Fetch mod time when getting added and removed items (#4266)

Also return mod time when available if
getting the set of added and removed
items. This will be leveraged in later
PRs to implement kopia assisted
incrementals for exchange

Does not change any logic in
collections right now, just adds the
fields to be returned

Also adds an additional return value
denoting if the mod times are expected
to be valid. This is required because
events delta cannot return mod time

---

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

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

#### Type of change

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

#### Issue(s)

* #2023

#### Test Plan

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

src/internal/m365/collection/exchange/backup.go

@@ -160,7 +160,7 @@ func populateCollections(
 
 		ictx = clues.Add(ictx, "previous_path", prevPath)
 
-		added, removed, newDelta, err := bh.itemEnumerator().
+		added, _, removed, newDelta, err := bh.itemEnumerator().
 			GetAddedAndRemovedItemIDs(
 				ictx,
 				qp.ProtectedResource.ID(),
@@ -201,7 +201,7 @@ func populateCollections(
 
 		collections[cID] = &edc
 
-		for _, add := range added {
+		for add := range added {
 			edc.added[add] = struct{}{}
 		}
 

src/internal/m365/collection/exchange/backup_test.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"sync"
 	"testing"
+	"time"
 
 	"github.com/alcionai/clues"
 	"github.com/stretchr/testify/assert"
@@ -72,14 +73,15 @@ func (mg mockGetter) GetAddedAndRemovedItemIDs(
 	_ bool,
 	_ bool,
 ) (
-	[]string,
+	map[string]time.Time,
+	bool,
 	[]string,
 	api.DeltaUpdate,
 	error,
 ) {
 	results, ok := mg.results[cID]
 	if !ok {
-		return nil, nil, api.DeltaUpdate{}, clues.New("mock not found for " + cID)
+		return nil, false, nil, api.DeltaUpdate{}, clues.New("mock not found for " + cID)
 	}
 
 	delta := results.newDelta
@@ -87,7 +89,12 @@ func (mg mockGetter) GetAddedAndRemovedItemIDs(
 		delta.URL = ""
 	}
 
-	return results.added, results.removed, delta, results.err
+	resAdded := make(map[string]time.Time, len(results.added))
+	for _, add := range results.added {
+		resAdded[add] = time.Time{}
+	}
+
+	return resAdded, false, results.removed, delta, results.err
 }
 
 var _ graph.ContainerResolver = &mockResolver{}

src/internal/m365/collection/exchange/handlers.go

@@ -2,6 +2,7 @@ package exchange
 
 import (
 	"context"
+	"time"
 
 	"github.com/microsoft/kiota-abstractions-go/serialization"
 
@@ -30,7 +31,7 @@ type addedAndRemovedItemGetter interface {
 		user, containerID, oldDeltaToken string,
 		immutableIDs bool,
 		canMakeDeltaQueries bool,
-	) ([]string, []string, api.DeltaUpdate, error)
+	) (map[string]time.Time, bool, []string, api.DeltaUpdate, error)
 }
 
 type itemGetterSerializer interface {

src/internal/m365/collection/groups/backup.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/alcionai/clues"
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
+	"golang.org/x/exp/maps"
 
 	"github.com/alcionai/corso/src/internal/common/pii"
 	"github.com/alcionai/corso/src/internal/common/ptr"
@@ -153,13 +154,13 @@ func populateCollections(
 		// and will return an error if a delta token is queried.
 		canMakeDeltaQueries := len(ptr.Val(c.GetEmail())) > 0
 
-		add, rem, du, err := bh.getChannelMessageIDs(ctx, cID, prevDelta, canMakeDeltaQueries)
+		add, _, rem, du, err := bh.getChannelMessageIDs(ctx, cID, prevDelta, canMakeDeltaQueries)
 		if err != nil {
 			el.AddRecoverable(ctx, clues.Stack(err))
 			continue
 		}
 
-		added := str.SliceToMap(add)
+		added := str.SliceToMap(maps.Keys(add))
 		removed := str.SliceToMap(rem)
 
 		if len(du.URL) > 0 {

src/internal/m365/collection/groups/backup_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"testing"
+	"time"
 
 	"github.com/alcionai/clues"
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
@@ -57,8 +58,14 @@ func (bh mockBackupHandler) getChannelMessageIDs(
 	_ context.Context,
 	_, _ string,
 	_ bool,
-) ([]string, []string, api.DeltaUpdate, error) {
+) (map[string]time.Time, bool, []string, api.DeltaUpdate, error) {
-	return bh.messageIDs, bh.deletedMsgIDs, api.DeltaUpdate{}, bh.messagesErr
+	idRes := make(map[string]time.Time, len(bh.messageIDs))
+
+	for _, id := range bh.messageIDs {
+		idRes[id] = time.Time{}
+	}
+
+	return idRes, true, bh.deletedMsgIDs, api.DeltaUpdate{}, bh.messagesErr
 }
 
 func (bh mockBackupHandler) includeContainer(

src/internal/m365/collection/groups/channel_handler.go

@@ -2,6 +2,7 @@ package groups
 
 import (
 	"context"
+	"time"
 
