feat: ensure elements on main track starts at 0

3 files changed, 63 insertions, 7 deletions

diff --git a/apps/web/src/lib/commands/timeline/element/insert-element.ts b/apps/web/src/lib/commands/timeline/element/insert-element.ts
index f95935a5..6067d72b 100644
--- a/apps/web/src/lib/commands/timeline/element/insert-element.ts
+++ b/apps/web/src/lib/commands/timeline/element/insert-element.ts
@@ -17,6 +17,7 @@ import {
 	canElementGoOnTrack,
 	getDefaultInsertIndexForTrack,
 	validateElementTrackCompatibility,
+	enforceMainTrackStart,
 } from "@/lib/timeline/track-utils";
 import type { MediaAsset } from "@/types/assets";
 import { TIMELINE_CONSTANTS } from "@/constants/timeline-constants";
@@ -204,9 +205,18 @@ export class InsertElementCommand extends Command {
 				return null;
 			}
 
+			const adjustedElement = this.adjustElementForMainTrack({
+				tracks,
+				targetTrackId: targetTrack.id,
+				element,
+			});
+
 			const updatedTracks = tracks.map((track) =>
 				track.id === targetTrack.id
-					? { ...track, elements: [...track.elements, element] }
+					? {
+							...track,
+							elements: [...track.elements, adjustedElement],
+						}
 					: track,
 			) as TimelineTrack[];
 
@@ -248,9 +258,18 @@ export class InsertElementCommand extends Command {
 		});
 
 		if (existingTrack) {
+			const adjustedElement = this.adjustElementForMainTrack({
+				tracks,
+				targetTrackId: existingTrack.id,
+				element,
+			});
+
 			const updatedTracks = tracks.map((track) =>
 				track.id === existingTrack.id
-					? { ...track, elements: [...track.elements, element] }
+					? {
+							...track,
+							elements: [...track.elements, adjustedElement],
+						}
 					: track,
 			) as TimelineTrack[];
 
@@ -298,6 +317,23 @@ export class InsertElementCommand extends Command {
 		});
 	}
 
+	private adjustElementForMainTrack({
+		tracks,
+		targetTrackId,
+		element,
+	}: {
+		tracks: TimelineTrack[];
+		targetTrackId: string;
+		element: TimelineElement;
+	}): TimelineElement {
+		const adjustedStartTime = enforceMainTrackStart({
+			tracks,
+			targetTrackId,
+			requestedStartTime: element.startTime,
+		});
+		return { ...element, startTime: adjustedStartTime };
+	}
+
 	private getTrackTypeForElement({
 		element,
 	}: {
diff --git a/apps/web/src/lib/commands/timeline/element/move-elements.ts b/apps/web/src/lib/commands/timeline/element/move-elements.ts
index 2d4f9236..2fe06694 100644
--- a/apps/web/src/lib/commands/timeline/element/move-elements.ts
+++ b/apps/web/src/lib/commands/timeline/element/move-elements.ts
@@ -9,6 +9,7 @@ import {
 	buildEmptyTrack,
 	isMainTrack,
 	validateElementTrackCompatibility,
+	enforceMainTrackStart,
 } from "@/lib/timeline/track-utils";
 
 export class MoveElementCommand extends Command {
@@ -66,9 +67,16 @@ export class MoveElementCommand extends Command {
 			return;
 		}
 
+		const adjustedStartTime = enforceMainTrackStart({
+			tracks: tracksToUpdate,
+			targetTrackId: this.targetTrackId,
+			requestedStartTime: this.newStartTime,
+			excludeElementId: this.elementId,
+		});
+
 		const movedElement: TimelineElement = {
 			...element,
-			startTime: this.newStartTime,
+			startTime: adjustedStartTime,
 		};
 
 		const isSameTrack = this.sourceTrackId === this.targetTrackId;
diff --git a/apps/web/src/lib/commands/timeline/element/update-element-start-time.ts b/apps/web/src/lib/commands/timeline/element/update-element-start-time.ts
index 5312000f..51dcb63d 100644
--- a/apps/web/src/lib/commands/timeline/element/update-element-start-time.ts
+++ b/apps/web/src/lib/commands/timeline/element/update-element-start-time.ts
@@ -1,6 +1,7 @@
 import { Command } from "@/lib/commands/base-command";
 import type { TimelineTrack } from "@/types/timeline";
 import { EditorCore } from "@/core";
+import { enforceMainTrackStart } from "@/lib/timeline/track-utils";
 
 export class UpdateElementStartTimeCommand extends Command {
 	private savedState: TimelineTrack[] | null = null;
@@ -16,7 +17,8 @@ export class UpdateElementStartTimeCommand extends Command {
 		const editor = EditorCore.getInstance();
 		this.savedState = editor.timeline.getTracks();
 
-		const updatedTracks = this.savedState.map((track) => {
+		const currentTracks = this.savedState;
+		const updatedTracks = currentTracks.map((track) => {
 			const hasElementsToUpdate = this.elements.some(
 				(el) => el.trackId === track.id,
 			);
@@ -29,9 +31,19 @@ export class UpdateElementStartTimeCommand extends Command {
 				const shouldUpdate = this.elements.some(
 					(el) => el.elementId === element.id && el.trackId === track.id,
 				);
-				return shouldUpdate
-					? { ...element, startTime: Math.max(0, this.startTime) }
-					: element;
+				if (!shouldUpdate) {
+					return element;
+				}
+
+				const baseStartTime = Math.max(0, this.startTime);
+				const adjustedStartTime = enforceMainTrackStart({
+					tracks: currentTracks,
+					targetTrackId: track.id,
+					requestedStartTime: baseStartTime,
+					excludeElementId: element.id,
+				});
+
+				return { ...element, startTime: adjustedStartTime };
 			});
 			return { ...track, elements: newElements } as typeof track;
 		});