add and delete file support in the tree (#4724)

now that folder handling is complete, we can ingest items in the delta tree as well.

---

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

- [x] ⛔ No

#### Type of change

- [x] 🌻 Feature

#### Issue(s)

* #4689

#### Test Plan

- [x] ⚡ Unit test

src/.golangci.yml

@@ -131,6 +131,9 @@ issues:
     - path: internal/m365/collection/drive/collections_test.go
       linters:
         - lll
+    - path: internal/m365/collection/drive/collections_tree_test.go
+      linters:
+        - lll
     - path: pkg/services/m365/api/graph/betasdk
       linters:
         - wsl

src/internal/m365/collection/drive/collection_test.go

@@ -107,7 +107,7 @@ func (suite *CollectionUnitSuite) TestCollection() {
 			name:         "oneDrive, no duplicates",
 			numInstances: 1,
 			service:      path.OneDriveService,
-			itemDeets:    nst{stubItemName, 42, now},
+			itemDeets:    nst{stubItemName, defaultItemSize, now},
 			itemInfo:     details.ItemInfo{OneDrive: &details.OneDriveInfo{ItemName: stubItemName, Modified: now}},
 			getBody:      io.NopCloser(bytes.NewReader(stubItemContent)),
 			getErr:       nil,
@@ -117,7 +117,7 @@ func (suite *CollectionUnitSuite) TestCollection() {
 			name:         "oneDrive, duplicates",
 			numInstances: 3,
 			service:      path.OneDriveService,
-			itemDeets:    nst{stubItemName, 42, now},
+			itemDeets:    nst{stubItemName, defaultItemSize, now},
 			getBody:      io.NopCloser(bytes.NewReader(stubItemContent)),
 			getErr:       nil,
 			itemInfo:     details.ItemInfo{OneDrive: &details.OneDriveInfo{ItemName: stubItemName, Modified: now}},
@@ -127,7 +127,7 @@ func (suite *CollectionUnitSuite) TestCollection() {
 			name:         "oneDrive, malware",
 			numInstances: 3,
 			service:      path.OneDriveService,
-			itemDeets:    nst{stubItemName, 42, now},
+			itemDeets:    nst{stubItemName, defaultItemSize, now},
 			itemInfo:     details.ItemInfo{},
 			getBody:      nil,
 			getErr:       clues.New("test malware").Label(graph.LabelsMalware),
@@ -138,7 +138,7 @@ func (suite *CollectionUnitSuite) TestCollection() {
 			name:         "oneDrive, not found",
 			numInstances: 3,
 			service:      path.OneDriveService,
-			itemDeets:    nst{stubItemName, 42, now},
+			itemDeets:    nst{stubItemName, defaultItemSize, now},
 			itemInfo:     details.ItemInfo{},
 			getBody:      nil,
 			getErr:       clues.New("test not found").Label(graph.LabelStatus(http.StatusNotFound)),
@@ -149,7 +149,7 @@ func (suite *CollectionUnitSuite) TestCollection() {
 			name:         "sharePoint, no duplicates",
 			numInstances: 1,
 			service:      path.SharePointService,
-			itemDeets:    nst{stubItemName, 42, now},
+			itemDeets:    nst{stubItemName, defaultItemSize, now},
 			itemInfo:     details.ItemInfo{SharePoint: &details.SharePointInfo{ItemName: stubItemName, Modified: now}},
 			getBody:      io.NopCloser(bytes.NewReader(stubItemContent)),
 			getErr:       nil,
@@ -159,7 +159,7 @@ func (suite *CollectionUnitSuite) TestCollection() {
 			name:         "sharePoint, duplicates",
 			numInstances: 3,
 			service:      path.SharePointService,
-			itemDeets:    nst{stubItemName, 42, now},
+			itemDeets:    nst{stubItemName, defaultItemSize, now},
 			itemInfo:     details.ItemInfo{SharePoint: &details.SharePointInfo{ItemName: stubItemName, Modified: now}},
 			getBody:      io.NopCloser(bytes.NewReader(stubItemContent)),
 			getErr:       nil,
@@ -304,7 +304,7 @@ func (suite *CollectionUnitSuite) TestCollectionReadError() {
 		collStatus = support.ControllerOperationStatus{}
 		wg         = sync.WaitGroup{}
 		name       = "name"
-		size       int64 = 42
+		size       = defaultItemSize
 		now        = time.Now()
 	)
 
@@ -374,7 +374,7 @@ func (suite *CollectionUnitSuite) TestCollectionReadUnauthorizedErrorRetry() {
 		collStatus = support.ControllerOperationStatus{}
 		wg         = sync.WaitGroup{}
 		name       = "name"
-		size       int64 = 42
+		size       = defaultItemSize
 		now        = time.Now()
 	)
 

src/internal/m365/collection/drive/collections_test.go

@@ -112,6 +112,7 @@ func coreItem(
 
 	switch it {
 	case isFile:
+		item.SetSize(ptr.To[int64](defaultItemSize))
 		item.SetFile(models.NewFile())
 	case isFolder:
 		item.SetFolder(models.NewFolder())
@@ -1719,7 +1720,7 @@ func (suite *CollectionsUnitSuite) TestGet_treeCannotBeUsedWhileIncomplete() {
 	c.ctrl = opts
 
 	_, _, err := c.Get(ctx, nil, nil, fault.New(true))
-	require.ErrorContains(t, err, "not yet implemented", clues.ToCore(err))
+	require.ErrorContains(t, err, "not implemented", clues.ToCore(err))
 }
 
 func (suite *CollectionsUnitSuite) TestGet() {

src/internal/m365/collection/drive/collections_tree.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/alcionai/clues"
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
+	"github.com/pkg/errors"
 
 	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/common/ptr"
@@ -300,7 +301,7 @@ func (c *Collections) populateTree(
 
 		if reset {
 			counter.Inc(count.PagerResets)
-			tree.Reset()
+			tree.reset()
 			c.resetStats()
 
 			*stats = driveEnumerationStats{}
@@ -316,6 +317,10 @@ func (c *Collections) populateTree(
 			counter,
 			errs)
 		if err != nil {
+			if errors.Is(err, errHitLimit) {
+				break
+			}
+
 			el.AddRecoverable(ctx, clues.Stack(err))
 		}
 
@@ -369,6 +374,7 @@ func (c *Collections) enumeratePageOfItems(
 
 		var (
 			isFolder = item.GetFolder() != nil || item.GetPackageEscaped() != nil
+			isFile   = item.GetFile() != nil
 			itemID   = ptr.Val(item.GetId())
 			err      error
 			skipped  *fault.Skipped
@@ -382,15 +388,19 @@ func (c *Collections) enumeratePageOfItems(
 			"item_is_folder", isFolder,
 			"item_is_package", item.GetPackageEscaped() != nil)
 
-		if isFolder {
+		switch {
-			// check if the preview needs to exit before adding each folder
+		case isFolder:
-			if !tree.ContainsFolder(itemID) && limiter.atLimit(stats, len(tree.folderIDToNode)) {
+			// check limits before adding the next new folder
-				break
+			if !tree.containsFolder(itemID) && limiter.atLimit(stats, len(tree.folderIDToNode)) {
+				return errHitLimit
 			}
 
 			skipped, err = c.addFolderToTree(ictx, tree, drv, item, stats, counter)
-		} else {
+		case isFile:
-			skipped, err = c.addFileToTree(ictx, tree, drv, item, stats, counter)
+			skipped, err = c.addFileToTree(ictx, tree, drv, item, limiter, stats, counter)
+		default:
+			err = clues.NewWC(ictx, "item is neither folder nor file").
+				Label(fault.LabelForceNoBackupCreation, count.UnknownItemType)
 		}
 
 		if skipped != nil {
@@ -398,7 +408,7 @@ func (c *Collections) enumeratePageOfItems(
 		}
 
 		if err != nil {
-			el.AddRecoverable(ictx, clues.Wrap(err, "adding folder"))
+			el.AddRecoverable(ictx, clues.Wrap(err, "adding item"))
 		}
 
