1 files changed, 103 insertions, 0 deletions
diff --git a/apps/web/src/lib/scenes.ts b/apps/web/src/lib/scenes.ts
new file mode 100644
index 00000000..8c043e83
--- /dev/null
+++ b/apps/web/src/lib/scenes.ts
@@ -0,0 +1,103 @@
+import type { TScene } from "@/types/timeline";
+import { generateUUID } from "@/utils/id";
+import { calculateTotalDuration } from "@/lib/timeline";
+import { ensureMainTrack } from "@/lib/timeline/track-utils";
+
+export function getMainScene({ scenes }: { scenes: TScene[] }): TScene | null {
+	return scenes.find((scene) => scene.isMain) || null;
+}
+
+export function ensureMainScene({ scenes }: { scenes: TScene[] }): TScene[] {
+	const hasMain = scenes.some((scene) => scene.isMain);
+	if (!hasMain) {
+		const mainScene = buildDefaultScene({ name: "Main scene", isMain: true });
+		return [mainScene, ...scenes];
+	}
+	return scenes;
+}
+
+export function buildDefaultScene({
+	name,
+	isMain,
+}: {
+	name: string;
+	isMain: boolean;
+}): TScene {
+	const tracks = ensureMainTrack({ tracks: [] });
+	return {
+		id: generateUUID(),
+		name,
+		isMain,
+		tracks,
+		bookmarks: [],
+		createdAt: new Date(),
+		updatedAt: new Date(),
+	};
+}
+
+export function canDeleteScene({ scene }: { scene: TScene }): {
+	canDelete: boolean;
+	reason?: string;
+} {
+	if (scene.isMain) {
+		return { canDelete: false, reason: "Cannot delete main scene" };
+	}
+	return { canDelete: true };
+}
+
+export function getFallbackSceneAfterDelete({
+	scenes,
+	deletedSceneId,
+	currentSceneId,
+}: {
+	scenes: TScene[];
+	deletedSceneId: string;
+	currentSceneId: string | null;
+}): TScene | null {
+	if (currentSceneId !== deletedSceneId) {
+		return scenes.find((s) => s.id === currentSceneId) || null;
+	}
+	return getMainScene({ scenes });
+}
+
+export function findCurrentScene({
+	scenes,
+	currentSceneId,
+}: {
+	scenes: TScene[];
+	currentSceneId: string;
+}): TScene | null {
+	return (
+		scenes.find((s) => s.id === currentSceneId) ||
+		getMainScene({ scenes }) ||
+		scenes[0] ||
+		null
+	);
+}
+
+export function getProjectDurationFromScenes({
+	scenes,
+}: {
+	scenes: TScene[];
+}): number {
+	const mainScene = getMainScene({ scenes }) ?? scenes[0] ?? null;
+	if (!mainScene) {
+		return 0;
+	}
+
+	return calculateTotalDuration({ tracks: mainScene.tracks });
+}
+
+export function updateSceneInArray({
+	scenes,
+	sceneId,
+	updates,
+}: {
+	scenes: TScene[];
+	sceneId: string;
+	updates: Partial<TScene>;
+}): TScene[] {
+	return scenes.map((scene) =>
+		scene.id === sceneId ? { ...scene, ...updates } : scene,
+	);
+}