp); err != nil {
-				return err
-			}
-
-			tmp = unescape(tmp)
-		}
-
-		pb.elements = append(pb.elements, tmp)
-	}
-
-	return nil
-}
-
-// UnescapeAndAppend creates a copy of this Builder and adds one or more already
-// escaped path elements to the end of the new Builder. Elements are added in
-// the order they are passed.
-func (pb Builder) UnescapeAndAppend(elements ...string) (*Builder, error) {
-	res := &Builder{elements: make([]string, 0, len(pb.elements))}
-	copy(res.elements, pb.elements)
-
-	if err := res.appendElements(true, elements); err != nil {
-		return nil, err
-	}
-
-	return res, nil
-}
-
-// SplitUnescapeAppend takes in an escaped string representing a directory
-// path, splits the string, and appends it to the current builder.
-func (pb Builder) SplitUnescapeAppend(s string) (*Builder, error) {
-	elems := Split(TrimTrailingSlash(s))
-
-	return pb.UnescapeAndAppend(elems...)
-}
-
-func (pb Builder) PopFront() *Builder {
-	if len(pb.elements) <= 1 {
-		return &Builder{}
-	}
-
-	elements := make([]string, len(pb.elements)-1)
-	copy(elements, pb.elements[1:])
-
-	return &Builder{
-		elements: elements,
-	}
-}
-
-// Dir removes the last element from the builder.
-func (pb Builder) Dir() *Builder {
-	if len(pb.elements) <= 1 {
-		return &Builder{}
-	}
-
-	return &Builder{
-		// Safe to use the same elements because Builders are immutable.
-		elements: pb.elements[:len(pb.elements)-1],
-	}
-}
-
-// HeadElem returns the first element in the Builder.
-func (pb Builder) HeadElem() string {
-	if len(pb.elements) == 0 {
-		return ""
-	}
-
-	return pb.elements[0]
-}
-
-// LastElem returns the last element in the Builder.
-func (pb Builder) LastElem() string {
-	if len(pb.elements) == 0 {
-		return ""
-	}
-
-	return pb.elements[len(pb.elements)-1]
-}
-
-// UpdateParent updates leading elements matching prev to be cur and returns
-// true if it was updated. If prev is not a prefix of this Builder changes
-// nothing and returns false. If either prev or cur is nil does nothing and
-// returns false.
-func (pb *Builder) UpdateParent(prev, cur *Builder) bool {
-	if prev == cur || prev == nil || cur == nil || len(prev.Elements()) > len(pb.Elements()) {
-		return false
-	}
-
-	parent := true
-
-	for i, e := range prev.Elements() {
-		if pb.elements[i] != e {
-			parent = false
-			break
-		}
-	}
-
-	if !parent {
-		return false
-	}
-
-	pb.elements = append(cur.Elements(), pb.elements[len(prev.Elements()):]...)
-
-	return true
-}
-
-// ShortRef produces a truncated hash of the builder that
-// acts as a unique identifier.
-func (pb Builder) ShortRef() string {
-	if len(pb.elements) == 0 {
-		return ""
-	}
-
-	data := bytes.Buffer{}
-
-	for _, element := range pb.elements {
-		data.WriteString(element)
-	}
-
-	sum := sha256.Sum256(data.Bytes())
-
-	// Some conversions to get the right number of characters in the output. This
-	// outputs hex, so we need to take the target number of characters and do the
-	// equivalent of (shortRefCharacters * 4) / 8. This is
-	// <number of bits represented> / <bits per byte> which gets us how many bytes
-	// to give to our format command.
-	numBytes := shortRefCharacters / 2
-
-	return fmt.Sprintf("%x", sum[:numBytes])
-}
-
-// Elements returns all the elements in the path. This is a temporary function
-// and will likely be updated to handle encoded elements instead of clear-text
-// elements in the future.
-func (pb Builder) Elements() Elements {
-	return append(Elements{}, pb.elements...)
-}
-
-func ServicePrefix(
+func BuildPrefix(
 	tenant, resourceOwner string,
 	s ServiceType,
 	c CategoryType,
@@ -336,197 +169,6 @@ func ServicePrefix(
 	}, nil
 }
 