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
 
@@ -40,7 +41,7 @@ func (bh channelsBackupHandler) getChannelMessageIDs(
 	ctx context.Context,
 	channelID, prevDelta string,
 	canMakeDeltaQueries bool,
-) ([]string, []string, api.DeltaUpdate, error) {
+) (map[string]time.Time, bool, []string, api.DeltaUpdate, error) {
 	return bh.ac.GetChannelMessageIDs(ctx, bh.protectedResource, channelID, prevDelta, canMakeDeltaQueries)
 }
 

src/internal/m365/collection/groups/handlers.go

@@ -2,6 +2,7 @@ package groups
 
 import (
 	"context"
+	"time"
 
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
 
@@ -25,7 +26,7 @@ type backupHandler interface {
 		ctx context.Context,
 		channelID, prevDelta string,
 		canMakeDeltaQueries bool,
-	) ([]string, []string, api.DeltaUpdate, error)
+	) (map[string]time.Time, bool, []string, api.DeltaUpdate, error)
 
 	// includeContainer evaluates whether the channel is included
 	// in the provided scope.

src/internal/operations/test/exchange_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"testing"
+	"time"
 
 	"github.com/alcionai/clues"
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
@@ -381,12 +382,12 @@ func testExchangeContinuousBackups(suite *ExchangeBackupIntgSuite, toggles contr
 
 		var (
 			err   error
-			items []string
+			items map[string]time.Time
 		)
 
 		switch category {
 		case path.EmailCategory:
-			items, _, _, err = ac.Mail().GetAddedAndRemovedItemIDs(
+			items, _, _, _, err = ac.Mail().GetAddedAndRemovedItemIDs(
 				ctx,
 				uidn.ID(),
 				containerID,
@@ -395,7 +396,7 @@ func testExchangeContinuousBackups(suite *ExchangeBackupIntgSuite, toggles contr
 				true)
 
 		case path.EventsCategory:
-			items, _, _, err = ac.Events().GetAddedAndRemovedItemIDs(
+			items, _, _, _, err = ac.Events().GetAddedAndRemovedItemIDs(
 				ctx,
 				uidn.ID(),
 				containerID,
@@ -404,7 +405,7 @@ func testExchangeContinuousBackups(suite *ExchangeBackupIntgSuite, toggles contr
 				true)
 
 		case path.ContactsCategory:
-			items, _, _, err = ac.Contacts().GetAddedAndRemovedItemIDs(
+			items, _, _, _, err = ac.Contacts().GetAddedAndRemovedItemIDs(
 				ctx,
 				uidn.ID(),
 				containerID,
@@ -423,7 +424,7 @@ func testExchangeContinuousBackups(suite *ExchangeBackupIntgSuite, toggles contr
 		dest := dataset[category].dests[destName]
 		dest.locRef = locRef.String()
 		dest.containerID = containerID
-		dest.itemRefs = items
+		dest.itemRefs = maps.Keys(items)
 		dataset[category].dests[destName] = dest
 
 		// Add the directory and all its ancestors to the cache so we can compare

src/pkg/services/m365/api/channels_pager.go

@@ -2,6 +2,7 @@ package api
 
 import (
 	"context"
+	"time"
 
 	"github.com/alcionai/clues"
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
@@ -35,6 +36,10 @@ func (p *channelMessagePageCtrl) GetPage(
 	return resp, graph.Stack(ctx, err).OrNil()
 }
 
+func (p *channelMessagePageCtrl) ValidModTimes() bool {
+	return true
+}
+
 func (c Channels) NewChannelMessagePager(
 	teamID, channelID string,
 	selectProps ...string,
@@ -100,6 +105,10 @@ func (p *channelMessageDeltaPageCtrl) Reset(context.Context) {
 		Delta()
 }
 
+func (p *channelMessageDeltaPageCtrl) ValidModTimes() bool {
+	return true
+}
+
 func (c Channels) NewChannelMessageDeltaPager(
 	teamID, channelID, prevDelta string,
 	selectProps ...string,
@@ -141,16 +150,16 @@ func (c Channels) GetChannelMessageIDs(
 	ctx context.Context,
 	teamID, channelID, prevDeltaLink string,
 	canMakeDeltaQueries bool,
-) ([]string, []string, DeltaUpdate, error) {
+) (map[string]time.Time, bool, []string, DeltaUpdate, error) {
-	added, removed, du, err := getAddedAndRemovedItemIDs(
+	added, validModTimes, removed, du, err := getAddedAndRemovedItemIDs[models.ChatMessageable](
 		ctx,
 		c.NewChannelMessagePager(teamID, channelID),
 		c.NewChannelMessageDeltaPager(teamID, channelID, prevDeltaLink),
 		prevDeltaLink,
 		canMakeDeltaQueries,
-		addedAndRemovedByDeletedDateTime)
+		addedAndRemovedByDeletedDateTime[models.ChatMessageable])
 
