add ViewerView decrypt from URL fragment via view store

frontend/src/stores/view.ts

@@ -0,0 +1,48 @@
+import { defineStore } from 'pinia';
+import { ref } from 'vue';
+import { api } from '@/plugins/axios';
+import type { GetZkUploadCiphertextResult } from '@/types/upload/GetZkUploadCiphertextResult';
+import { base64ToBytes } from '@/utils/encoding/base64ToBytes';
+import { toArrayBuffer } from '@/utils/toArrayBuffer';
+import { decryptZkUpload } from '@/utils/upload/decryptZkUpload';
+
+export const useViewStore = defineStore('view', () => {
+    const imageObjectUrl = ref<string | null>(null);
+
+    const clearImage = (): void => {
+        if (imageObjectUrl.value) {
+            URL.revokeObjectURL(imageObjectUrl.value);
+            imageObjectUrl.value = null;
+        }
+    };
+
+    const fetchZkCiphertext = async (uploadId: string): Promise<GetZkUploadCiphertextResult> => {
+        const { data } = await api.get<GetZkUploadCiphertextResult>(`/uploads/${uploadId}`);
+
+        return data;
+    };
+
+    const loadZk = async (payload: GetZkUploadCiphertextResult, fragmentKey: string): Promise<void> => {
+        clearImage();
+
+        const iv = base64ToBytes(payload.iv);
+        const ciphertext = base64ToBytes(payload.ciphertext);
+
+        const plaintext = await decryptZkUpload(ciphertext, iv, fragmentKey);
+
+        const buffer = toArrayBuffer(plaintext);
+
+        if (!buffer) {
+            throw new Error('Could not build image blob');
+        }
+
+        imageObjectUrl.value = URL.createObjectURL(new Blob([buffer]));
+    };
+
+    return {
+        imageObjectUrl,
+        fetchZkCiphertext,
+        loadZk,
+        clearImage
+    };
+});