-// withPrefix creates a Builder prefixed with the parameter values, and
-// concatenated with the current builder elements.
-func (pb Builder) withPrefix(elements ...string) *Builder {
-	res := Builder{}.Append(elements...)
-	res.elements = append(res.elements, pb.elements...)
-
-	return res
-}
-
-// ---------------------------------------------------------------------------
-// Data Layer Path Transformers
-// ---------------------------------------------------------------------------
-
-func (pb Builder) ToStreamStorePath(
-	tenant, purpose string,
-	service ServiceType,
-	isItem bool,
-) (Path, error) {
-	if err := verifyInputValues(tenant, purpose); err != nil {
-		return nil, err
-	}
-
-	if isItem && len(pb.elements) == 0 {
-		return nil, clues.New("missing path beyond prefix")
-	}
-
-	metadataService := UnknownService
-
-	switch service {
-	case ExchangeService:
-		metadataService = ExchangeMetadataService
-	case OneDriveService:
-		metadataService = OneDriveMetadataService
-	case SharePointService:
-		metadataService = SharePointMetadataService
-	}
-
-	return &dataLayerResourcePath{
-		Builder: *pb.withPrefix(
-			tenant,
-			metadataService.String(),
-			purpose,
-			DetailsCategory.String()),
-		service:  metadataService,
-		category: DetailsCategory,
-		hasItem:  isItem,
-	}, nil
-}
-
-func (pb Builder) ToServiceCategoryMetadataPath(
-	tenant, user string,
-	service ServiceType,
-	category CategoryType,
-	isItem bool,
-) (Path, error) {
-	if err := ValidateServiceAndCategory(service, category); err != nil {
-		return nil, err
-	}
-
-	if err := verifyInputValues(tenant, user); err != nil {
-		return nil, err
-	}
-
-	if isItem && len(pb.elements) == 0 {
-		return nil, clues.New("missing path beyond prefix")
-	}
-
-	metadataService := UnknownService
-
-	switch service {
-	case ExchangeService:
-		metadataService = ExchangeMetadataService
-	case OneDriveService:
-		metadataService = OneDriveMetadataService
-	case SharePointService:
-		metadataService = SharePointMetadataService
-	}
-
-	return &dataLayerResourcePath{
-		Builder: *pb.withPrefix(
-			tenant,
-			metadataService.String(),
-			user,
-			category.String(),
-		),
-		service:  metadataService,
-		category: category,
-		hasItem:  isItem,
-	}, nil
-}
-
-func (pb Builder) ToDataLayerPath(
-	tenant, user string,
-	service ServiceType,
-	category CategoryType,
-	isItem bool,
-) (Path, error) {
-	if err := ValidateServiceAndCategory(service, category); err != nil {
-		return nil, err
-	}
-
-	if err := pb.verifyPrefix(tenant, user); err != nil {
-		return nil, err
-	}
-
-	return &dataLayerResourcePath{
-		Builder: *pb.withPrefix(
-			tenant,
-			service.String(),
-			user,
-			category.String()),
-		service:  service,
-		category: category,
-		hasItem:  isItem,
-	}, nil
-}
-
-func (pb Builder) ToDataLayerExchangePathForCategory(
-	tenant, user string,
-	category CategoryType,
-	isItem bool,
-) (Path, error) {
-	return pb.ToDataLayerPath(tenant, user, ExchangeService, category, isItem)
-}
-
-func (pb Builder) ToDataLayerOneDrivePath(
-	tenant, user string,
-	isItem bool,
-) (Path, error) {
-	return pb.ToDataLayerPath(tenant, user, OneDriveService, FilesCategory, isItem)
-}
-
-func (pb Builder) ToDataLayerSharePointPath(
-	tenant, site string,
-	category CategoryType,
-	isItem bool,
-) (Path, error) {
-	return pb.ToDataLayerPath(tenant, site, SharePointService, category, isItem)
-}
-
-// ---------------------------------------------------------------------------
-// Stringers and PII Concealer Compliance
-// ---------------------------------------------------------------------------
-
-// Conceal produces a concealed representation of the builder, suitable for
-// logging, storing in errors, and other output.
-func (pb Builder) Conceal() string {
-	return pb.elements.Conceal()
-}
-
-// Format produces a concealed representation of the builder, even when
-// used within a PrintF, suitable for logging, storing in errors,
-// and other output.
-func (pb Builder) Format(fs fmt.State, _ rune) {
-	fmt.Fprint(fs, pb.Conceal())
-}
-
-// String returns a string that contains all path elements joined together.
-// Elements of the path that need escaping are escaped.
-// The result is not concealed, and is not suitable for logging or structured
-// errors.
-func (pb Builder) String() string {
-	return pb.elements.String()
-}
-
-// PlainString returns an unescaped, unmodified string of the builder.
-// The result is not concealed, and is not suitable for logging or structured
-// errors.
-func (pb Builder) PlainString() string {
-	return pb.elements.PlainString()
-}
-
-// ---------------------------------------------------------------------------
-// Exported Helpers
-// ---------------------------------------------------------------------------
-
-func Build(
-	tenant, resourceOwner string,
-	service ServiceType,
-	category CategoryType,
-	hasItem bool,
-	elements ...string,
-) (Path, error) {
-	b := Builder{}.Append(elements...)
-
-	return b.ToDataLayerPath(
-		tenant, resourceOwner,
-		service, category,
-		hasItem)
-}
-
 // FromDataLayerPath parses the escaped path p, validates the elements in p
 // match a resource-specific path format, and returns a Path struct for that
 // resource-specific type. If p does not match any resource-specific paths or
@@ -762,17 +404,3 @@ func join(elements []string) string {
 	// '\' according to the escaping rules.
 	return strings.Join(elements, string(PathSeparator))
 }
-
-// verifyPrefix ensures that the tenant and resourceOwner are valid
-// values, and that the builder has some directory structure.
-func (pb Builder) verifyPrefix(tenant, resourceOwner string) error {
-	if err := verifyInputValues(tenant, resourceOwner); err != nil {
-		return err
-	}
-
-	if len(pb.elements) == 0 {
-		return clues.New("missing path beyond prefix")
-	}
-
-	return nil
-}

