From 70a6d58b8432e455ab1443d45bc23dd70b363bea Mon Sep 17 00:00:00 2001
From: Maze Winther <mazewinther@gmail.com>
Date: Tue, 31 Mar 2026 15:47:30 +0200
Subject: refactor: centralize track placement into its own module

---
 apps/web/src/lib/timeline/placement/apply.ts | 45 ++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 apps/web/src/lib/timeline/placement/apply.ts

(limited to 'apps/web/src/lib/timeline/placement/apply.ts')

diff --git a/apps/web/src/lib/timeline/placement/apply.ts b/apps/web/src/lib/timeline/placement/apply.ts
new file mode 100644
index 00000000..4ff5d50d
--- /dev/null
+++ b/apps/web/src/lib/timeline/placement/apply.ts
@@ -0,0 +1,45 @@
+import type { TimelineElement, TimelineTrack } from "@/lib/timeline";
+import { generateUUID } from "@/utils/id";
+import { buildEmptyTrack } from "./track-factory";
+import type { PlacementResult } from "./types";
+
+export function applyPlacement({
+	tracks,
+	placementResult,
+	elements,
+	newTrackInsertIndexOverride,
+}: {
+	tracks: TimelineTrack[];
+	placementResult: PlacementResult;
+	elements: TimelineElement[];
+	newTrackInsertIndexOverride?: number;
+}): { updatedTracks: TimelineTrack[]; targetTrackId: string } | null {
+	if (placementResult.kind === "existingTrack") {
+		const targetTrack = tracks[placementResult.trackIndex];
+		if (!targetTrack) {
+			return null;
+		}
+
+		const updatedTracks = tracks.map((track, trackIndex) =>
+			trackIndex === placementResult.trackIndex
+				? {
+						...track,
+						elements: [...track.elements, ...elements],
+					}
+				: track,
+		) as TimelineTrack[];
+
+		return { updatedTracks, targetTrackId: targetTrack.id };
+	}
+
+	const newTrackId = generateUUID();
+	const newTrack = {
+		...buildEmptyTrack({ id: newTrackId, type: placementResult.trackType }),
+		elements,
+	} as TimelineTrack;
+	const insertIndex =
+		newTrackInsertIndexOverride ?? placementResult.insertIndex;
+	const updatedTracks = [...tracks];
+	updatedTracks.splice(insertIndex, 0, newTrack);
+	return { updatedTracks, targetTrackId: newTrackId };
+}
-- 
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