-	return added, removed, du, clues.Stack(err).OrNil()
+	return added, validModTimes, removed, du, clues.Stack(err).OrNil()
 }
 
 // ---------------------------------------------------------------------------
@@ -180,6 +189,10 @@ func (p *channelMessageRepliesPageCtrl) GetOdataNextLink() *string {
 	return ptr.To("")
 }
 
+func (p *channelMessageRepliesPageCtrl) ValidModTimes() bool {
+	return true
+}
+
 func (c Channels) NewChannelMessageRepliesPager(
 	teamID, channelID, messageID string,
 	selectProps ...string,
@@ -242,6 +255,10 @@ func (p *channelPageCtrl) GetPage(
 	return resp, graph.Stack(ctx, err).OrNil()
 }
 
+func (p *channelPageCtrl) ValidModTimes() bool {
+	return false
+}
+
 func (c Channels) NewChannelPager(
 	teamID string,
 ) *channelPageCtrl {

src/pkg/services/m365/api/channels_pager_test.go

@@ -56,7 +56,7 @@ func (suite *ChannelsPagerIntgSuite) TestEnumerateChannelMessages() {
 	ctx, flush := tester.NewContext(t)
 	defer flush()
 
-	addedIDs, _, du, err := ac.GetChannelMessageIDs(
+	addedIDs, _, _, du, err := ac.GetChannelMessageIDs(
 		ctx,
 		suite.its.group.id,
 		suite.its.group.testContainerID,
@@ -67,7 +67,7 @@ func (suite *ChannelsPagerIntgSuite) TestEnumerateChannelMessages() {
 	require.NotZero(t, du.URL, "delta link")
 	require.True(t, du.Reset, "reset due to empty prev delta link")
 
-	addedIDs, deletedIDs, du, err := ac.GetChannelMessageIDs(
+	addedIDs, _, deletedIDs, du, err := ac.GetChannelMessageIDs(
 		ctx,
 		suite.its.group.id,
 		suite.its.group.testContainerID,
@@ -79,7 +79,7 @@ func (suite *ChannelsPagerIntgSuite) TestEnumerateChannelMessages() {
 	require.NotZero(t, du.URL, "delta link")
 	require.False(t, du.Reset, "prev delta link should be valid")
 
-	for _, id := range addedIDs {
+	for id := range addedIDs {
 		suite.Run(id+"-replies", func() {
 			testEnumerateChannelMessageReplies(
 				suite.T(),

src/pkg/services/m365/api/config.go

@@ -17,22 +17,23 @@ const (
 // get easily misspelled.
 // eg: we don't need a const for "id"
 const (
-	bccRecipients     = "bccRecipients"
+	bccRecipients        = "bccRecipients"
-	ccRecipients      = "ccRecipients"
+	ccRecipients         = "ccRecipients"
-	createdDateTime   = "createdDateTime"
+	createdDateTime      = "createdDateTime"
-	displayName       = "displayName"
+	displayName          = "displayName"
-	emailAddresses    = "emailAddresses"
+	emailAddresses       = "emailAddresses"
-	givenName         = "givenName"
+	givenName            = "givenName"
-	isCancelled       = "isCancelled"
+	isCancelled          = "isCancelled"
-	isDraft           = "isDraft"
+	isDraft              = "isDraft"
-	mobilePhone       = "mobilePhone"
+	lastModifiedDateTime = "lastModifiedDateTime"
-	parentFolderID    = "parentFolderId"
+	mobilePhone          = "mobilePhone"
-	receivedDateTime  = "receivedDateTime"
+	parentFolderID       = "parentFolderId"
-	recurrence        = "recurrence"
+	receivedDateTime     = "receivedDateTime"
-	sentDateTime      = "sentDateTime"
+	recurrence           = "recurrence"
-	surname           = "surname"
+	sentDateTime         = "sentDateTime"
-	toRecipients      = "toRecipients"
+	surname              = "surname"
-	userPrincipalName = "userPrincipalName"
+	toRecipients         = "toRecipients"
+	userPrincipalName    = "userPrincipalName"
 )
 
 // header keys

src/pkg/services/m365/api/contacts_pager.go

@@ -2,6 +2,7 @@ package api
 
 import (
 	"context"
+	"time"
 
 	"github.com/alcionai/clues"
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
@@ -136,6 +137,10 @@ func (p *contactsPageCtrl) SetNextLink(nextLink string) {
 	p.builder = users.NewItemContactFoldersItemContactsRequestBuilder(nextLink, p.gs.Adapter())
 }
 
+func (p *contactsPageCtrl) ValidModTimes() bool {
+	return true
+}
+
 func (c Contacts) GetItemsInContainerByCollisionKey(
 	ctx context.Context,
 	userID, containerID string,
@@ -249,12 +254,16 @@ func (p *contactDeltaPager) Reset(ctx context.Context) {
 	p.builder = getContactDeltaBuilder(ctx, p.gs, p.userID, p.containerID)
 }
 