src/pkg/path/path_test.go

@@ -2,7 +2,6 @@ package path
 
 import (
 	"fmt"
-	"strings"
 	"testing"
 
 	"github.com/alcionai/clues"
@@ -233,239 +232,7 @@ func (suite *PathUnitSuite) TeardownSuite() {
 	clues.SetHasher(clues.NoHash())
 }
 
-func (suite *PathUnitSuite) TestAppend() {
-	table := append(append([]testData{}, genericCases...), basicUnescapedInputs...)
-	for _, test := range table {
-		suite.Run(test.name, func() {
-			t := suite.T()
-
-			p := Builder{}.Append(test.input...)
-			assert.Equal(t, test.expectedString, p.String())
-		})
-	}
-}
-
-func (suite *PathUnitSuite) TestAppendItem() {
-	t := suite.T()
-
-	p, err := Build("t", "ro", ExchangeService, EmailCategory, false, "foo", "bar")
-	require.NoError(t, err, clues.ToCore(err))
-
-	pb := p.ToBuilder()
-	assert.Equal(t, pb.String(), p.String())
-
-	pb = pb.Append("qux")
-
-	p, err = p.AppendItem("qux")
-
-	require.NoError(t, err, clues.ToCore(err))
-	assert.Equal(t, pb.String(), p.String())
-
-	_, err = p.AppendItem("fnords")
-	require.Error(t, err, clues.ToCore(err))
-}
-
-func (suite *PathUnitSuite) TestUnescapeAndAppend() {
-	table := append(append([]testData{}, genericCases...), basicEscapedInputs...)
-	for _, test := range table {
-		suite.Run(test.name, func() {
-			t := suite.T()
-
-			p, err := Builder{}.UnescapeAndAppend(test.input...)
-			require.NoError(t, err, clues.ToCore(err))
-
-			assert.Equal(t, test.expectedString, p.String())
-		})
-	}
-}
-
-func (suite *PathUnitSuite) TestEscapedFailure() {
-	target := "i_s"
-
-	for c := range charactersToEscape {
-		suite.Run(fmt.Sprintf("Unescaped-%c", c), func() {
-			tmp := strings.ReplaceAll(target, "_", string(c))
-
-			_, err := Builder{}.UnescapeAndAppend("this", tmp, "path")
-			assert.Errorf(suite.T(), err, "path with unescaped %s did not error", string(c))
-		})
-	}
-}
-
-func (suite *PathUnitSuite) TestBadEscapeSequenceErrors() {
-	target := `i\_s/a`
-	notEscapes := []rune{'a', 'b', '#', '%'}
-
-	for _, c := range notEscapes {
-		suite.Run(fmt.Sprintf("Escaped-%c", c), func() {
-			tmp := strings.ReplaceAll(target, "_", string(c))
-
-			_, err := Builder{}.UnescapeAndAppend("this", tmp, "path")
-			assert.Errorf(
-				suite.T(),
-				err,
-				"path with bad escape sequence %c%c did not error",
-				escapeCharacter,
-				c)
-		})
-	}
-}
-
-func (suite *PathUnitSuite) TestTrailingEscapeChar() {
-	base := []string{"this", "is", "a", "path"}
-
-	for i := 0; i < len(base); i++ {
-		suite.Run(fmt.Sprintf("Element%v", i), func() {
-			path := make([]string, len(base))
-			copy(path, base)
-			path[i] = path[i] + string(escapeCharacter)
-
-			_, err := Builder{}.UnescapeAndAppend(path...)
-			assert.Error(
-				suite.T(),
-				err,
-				"path with trailing escape character did not error")
-		})
-	}
-}
-
-func (suite *PathUnitSuite) TestElements() {
-	table := []struct {
-		name     string
-		input    []string
-		output   []string
-		pathFunc func(elements []string) (*Builder, error)
-	}{
-		{
-			name:   "SimpleEscapedPath",
-			input:  []string{"this", "is", "a", "path"},
-			output: []string{"this", "is", "a", "path"},
-			pathFunc: func(elements []string) (*Builder, error) {
-				return Builder{}.UnescapeAndAppend(elements...)
-			},
-		},
-		{
-			name:   "SimpleUnescapedPath",
-			input:  []string{"this", "is", "a", "path"},
-			output: []string{"this", "is", "a", "path"},
