1 files changed, 219 insertions, 0 deletions
diff --git a/apps/web/src/lib/preview/element-bounds.ts b/apps/web/src/lib/preview/element-bounds.ts
new file mode 100644
index 00000000..ec26c14d
--- /dev/null
+++ b/apps/web/src/lib/preview/element-bounds.ts
@@ -0,0 +1,219 @@
+import type { TimelineTrack, TimelineElement } from "@/types/timeline";
+import type { MediaAsset } from "@/types/assets";
+import { isMainTrack } from "@/lib/timeline";
+import {
+	DEFAULT_LINE_HEIGHT,
+	FONT_SIZE_SCALE_REFERENCE,
+} from "@/constants/text-constants";
+
+export interface ElementBounds {
+	cx: number;
+	cy: number;
+	width: number;
+	height: number;
+	rotation: number;
+}
+
+export interface ElementWithBounds {
+	trackId: string;
+	elementId: string;
+	element: TimelineElement;
+	bounds: ElementBounds;
+}
+
+function getVisualElementBounds({
+	canvasWidth,
+	canvasHeight,
+	sourceWidth,
+	sourceHeight,
+	transform,
+}: {
+	canvasWidth: number;
+	canvasHeight: number;
+	sourceWidth: number;
+	sourceHeight: number;
+	transform: {
+		scale: number;
+		position: { x: number; y: number };
+		rotate: number;
+	};
+}): ElementBounds {
+	const containScale = Math.min(
+		canvasWidth / sourceWidth,
+		canvasHeight / sourceHeight,
+	);
+	const scaledWidth = sourceWidth * containScale * transform.scale;
+	const scaledHeight = sourceHeight * containScale * transform.scale;
+	const cx = canvasWidth / 2 + transform.position.x;
+	const cy = canvasHeight / 2 + transform.position.y;
+
+	return {
+		cx,
+		cy,
+		width: scaledWidth,
+		height: scaledHeight,
+		rotation: transform.rotate,
+	};
+}
+
+export function getElementBounds({
+	element,
+	canvasSize,
+	mediaAsset,
+}: {
+	element: TimelineElement;
+	canvasSize: { width: number; height: number };
+	mediaAsset?: MediaAsset | null;
+}): ElementBounds | null {
+	if (element.type === "audio") return null;
+	if ("hidden" in element && element.hidden) return null;
+
+	const { width: canvasWidth, height: canvasHeight } = canvasSize;
+
+	if (element.type === "video" || element.type === "image") {
+		const sourceWidth = mediaAsset?.width ?? canvasWidth;
+		const sourceHeight = mediaAsset?.height ?? canvasHeight;
+		return getVisualElementBounds({
+			canvasWidth,
+			canvasHeight,
+			sourceWidth,
+			sourceHeight,
+			transform: element.transform,
+		});
+	}
+
+	if (element.type === "sticker") {
+		return getVisualElementBounds({
+			canvasWidth,
+			canvasHeight,
+			sourceWidth: 200,
+			sourceHeight: 200,
+			transform: element.transform,
+		});
+	}
+
+	if (element.type === "text") {
+		const scaledFontSize =
+			element.fontSize * (canvasHeight / FONT_SIZE_SCALE_REFERENCE);
+		const letterSpacing = element.letterSpacing ?? 0;
+		const lineHeight = element.lineHeight ?? DEFAULT_LINE_HEIGHT;
+		const lineHeightPx = scaledFontSize * lineHeight;
+
+		let measuredWidth = 100;
+		let measuredHeight = scaledFontSize;
+
+		const canvas = document.createElement("canvas");
+		canvas.width = 4096;
+		canvas.height = 4096;
+		const ctx = canvas.getContext("2d");
+
+		if (ctx) {
+			const fontWeight = element.fontWeight === "bold" ? "bold" : "normal";
+			const fontStyle = element.fontStyle === "italic" ? "italic" : "normal";
+			const fontFamily = `"${element.fontFamily.replace(/"/g, '\\"')}"`;
+			ctx.font = `${fontStyle} ${fontWeight} ${scaledFontSize}px ${fontFamily}, sans-serif`;
+			ctx.textAlign = element.textAlign as CanvasTextAlign;
+			if ("letterSpacing" in ctx) {
+				(
+					ctx as CanvasRenderingContext2D & { letterSpacing: string }
+				).letterSpacing = `${letterSpacing}px`;
+			}
+
+			const lines = element.content.split("\n");
+			const lineMetrics = lines.map((line) => ctx.measureText(line));
+
+			let top = Number.POSITIVE_INFINITY;
+			let bottom = Number.NEGATIVE_INFINITY;
+			let maxWidth = 0;
+
+			for (let i = 0; i < lineMetrics.length; i++) {
+				const metrics = lineMetrics[i];
+				const y = i * lineHeightPx;
+				top = Math.min(
+					top,
+					y - (metrics.actualBoundingBoxAscent ?? scaledFontSize * 0.8),
+				);
+				bottom = Math.max(
+					bottom,
+					y + (metrics.actualBoundingBoxDescent ?? scaledFontSize * 0.2),
+				);
+				maxWidth = Math.max(maxWidth, metrics.width);
+			}
+
+			measuredWidth = maxWidth;
+			measuredHeight = bottom - top;
+		}
+
+		const width = measuredWidth * element.transform.scale;
+		const height = measuredHeight * element.transform.scale;
+		return {
+			cx: canvasWidth / 2 + element.transform.position.x,
+			cy: canvasHeight / 2 + element.transform.position.y,
+			width,
+			height,
+			rotation: element.transform.rotate,
+		};
+	}
+
+	return null;
+}
+
+export function getVisibleElementsWithBounds({
+	tracks,
+	currentTime,
+	canvasSize,
+	mediaAssets,
+}: {
+	tracks: TimelineTrack[];
+	currentTime: number;
+	canvasSize: { width: number; height: number };
+	mediaAssets: MediaAsset[];
+}): ElementWithBounds[] {
+	const mediaMap = new Map(mediaAssets.map((m) => [m.id, m]));
+	const visibleTracks = tracks.filter(
+		(track) => !("hidden" in track && track.hidden),
+	);
+	const orderedTracks = [
+		...visibleTracks.filter((track) => !isMainTrack(track)),
+		...visibleTracks.filter((track) => isMainTrack(track)),
+	].reverse();
+
+	const result: ElementWithBounds[] = [];
+
+	for (const track of orderedTracks) {
+		const elements = track.elements
+			.filter((element) => !("hidden" in element && element.hidden))
+			.filter(
+				(element) =>
+					currentTime >= element.startTime &&
+					currentTime < element.startTime + element.duration,
+			)
+			.slice()
+			.sort((a, b) => {
+				if (a.startTime !== b.startTime) return a.startTime - b.startTime;
+				return a.id.localeCompare(b.id);
+			});
+
+		for (const element of elements) {
+			const mediaAsset =
+				element.type === "video" || element.type === "image"
+					? mediaMap.get(element.mediaId)
+					: undefined;
+			const bounds = getElementBounds({
+				element,
+				canvasSize,
+				mediaAsset,
+			});
+			if (bounds) {
+				result.push({
+					trackId: track.id,
+					elementId: element.id,
+					element,
+					bounds,
+				});
+			}
+		}
+	}
+
+	return result;
+}