refactor(sequence): make transient interval creation reusable without Client

Extract resolvePositionRef helper and change createPositionReferenceFromSegoff
to accept ISharedSegmentSequence<any> instead of Client, enabling transient
interval creation from code that only has a sequence reference. Refactor
createSequenceInterval to use resolvePositionRef for non-op paths.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-Authored-By: anthony-murphy <anthony.murphy@microsoft.com>

Author: 3 people

packages/dds/sequence/src/intervalCollection.ts

@@ -61,6 +61,7 @@ import {
 	createSequenceInterval,
 	getSerializedProperties,
 } from "./intervals/index.js";
+import type { ISharedSegmentSequence } from "./sequence.js";
 
 export type ISerializedIntervalCollectionV1 = ISerializedInterval[];
 
@@ -1596,7 +1597,7 @@ export class IntervalCollection
 			if (needsStartUpdate) {
 				const props = interval.start.properties;
 				interval.start = createPositionReferenceFromSegoff({
-					client: this.client,
+					sequence: this.client as unknown as ISharedSegmentSequence<any>,
 					segoff: newStart,
 					refType: interval.start.refType,
 					op,
@@ -1615,7 +1616,7 @@ export class IntervalCollection
 			if (needsEndUpdate) {
 				const props = interval.end.properties;
 				interval.end = createPositionReferenceFromSegoff({
-					client: this.client,
+					sequence: this.client as unknown as ISharedSegmentSequence<any>,
 					segoff: newEnd,
 					refType: interval.end.refType,
 					op,

packages/dds/sequence/src/intervals/index.ts

@@ -22,5 +22,6 @@ export {
 	createSequenceInterval,
 	createPositionReferenceFromSegoff,
 	createTransientInterval,
+	resolvePositionRef,
 	getSerializedProperties,
 } from "./sequenceInterval.js";

packages/dds/sequence/src/intervals/sequenceInterval.ts

@@ -35,6 +35,8 @@ import {
 import { LoggingError, UsageError } from "@fluidframework/telemetry-utils/internal";
 import { v4 as uuid } from "uuid";
 
+import type { ISharedSegmentSequence } from "../sequence.js";
+
 import {
 	ISerializableInterval,
 	ISerializedInterval,
@@ -504,7 +506,7 @@ export class SequenceIntervalClass
 		this.verifyNotDispose();
 
 		const startRef = createPositionReferenceFromSegoff({
-			client: this.client,
+			sequence: this.client as unknown as ISharedSegmentSequence<any>,
 			segoff: rebased.start,
 			refType: this.start.refType,
 			slidingPreference: this.start.slidingPreference,
@@ -516,7 +518,7 @@ export class SequenceIntervalClass
 		this.start = startRef;
 
 		const endRef = createPositionReferenceFromSegoff({
-			client: this.client,
+			sequence: this.client as unknown as ISharedSegmentSequence<any>,
 			segoff: rebased.end,
 			refType: this.end.refType,
 			slidingPreference: this.end.slidingPreference,
@@ -636,7 +638,7 @@ export class SequenceIntervalClass
 }
 
 export function createPositionReferenceFromSegoff({
-	client,
+	sequence,
 	segoff,
 	refType,
 	op,
@@ -646,7 +648,7 @@ export function createPositionReferenceFromSegoff({
 	canSlideToEndpoint,
 	rollback,
 }: {
-	client: Client;
+	sequence: ISharedSegmentSequence<any>;
 	segoff: { segment: ISegment; offset: number } | undefined | "start" | "end";
 	refType: ReferenceType;
 	op?: ISequencedDocumentMessage;
@@ -657,9 +659,9 @@ export function createPositionReferenceFromSegoff({
 	rollback?: boolean;
 }): LocalReferencePosition {
 	if (segoff === "start" || segoff === "end") {
-		return client.createLocalReferencePosition(
-			segoff,
-			undefined,
+		return sequence.createLocalReferencePosition(
+			segoff as any,
+			undefined as any,
 			refType,
 			undefined,
 			slidingPreference,
@@ -668,7 +670,7 @@ export function createPositionReferenceFromSegoff({
 	}
 
 	if (segoff?.segment) {
-		const ref = client.createLocalReferencePosition(
+		const ref = sequence.createLocalReferencePosition(
 			segoff.segment,
 			segoff.offset,
 			refType,
@@ -697,6 +699,39 @@ export function createPositionReferenceFromSegoff({
 	return createDetachedLocalReferencePosition(slidingPreference, refType);
 }
 