 		// Check if we reached the item or size limit while processing this page.
@@ -406,8 +416,9 @@ func (c *Collections) enumeratePageOfItems(
 		// We don't want to check all limits because it's possible we've reached
 		// the container limit but haven't reached the item limit or really added
 		// items to the last container we found.
+		// FIXME(keepers): this isn't getting handled properly at the moment
 		if limiter.atItemLimit(stats) {
-			break
+			return errHitLimit
 		}
 	}
 
@@ -466,13 +477,13 @@ func (c *Collections) addFolderToTree(
 			folderName,
 			graph.ItemInfo(folder))
 
-		logger.Ctx(ctx).Infow("malware detected")
+		logger.Ctx(ctx).Infow("malware folder detected")
 
 		return skip, nil
 	}
 
 	if isDeleted {
-		err := tree.SetTombstone(ctx, folderID)
+		err := tree.setTombstone(ctx, folderID)
 		return nil, clues.Stack(err).OrNil()
 	}
 
@@ -488,7 +499,7 @@ func (c *Collections) addFolderToTree(
 		return nil, nil
 	}
 
-	err = tree.SetFolder(ctx, parentID, folderID, folderName, isPkg)
+	err = tree.setFolder(ctx, parentID, folderID, folderName, isPkg)
 
 	return nil, clues.Stack(err).OrNil()
 }
@@ -528,11 +539,98 @@ func (c *Collections) addFileToTree(
 	ctx context.Context,
 	tree *folderyMcFolderFace,
 	drv models.Driveable,
-	item models.DriveItemable,
+	file models.DriveItemable,
+	limiter *pagerLimiter,
 	stats *driveEnumerationStats,
 	counter *count.Bus,
 ) (*fault.Skipped, error) {
-	return nil, clues.New("not yet implemented")
+	var (
+		driveID   = ptr.Val(drv.GetId())
+		fileID    = ptr.Val(file.GetId())
+		fileName  = ptr.Val(file.GetName())
+		fileSize  = ptr.Val(file.GetSize())
+		isDeleted = file.GetDeleted() != nil
+		isMalware = file.GetMalware() != nil
+		parent    = file.GetParentReference()
+		parentID  string
+	)
+
+	if parent != nil {
+		parentID = ptr.Val(parent.GetId())
+	}
+
+	defer func() {
+		switch {
+		case isMalware:
+			counter.Inc(count.TotalMalwareProcessed)
+		case isDeleted:
+			counter.Inc(count.TotalDeleteFilesProcessed)
+		default:
+			counter.Inc(count.TotalFilesProcessed)
+		}
+	}()
+
+	if isMalware {
+		skip := fault.FileSkip(
+			fault.SkipMalware,
+			driveID,
+			fileID,
+			fileName,
+			graph.ItemInfo(file))
+
+		logger.Ctx(ctx).Infow("malware file detected")
+
+		return skip, nil
+	}
+
+	_, alreadySeen := tree.fileIDToParentID[fileID]
+
+	if isDeleted {
+		tree.deleteFile(fileID)
+
+		if alreadySeen {
+			stats.numAddedFiles--
+			// FIXME(keepers): this might be faulty,
+			// since deletes may not include the file size.
+			// it will likely need to be tracked in
+			// the tree alongside the file modtime.
+			stats.numBytes -= fileSize
+		} else {
+			c.NumItems++
+			c.NumFiles++
+		}
+
+		return nil, nil
+	}
+
+	parentNode, ok := tree.folderIDToNode[parentID]
+
+	// Don't add new items if the new collection is already reached it's limit.
+	// item moves and updates are generally allowed through.
+	if ok && !alreadySeen && limiter.atContainerItemsLimit(len(parentNode.files)) {
+		return nil, nil
+	}
+
+	// Skip large files that don't fit within the size limit.
+	if limiter.aboveSizeLimit(fileSize + stats.numBytes) {
+		return nil, nil
+	}
+
+	err := tree.addFile(parentID, fileID, ptr.Val(file.GetLastModifiedDateTime()))
+	if err != nil {
+		return nil, clues.StackWC(ctx, err)
+	}
+
+	// Only increment counters for new files
+	if !alreadySeen {
+		// todo: remmove c.NumItems/Files in favor of counter and tree counting.
+		c.NumItems++
+		c.NumFiles++
+		stats.numAddedFiles++
+		stats.numBytes += fileSize
+	}
+
+	return nil, nil
 }
 
 // quality-of-life wrapper that transforms each tombstone in the map

src/internal/m365/collection/drive/collections_tree_test.go

@@ -557,6 +557,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 		treeSize                      int
 		treeContainsFolderIDs         []string
 		treeContainsTombstoneIDs      []string
+		treeContainsFileIDsWithParent map[string]string
 	}
 