+func (p *contactDeltaPager) ValidModTimes() bool {
+	return true
+}
+
 func (c Contacts) GetAddedAndRemovedItemIDs(
 	ctx context.Context,
 	userID, containerID, prevDeltaLink string,
 	immutableIDs bool,
 	canMakeDeltaQueries bool,
-) ([]string, []string, DeltaUpdate, error) {
+) (map[string]time.Time, bool, []string, DeltaUpdate, error) {
 	ctx = clues.Add(
 		ctx,
 		"data_category", path.ContactsCategory,
@@ -266,12 +275,12 @@ func (c Contacts) GetAddedAndRemovedItemIDs(
 		containerID,
 		prevDeltaLink,
 		immutableIDs,
-		idAnd()...)
+		idAnd(lastModifiedDateTime)...)
 	pager := c.NewContactsPager(
 		userID,
 		containerID,
 		immutableIDs,
-		idAnd()...)
+		idAnd(lastModifiedDateTime)...)
 
 	return getAddedAndRemovedItemIDs[models.Contactable](
 		ctx,
@@ -279,5 +288,5 @@ func (c Contacts) GetAddedAndRemovedItemIDs(
 		deltaPager,
 		prevDeltaLink,
 		canMakeDeltaQueries,
-		addedAndRemovedByAddtlData)
+		addedAndRemovedByAddtlData[models.Contactable])
 }

src/pkg/services/m365/api/drive_pager.go

@@ -61,6 +61,10 @@ func (p *driveItemPageCtrl) SetNextLink(nextLink string) {
 	p.builder = drives.NewItemItemsItemChildrenRequestBuilder(nextLink, p.gs.Adapter())
 }
 
+func (p *driveItemPageCtrl) ValidModTimes() bool {
+	return true
+}
+
 type DriveItemIDType struct {
 	ItemID   string
 	IsFolder bool
@@ -185,6 +189,10 @@ func (p *DriveItemDeltaPageCtrl) Reset(context.Context) {
 		Delta()
 }
 
+func (p *DriveItemDeltaPageCtrl) ValidModTimes() bool {
+	return true
+}
+
 // ---------------------------------------------------------------------------
 // user's drives pager
 // ---------------------------------------------------------------------------
@@ -252,6 +260,10 @@ func (p *userDrivePager) SetNextLink(link string) {
 	p.builder = users.NewItemDrivesRequestBuilder(link, p.gs.Adapter())
 }
 
+func (p *userDrivePager) ValidModTimes() bool {
+	return true
+}
+
 // ---------------------------------------------------------------------------
 // site's libraries pager
 // ---------------------------------------------------------------------------
@@ -303,6 +315,10 @@ func (p *siteDrivePager) SetNextLink(link string) {
 	p.builder = sites.NewItemDrivesRequestBuilder(link, p.gs.Adapter())
 }
 
+func (p *siteDrivePager) ValidModTimes() bool {
+	return true
+}
+
 // ---------------------------------------------------------------------------
 // drive pager
 // ---------------------------------------------------------------------------

src/pkg/services/m365/api/events_pager.go

@@ -3,6 +3,7 @@ package api
 import (
 	"context"
 	"fmt"
+	"time"
 
 	"github.com/alcionai/clues"
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
@@ -141,6 +142,10 @@ func (p *eventsPageCtrl) SetNextLink(nextLink string) {
 	p.builder = users.NewItemCalendarsItemEventsRequestBuilder(nextLink, p.gs.Adapter())
 }
 
+func (p *eventsPageCtrl) ValidModTimes() bool {
+	return true
+}
+
 func (c Events) GetItemsInContainerByCollisionKey(
 	ctx context.Context,
 	userID, containerID string,
@@ -248,12 +253,16 @@ func (p *eventDeltaPager) Reset(ctx context.Context) {
 	p.builder = getEventDeltaBuilder(ctx, p.gs, p.userID, p.containerID)
 }
 
+func (p *eventDeltaPager) ValidModTimes() bool {
+	return false
+}
+
 func (c Events) GetAddedAndRemovedItemIDs(
 	ctx context.Context,
 	userID, containerID, prevDeltaLink string,
 	immutableIDs bool,
 	canMakeDeltaQueries bool,
-) ([]string, []string, DeltaUpdate, error) {
+) (map[string]time.Time, bool, []string, DeltaUpdate, error) {
 	ctx = clues.Add(
 		ctx,
 		"data_category", path.EventsCategory,
@@ -270,7 +279,7 @@ func (c Events) GetAddedAndRemovedItemIDs(
 		userID,
 		containerID,
 		immutableIDs,
-		idAnd()...)
+		idAnd(lastModifiedDateTime)...)
 