-			pathFunc: func(elements []string) (*Builder, error) {
-				return Builder{}.Append(elements...), nil
-			},
-		},
-		{
-			name:   "EscapedPath",
-			input:  []string{"this", `is\/`, "a", "path"},
-			output: []string{"this", "is/", "a", "path"},
-			pathFunc: func(elements []string) (*Builder, error) {
-				return Builder{}.UnescapeAndAppend(elements...)
-			},
-		},
-	}
-	for _, test := range table {
-		suite.Run(test.name, func() {
-			t := suite.T()
-
-			p, err := test.pathFunc(test.input)
-			require.NoError(t, err, clues.ToCore(err))
-
-			assert.Equal(t, Elements(test.output), p.Elements())
-		})
-	}
-}
-
-func (suite *PathUnitSuite) TestPopFront() {
-	table := []struct {
-		name           string
-		base           *Builder
-		expectedString string
-	}{
-		{
-			name:           "Empty",
-			base:           &Builder{},
-			expectedString: "",
-		},
-		{
-			name:           "OneElement",
-			base:           Builder{}.Append("something"),
-			expectedString: "",
-		},
-		{
-			name:           "TwoElements",
-			base:           Builder{}.Append("something", "else"),
-			expectedString: "else",
-		},
-	}
-	for _, test := range table {
-		suite.Run(test.name, func() {
-			t := suite.T()
-
-			assert.Equal(t, test.expectedString, test.base.PopFront().String())
-		})
-	}
-}
-
-func (suite *PathUnitSuite) TestShortRef() {
-	table := []struct {
-		name          string
-		inputElements []string
-		expectedLen   int
-	}{
-		{
-			name:          "PopulatedPath",
-			inputElements: []string{"this", "is", "a", "path"},
-			expectedLen:   shortRefCharacters,
-		},
-		{
-			name:          "EmptyPath",
-			inputElements: nil,
-			expectedLen:   0,
-		},
-	}
-	for _, test := range table {
-		suite.Run(test.name, func() {
-			pb := Builder{}.Append(test.inputElements...)
-			ref := pb.ShortRef()
-			assert.Len(suite.T(), ref, test.expectedLen)
-		})
-	}
-}
-
-func (suite *PathUnitSuite) TestShortRefIsStable() {
-	t := suite.T()
-	pb := Builder{}.Append("this", "is", "a", "path")
-	prevRef := pb.ShortRef()
-	assert.Len(t, prevRef, shortRefCharacters)
-
-	for i := 0; i < 5; i++ {
-		ref := pb.ShortRef()
-		assert.Len(t, ref, shortRefCharacters)
-		assert.Equal(t, prevRef, ref, "ShortRef changed between calls")
-
-		prevRef = ref
-	}
-}
-
-func (suite *PathUnitSuite) TestShortRefIsUnique() {
-	pb1 := Builder{}.Append("this", "is", "a", "path")
-	pb2 := pb1.Append("also")
-
-	require.NotEqual(suite.T(), pb1, pb2)
-	assert.NotEqual(suite.T(), pb1.ShortRef(), pb2.ShortRef())
-}
-
-// TestShortRefUniqueWithEscaping tests that two paths that output the same
-// unescaped string but different escaped strings have different shortrefs. This
-// situation can occur when one path has embedded path separators while the
-// other does not but contains the same characters.
-func (suite *PathUnitSuite) TestShortRefUniqueWithEscaping() {
-	pb1 := Builder{}.Append(`this`, `is`, `a`, `path`)
-	pb2 := Builder{}.Append(`this`, `is/a`, `path`)
-
-	require.NotEqual(suite.T(), pb1, pb2)
-	assert.NotEqual(suite.T(), pb1.ShortRef(), pb2.ShortRef())
-}
-
-func (suite *PathUnitSuite) TestFromStringErrors() {
+func (suite *PathUnitSuite) TestFromDataLayerPathErrors() {
 	table := []struct {
 		name        string
 		escapedPath string
@@ -521,82 +288,7 @@ func (suite *PathUnitSuite) TestFromStringErrors() {
 	}
 }
 
