add AI metadata checking to block image uploads with notice

apps/frontend/src/helpers/c2pa.ts

@@ -0,0 +1,41 @@
+import type { C2paSdk } from '@contentauth/c2pa-web'
+import { createC2pa, isSupportedReaderFormat } from '@contentauth/c2pa-web/inline'
+
+// https://cv.iptc.org/newscodes/digitalsourcetype/
+// only detecting generative AI types
+const AI_DIGITAL_SOURCE_TYPES = [
+	'http://cv.iptc.org/newscodes/digitalsourcetype/trainedAlgorithmicMedia',
+	'http://cv.iptc.org/newscodes/digitalsourcetype/trainedAlgorithmicData',
+	'http://cv.iptc.org/newscodes/digitalsourcetype/compositeWithTrainedAlgorithmicMedia',
+	'http://cv.iptc.org/newscodes/digitalsourcetype/compositeSynthetic',
+]
+
+let c2paInstance: Promise<C2paSdk> | null = null
+
+function getC2pa() {
+	if (!c2paInstance) {
+		c2paInstance = createC2pa()
+	}
+	return c2paInstance
+}
+
+// reference: https://github.com/contentauth/c2pa-js/blob/main/packages/c2pa-web/README.md
+export async function fileDeclaresAi(file: File): Promise<boolean> {
+	try {
+		if (!isSupportedReaderFormat(file.type)) {
+			return false
+		}
+
+		const c2pa = await getC2pa()
+
+		const reader = await c2pa.reader.fromBlob(file.type, file)
+		const manifestStore = await reader.manifestStore()
+
+		await reader.free()
+
+		const manifestJson = JSON.stringify(manifestStore)
+		return AI_DIGITAL_SOURCE_TYPES.some((type) => manifestJson.includes(type))
+	} catch {
+		return false
+	}
+}