 	return getAddedAndRemovedItemIDs[models.Eventable](
 		ctx,
@@ -278,5 +287,5 @@ func (c Events) GetAddedAndRemovedItemIDs(
 		deltaPager,
 		prevDeltaLink,
 		canMakeDeltaQueries,
-		addedAndRemovedByAddtlData)
+		addedAndRemovedByAddtlData[models.Eventable])
 }

src/pkg/services/m365/api/item_pager.go

@@ -52,6 +52,10 @@ type Resetter interface {
 	Reset(context.Context)
 }
 
+type ValidModTimer interface {
+	ValidModTimes() bool
+}
+
 // ---------------------------------------------------------------------------
 // common funcs
 // ---------------------------------------------------------------------------
@@ -76,6 +80,7 @@ func NextAndDeltaLink(pl DeltaLinker) (string, string) {
 type Pager[T any] interface {
 	GetPager[NextLinkValuer[T]]
 	SetNextLinker
+	ValidModTimer
 }
 
 func enumerateItems[T any](
@@ -114,6 +119,7 @@ type DeltaPager[T any] interface {
 	GetPager[DeltaLinkValuer[T]]
 	Resetter
 	SetNextLinker
+	ValidModTimer
 }
 
 func deltaEnumerateItems[T any](
@@ -173,7 +179,7 @@ func deltaEnumerateItems[T any](
 // shared enumeration runner funcs
 // ---------------------------------------------------------------------------
 
-type addedAndRemovedHandler[T any] func(items []T) ([]string, []string, error)
+type addedAndRemovedHandler[T any] func(items []T) (map[string]time.Time, []string, error)
 
 func getAddedAndRemovedItemIDs[T any](
 	ctx context.Context,
@@ -182,16 +188,16 @@ func getAddedAndRemovedItemIDs[T any](
 	prevDeltaLink string,
 	canMakeDeltaQueries bool,
 	aarh addedAndRemovedHandler[T],
-) ([]string, []string, DeltaUpdate, error) {
+) (map[string]time.Time, bool, []string, DeltaUpdate, error) {
 	if canMakeDeltaQueries {
 		ts, du, err := deltaEnumerateItems[T](ctx, deltaPager, prevDeltaLink)
 		if err != nil && (!graph.IsErrInvalidDelta(err) || len(prevDeltaLink) == 0) {
-			return nil, nil, DeltaUpdate{}, graph.Stack(ctx, err)
+			return nil, false, nil, DeltaUpdate{}, graph.Stack(ctx, err)
 		}
 
 		if err == nil {
 			a, r, err := aarh(ts)
-			return a, r, du, graph.Stack(ctx, err).OrNil()
+			return a, deltaPager.ValidModTimes(), r, du, graph.Stack(ctx, err).OrNil()
 		}
 	}
 
@@ -199,12 +205,12 @@ func getAddedAndRemovedItemIDs[T any](
 
 	ts, err := enumerateItems(ctx, pager)
 	if err != nil {
-		return nil, nil, DeltaUpdate{}, graph.Stack(ctx, err)
+		return nil, false, nil, DeltaUpdate{}, graph.Stack(ctx, err)
 	}
 
 	a, r, err := aarh(ts)
 
-	return a, r, du, graph.Stack(ctx, err).OrNil()
+	return a, pager.ValidModTimes(), r, du, graph.Stack(ctx, err).OrNil()
 }
 
 type getIDer interface {
@@ -218,8 +224,15 @@ type getIDAndAddtler interface {
 	GetAdditionalData() map[string]any
 }
 
-func addedAndRemovedByAddtlData[T any](items []T) ([]string, []string, error) {
+type getModTimer interface {
-	added, removed := []string{}, []string{}
+	GetLastModifiedDateTime() *time.Time
+}
+
+func addedAndRemovedByAddtlData[T any](
+	items []T,
+) (map[string]time.Time, []string, error) {
+	added := map[string]time.Time{}
+	removed := []string{}
 
 	for _, item := range items {
 		giaa, ok := any(item).(getIDAndAddtler)
@@ -232,7 +245,13 @@ func addedAndRemovedByAddtlData[T any](items []T) ([]string, []string, error) {
 		// be 'changed' or 'deleted'.  We don't really care about the cause: both
 		// cases are handled the same way in storage.
 		if giaa.GetAdditionalData()[graph.AddtlDataRemoved] == nil {
-			added = append(added, ptr.Val(giaa.GetId()))
+			var modTime time.Time
+
+			if mt, ok := giaa.(getModTimer); ok {
+				modTime = ptr.Val(mt.GetLastModifiedDateTime())
+			}
+
+			added[ptr.Val(giaa.GetId())] = modTime
 		} else {
 			removed = append(removed, ptr.Val(giaa.GetId()))
 		}
@@ -248,8 +267,11 @@ type getIDAndDeletedDateTimer interface {
 	GetDeletedDateTime() *time.Time
 }
 