-func (suite *PathUnitSuite) TestFolder() {
-	table := []struct {
-		name         string
-		p            func(t *testing.T) Path
-		escape       bool
-		expectFolder string
-		expectSplit  []string
-	}{
-		{
-			name: "clean path",
-			p: func(t *testing.T) Path {
-				p, err := Builder{}.
-					Append("a", "b", "c").
-					ToDataLayerExchangePathForCategory("t", "u", EmailCategory, false)
-				require.NoError(t, err, clues.ToCore(err))
-
-				return p
-			},
-			expectFolder: "a/b/c",
-			expectSplit:  []string{"a", "b", "c"},
-		},
-		{
-			name: "clean path escaped",
-			p: func(t *testing.T) Path {
-				p, err := Builder{}.
-					Append("a", "b", "c").
-					ToDataLayerExchangePathForCategory("t", "u", EmailCategory, false)
-				require.NoError(t, err, clues.ToCore(err))
-
-				return p
-			},
-			escape:       true,
-			expectFolder: "a/b/c",
-			expectSplit:  []string{"a", "b", "c"},
-		},
-		{
-			name: "escapable path",
-			p: func(t *testing.T) Path {
-				p, err := Builder{}.
-					Append("a/", "b", "c").
-					ToDataLayerExchangePathForCategory("t", "u", EmailCategory, false)
-				require.NoError(t, err, clues.ToCore(err))
-
-				return p
-			},
-			expectFolder: "a//b/c",
-			expectSplit:  []string{"a", "b", "c"},
-		},
-		{
-			name: "escapable path escaped",
-			p: func(t *testing.T) Path {
-				p, err := Builder{}.
-					Append("a/", "b", "c").
-					ToDataLayerExchangePathForCategory("t", "u", EmailCategory, false)
-				require.NoError(t, err, clues.ToCore(err))
-
-				return p
-			},
-			escape:       true,
-			expectFolder: "a\\//b/c",
-			expectSplit:  []string{"a\\/", "b", "c"},
-		},
-	}
-	for _, test := range table {
-		suite.Run(test.name, func() {
-			t := suite.T()
-
-			p := test.p(t)
-			result := p.Folder(test.escape)
-			assert.Equal(t, test.expectFolder, result)
-			assert.Equal(t, test.expectSplit, Split(result))
-		})
-	}
-}
-
-func (suite *PathUnitSuite) TestFromString() {
+func (suite *PathUnitSuite) TestFromDataLayerPath() {
 	const (
 		testTenant         = "tenant"
 		testUser           = "user"
@@ -740,37 +432,7 @@ func (suite *PathUnitSuite) TestFromString() {
 	}
 }
 
