From 3e89d2998588f8e35c524e523ba2ee853f0f6475 Mon Sep 17 00:00:00 2001
From: Maze Winther <mazewinther@gmail.com>
Date: Mon, 20 Apr 2026 11:31:17 +0200
Subject: refactor: restructure files to their domains,  new preview overlay
 system, and dep graph

---
 .../commands/timeline/element/split-elements.ts    | 182 +++++++++++++++++++++
 1 file changed, 182 insertions(+)
 create mode 100644 apps/web/src/commands/timeline/element/split-elements.ts

(limited to 'apps/web/src/commands/timeline/element/split-elements.ts')

diff --git a/apps/web/src/commands/timeline/element/split-elements.ts b/apps/web/src/commands/timeline/element/split-elements.ts
new file mode 100644
index 00000000..11c317f4
--- /dev/null
+++ b/apps/web/src/commands/timeline/element/split-elements.ts
@@ -0,0 +1,182 @@
+import {
+	Command,
+	createElementSelectionResult,
+	type CommandResult,
+} from "@/commands/base-command";
+import type { SceneTracks, TimelineElement } from "@/timeline";
+import { generateUUID } from "@/utils/id";
+import { EditorCore } from "@/core";
+import { isRetimableElement } from "@/timeline";
+import { splitAnimationsAtTime } from "@/animation";
+import { getSourceSpanAtClipTime } from "@/retime";
+
+export class SplitElementsCommand extends Command {
+	private savedState: SceneTracks | null = null;
+	private rightSideElements: { trackId: string; elementId: string }[] = [];
+	private readonly elements: { trackId: string; elementId: string }[];
+	private readonly splitTime: number;
+	private readonly retainSide: "both" | "left" | "right";
+
+	constructor({
+		elements,
+		splitTime,
+		retainSide = "both",
+	}: {
+		elements: { trackId: string; elementId: string }[];
+		splitTime: number;
+		retainSide?: "both" | "left" | "right";
+	}) {
+		super();
+		this.elements = elements;
+		this.splitTime = splitTime;
+		this.retainSide = retainSide;
+	}
+
+	getRightSideElements(): { trackId: string; elementId: string }[] {
+		return this.rightSideElements;
+	}
+
+	execute(): CommandResult | undefined {
+		const editor = EditorCore.getInstance();
+		this.savedState = editor.scenes.getActiveScene().tracks;
+		this.rightSideElements = [];
+
+		const splitTrack = <
+			TTrack extends { id: string; elements: TimelineElement[] },
+		>(
+			track: TTrack,
+		): TTrack => {
+			const elementsToSplit = this.elements.filter(
+				(target) => target.trackId === track.id,
+			);
+
+			if (elementsToSplit.length === 0) {
+				return track;
+			}
+
+			const elements = track.elements.flatMap((element) => {
+				const shouldSplit = elementsToSplit.some(
+					(target) => target.elementId === element.id,
+				);
+
+				if (!shouldSplit) {
+					return [element];
+				}
+
+				const effectiveStart = element.startTime;
+				const effectiveEnd = element.startTime + element.duration;
+
+				if (
+					this.splitTime <= effectiveStart ||
+					this.splitTime >= effectiveEnd
+				) {
+					return [element];
+				}
+
+				const relativeTime = this.splitTime - element.startTime;
+				const leftVisibleDuration = relativeTime;
+				const rightVisibleDuration = element.duration - relativeTime;
+				const retimeRef = isRetimableElement(element)
+					? element.retime
+					: undefined;
+				const leftSourceSpan = getSourceSpanAtClipTime({
+					clipTime: leftVisibleDuration,
+					retime: retimeRef,
+				});
+				const totalSourceSpan = getSourceSpanAtClipTime({
+					clipTime: element.duration,
+					retime: retimeRef,
+				});
+				const rightSourceSpan = totalSourceSpan - leftSourceSpan;
+				const { leftAnimations, rightAnimations } = splitAnimationsAtTime({
+					animations: element.animations,
+					splitTime: relativeTime,
+					shouldIncludeSplitBoundary: true,
+				});
+				let splitResult: TimelineElement[];
+
+				if (this.retainSide === "left") {
+					splitResult = [
+						{
+							...element,
+							duration: leftVisibleDuration,
+							trimEnd: element.trimEnd + rightSourceSpan,
+							name: `${element.name} (left)`,
+							animations: leftAnimations,
+							...(retimeRef !== undefined ? { retime: retimeRef } : {}),
+						},
+					];
+				} else if (this.retainSide === "right") {
+					const newId = generateUUID();
+					this.rightSideElements.push({
+						trackId: track.id,
+						elementId: newId,
+					});
+					splitResult = [
+						{
+							...element,
+							id: newId,
+							startTime: this.splitTime,
+							duration: rightVisibleDuration,
+							trimStart: element.trimStart + leftSourceSpan,
+							name: `${element.name} (right)`,
+							animations: rightAnimations,
+							...(retimeRef !== undefined ? { retime: retimeRef } : {}),
+						},
+					];
+				} else {
+					// "both" - split into two pieces
+					const secondElementId = generateUUID();
+					this.rightSideElements.push({
+						trackId: track.id,
+						elementId: secondElementId,
+					});
+					splitResult = [
+						{
+							...element,
+							duration: leftVisibleDuration,
+							trimEnd: element.trimEnd + rightSourceSpan,
+							name: `${element.name} (left)`,
+							animations: leftAnimations,
+							...(retimeRef !== undefined ? { retime: retimeRef } : {}),
+						},
+						{
+							...element,
+							id: secondElementId,
+							startTime: this.splitTime,
+							duration: rightVisibleDuration,
+							trimStart: element.trimStart + leftSourceSpan,
+							name: `${element.name} (right)`,
+							animations: rightAnimations,
+							...(retimeRef !== undefined ? { retime: retimeRef } : {}),
+						},
+					];
+				}
+
+				return splitResult;
+			});
+
+			return { ...track, elements } as TTrack;
+		};
+
+		const updatedTracks: SceneTracks = {
+			overlay: this.savedState.overlay.map((track) => splitTrack(track)),
+			main: splitTrack(this.savedState.main),
+			audio: this.savedState.audio.map((track) => splitTrack(track)),
+		};
+
+		editor.timeline.updateTracks(updatedTracks);
+
+		if (this.rightSideElements.length > 0) {
+			return createElementSelectionResult(this.rightSideElements);
+		}
+		return undefined;
+	}
+
+	undo(): void {
+		if (this.savedState) {
+			const editor = EditorCore.getInstance();
+			editor.timeline.updateTracks(this.savedState);
+		}
+	}
+}
-- 
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