 	table := []struct {
@@ -584,6 +585,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 				treeSize:                      0,
 				treeContainsFolderIDs:         []string{},
 				treeContainsTombstoneIDs:      []string{},
+				treeContainsFileIDsWithParent: map[string]string{},
 			},
 		},
 		{
@@ -601,6 +603,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 			expect: expected{
 				counts: countTD.Expected{
 					count.TotalFoldersProcessed: 1,
+					count.TotalFilesProcessed:   0,
 					count.PagesEnumerated:       1,
 				},
 				err:      require.NoError,
@@ -609,6 +612,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 					rootID,
 				},
 				treeContainsTombstoneIDs:      []string{},
+				treeContainsFileIDsWithParent: map[string]string{},
 			},
 		},
 		{
@@ -626,6 +630,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 			expect: expected{
 				counts: countTD.Expected{
 					count.TotalFoldersProcessed: 2,
+					count.TotalFilesProcessed:   0,
 					count.PagesEnumerated:       2,
 				},
 				err:      require.NoError,
@@ -634,6 +639,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 					rootID,
 				},
 				treeContainsTombstoneIDs:      []string{},
+				treeContainsFileIDsWithParent: map[string]string{},
 			},
 		},
 		{
@@ -657,6 +663,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 				counts: countTD.Expected{
 					count.TotalFoldersProcessed: 7,
 					count.PagesEnumerated:       3,
+					count.TotalFilesProcessed:   0,
 				},
 				err:      require.NoError,
 				treeSize: 4,
@@ -667,6 +674,51 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 					idx(folder, "chld"),
 				},
 				treeContainsTombstoneIDs:      []string{},
+				treeContainsFileIDsWithParent: map[string]string{},
+			},
+		},
+		{
+			name: "many folders with files",
+			tree: newFolderyMcFolderFace(nil),
+			enumerator: mock.EnumerateItemsDeltaByDrive{
+				DrivePagers: map[string]*mock.DriveItemsDeltaPager{
+					id(drive): {
+						Pages: pagesOf(
+							rootAnd(
+								driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
+								driveItem(id(file), name(file), parent(0, name(folder)), id(folder), isFile)),
+							rootAnd(
+								driveItem(idx(folder, "sib"), namex(folder, "sib"), parent(0), rootID, isFolder),
+								driveItem(idx(file, "sib"), namex(file, "sib"), parent(0, namex(folder, "sib")), idx(folder, "sib"), isFile)),
+							rootAnd(
+								driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
+								driveItem(idx(folder, "chld"), namex(folder, "chld"), parent(0), id(folder), isFolder),
+								driveItem(idx(file, "chld"), namex(file, "chld"), parent(0, namex(folder, "chld")), idx(folder, "chld"), isFile))),
+						DeltaUpdate: pagers.DeltaUpdate{URL: id(delta)},
+					},
+				},
+			},
+			limiter: newPagerLimiter(control.DefaultOptions()),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalFoldersProcessed: 7,
+					count.TotalFilesProcessed:   3,
+					count.PagesEnumerated:       3,
+				},
+				err:      require.NoError,
+				treeSize: 4,
+				treeContainsFolderIDs: []string{
+					rootID,
+					id(folder),
+					idx(folder, "sib"),
+					idx(folder, "chld"),
+				},
+				treeContainsTombstoneIDs: []string{},
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file):          id(folder),
+					idx(file, "sib"):  idx(folder, "sib"),
+					idx(file, "chld"): idx(folder, "chld"),
+				},
 			},
 		},
 		{
@@ -678,7 +730,9 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 				DrivePagers: map[string]*mock.DriveItemsDeltaPager{
 					id(drive): {
 						Pages: pagesOf(
-							rootAnd(driveItem(id(folder), name(folder), parent(0), rootID, isFolder)),
+							rootAnd(
+								driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
+								driveItem(id(file), name(file), parent(0, name(folder)), id(folder), isFile)),
 							rootAnd(delItem(id(folder), parent(0), rootID, isFolder))),
 						DeltaUpdate: pagers.DeltaUpdate{URL: id(delta)},
 					},
@@ -688,6 +742,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 			expect: expected{
 				counts: countTD.Expected{
 					count.TotalFoldersProcessed:       3,
+					count.TotalFilesProcessed:         1,
 					count.TotalDeleteFoldersProcessed: 1,
 					count.PagesEnumerated:             2,
 				},
@@ -697,12 +752,15 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 					rootID,
 				},
 				treeContainsTombstoneIDs: []string{},
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file): id(folder),
+				},
 			},
 		},
 		{
 			// technically you won't see this behavior from graph deltas, since deletes always
 			// precede creates/updates.  But it's worth checking that we can handle it anyways.
-			name: "move, delete on next page",
+			name: "move->delete folder with populated tree",
 			tree: treeWithFolders(),
 			enumerator: mock.EnumerateItemsDeltaByDrive{
 				DrivePagers: map[string]*mock.DriveItemsDeltaPager{
@@ -710,7 +768,8 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 						Pages: pagesOf(
 							rootAnd(
 								driveItem(idx(folder, "parent"), namex(folder, "parent"), parent(0), rootID, isFolder),
-								driveItem(id(folder), namex(folder, "moved"), parent(0), idx(folder, "parent"), isFolder)),
+								driveItem(id(folder), namex(folder, "moved"), parent(0), idx(folder, "parent"), isFolder),
+								driveItem(id(file), name(file), parent(0, namex(folder, "parent"), name(folder)), id(folder), isFile)),
 							rootAnd(delItem(id(folder), parent(0), idx(folder, "parent"), isFolder))),
 						DeltaUpdate: pagers.DeltaUpdate{URL: id(delta)},
 					},
@@ -721,6 +780,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 				counts: countTD.Expected{
 					count.TotalFoldersProcessed:       4,
 					count.TotalDeleteFoldersProcessed: 1,
+					count.TotalFilesProcessed:         1,
 					count.PagesEnumerated:             2,
 				},
 				err:      require.NoError,
@@ -732,20 +792,28 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 				treeContainsTombstoneIDs: []string{
 					id(folder),
 				},
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file): id(folder),
+				},
 			},
 		},
 		{
-			name: "at limit before enumeration",
+			name: "at folder limit before enumeration",
 			tree: treeWithRoot(),
 			enumerator: mock.EnumerateItemsDeltaByDrive{
 				DrivePagers: map[string]*mock.DriveItemsDeltaPager{
 					id(drive): {
 						Pages: pagesOf(
-							rootAnd(driveItem(id(folder), name(folder), parent(0), rootID, isFolder)),
-							rootAnd(driveItem(idx(folder, "sib"), namex(folder, "sib"), parent(0), rootID, isFolder)),
 							rootAnd(
 								driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
-								driveItem(idx(folder, "chld"), namex(folder, "chld"), parent(0), id(folder), isFolder))),
+								driveItem(id(file), name(file), parent(0, name(folder)), id(folder), isFile)),
+							rootAnd(
+								driveItem(idx(folder, "sib"), namex(folder, "sib"), parent(0), rootID, isFolder),
+								driveItem(idx(file, "sib"), namex(file, "sib"), parent(0, namex(folder, "sib")), idx(folder, "sib"), isFile)),
+							rootAnd(
+								driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
+								driveItem(idx(folder, "chld"), namex(folder, "chld"), parent(0), id(folder), isFolder),
+								driveItem(idx(file, "chld"), namex(file, "chld"), parent(0, namex(folder, "chld")), idx(folder, "chld"), isFile))),
 						DeltaUpdate: pagers.DeltaUpdate{URL: id(delta)},
 					},
 				},
@@ -755,6 +823,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 				counts: countTD.Expected{
 					count.TotalDeleteFoldersProcessed: 0,
 					count.TotalFoldersProcessed:       1,
+					count.TotalFilesProcessed:         0,
 					count.PagesEnumerated:             1,
 				},
 				err:      require.NoError,
@@ -763,20 +832,26 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 					rootID,
 				},
 				treeContainsTombstoneIDs:      []string{},
+				treeContainsFileIDsWithParent: map[string]string{},
 			},
 		},
 		{
-			name: "hit limit during enumeration",
+			name: "hit folder limit during enumeration",
 			tree: newFolderyMcFolderFace(nil),
 			enumerator: mock.EnumerateItemsDeltaByDrive{
 				DrivePagers: map[string]*mock.DriveItemsDeltaPager{
 					id(drive): {
 						Pages: pagesOf(
-							rootAnd(driveItem(id(folder), name(folder), parent(0), rootID, isFolder)),
-							rootAnd(driveItem(idx(folder, "sib"), namex(folder, "sib"), parent(0), rootID, isFolder)),
 							rootAnd(
 								driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
-								driveItem(idx(folder, "chld"), namex(folder, "chld"), parent(0), id(folder), isFolder))),
+								driveItem(id(file), name(file), parent(0, name(folder)), id(folder), isFile)),
+							rootAnd(
+								driveItem(idx(folder, "sib"), namex(folder, "sib"), parent(0), rootID, isFolder),
+								driveItem(idx(file, "sib"), namex(file, "sib"), parent(0, namex(folder, "sib")), idx(folder, "sib"), isFile)),
+							rootAnd(
+								driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
+								driveItem(idx(folder, "chld"), namex(folder, "chld"), parent(0), id(folder), isFolder),
+								driveItem(idx(file, "chld"), namex(file, "chld"), parent(0, namex(folder, "chld")), idx(folder, "chld"), isFile))),
 						DeltaUpdate: pagers.DeltaUpdate{URL: id(delta)},
 					},
 				},
@@ -786,6 +861,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 				counts: countTD.Expected{
 					count.TotalDeleteFoldersProcessed: 0,
 					count.TotalFoldersProcessed:       1,
+					count.TotalFilesProcessed:         0,
 					count.PagesEnumerated:             1,
 				},
 				err:      require.NoError,
@@ -794,6 +870,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 					rootID,
 				},
 				treeContainsTombstoneIDs:      []string{},
+				treeContainsFileIDsWithParent: map[string]string{},
 			},
 		},
 	}
@@ -824,20 +901,29 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_PopulateTree() {
 				counter,
 				fault.New(true))
 			test.expect.err(t, err, clues.ToCore(err))
-			assert.Equal(t, test.expect.treeSize, test.tree.CountFolders(), "count folders in tree")
+			assert.Equal(t, test.expect.treeSize, test.tree.countFolders(), "count folders in tree")
 			test.expect.counts.Compare(t, counter)
 