+/**
+ * Resolves a position (number or "start"/"end" sentinel) to a {@link LocalReferencePosition}
+ * using an {@link ISharedSegmentSequence}. This is the simple (non-op) path for creating
+ * position references, usable from code that doesn't have a `Client` reference.
+ */
+export function resolvePositionRef(
+	sequence: ISharedSegmentSequence<any>,
+	pos: number | "start" | "end",
+	refType: ReferenceType,
+	slidingPreference: SlidingPreference,
+	canSlideToEndpoint?: boolean,
+): LocalReferencePosition {
+	if (pos === "start" || pos === "end") {
+		return createPositionReferenceFromSegoff({
+			sequence,
+			segoff: pos,
+			refType,
+			slidingPreference,
+			canSlideToEndpoint,
+		});
+	}
+	const { segment, offset } = sequence.getContainingSegment(pos);
+	const segoff =
+		segment !== undefined && offset !== undefined ? { segment, offset } : undefined;
+	return createPositionReferenceFromSegoff({
+		sequence,
+		segoff,
+		refType,
+		slidingPreference,
+		canSlideToEndpoint,
+	});
+}
+
 function createPositionReference({
 	client,
 	pos,
@@ -746,7 +781,7 @@ function createPositionReference({
 	}
 
 	return createPositionReferenceFromSegoff({
-		client,
+		sequence: client as unknown as ISharedSegmentSequence<any>,
 		segoff,
 		refType,
 		op,
@@ -761,14 +796,14 @@ function createPositionReference({
 export function createTransientInterval(
 	start: SequencePlace | undefined,
 	end: SequencePlace | undefined,
-	client: Client,
+	clientOrSequence: Client | ISharedSegmentSequence<any>,
 ) {
 	return createSequenceInterval(
 		"transient",
 		uuid(),
 		start,
 		end,
-		client,
+		clientOrSequence as unknown as Client,
 		IntervalType.Transient,
 	);
 }
@@ -824,34 +859,57 @@ export function createSequenceInterval(
 		endSide,
 	);
 
-	const startLref = createPositionReference({
-		client,
-		pos: startPos,
-		refType: beginRefType,
-		op,
-		fromSnapshot,
-		slidingPreference: startSlidingPreference,
-		canSlideToEndpoint: canSlideToEndpoint && stickiness !== IntervalStickiness.NONE,
-		rollback,
-	});
-
 	const endSlidingPreference = endReferenceSlidingPreference(
 		startPos,
 		startSide,
 		endPos,
 		endSide,
 	);
 
-	const endLref = createPositionReference({
-		client,
-		pos: endPos,
-		refType: endRefType,
-		op,
-		fromSnapshot,
-		slidingPreference: endSlidingPreference,
-		canSlideToEndpoint: canSlideToEndpoint && stickiness !== IntervalStickiness.NONE,
-		rollback,
-	});
+	const canSlide = canSlideToEndpoint && stickiness !== IntervalStickiness.NONE;
+
+	let startLref: LocalReferencePosition;
+	let endLref: LocalReferencePosition;
+
+	if (op ?? fromSnapshot) {
+		// Op-context path: needs Client-specific getContainingSegment with op context
+		startLref = createPositionReference({
+			client,
+			pos: startPos,
+			refType: beginRefType,
+			op,
+			fromSnapshot,
+			slidingPreference: startSlidingPreference,
+			canSlideToEndpoint: canSlide,
+			rollback,
+		});
+		endLref = createPositionReference({
+			client,
+			pos: endPos,
+			refType: endRefType,
+			op,
+			fromSnapshot,
+			slidingPreference: endSlidingPreference,
+			canSlideToEndpoint: canSlide,
+			rollback,
+		});
+	} else {
+		// Non-op path (transient or local creation): use resolvePositionRef
+		startLref = resolvePositionRef(
+			client as unknown as ISharedSegmentSequence<any>,
+			startPos,
+			beginRefType,
+			startSlidingPreference,
+			canSlide,
+		);
+		endLref = resolvePositionRef(
+			client as unknown as ISharedSegmentSequence<any>,
+			endPos,
+			endRefType,
+			endSlidingPreference,
+			canSlide,
+		);
+	}
 
 	const rangeProp = {
 		[reservedRangeLabelsKey]: [label],