Create folder struct for backup details (#869)

## Description

<!-- Insert PR description-->
Folder entries allow recording the directory hierarchy of a backup in backup details for other consumers.

Although folders are present in the backup details and they have the logic to be displayed, they are not expected to be shown to users (later PRs will ensure this).

## Type of change

<!--- Please check the type of change your PR introduces: --->
- [x] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Test
- [ ] 💻 CI/Deployment
- [ ] 🐹 Trivial/Minor

## Issue(s)

<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
* closes #860 

## Test Plan

<!-- How will this be tested prior to merging.-->
- [ ] 💪 Manual
- [x] ⚡ Unit test
- [ ] 💚 E2E

src/pkg/backup/details/details.go

@@ -11,6 +11,12 @@ import (
 	"github.com/alcionai/corso/src/internal/model"
 )
 
+type FolderEntry struct {
+	RepoRef  string
+	ShortRef string
+	Info     ItemInfo
+}
+
 // --------------------------------------------------------------------------------
 // Model
 // --------------------------------------------------------------------------------
@@ -83,7 +89,8 @@ type Details struct {
 	DetailsModel
 
 	// internal
-	mu sync.Mutex `json:"-"`
+	mu           sync.Mutex          `json:"-"`
+	knownFolders map[string]struct{} `json:"-"`
 }
 
 func (d *Details) Add(repoRef, shortRef string, info ItemInfo) {
@@ -96,6 +103,31 @@ func (d *Details) Add(repoRef, shortRef string, info ItemInfo) {
 	})
 }
 
+// AddFolders adds entries for the given folders. It skips adding entries that
+// have been added by previous calls.
+func (d *Details) AddFolders(folders []FolderEntry) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	if d.knownFolders == nil {
+		d.knownFolders = map[string]struct{}{}
+	}
+
+	for _, folder := range folders {
+		if _, ok := d.knownFolders[folder.ShortRef]; ok {
+			// Entry already exists, nothing to do.
+			continue
+		}
+
+		d.knownFolders[folder.ShortRef] = struct{}{}
+		d.Entries = append(d.Entries, DetailsEntry{
+			RepoRef:  folder.RepoRef,
+			ShortRef: folder.ShortRef,
+			ItemInfo: folder.Info,
+		})
+	}
+}
+
 // --------------------------------------------------------------------------------
 // Entry
 // --------------------------------------------------------------------------------
@@ -127,6 +159,10 @@ func (de DetailsEntry) MinimumPrintable() any {
 func (de DetailsEntry) Headers() []string {
 	hs := []string{"Reference"}
 
+	if de.ItemInfo.Folder != nil {
+		hs = append(hs, de.ItemInfo.Folder.Headers()...)
+	}
+
 	if de.ItemInfo.Exchange != nil {
 		hs = append(hs, de.ItemInfo.Exchange.Headers()...)
 	}
@@ -146,6 +182,10 @@ func (de DetailsEntry) Headers() []string {
 func (de DetailsEntry) Values() []string {
 	vs := []string{de.ShortRef}
 
+	if de.ItemInfo.Folder != nil {
+		vs = append(vs, de.ItemInfo.Folder.Values()...)
+	}
+
 	if de.ItemInfo.Exchange != nil {
 		vs = append(vs, de.ItemInfo.Exchange.Values()...)
 	}
@@ -174,11 +214,14 @@ const (
 	SharepointItem itemType = iota + 100
 
 	OneDriveItem itemType = iota + 200
+
+	FolderItem itemType = iota + 300
 )
 
 // ItemInfo is a oneOf that contains service specific
 // information about the item it tracks
 type ItemInfo struct {
+	Folder     *FolderInfo     `json:"folder,omitempty"`
 	Exchange   *ExchangeInfo   `json:"exchange,omitempty"`
 	Sharepoint *SharepointInfo `json:"sharepoint,omitempty"`
 	OneDrive   *OneDriveInfo   `json:"oneDrive,omitempty"`
@@ -192,6 +235,9 @@ type ItemInfo struct {
 // calendar event).
 func (i ItemInfo) infoType() itemType {
 	switch {
+	case i.Folder != nil:
+		return i.Folder.ItemType
+
 	case i.Exchange != nil:
 		return i.Exchange.ItemType
 
@@ -205,6 +251,19 @@ func (i ItemInfo) infoType() itemType {
 	return UnknownType
 }
 
+type FolderInfo struct {
+	ItemType    itemType
+	DisplayName string `json:"displayName"`
+}
+
+func (i FolderInfo) Headers() []string {
+	return []string{"Display Name"}
+}
+
+func (i FolderInfo) Values() []string {
+	return []string{i.DisplayName}
+}
+
 // ExchangeInfo describes an exchange item
 type ExchangeInfo struct {
 	ItemType    itemType

src/pkg/backup/details/details_test.go

@@ -170,3 +170,60 @@ func (suite *DetailsUnitSuite) TestDetailsModel_Path() {
 		})
 	}
 }
+
+func (suite *DetailsUnitSuite) TestDetails_AddFolders() {
+	table := []struct {
+		name              string
+		folders           []details.FolderEntry
+		expectedShortRefs []string
+	}{
+		{
+			name: "MultipleFolders",
+			folders: []details.FolderEntry{
+				{
+					RepoRef:  "rr1",
+					ShortRef: "sr1",
+				},
+				{
+					RepoRef:  "rr2",
+					ShortRef: "sr2",
+				},
+			},
+			expectedShortRefs: []string{"sr1", "sr2"},
+		},
+		{
+			name: "MultipleFoldersWithRepeats",
+			folders: []details.FolderEntry{
+				{
+					RepoRef:  "rr1",
+					ShortRef: "sr1",
+				},
+				{
+					RepoRef:  "rr2",
+					ShortRef: "sr2",
+				},
+				{
+					RepoRef:  "rr1",
+					ShortRef: "sr1",
+				},
+				{
+					RepoRef:  "rr3",
+					ShortRef: "sr3",
+				},
+			},
+			expectedShortRefs: []string{"sr1", "sr2", "sr3"},
+		},
+	}
+	for _, test := range table {
+		suite.T().Run(test.name, func(t *testing.T) {
+			deets := details.Details{}
+			deets.AddFolders(test.folders)
+
+			assert.Len(t, deets.Entries, len(test.expectedShortRefs))
+
+			for _, e := range deets.Entries {
+				assert.Contains(t, test.expectedShortRefs, e.ShortRef)
+			}
+		})
+	}
+}