 			for _, id := range test.expect.treeContainsFolderIDs {
-				require.NotNil(t, test.tree.folderIDToNode[id], "node exists")
+				assert.NotNil(t, test.tree.folderIDToNode[id], "node exists")
 			}
 
 			for _, id := range test.expect.treeContainsTombstoneIDs {
-				require.NotNil(t, test.tree.tombstones[id], "tombstone exists")
+				assert.NotNil(t, test.tree.tombstones[id], "tombstone exists")
+			}
+
+			for iID, pID := range test.expect.treeContainsFileIDsWithParent {
+				assert.Contains(t, test.tree.fileIDToParentID, iID)
+				assert.Equal(t, pID, test.tree.fileIDToParentID[iID])
 			}
 		})
 	}
 }
 
+// ---------------------------------------------------------------------------
+// folder tests
+// ---------------------------------------------------------------------------
+
 // This test focuses on folder assertions when enumerating a page of items.
 // File-specific assertions are focused in the _folders test variant.
 func (suite *CollectionsTreeUnitSuite) TestCollections_EnumeratePageOfItems_folders() {
@@ -913,7 +999,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_EnumeratePageOfItems_fold
 			page: rootAnd(
 				driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
 				driveItem(idx(folder, "sib"), namex(folder, "sib"), parent(0), rootID, isFolder),
-				driveItem(idx(folder, "chld"), namex(folder, "chld"), parent(0), id(folder), isFolder)),
+				driveItem(idx(folder, "chld"), namex(folder, "chld"), parent(0, name(folder)), id(folder), isFolder)),
 			limiter: newPagerLimiter(control.DefaultOptions()),
 			expect: expected{
 				counts: countTD.Expected{
@@ -936,13 +1022,13 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_EnumeratePageOfItems_fold
 			page: rootAnd(
 				driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
 				driveItem(idx(folder, "sib"), namex(folder, "sib"), parent(0), rootID, isFolder),
-				driveItem(idx(folder, "chld"), namex(folder, "chld"), parent(0), id(folder), isFolder)),
+				driveItem(idx(folder, "chld"), namex(folder, "chld"), parent(0, name(folder)), id(folder), isFolder)),
 			limiter: newPagerLimiter(minimumLimitOpts()),
 			expect: expected{
 				counts: countTD.Expected{
 					count.TotalFoldersProcessed: 1,
 				},
-				err:      require.NoError,
+				err:      require.Error,
 				treeSize: 1,
 				treeContainsFolderIDs: []string{
 					rootID,
@@ -975,7 +1061,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_EnumeratePageOfItems_fold
 			tree: treeWithFolders(),
 			page: rootAnd(
 				driveItem(idx(folder, "parent"), namex(folder, "parent"), parent(0), rootID, isFolder),
-				driveItem(id(folder), namex(folder, "moved"), parent(0), idx(folder, "parent"), isFolder),
+				driveItem(id(folder), namex(folder, "moved"), parent(0, namex(folder, "parent")), idx(folder, "parent"), isFolder),
 				delItem(id(folder), parent(0), idx(folder, "parent"), isFolder)),
 			limiter: newPagerLimiter(control.DefaultOptions()),
 			expect: expected{
@@ -1036,7 +1122,7 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_EnumeratePageOfItems_fold
 				counter,
 				fault.New(true))
 			test.expect.err(t, err, clues.ToCore(err))
-			assert.Equal(t, test.expect.treeSize, test.tree.CountFolders(), "count folders in tree")
+			assert.Equal(t, test.expect.treeSize, test.tree.countFolders(), "count folders in tree")
 			test.expect.counts.Compare(t, counter)
 
 			for _, id := range test.expect.treeContainsFolderIDs {
@@ -1181,8 +1267,8 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_AddFolderToTree() {
 			test.expect.err(t, err, clues.ToCore(err))
 			test.expect.skipped(t, skipped)
 			test.expect.counts.Compare(t, counter)
-			assert.Equal(t, test.expect.treeSize, test.tree.CountFolders(), "folders in tree")
+			assert.Equal(t, test.expect.treeSize, test.tree.countFolders(), "folders in tree")
-			test.expect.treeContainsFolder(t, test.tree.ContainsFolder(ptr.Val(test.folder.GetId())))
+			test.expect.treeContainsFolder(t, test.tree.containsFolder(ptr.Val(test.folder.GetId())))
 		})
 	}
 }
@@ -1238,21 +1324,444 @@ func (suite *CollectionsTreeUnitSuite) TestCollections_MakeFolderCollectionPath(
 	}
 }
 