-func addedAndRemovedByDeletedDateTime[T any](items []T) ([]string, []string, error) {
+func addedAndRemovedByDeletedDateTime[T any](
-	added, removed := []string{}, []string{}
+	items []T,
+) (map[string]time.Time, []string, error) {
+	added := map[string]time.Time{}
+	removed := []string{}
 
 	for _, item := range items {
 		giaddt, ok := any(item).(getIDAndDeletedDateTimer)
@@ -259,7 +281,13 @@ func addedAndRemovedByDeletedDateTime[T any](items []T) ([]string, []string, err
 		}
 
 		if giaddt.GetDeletedDateTime() == nil {
-			added = append(added, ptr.Val(giaddt.GetId()))
+			var modTime time.Time
+
+			if mt, ok := giaddt.(getModTimer); ok {
+				modTime = ptr.Val(mt.GetLastModifiedDateTime())
+			}
+
+			added[ptr.Val(giaddt.GetId())] = modTime
 		} else {
 			removed = append(removed, ptr.Val(giaddt.GetId()))
 		}

src/pkg/services/m365/api/item_pager_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/alcionai/clues"
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
@@ -76,16 +77,19 @@ func (p *testPager) GetPage(ctx context.Context) (NextLinkValuer[any], error) {
 
 func (p *testPager) SetNextLink(nextLink string) {}
 
+func (p testPager) ValidModTimes() bool { return true }
+
 // mock id pager
 
 var _ Pager[any] = &testIDsPager{}
 
 type testIDsPager struct {
-	t          *testing.T
+	t             *testing.T
-	added      []string
+	added         map[string]time.Time
-	removed    []string
+	removed       []string
-	errorCode  string
+	errorCode     string
-	needsReset bool
+	needsReset    bool
+	validModTimes bool
 }
 
 func (p *testIDsPager) GetPage(
@@ -103,10 +107,11 @@ func (p *testIDsPager) GetPage(
 
 	values := make([]any, 0, len(p.added)+len(p.removed))
 
-	for _, a := range p.added {
+	for a, modTime := range p.added {
 		// contact chosen arbitrarily, any exchange model should work
 		itm := models.NewContact()
 		itm.SetId(ptr.To(a))
+		itm.SetLastModifiedDateTime(ptr.To(modTime))
 		values = append(values, itm)
 	}
 
@@ -132,14 +137,19 @@ func (p *testIDsPager) Reset(context.Context) {
 	p.errorCode = ""
 }
 
+func (p testIDsPager) ValidModTimes() bool {
+	return p.validModTimes
+}
+
 var _ DeltaPager[any] = &testIDsDeltaPager{}
 
 type testIDsDeltaPager struct {
-	t          *testing.T
+	t             *testing.T
-	added      []string
+	added         map[string]time.Time
-	removed    []string
+	removed       []string
-	errorCode  string
+	errorCode     string
-	needsReset bool
+	needsReset    bool
+	validModTimes bool
 }
 
 func (p *testIDsDeltaPager) GetPage(
@@ -157,10 +167,11 @@ func (p *testIDsDeltaPager) GetPage(
 
 	values := make([]any, 0, len(p.added)+len(p.removed))
 
-	for _, a := range p.added {
+	for a, modTime := range p.added {
 		// contact chosen arbitrarily, any exchange model should work
 		itm := models.NewContact()
 		itm.SetId(ptr.To(a))
+		itm.SetLastModifiedDateTime(ptr.To(modTime))
 		values = append(values, itm)
 	}
 
@@ -186,6 +197,10 @@ func (p *testIDsDeltaPager) Reset(context.Context) {
 	p.errorCode = ""
 }
 
+func (p testIDsDeltaPager) ValidModTimes() bool {
+	return p.validModTimes
+}
+
 // ---------------------------------------------------------------------------
 // Tests
 // ---------------------------------------------------------------------------
@@ -252,11 +267,14 @@ func (suite *PagerUnitSuite) TestEnumerateItems() {
 
 func (suite *PagerUnitSuite) TestGetAddedAndRemovedItemIDs() {
 	type expected struct {
-		added       []string
+		added         map[string]time.Time
-		removed     []string
+		removed       []string
-		deltaUpdate DeltaUpdate
+		deltaUpdate   DeltaUpdate
+		validModTimes bool
 	}
 