-func (suite *PathUnitSuite) TestPath_piiHandling() {
-	p, err := Build("t", "ro", ExchangeService, EventsCategory, true, "dir", "item")
-	require.NoError(suite.T(), err)
-
-	table := []struct {
-		name        string
-		p           Path
-		expect      string
-		expectPlain string
-	}{
-		{
-			name:        "standard path",
-			p:           p,
-			expect:      "***/exchange/***/events/***/***",
-			expectPlain: "t/exchange/ro/events/dir/item",
-		},
-	}
-	for _, test := range table {
-		suite.Run(test.name, func() {
-			t := suite.T()
-
-			assert.Equal(t, test.expect, test.p.Conceal(), "conceal")
-			assert.Equal(t, test.expectPlain, test.p.String(), "string")
-			assert.Equal(t, test.expect, fmt.Sprintf("%s", test.p), "fmt %%s")
-			assert.Equal(t, test.expect, fmt.Sprintf("%+v", test.p), "fmt %%+v")
-			assert.Equal(t, test.expectPlain, test.p.PlainString(), "plain")
-		})
-	}
-}
-
-func (suite *PathUnitSuite) TestToServicePrefix() {
+func (suite *PathUnitSuite) TestBuildPrefix() {
 	table := []struct {
 		name      string
 		service   ServiceType
@@ -818,7 +480,7 @@ func (suite *PathUnitSuite) TestToServicePrefix() {
 		suite.Run(test.name, func() {
 			t := suite.T()
 
-			r, err := ServicePrefix(test.tenant, test.owner, test.service, test.category)
+			r, err := BuildPrefix(test.tenant, test.owner, test.service, test.category)
 			test.expectErr(t, err, clues.ToCore(err))
 
 			if r == nil {

src/pkg/path/resource_path.go

@@ -1,154 +1,9 @@
 package path
 
 import (
-	"fmt"
-	"strings"
-
 	"github.com/alcionai/clues"
 )
 
-var ErrorUnknownService = clues.New("unknown service string")
-
-// ServiceType denotes what service the path corresponds to. Metadata services
-// are also included though they are only used for paths that house metadata for
-// Corso backups.
-//
-// Metadata services are not considered valid service types for resource paths
-// though they can be used for metadata paths.
-//
-// The order of the enums below can be changed, but the string representation of
-// each enum must remain the same or migration code needs to be added to handle
-// changes to the string format.
-type ServiceType int
-
-//go:generate stringer -type=ServiceType -linecomment
-const (
-	UnknownService            ServiceType = iota
-	ExchangeService                       // exchange
-	OneDriveService                       // onedrive
-	SharePointService                     // sharepoint
-	ExchangeMetadataService               // exchangeMetadata
-	OneDriveMetadataService               // onedriveMetadata
-	SharePointMetadataService             // sharepointMetadata
-)
-
-func toServiceType(service string) ServiceType {
-	s := strings.ToLower(service)
-
-	switch s {
-	case strings.ToLower(ExchangeService.String()):
-		return ExchangeService
-	case strings.ToLower(OneDriveService.String()):
-		return OneDriveService
-	case strings.ToLower(SharePointService.String()):
-		return SharePointService
-	case strings.ToLower(ExchangeMetadataService.String()):
-		return ExchangeMetadataService
-	case strings.ToLower(OneDriveMetadataService.String()):
-		return OneDriveMetadataService
-	case strings.ToLower(SharePointMetadataService.String()):
-		return SharePointMetadataService
-	default:
-		return UnknownService
-	}
-}
-
-var ErrorUnknownCategory = clues.New("unknown category string")
-
-// CategoryType denotes what category of data the path corresponds to. The order
-// of the enums below can be changed, but the string representation of each enum
-// must remain the same or migration code needs to be added to handle changes to
-// the string format.
-type CategoryType int
-
-//go:generate stringer -type=CategoryType -linecomment
-const (
-	UnknownCategory   CategoryType = iota
-	EmailCategory                  // email
-	ContactsCategory               // contacts
-	EventsCategory                 // events
-	FilesCategory                  // files
-	ListsCategory                  // lists
-	LibrariesCategory              // libraries
-	PagesCategory                  // pages
-	DetailsCategory                // details
-)
-
-func ToCategoryType(category string) CategoryType {
-	cat := strings.ToLower(category)
-
-	switch cat {
-	case strings.ToLower(EmailCategory.String()):
-		return EmailCategory
-	case strings.ToLower(ContactsCategory.String()):
-		return ContactsCategory
-	case strings.ToLower(EventsCategory.String()):
-		return EventsCategory
-	case strings.ToLower(FilesCategory.String()):
-		return FilesCategory
-	case strings.ToLower(LibrariesCategory.String()):
-		return LibrariesCategory
-	case strings.ToLower(ListsCategory.String()):
-		return ListsCategory
-	case strings.ToLower(PagesCategory.String()):
-		return PagesCategory
-	case strings.ToLower(DetailsCategory.String()):
-		return DetailsCategory
-	default:
-		return UnknownCategory
-	}
-}
-
-// serviceCategories is a mapping of all valid service/category pairs for
-// non-metadata paths.
-var serviceCategories = map[ServiceType]map[CategoryType]struct{}{
-	ExchangeService: {
-		EmailCategory:    {},
-		ContactsCategory: {},
-		EventsCategory:   {},
-	},
-	OneDriveService: {
-		FilesCategory: {},
-	},
-	SharePointService: {
-		LibrariesCategory: {},
-		ListsCategory:     {},
-		PagesCategory:     {},
-	},
-}
-
-func validateServiceAndCategoryStrings(s, c string) (ServiceType, CategoryType, error) {
-	service := toServiceType(s)
-	if service == UnknownService {
-		return UnknownService, UnknownCategory, clues.Stack(ErrorUnknownService).With("service", fmt.Sprintf("%q", s))
-	}
-
-	category := ToCategoryType(c)
-	if category == UnknownCategory {
-		return UnknownService, UnknownCategory, clues.Stack(ErrorUnknownService).With("category", fmt.Sprintf("%q", c))
-	}
-
-	if err := ValidateServiceAndCategory(service, category); err != nil {
-		return UnknownService, UnknownCategory, err
-	}
-
-	return service, category, nil
-}
-
-func ValidateServiceAndCategory(service ServiceType, category CategoryType) error {
-	cats, ok := serviceCategories[service]
-	if !ok {
-		return clues.New("unsupported service").With("service", fmt.Sprintf("%q", service))
-	}
-
-	if _, ok := cats[category]; !ok {
-		return clues.New("unknown service/category combination").
-			With("service", fmt.Sprintf("%q", service), "category", fmt.Sprintf("%q", category))
-	}
-
-	return nil
-}
-
 // dataLayerResourcePath allows callers to extract information from a
 // resource-specific path. This struct is unexported so that callers are
 // forced to use the pre-defined constructors, making it impossible to create a