-func (suite *CollectionsTreeUnitSuite) TestCollections_AddFileToTree() {
+// ---------------------------------------------------------------------------
+// file tests
+// ---------------------------------------------------------------------------
+
+// this test focuses on folder assertions when enumerating a page of items
+// file-specific assertions are in the next test
+func (suite *CollectionsTreeUnitSuite) TestCollections_EnumeratePageOfItems_files() {
+	drv := models.NewDrive()
+	drv.SetId(ptr.To(id(drive)))
+	drv.SetName(ptr.To(name(drive)))
+
+	type expected struct {
+		counts                        countTD.Expected
+		err                           require.ErrorAssertionFunc
+		treeContainsFileIDsWithParent map[string]string
+		statsNumAddedFiles            int
+		statsNumBytes                 int64
+	}
+
+	table := []struct {
+		name   string
+		tree   *folderyMcFolderFace
+		page   []models.DriveItemable
+		expect expected
+	}{
+		{
+			name: "one file at root",
+			tree: treeWithRoot(),
+			page: rootAnd(driveItem(id(file), name(file), parent(0, name(folder)), rootID, isFile)),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 0,
+					count.TotalFoldersProcessed:     1,
+					count.TotalFilesProcessed:       1,
+				},
+				err: require.NoError,
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file): rootID,
+				},
+				statsNumAddedFiles: 1,
+				statsNumBytes:      defaultItemSize,
+			},
+		},
+		{
+			name: "one file in a folder",
+			tree: newFolderyMcFolderFace(nil),
+			page: rootAnd(
+				driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
+				driveItem(id(file), name(file), parent(0, name(folder)), id(folder), isFile)),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 0,
+					count.TotalFoldersProcessed:     2,
+					count.TotalFilesProcessed:       1,
+				},
+				err: require.NoError,
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file): id(folder),
+				},
+				statsNumAddedFiles: 1,
+				statsNumBytes:      defaultItemSize,
+			},
+		},
+		{
+			name: "many files in a hierarchy",
+			tree: treeWithRoot(),
+			page: rootAnd(
+				driveItem(id(file), name(file), parent(0), rootID, isFile),
+				driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
+				driveItem(idx(file, "chld"), namex(file, "chld"), parent(0, name(folder)), id(folder), isFile)),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 0,
+					count.TotalFoldersProcessed:     2,
+					count.TotalFilesProcessed:       2,
+				},
+				err: require.NoError,
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file):          rootID,
+					idx(file, "chld"): id(folder),
+				},
+				statsNumAddedFiles: 2,
+				statsNumBytes:      defaultItemSize * 2,
+			},
+		},
+		{
+			name: "many updates to the same file",
+			tree: treeWithRoot(),
+			page: rootAnd(
+				driveItem(id(file), name(file), parent(0), rootID, isFile),
+				driveItem(id(file), namex(file, 1), parent(0), rootID, isFile),
+				driveItem(id(file), namex(file, 2), parent(0), rootID, isFile)),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 0,
+					count.TotalFoldersProcessed:     1,
+					count.TotalFilesProcessed:       3,
+				},
+				err: require.NoError,
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file): rootID,
+				},
+				statsNumAddedFiles: 1,
+				statsNumBytes:      defaultItemSize,
+			},
+		},
+		{
+			name: "delete an existing file",
+			tree: treeWithFileAtRoot(),
+			page: rootAnd(delItem(id(file), parent(0), rootID, isFile)),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 1,
+					count.TotalFoldersProcessed:     1,
+					count.TotalFilesProcessed:       0,
+				},
+				err:                           require.NoError,
+				treeContainsFileIDsWithParent: map[string]string{},
+				statsNumAddedFiles:            -1,
+				statsNumBytes:                 0,
+			},
+		},
+		{
+			name: "delete the same file twice",
+			tree: treeWithFileAtRoot(),
+			page: rootAnd(
+				delItem(id(file), parent(0), rootID, isFile),
+				delItem(id(file), parent(0), rootID, isFile)),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 2,
+					count.TotalFoldersProcessed:     1,
+					count.TotalFilesProcessed:       0,
+				},
+				err:                           require.NoError,
+				treeContainsFileIDsWithParent: map[string]string{},
+				statsNumAddedFiles:            -1,
+				statsNumBytes:                 0,
+			},
+		},
+		{
+			name: "create->delete",
+			tree: treeWithRoot(),
+			page: rootAnd(
+				driveItem(id(file), name(file), parent(0), rootID, isFile),
+				delItem(id(file), parent(0), rootID, isFile)),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 1,
+					count.TotalFoldersProcessed:     1,
+					count.TotalFilesProcessed:       1,
+				},
+				err:                           require.NoError,
+				treeContainsFileIDsWithParent: map[string]string{},
+				statsNumAddedFiles:            0,
+				statsNumBytes:                 defaultItemSize,
+			},
+		},
+		{
+			name: "move->delete",
+			tree: treeWithFileAtRoot(),
+			page: rootAnd(
+				driveItem(id(folder), name(folder), parent(0), rootID, isFolder),
+				driveItem(id(file), name(file), parent(0, name(folder)), id(folder), isFile),
+				delItem(id(file), parent(0, name(folder)), id(folder), isFile)),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 1,
+					count.TotalFoldersProcessed:     2,
+					count.TotalFilesProcessed:       1,
+				},
+				err:                           require.NoError,
+				treeContainsFileIDsWithParent: map[string]string{},
+				statsNumAddedFiles:            -1,
+				statsNumBytes:                 0,
+			},
+		},
+		{
+			name: "delete->create an existing file",
+			tree: treeWithFileAtRoot(),
+			page: rootAnd(
+				delItem(id(file), parent(0), rootID, isFile),
+				driveItem(id(file), name(file), parent(0), rootID, isFile)),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 1,
+					count.TotalFoldersProcessed:     1,
+					count.TotalFilesProcessed:       1,
+				},
+				err: require.NoError,
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file): rootID,
+				},
+				statsNumAddedFiles: 0,
+				statsNumBytes:      defaultItemSize,
+			},
+		},
+		{
+			name: "delete->create a non-existing file",
+			tree: treeWithRoot(),
+			page: rootAnd(
+				delItem(id(file), parent(0), rootID, isFile),
+				driveItem(id(file), name(file), parent(0), rootID, isFile)),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 1,
+					count.TotalFoldersProcessed:     1,
+					count.TotalFilesProcessed:       1,
+				},
+				err: require.NoError,
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file): rootID,
+				},
+				statsNumAddedFiles: 1,
+				statsNumBytes:      defaultItemSize,
+			},
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.name, func() {
 			t := suite.T()
 
 			ctx, flush := tester.NewContext(t)
 			defer flush()
 
 			c := collWithMBH(mock.DefaultOneDriveBH(user))
+			counter := count.New()
+			stats := &driveEnumerationStats{}
+
+			err := c.enumeratePageOfItems(
+				ctx,
+				test.tree,
+				newPagerLimiter(control.DefaultOptions()),
+				stats,
+				drv,
+				test.page,
+				counter,
+				fault.New(true))
+			test.expect.err(t, err, clues.ToCore(err))
+			assert.Equal(t, test.expect.statsNumAddedFiles, stats.numAddedFiles, "num added files")
+			assert.Equal(t, test.expect.statsNumBytes, stats.numBytes, "num bytes")
+			assert.Equal(t, test.expect.treeContainsFileIDsWithParent, test.tree.fileIDToParentID)
+			test.expect.counts.Compare(t, counter)
+		})
+	}
+}
+
+func (suite *CollectionsTreeUnitSuite) TestCollections_AddFileToTree() {
+	drv := models.NewDrive()
+	drv.SetId(ptr.To(id(drive)))
+	drv.SetName(ptr.To(name(drive)))
+
+	type expected struct {
+		counts                        countTD.Expected
+		err                           require.ErrorAssertionFunc
+		skipped                       assert.ValueAssertionFunc
+		treeFileCount                 int
+		treeContainsFileIDsWithParent map[string]string
+		statsNumAddedFiles            int
+		statsNumBytes                 int64
+	}
+
+	table := []struct {
+		name    string
+		tree    *folderyMcFolderFace
+		file    models.DriveItemable
+		limiter *pagerLimiter
+		expect  expected
+	}{
+		{
+			name:    "add new file",
+			tree:    treeWithRoot(),
+			file:    driveItem(id(file), name(file), parent(0), rootID, isFile),
+			limiter: newPagerLimiter(control.DefaultOptions()),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalFilesProcessed: 1,
+				},
+				err:           require.NoError,
+				skipped:       assert.Nil,
+				treeFileCount: 1,
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file): rootID,
+				},
+				statsNumAddedFiles: 1,
+				statsNumBytes:      defaultItemSize,
+			},
+		},
+		{
+			name:    "duplicate file",
+			tree:    treeWithFileAtRoot(),
+			file:    driveItem(id(file), name(file), parent(0), rootID, isFile),
+			limiter: newPagerLimiter(control.DefaultOptions()),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalFilesProcessed: 1,
+				},
+				err:           require.NoError,
+				skipped:       assert.Nil,
+				treeFileCount: 1,
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file): rootID,
+				},
+				statsNumAddedFiles: 0,
+				statsNumBytes:      0,
+			},
+		},
+		{
+			name:    "error file seen before parent",
+			tree:    treeWithRoot(),
+			file:    driveItem(id(file), name(file), parent(0, name(folder)), id(folder), isFile),
+			limiter: newPagerLimiter(control.DefaultOptions()),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalFilesProcessed: 1,
+				},
+				err:                           require.Error,
+				skipped:                       assert.Nil,
+				treeFileCount:                 0,
+				treeContainsFileIDsWithParent: map[string]string{},
+				statsNumAddedFiles:            0,
+				statsNumBytes:                 0,
+			},
+		},
+		{
+			name:    "malware file",
+			tree:    treeWithRoot(),
+			file:    malwareItem(id(file), name(file), parent(0, name(folder)), rootID, isFile),
+			limiter: newPagerLimiter(control.DefaultOptions()),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalMalwareProcessed: 1,
+				},
+				err:                           require.NoError,
+				skipped:                       assert.NotNil,
+				treeFileCount:                 0,
+				treeContainsFileIDsWithParent: map[string]string{},
+				statsNumAddedFiles:            0,
+				statsNumBytes:                 0,
+			},
+		},
+		{
+			name:    "delete non-existing file",
+			tree:    treeWithRoot(),
+			file:    delItem(id(file), parent(0, name(folder)), id(folder), isFile),
+			limiter: newPagerLimiter(control.DefaultOptions()),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 1,
+				},
+				err:                           require.NoError,
+				skipped:                       assert.Nil,
+				treeFileCount:                 0,
+				treeContainsFileIDsWithParent: map[string]string{},
+				statsNumAddedFiles:            0,
+				statsNumBytes:                 0,
+			},
+		},
+		{
+			name:    "delete existing file",
+			tree:    treeWithFileAtRoot(),
+			file:    delItem(id(file), parent(0), rootID, isFile),
+			limiter: newPagerLimiter(control.DefaultOptions()),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalDeleteFilesProcessed: 1,
+				},
+				err:                           require.NoError,
+				skipped:                       assert.Nil,
+				treeFileCount:                 0,
+				treeContainsFileIDsWithParent: map[string]string{},
+				statsNumAddedFiles:            -1,
+				statsNumBytes:                 0,
+			},
+		},
+		{
+			name:    "already at container file limit",
+			tree:    treeWithFileAtRoot(),
+			file:    driveItem(id(file), name(file), parent(0), rootID, isFile),
+			limiter: newPagerLimiter(minimumLimitOpts()),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalFilesProcessed: 1,
+				},
+				err:           require.NoError,
+				skipped:       assert.Nil,
+				treeFileCount: 1,
+				treeContainsFileIDsWithParent: map[string]string{
+					id(file): rootID,
+				},
+				statsNumAddedFiles: 0,
+				statsNumBytes:      0,
+			},
+		},
+		{
+			name:    "goes over total byte limit",
+			tree:    treeWithRoot(),
+			file:    driveItem(id(file), name(file), parent(0), rootID, isFile),
+			limiter: newPagerLimiter(minimumLimitOpts()),
+			expect: expected{
+				counts: countTD.Expected{
+					count.TotalFilesProcessed: 1,
+				},
+				err:                           require.NoError,
+				skipped:                       assert.Nil,
+				treeFileCount:                 0,
+				treeContainsFileIDsWithParent: map[string]string{},
+				statsNumAddedFiles:            0,
+				statsNumBytes:                 0,
+			},
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			t := suite.T()
+
+			ctx, flush := tester.NewContext(t)
+			defer flush()
+
+			c := collWithMBH(mock.DefaultOneDriveBH(user))
+			counter := count.New()
+			stats := &driveEnumerationStats{}
 