+	now := time.Now()
+
 	tests := []struct {
 		name        string
 		pagerGetter func(
@@ -265,9 +283,10 @@ func (suite *PagerUnitSuite) TestGetAddedAndRemovedItemIDs() {
 		deltaPagerGetter func(
 			*testing.T,
 		) DeltaPager[any]
-		prevDelta string
+		prevDelta     string
-		expect    expected
+		expect        expected
-		canDelta  bool
+		canDelta      bool
+		validModTimes bool
 	}{
 		{
 			name: "no prev delta",
@@ -276,13 +295,46 @@ func (suite *PagerUnitSuite) TestGetAddedAndRemovedItemIDs() {
 			},
 			deltaPagerGetter: func(t *testing.T) DeltaPager[any] {
 				return &testIDsDeltaPager{
-					t:       t,
+					t: t,
-					added:   []string{"uno", "dos"},
+					added: map[string]time.Time{
+						"uno": now.Add(time.Minute),
+						"dos": now.Add(2 * time.Minute),
+					},
+					removed:       []string{"tres", "quatro"},
+					validModTimes: true,
+				}
+			},
+			expect: expected{
+				added: map[string]time.Time{
+					"uno": now.Add(time.Minute),
+					"dos": now.Add(2 * time.Minute),
+				},
+				removed:       []string{"tres", "quatro"},
+				deltaUpdate:   DeltaUpdate{Reset: true},
+				validModTimes: true,
+			},
+			canDelta: true,
+		},
+		{
+			name: "no prev delta invalid mod times",
+			pagerGetter: func(t *testing.T) Pager[any] {
+				return nil
+			},
+			deltaPagerGetter: func(t *testing.T) DeltaPager[any] {
+				return &testIDsDeltaPager{
+					t: t,
+					added: map[string]time.Time{
+						"uno": {},
+						"dos": {},
+					},
 					removed: []string{"tres", "quatro"},
 				}
 			},
 			expect: expected{
-				added:       []string{"uno", "dos"},
+				added: map[string]time.Time{
+					"uno": {},
+					"dos": {},
+				},
 				removed:     []string{"tres", "quatro"},
 				deltaUpdate: DeltaUpdate{Reset: true},
 			},
@@ -295,16 +347,24 @@ func (suite *PagerUnitSuite) TestGetAddedAndRemovedItemIDs() {
 			},
 			deltaPagerGetter: func(t *testing.T) DeltaPager[any] {
 				return &testIDsDeltaPager{
-					t:       t,
+					t: t,
-					added:   []string{"uno", "dos"},
+					added: map[string]time.Time{
-					removed: []string{"tres", "quatro"},
+						"uno": now.Add(time.Minute),
+						"dos": now.Add(2 * time.Minute),
+					},
+					removed:       []string{"tres", "quatro"},
+					validModTimes: true,
 				}
 			},
 			prevDelta: "delta",
 			expect: expected{
-				added:       []string{"uno", "dos"},
+				added: map[string]time.Time{
-				removed:     []string{"tres", "quatro"},
+					"uno": now.Add(time.Minute),
-				deltaUpdate: DeltaUpdate{Reset: false},
+					"dos": now.Add(2 * time.Minute),
+				},
+				removed:       []string{"tres", "quatro"},
+				deltaUpdate:   DeltaUpdate{Reset: false},
+				validModTimes: true,
 			},
 			canDelta: true,
 		},
@@ -315,18 +375,26 @@ func (suite *PagerUnitSuite) TestGetAddedAndRemovedItemIDs() {
 			},
 			deltaPagerGetter: func(t *testing.T) DeltaPager[any] {
 				return &testIDsDeltaPager{
-					t:          t,
+					t: t,
-					added:      []string{"uno", "dos"},
+					added: map[string]time.Time{
-					removed:    []string{"tres", "quatro"},
+						"uno": now.Add(time.Minute),
-					errorCode:  "SyncStateNotFound",
+						"dos": now.Add(2 * time.Minute),
-					needsReset: true,
+					},
+					removed:       []string{"tres", "quatro"},
+					errorCode:     "SyncStateNotFound",
+					needsReset:    true,
+					validModTimes: true,
 				}
 			},
 			prevDelta: "delta",
 			expect: expected{
-				added:       []string{"uno", "dos"},
+				added: map[string]time.Time{
-				removed:     []string{"tres", "quatro"},
+					"uno": now.Add(time.Minute),
-				deltaUpdate: DeltaUpdate{Reset: true},
+					"dos": now.Add(2 * time.Minute),
+				},
+				removed:       []string{"tres", "quatro"},
+				deltaUpdate:   DeltaUpdate{Reset: true},
+				validModTimes: true,
 			},
 			canDelta: true,
 		},
@@ -334,18 +402,26 @@ func (suite *PagerUnitSuite) TestGetAddedAndRemovedItemIDs() {
 			name: "delta not allowed",
 			pagerGetter: func(t *testing.T) Pager[any] {
 				return &testIDsPager{
-					t:       t,
+					t: t,
-					added:   []string{"uno", "dos"},
+					added: map[string]time.Time{
-					removed: []string{"tres", "quatro"},
+						"uno": now.Add(time.Minute),
+						"dos": now.Add(2 * time.Minute),
+					},
+					removed:       []string{"tres", "quatro"},
+					validModTimes: true,
 				}
 			},
 			deltaPagerGetter: func(t *testing.T) DeltaPager[any] {
 				return nil
 			},
 			expect: expected{
-				added:       []string{"uno", "dos"},
+				added: map[string]time.Time{
-				removed:     []string{"tres", "quatro"},
+					"uno": now.Add(time.Minute),
-				deltaUpdate: DeltaUpdate{Reset: true},
+					"dos": now.Add(2 * time.Minute),
+				},
+				removed:       []string{"tres", "quatro"},
+				deltaUpdate:   DeltaUpdate{Reset: true},
+				validModTimes: true,
 			},
 			canDelta: false,
 		},
@@ -358,18 +434,19 @@ func (suite *PagerUnitSuite) TestGetAddedAndRemovedItemIDs() {
 			ctx, flush := tester.NewContext(t)
 			defer flush()
 