src/pkg/path/service_type.go

@@ -0,0 +1,53 @@
+package path
+
+import (
+	"strings"
+
+	"github.com/alcionai/clues"
+)
+
+var ErrorUnknownService = clues.New("unknown service string")
+
+// ServiceType denotes what service the path corresponds to. Metadata services
+// are also included though they are only used for paths that house metadata for
+// Corso backups.
+//
+// Metadata services are not considered valid service types for resource paths
+// though they can be used for metadata paths.
+//
+// The order of the enums below can be changed, but the string representation of
+// each enum must remain the same or migration code needs to be added to handle
+// changes to the string format.
+type ServiceType int
+
+//go:generate stringer -type=ServiceType -linecomment
+const (
+	UnknownService            ServiceType = iota
+	ExchangeService                       // exchange
+	OneDriveService                       // onedrive
+	SharePointService                     // sharepoint
+	ExchangeMetadataService               // exchangeMetadata
+	OneDriveMetadataService               // onedriveMetadata
+	SharePointMetadataService             // sharepointMetadata
+)
+
+func toServiceType(service string) ServiceType {
+	s := strings.ToLower(service)
+
+	switch s {
+	case strings.ToLower(ExchangeService.String()):
+		return ExchangeService
+	case strings.ToLower(OneDriveService.String()):
+		return OneDriveService
+	case strings.ToLower(SharePointService.String()):
+		return SharePointService
+	case strings.ToLower(ExchangeMetadataService.String()):
+		return ExchangeMetadataService
+	case strings.ToLower(OneDriveMetadataService.String()):
+		return OneDriveMetadataService
+	case strings.ToLower(SharePointMetadataService.String()):
+		return SharePointMetadataService
+	default:
+		return UnknownService
+	}
+}

src/pkg/selectors/reasons.go

@@ -38,7 +38,7 @@ func (br backupReason) Category() path.CategoryType {
 }
 
 func (br backupReason) SubtreePath() (path.Path, error) {
-	return path.ServicePrefix(
+	return path.BuildPrefix(
 		br.tenant,
 		br.resource,
 		br.service,