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
+    };
+});

frontend/src/types/upload/GetZkUploadCiphertextResult.ts

@@ -0,0 +1,8 @@
+export type GetZkUploadCiphertextResult = {
+    iv: string;
+    ciphertext: string;
+    passwordProtected: boolean;
+    wrappedDek?: string;
+    wrapIv?: string;
+    salt?: string;
+};

frontend/src/views/ViewerView.vue

@@ -1,6 +1,54 @@
 <template>
-    <main class="flex min-h-screen flex-col p-8">
-        <h1 class="text-2xl font-semibold tracking-tight">Viewer</h1>
-        <p class="mt-2 text-muted-foreground">Zero-knowledge viewer — coming soon.</p>
+    <main class="flex min-h-screen items-center justify-center p-4">
+        <p v-if="fetching" class="text-sm text-muted-foreground">Loading image...</p>
+
+        <img v-else-if="imageObjectUrl" :src="imageObjectUrl" class="max-h-[80vh] max-w-full object-contain" />
     </main>
 </template>
+
+<script setup lang="ts">
+import { storeToRefs } from 'pinia';
+import { onBeforeMount, onBeforeUnmount, ref } from 'vue';
+import { useRoute } from 'vue-router';
+import { useViewStore } from '@/stores/view';
+
+const route = useRoute();
+const viewStore = useViewStore();
+const { imageObjectUrl } = storeToRefs(viewStore);
+
+const fetching = ref(false);
+
+onBeforeMount(async () => {
+    const uploadId = route.params.id;
+
+    if (typeof uploadId !== 'string') {
+        return;
+    }
+
+    const fragmentKey = route.hash.slice(1);
+
+    if (!fragmentKey) {
+        return;
+    }
+
+    fetching.value = true;
+
+    try {
+        const payload = await viewStore.fetchZkCiphertext(uploadId);
+
+        if (payload.passwordProtected) {
+            return;
+        }
+
+        await viewStore.loadZk(payload, fragmentKey);
+    } catch (error) {
+        console.error('[viewer] load failed', { uploadId, error });
+    } finally {
+        fetching.value = false;
+    }
+});
+
+onBeforeUnmount(() => {
+    viewStore.clearImage();
+});
+</script>