Move app to apps/web-react in pnpm workspace layout

apps/web-react/app/features/img-upload/image-bytes.server.ts

@@ -0,0 +1,53 @@
+import invariant from "~/utils/invariant";
+
+export type ImageExtension = "webp" | "png" | "jpeg";
+
+/**
+ * Decodes a base64 image data URL to a buffer, resolving the format from the buffer's own magic
+ * bytes rather than trusting the client-declared mime type, and asserting it is one of
+ * `allowedExtensions`.
+ */
+export function dataUrlToImageBuffer(
+	dataUrl: string,
+	allowedExtensions: ReadonlyArray<ImageExtension>,
+) {
+	const base64 = dataUrl.slice(dataUrl.indexOf(",") + 1);
+	const buffer = Buffer.from(base64, "base64");
+
+	const extension = imageExtensionFromMagicBytes(buffer);
+	invariant(
+		extension && allowedExtensions.includes(extension),
+		`Submitted image is not a valid ${allowedExtensions.join(" or ")}`,
+	);
+
+	return { buffer, extension };
+}
+
+function imageExtensionFromMagicBytes(buffer: Buffer): ImageExtension | null {
+	if (
+		buffer.length > 12 &&
+		buffer.toString("ascii", 0, 4) === "RIFF" &&
+		buffer.toString("ascii", 8, 12) === "WEBP"
+	) {
+		return "webp";
+	}
+
+	if (
+		buffer.length > 8 &&
+		buffer[0] === 0x89 &&
+		buffer.toString("ascii", 1, 4) === "PNG"
+	) {
+		return "png";
+	}
+
+	if (
+		buffer.length > 3 &&
+		buffer[0] === 0xff &&
+		buffer[1] === 0xd8 &&
+		buffer[2] === 0xff
+	) {
+		return "jpeg";
+	}
+
+	return null;
+}