 			skipped, err := c.addFileToTree(
 				ctx,
-		nil,
+				test.tree,
-		nil,
+				drv,
-		nil,
+				test.file,
-		nil,
+				test.limiter,
-		nil)
+				stats,
-	require.ErrorContains(t, err, "not yet implemented", clues.ToCore(err))
+				counter)
-	require.Nil(t, skipped)
+			test.expect.err(t, err, clues.ToCore(err))
+			test.expect.skipped(t, skipped)
+			assert.Len(t, test.tree.fileIDToParentID, test.expect.treeFileCount, "count of files in tree")
+			assert.Equal(t, test.expect.treeContainsFileIDsWithParent, test.tree.fileIDToParentID)
+			test.expect.counts.Compare(t, counter)
+			assert.Equal(t, test.expect.statsNumAddedFiles, stats.numAddedFiles)
+			assert.Equal(t, test.expect.statsNumBytes, stats.numBytes)
+		})
+	}
 }

src/internal/m365/collection/drive/delta_tree.go

@@ -33,9 +33,11 @@ type folderyMcFolderFace struct {
 	// and forth between live and tombstoned states.
 	tombstones map[string]*nodeyMcNodeFace
 
-	// it's just a sensible place to store the data, since we're
+	// will also be used to construct the excluded file id map
-	// already pushing file additions through the api.
+	// during the post-processing step
-	excludeFileIDs map[string]struct{}
+	fileIDToParentID map[string]string
+	// required for populating the excluded file id map
+	deletedFileIDs map[string]struct{}
 
 	// true if Reset() was called
 	hadReset bool
@@ -48,20 +50,21 @@ func newFolderyMcFolderFace(
 		prefix:           prefix,
 		folderIDToNode:   map[string]*nodeyMcNodeFace{},
 		tombstones:       map[string]*nodeyMcNodeFace{},
-		excludeFileIDs: map[string]struct{}{},
+		fileIDToParentID: map[string]string{},
+		deletedFileIDs:   map[string]struct{}{},
 	}
 }
 
-// Reset erases all data contained in the tree.  This is intended for
+// reset erases all data contained in the tree.  This is intended for
 // tracking a delta enumeration reset, not for tree re-use, and will
 // cause the tree to flag itself as dirty in order to appropriately
 // post-process the data.
-func (face *folderyMcFolderFace) Reset() {
+func (face *folderyMcFolderFace) reset() {
 	face.hadReset = true
 	face.root = nil
 	face.folderIDToNode = map[string]*nodeyMcNodeFace{}
 	face.tombstones = map[string]*nodeyMcNodeFace{}
-	face.excludeFileIDs = map[string]struct{}{}
+	face.fileIDToParentID = map[string]string{}
 }
 
 type nodeyMcNodeFace struct {
@@ -75,10 +78,10 @@ type nodeyMcNodeFace struct {
 	name string
 	// only contains the folders starting at and including '/root:'
 	prev path.Elements
-	// map folderID -> node
+	// folderID -> node
 	children map[string]*nodeyMcNodeFace
-	// items are keyed by item ID
+	// file item ID -> last modified time
-	items map[string]time.Time
+	files map[string]time.Time
 	// for special handling protocols around packages
 	isPackage bool
 }
@@ -93,7 +96,7 @@ func newNodeyMcNodeFace(
 		id:        id,
 		name:      name,
 		children:  map[string]*nodeyMcNodeFace{},
-		items:     map[string]time.Time{},
+		files:     map[string]time.Time{},
 		isPackage: isPackage,
 	}
 }
@@ -102,9 +105,9 @@ func newNodeyMcNodeFace(
 // folder handling
 // ---------------------------------------------------------------------------
 
-// ContainsFolder returns true if the given folder id is present as either
+// containsFolder returns true if the given folder id is present as either
 // a live node or a tombstone.
-func (face *folderyMcFolderFace) ContainsFolder(id string) bool {
+func (face *folderyMcFolderFace) containsFolder(id string) bool {
 	_, stillKicking := face.folderIDToNode[id]
 	_, alreadyBuried := face.tombstones[id]
 
@@ -113,14 +116,22 @@ func (face *folderyMcFolderFace) ContainsFolder(id string) bool {
 
 // CountNodes returns a count that is the sum of live folders and
 // tombstones recorded in the tree.
-func (face *folderyMcFolderFace) CountFolders() int {
+func (face *folderyMcFolderFace) countFolders() int {
 	return len(face.tombstones) + len(face.folderIDToNode)
 }
 