-			added, removed, deltaUpdate, err := getAddedAndRemovedItemIDs[any](
+			added, validModTimes, removed, deltaUpdate, err := getAddedAndRemovedItemIDs[any](
 				ctx,
 				test.pagerGetter(t),
 				test.deltaPagerGetter(t),
 				test.prevDelta,
 				test.canDelta,
-				addedAndRemovedByAddtlData)
+				addedAndRemovedByAddtlData[any])
 
 			require.NoErrorf(t, err, "getting added and removed item IDs: %+v", clues.ToCore(err))
-			require.EqualValues(t, test.expect.added, added, "added item IDs")
+			assert.Equal(t, test.expect.added, added, "added item IDs and mod times")
-			require.EqualValues(t, test.expect.removed, removed, "removed item IDs")
+			assert.Equal(t, test.expect.validModTimes, validModTimes, "valid mod times")
-			require.Equal(t, test.expect.deltaUpdate, deltaUpdate, "delta update")
+			assert.EqualValues(t, test.expect.removed, removed, "removed item IDs")
+			assert.Equal(t, test.expect.deltaUpdate, deltaUpdate, "delta update")
 		})
 	}
 }

src/pkg/services/m365/api/mail_pager.go

@@ -3,6 +3,7 @@ package api
 import (
 	"context"
 	"fmt"
+	"time"
 
 	"github.com/alcionai/clues"
 	"github.com/microsoftgraph/msgraph-sdk-go/models"
@@ -166,6 +167,10 @@ func (p *mailsPageCtrl) SetNextLink(nextLink string) {
 	p.builder = users.NewItemMailFoldersItemMessagesRequestBuilder(nextLink, p.gs.Adapter())
 }
 
+func (p *mailsPageCtrl) ValidModTimes() bool {
+	return true
+}
+
 func (c Mail) GetItemsInContainerByCollisionKey(
 	ctx context.Context,
 	userID, containerID string,
@@ -279,12 +284,16 @@ func (p *mailDeltaPager) Reset(ctx context.Context) {
 	p.builder = getMailDeltaBuilder(ctx, p.gs, p.userID, p.containerID)
 }
 
+func (p *mailDeltaPager) ValidModTimes() bool {
+	return true
+}
+
 func (c Mail) GetAddedAndRemovedItemIDs(
 	ctx context.Context,
 	userID, containerID, prevDeltaLink string,
 	immutableIDs bool,
 	canMakeDeltaQueries bool,
-) ([]string, []string, DeltaUpdate, error) {
+) (map[string]time.Time, bool, []string, DeltaUpdate, error) {
 	ctx = clues.Add(
 		ctx,
 		"data_category", path.EmailCategory,
@@ -296,12 +305,12 @@ func (c Mail) GetAddedAndRemovedItemIDs(
 		containerID,
 		prevDeltaLink,
 		immutableIDs,
-		idAnd()...)
+		idAnd(lastModifiedDateTime)...)
 	pager := c.NewMailPager(
 		userID,
 		containerID,
 		immutableIDs,
-		idAnd()...)
+		idAnd(lastModifiedDateTime)...)
 
 	return getAddedAndRemovedItemIDs[models.Messageable](
 		ctx,
@@ -309,5 +318,5 @@ func (c Mail) GetAddedAndRemovedItemIDs(
 		deltaPager,
 		prevDeltaLink,
 		canMakeDeltaQueries,
-		addedAndRemovedByAddtlData)
+		addedAndRemovedByAddtlData[models.Messageable])
 }

src/pkg/services/m365/api/mock/pager.go

@@ -8,6 +8,11 @@ import (
 	"github.com/alcionai/corso/src/pkg/services/m365/api"
 )
 
+var (
+	_ api.Pager[any]      = &Pager[any]{}
+	_ api.DeltaPager[any] = &DeltaPager[any]{}
+)
+
 type DeltaNextLinkValues[T any] struct {
 	Next   *string
 	Delta  *string
@@ -61,7 +66,8 @@ func (p *Pager[T]) GetPage(
 	return &link, p.ToReturn[idx].Err
 }
 
-func (p *Pager[T]) SetNextLink(string) {}
+func (p *Pager[T]) SetNextLink(string)  {}
+func (p *Pager[T]) ValidModTimes() bool { return true }
 
 // ---------------------------------------------------------------------------
 // delta pager
@@ -94,3 +100,4 @@ func (p *DeltaPager[T]) GetPage(
 
 func (p *DeltaPager[T]) SetNextLink(string)    {}
 func (p *DeltaPager[T]) Reset(context.Context) {}
+func (p *DeltaPager[T]) ValidModTimes() bool   { return true }