1 files changed, 83 insertions, 0 deletions
diff --git a/apps/web/src/timeline/group-move/track-placement.ts b/apps/web/src/timeline/group-move/track-placement.ts
new file mode 100644
index 00000000..c4c5efb5
--- /dev/null
+++ b/apps/web/src/timeline/group-move/track-placement.ts
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+import type { SceneTracks, TimelineTrack } from "@/timeline";
+import type { GroupTrackSection } from "./types";
+
+export interface TrackPlacement {
+	trackId: string;
+	trackType: TimelineTrack["type"];
+	section: GroupTrackSection;
+	sectionIndex: number;
+	displayIndex: number;
+}
+
+export function getDisplayTracks({
+	tracks,
+}: {
+	tracks: SceneTracks;
+}): TimelineTrack[] {
+	return [...tracks.overlay, tracks.main, ...tracks.audio];
+}
+
+export function getTrackPlacementById({
+	tracks,
+	trackId,
+}: {
+	tracks: SceneTracks;
+	trackId: string;
+}): TrackPlacement | null {
+	if (tracks.main.id === trackId) {
+		return {
+			trackId,
+			trackType: tracks.main.type,
+			section: "main",
+			sectionIndex: -1,
+			displayIndex: tracks.overlay.length,
+		};
+	}
+
+	const overlayTrackIndex = tracks.overlay.findIndex(
+		(track) => track.id === trackId,
+	);
+	if (overlayTrackIndex >= 0) {
+		return {
+			trackId,
+			trackType: tracks.overlay[overlayTrackIndex].type,
+			section: "overlay",
+			sectionIndex: overlayTrackIndex,
+			displayIndex: overlayTrackIndex,
+		};
+	}
+
+	const audioTrackIndex = tracks.audio.findIndex(
+		(track) => track.id === trackId,
+	);
+	if (audioTrackIndex >= 0) {
+		return {
+			trackId,
+			trackType: tracks.audio[audioTrackIndex].type,
+			section: "audio",
+			sectionIndex: audioTrackIndex,
+			displayIndex: tracks.overlay.length + 1 + audioTrackIndex,
+		};
+	}
+
+	return null;
+}
+
+export function getTrackPlacementByDisplayIndex({
+	tracks,
+	displayIndex,
+}: {
+	tracks: SceneTracks;
+	displayIndex: number;
+}): TrackPlacement | null {
+	const displayTracks = getDisplayTracks({ tracks });
+	const track = displayTracks[displayIndex];
+	if (!track) {
+		return null;
+	}
+
+	return getTrackPlacementById({
+		tracks,
+		trackId: track.id,
+	});
+}