-// SetFolder adds a node with the following details to the tree.
+func (face *folderyMcFolderFace) getNode(id string) *nodeyMcNodeFace {
+	if zombey, alreadyBuried := face.tombstones[id]; alreadyBuried {
+		return zombey
+	}
+
+	return face.folderIDToNode[id]
+}
+
+// setFolder adds a node with the following details to the tree.
 // If the node already exists with the given ID, the name and parent
 // values are updated to match (isPackage is assumed not to change).
-func (face *folderyMcFolderFace) SetFolder(
+func (face *folderyMcFolderFace) setFolder(
 	ctx context.Context,
 	parentID, id, name string,
 	isPackage bool,
@@ -217,7 +228,7 @@ func (face *folderyMcFolderFace) SetFolder(
 	return nil
 }
 
-func (face *folderyMcFolderFace) SetTombstone(
+func (face *folderyMcFolderFace) setTombstone(
 	ctx context.Context,
 	id string,
 ) error {
@@ -252,3 +263,61 @@ func (face *folderyMcFolderFace) SetTombstone(
 
 	return nil
 }
+
+// addFile places the file in the correct parent node.  If the
+// file was already added to the tree and is getting relocated,
+// this func will update and/or clean up all the old references.
+func (face *folderyMcFolderFace) addFile(
+	parentID, id string,
+	lastModifed time.Time,
+) error {
+	if len(parentID) == 0 {
+		return clues.New("item added without parent folder ID")
+	}
+
+	if len(id) == 0 {
+		return clues.New("item added without ID")
+	}
+
+	// in case of file movement, clean up any references
+	// to the file in the old parent
+	oldParentID, ok := face.fileIDToParentID[id]
+	if ok && oldParentID != parentID {
+		if nodey, ok := face.folderIDToNode[oldParentID]; ok {
+			delete(nodey.files, id)
+		}
+
+		if zombey, ok := face.tombstones[oldParentID]; ok {
+			delete(zombey.files, id)
+		}
+	}
+
+	parent, ok := face.folderIDToNode[parentID]
+	if !ok {
+		return clues.New("item added before parent")
+	}
+
+	face.fileIDToParentID[id] = parentID
+	parent.files[id] = lastModifed
+
+	delete(face.deletedFileIDs, id)
+
+	return nil
+}
+
+func (face *folderyMcFolderFace) deleteFile(id string) {
+	parentID, ok := face.fileIDToParentID[id]
+	if ok {
+		if nodey, ok := face.folderIDToNode[parentID]; ok {
+			delete(nodey.files, id)
+		}
+
+		if zombey, ok := face.tombstones[parentID]; ok {
+			delete(zombey.files, id)
+		}
+	}
+
+	delete(face.fileIDToParentID, id)
+
+	face.deletedFileIDs[id] = struct{}{}
+}

src/internal/m365/collection/drive/delta_tree_test.go

@@ -2,6 +2,7 @@ package drive
 
 import (
 	"testing"
+	"time"
 
 	"github.com/alcionai/clues"
 	"github.com/stretchr/testify/assert"
@@ -47,6 +48,30 @@ func treeWithFolders() *folderyMcFolderFace {
 	return tree
 }
 
+func treeWithFileAtRoot() *folderyMcFolderFace {
+	tree := treeWithFolders()
+	tree.root.files[id(file)] = time.Now()
+	tree.fileIDToParentID[id(file)] = rootID
+
+	return tree
+}
+
+func treeWithFileInFolder() *folderyMcFolderFace {
+	tree := treeWithFileAtRoot()
+	tree.folderIDToNode[id(folder)].files[id(file)] = time.Now()
+	tree.fileIDToParentID[id(file)] = id(folder)
+
+	return tree
+}
+
+func treeWithFileInTombstone() *folderyMcFolderFace {
+	tree := treeWithTombstone()
+	tree.tombstones[id(folder)].files[id(file)] = time.Now()
+	tree.fileIDToParentID[id(file)] = id(folder)
+
+	return tree
+}
+
 // ---------------------------------------------------------------------------
 // tests
 // ---------------------------------------------------------------------------
@@ -72,7 +97,7 @@ func (suite *DeltaTreeUnitSuite) TestNewFolderyMcFolderFace() {
 	assert.Nil(t, folderFace.root)
 	assert.NotNil(t, folderFace.folderIDToNode)
 	assert.NotNil(t, folderFace.tombstones)
-	assert.NotNil(t, folderFace.excludeFileIDs)
+	assert.NotNil(t, folderFace.fileIDToParentID)
 }
 
 func (suite *DeltaTreeUnitSuite) TestNewNodeyMcNodeFace() {
@@ -88,9 +113,13 @@ func (suite *DeltaTreeUnitSuite) TestNewNodeyMcNodeFace() {
 	assert.NotEqual(t, loc, nodeFace.prev)
 	assert.True(t, nodeFace.isPackage)
 	assert.NotNil(t, nodeFace.children)
-	assert.NotNil(t, nodeFace.items)
+	assert.NotNil(t, nodeFace.files)
 }
 
+// ---------------------------------------------------------------------------
+// folder tests
+// ---------------------------------------------------------------------------
+
 // note that this test is focused on the SetFolder function,
 // and intentionally does not verify the resulting node tree
 func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_SetFolder() {
@@ -105,9 +134,7 @@ func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_SetFolder() {
 	}{
 		{
 			tname:     "add root",
-			tree: &folderyMcFolderFace{
+			tree:      newFolderyMcFolderFace(nil),
-				folderIDToNode: map[string]*nodeyMcNodeFace{},
-			},
 			id:        rootID,
 			name:      rootName,
 			isPackage: true,
@@ -196,7 +223,7 @@ func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_SetFolder() {
 			ctx, flush := tester.NewContext(t)
 			defer flush()
 
-			err := test.tree.SetFolder(
+			err := test.tree.setFolder(
 				ctx,
 				test.parentID,
 				test.id,
@@ -269,7 +296,7 @@ func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_AddTombstone() {
 			ctx, flush := tester.NewContext(t)
 			defer flush()
 
-			err := test.tree.SetTombstone(ctx, test.id)
+			err := test.tree.setTombstone(ctx, test.id)
 			test.expectErr(t, err, clues.ToCore(err))
 
 			if err != nil {
@@ -404,7 +431,7 @@ func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_SetFolder_correctTree()
 		parentID, fid, fname string,
 		isPackage bool,
 	) {
-		err := tree.SetFolder(ctx, parentID, fid, fname, isPackage)
+		err := tree.setFolder(ctx, parentID, fid, fname, isPackage)
 		require.NoError(t, err, clues.ToCore(err))
 	}
 
@@ -490,7 +517,7 @@ func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_SetFolder_correctTombst
 		parentID, fid, fname string,
 		isPackage bool,
 	) {
-		err := tree.SetFolder(ctx, parentID, fid, fname, isPackage)
+		err := tree.setFolder(ctx, parentID, fid, fname, isPackage)
 		require.NoError(t, err, clues.ToCore(err))
 	}
 
@@ -498,7 +525,7 @@ func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_SetFolder_correctTombst
 		tid string,
 		loc path.Elements,
 	) {
-		err := tree.SetTombstone(ctx, tid)
+		err := tree.setTombstone(ctx, tid)
 		require.NoError(t, err, clues.ToCore(err))
 	}
 
