1 files changed, 115 insertions, 0 deletions
diff --git a/apps/web/src/commands/timeline/track/add-track.ts b/apps/web/src/commands/timeline/track/add-track.ts
new file mode 100644
index 00000000..6b58b687
--- /dev/null
+++ b/apps/web/src/commands/timeline/track/add-track.ts
@@ -0,0 +1,115 @@
+import { Command, type CommandResult } from "@/commands/base-command";
+import type { SceneTracks, TrackType } from "@/timeline";
+import { generateUUID } from "@/utils/id";
+import { EditorCore } from "@/core";
+import {
+	buildEmptyTrack,
+	getDefaultInsertIndexForTrack,
+} from "@/timeline/placement";
+
+export class AddTrackCommand extends Command {
+	private trackId: string;
+	private savedState: SceneTracks | null = null;
+
+	constructor(
+		private type: TrackType,
+		private index?: number,
+	) {
+		super();
+		this.trackId = generateUUID();
+	}
+
+	execute(): CommandResult | undefined {
+		const editor = EditorCore.getInstance();
+		this.savedState = editor.scenes.getActiveScene().tracks;
+
+		const insertIndex =
+			this.index ??
+			getDefaultInsertIndexForTrack({
+				tracks: this.savedState,
+				trackType: this.type,
+			});
+
+		const updatedTracks =
+			this.type === "audio"
+				? buildAudioTrackState({
+						tracks: this.savedState,
+						insertIndex,
+						trackId: this.trackId,
+					})
+				: buildOverlayTrackState({
+						tracks: this.savedState,
+						insertIndex,
+						trackId: this.trackId,
+						trackType: this.type,
+					});
+
+		editor.timeline.updateTracks(updatedTracks);
+		return undefined;
+	}
+
+	undo(): void {
+		if (this.savedState) {
+			const editor = EditorCore.getInstance();
+			editor.timeline.updateTracks(this.savedState);
+		}
+	}
+
+	getTrackId(): string {
+		return this.trackId;
+	}
+}
+
+function buildAudioTrackState({
+	tracks,
+	insertIndex,
+	trackId,
+}: {
+	tracks: SceneTracks;
+	insertIndex: number;
+	trackId: string;
+}): SceneTracks {
+	const audioInsertIndex = Math.max(0, insertIndex - tracks.overlay.length - 1);
+	const newTrack = buildEmptyTrack({
+		id: trackId,
+		type: "audio",
+	});
+	return {
+		...tracks,
+		audio: [
+			...tracks.audio.slice(0, audioInsertIndex),
+			newTrack,
+			...tracks.audio.slice(audioInsertIndex),
+		],
+	};
+}
+
+function buildOverlayTrackState({
+	tracks,
+	insertIndex,
+	trackId,
+	trackType,
+}: {
+	tracks: SceneTracks;
+	insertIndex: number;
+	trackId: string;
+	trackType: Exclude<TrackType, "audio">;
+}): SceneTracks {
+	const overlayInsertIndex = Math.min(insertIndex, tracks.overlay.length);
+	const newTrack =
+		trackType === "video"
+			? buildEmptyTrack({ id: trackId, type: "video" })
+			: trackType === "text"
+				? buildEmptyTrack({ id: trackId, type: "text" })
+				: trackType === "graphic"
+					? buildEmptyTrack({ id: trackId, type: "graphic" })
+					: buildEmptyTrack({ id: trackId, type: "effect" });
+	return {
+		...tracks,
+		overlay: [
+			...tracks.overlay.slice(0, overlayInsertIndex),
+			newTrack,
+			...tracks.overlay.slice(overlayInsertIndex),
+		],
+	};
+}