@@ -651,3 +678,188 @@ func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_SetFolder_correctTombst
 
 	entomb().compare(t, tree.tombstones)
 }
+
+// ---------------------------------------------------------------------------
+// file tests
+// ---------------------------------------------------------------------------
+
+func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_AddFile() {
+	table := []struct {
+		tname       string
+		tree        *folderyMcFolderFace
+		oldParentID string
+		parentID    string
+		expectErr   assert.ErrorAssertionFunc
+		expectFiles map[string]string
+	}{
+		{
+			tname:       "add file to root",
+			tree:        treeWithRoot(),
+			oldParentID: "",
+			parentID:    rootID,
+			expectErr:   assert.NoError,
+			expectFiles: map[string]string{id(file): rootID},
+		},
+		{
+			tname:       "add file to folder",
+			tree:        treeWithFolders(),
+			oldParentID: "",
+			parentID:    id(folder),
+			expectErr:   assert.NoError,
+			expectFiles: map[string]string{id(file): id(folder)},
+		},
+		{
+			tname:       "re-add file at the same location",
+			tree:        treeWithFileAtRoot(),
+			oldParentID: rootID,
+			parentID:    rootID,
+			expectErr:   assert.NoError,
+			expectFiles: map[string]string{id(file): rootID},
+		},
+		{
+			tname:       "move file from folder to root",
+			tree:        treeWithFileInFolder(),
+			oldParentID: id(folder),
+			parentID:    rootID,
+			expectErr:   assert.NoError,
+			expectFiles: map[string]string{id(file): rootID},
+		},
+		{
+			tname:       "move file from tombstone to root",
+			tree:        treeWithFileInTombstone(),
+			oldParentID: id(folder),
+			parentID:    rootID,
+			expectErr:   assert.NoError,
+			expectFiles: map[string]string{id(file): rootID},
+		},
+		{
+			tname:       "error adding file to tombstone",
+			tree:        treeWithTombstone(),
+			oldParentID: "",
+			parentID:    id(folder),
+			expectErr:   assert.Error,
+			expectFiles: map[string]string{},
+		},
+		{
+			tname:       "error adding file before parent",
+			tree:        treeWithTombstone(),
+			oldParentID: "",
+			parentID:    idx(folder, 1),
+			expectErr:   assert.Error,
+			expectFiles: map[string]string{},
+		},
+		{
+			tname:       "error adding file without parent id",
+			tree:        treeWithTombstone(),
+			oldParentID: "",
+			parentID:    "",
+			expectErr:   assert.Error,
+			expectFiles: map[string]string{},
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.tname, func() {
+			t := suite.T()
+
+			err := test.tree.addFile(
+				test.parentID,
+				id(file),
+				time.Now())
+			test.expectErr(t, err, clues.ToCore(err))
+			assert.Equal(t, test.expectFiles, test.tree.fileIDToParentID)
+
+			if err != nil {
+				return
+			}
+
+			parent := test.tree.getNode(test.parentID)
+
+			require.NotNil(t, parent)
+			assert.Contains(t, parent.files, id(file))
+
+			if len(test.oldParentID) > 0 && test.oldParentID != test.parentID {
+				old, ok := test.tree.folderIDToNode[test.oldParentID]
+				if !ok {
+					old = test.tree.tombstones[test.oldParentID]
+				}
+
+				require.NotNil(t, old)
+				assert.NotContains(t, old.files, id(file))
+			}
+		})
+	}
+}
+
+func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_DeleteFile() {
+	table := []struct {
+		tname    string
+		tree     *folderyMcFolderFace
+		parentID string
+	}{
+		{
+			tname:    "delete unseen file",
+			tree:     treeWithRoot(),
+			parentID: rootID,
+		},
+		{
+			tname:    "delete file from root",
+			tree:     treeWithFolders(),
+			parentID: rootID,
+		},
+		{
+			tname:    "delete file from folder",
+			tree:     treeWithFileInFolder(),
+			parentID: id(folder),
+		},
+		{
+			tname:    "delete file from tombstone",
+			tree:     treeWithFileInTombstone(),
+			parentID: id(folder),
+		},
+	}
+	for _, test := range table {
+		suite.Run(test.tname, func() {
+			t := suite.T()
+
+			test.tree.deleteFile(id(file))
+
+			parent := test.tree.getNode(test.parentID)
+
+			require.NotNil(t, parent)
+			assert.NotContains(t, parent.files, id(file))
+			assert.NotContains(t, test.tree.fileIDToParentID, id(file))
+			assert.Contains(t, test.tree.deletedFileIDs, id(file))
+		})
+	}
+}
+
+func (suite *DeltaTreeUnitSuite) TestFolderyMcFolderFace_addAndDeleteFile() {
+	t := suite.T()
+	tree := treeWithRoot()
+	fID := id(file)
+
+	require.Len(t, tree.fileIDToParentID, 0)
+	require.Len(t, tree.deletedFileIDs, 0)
+
+	tree.deleteFile(fID)
+
+	assert.Len(t, tree.fileIDToParentID, 0)
+	assert.NotContains(t, tree.fileIDToParentID, fID)
+	assert.Len(t, tree.deletedFileIDs, 1)
+	assert.Contains(t, tree.deletedFileIDs, fID)
+
+	err := tree.addFile(rootID, fID, time.Now())
+	require.NoError(t, err, clues.ToCore(err))
+
+	assert.Len(t, tree.fileIDToParentID, 1)
+	assert.Contains(t, tree.fileIDToParentID, fID)
+	assert.Len(t, tree.deletedFileIDs, 0)
+	assert.NotContains(t, tree.deletedFileIDs, fID)
+
+	tree.deleteFile(fID)
+
+	assert.Len(t, tree.fileIDToParentID, 0)
+	assert.NotContains(t, tree.fileIDToParentID, fID)
+	assert.Len(t, tree.deletedFileIDs, 1)
+	assert.Contains(t, tree.deletedFileIDs, fID)
+}

src/internal/m365/collection/drive/helper_test.go

@@ -14,6 +14,8 @@ import (
 	"github.com/alcionai/corso/src/pkg/services/m365/api"
 )
 
+const defaultItemSize int64 = 42
+
 // TODO(ashmrtn): Merge with similar structs in graph and exchange packages.
 type oneDriveService struct {
 	credentials account.M365Config

src/internal/m365/collection/drive/limiter.go

@@ -1,10 +1,16 @@
 package drive
 
-import "github.com/alcionai/corso/src/pkg/control"
+import (
+	"github.com/alcionai/clues"
+
+	"github.com/alcionai/corso/src/pkg/control"
+)
 
 // used to mark an unused variable while we transition handling.
 const ignoreMe = -1
 
+var errHitLimit = clues.New("hit limiter limits")
+
 type driveEnumerationStats struct {
 	numPages      int
 	numAddedFiles int
@@ -56,6 +62,10 @@ func (l pagerLimiter) sizeLimit() int64 {
 	return l.limits.MaxBytes
 }
 
+func (l pagerLimiter) aboveSizeLimit(i int64) bool {
+	return l.limits.Enabled && (i >= l.limits.MaxBytes)
+}
+
 // atItemLimit returns true if the limiter is enabled and has reached the limit
 // for individual items added to collections for this backup.
 func (l pagerLimiter) atItemLimit(stats *driveEnumerationStats) bool {

src/pkg/count/keys.go

@@ -78,7 +78,9 @@ const (
 // and use a separate Key (Folders) for the end count of folders produced
 // at the end of the delta enumeration.
 const (
+	TotalDeleteFilesProcessed   Key = "total-delete-files-processed"
 	TotalDeleteFoldersProcessed Key = "total-delete-folders-processed"
+	TotalFilesProcessed         Key = "total-files-processed"
 	TotalFoldersProcessed       Key = "total-folders-processed"
 	TotalMalwareProcessed       Key = "total-malware-processed"
 	TotalPackagesProcessed      Key = "total-packages-processed"