frontend/src/api/response.ts

@@ -0,0 +1,24 @@
+export interface LetterResponseData {
+  public_id: string;
+  type: "KEPT" | "SENT" | "VAULT";
+  status: "DRAFT" | "SEALED" | "BURNED";
+  encrypted_content: string;
+  encrypted_metadata: string;
+  encrypted_dek: string;
+  unlock_at: string | null;
+  sealed_at: string | null;
+  created_at: string;
+  updated_at: string;
+  images: LetterImageData[];
+}
+
+export interface LetterImageData {
+  public_id: string;
+  file: string;
+  file_name: string;
+}
+
+export interface LetterMetadata {
+  recipient: string;
+  tags?: string[];
+}

frontend/src/hooks/useLetters.tsx

@@ -1,32 +1,16 @@
 import { useEffect, useMemo, useState } from "react";
 import { api } from "../api/apiClient";
+import type { LetterMetadata, LetterResponseData } from "../api/response";
 import { endpoints } from "../config/endpoints";
 import { useKeyStore } from "../store/useKeyStore";
 import { CryptoUtils } from "../utils/crypto";
 
-export interface Letter {
-  public_id: string;
-  type: "KEPT" | "VAULT" | "SENT";
-  status: "DRAFT" | "SEALED" | "BURNED";
-  updated_at: string;
-  sealed_at?: string;
-  unlock_at: string;
-  encrypted_metadata: string;
-  encrypted_content: string;
-  encrypted_dek: string;
-}
-
-export interface LetterMetadata {
-  recipient: string;
-  tags?: string[];
-}
-
-export interface ProcessedLetter extends Letter {
+export interface ProcessedLetter extends LetterResponseData {
     metadata: LetterMetadata;
 }
 
 async function decryptLettersMetadata(
-  letters: Letter[],
+    letters: LetterResponseData[],
     masterKey: CryptoKey,
 ): Promise<ProcessedLetter[]> {
     const cryptoUtils = new CryptoUtils();
@@ -43,7 +27,7 @@ async function decryptLettersMetadata(
                 )) as LetterMetadata;
 
                 return { ...letter, metadata };
-      } catch (_err) {
+            } catch {
                 return {
                     ...letter,
                     metadata: { recipient: "Encrypted Letter" },

frontend/src/pages/Reader.tsx

@@ -1,4 +1,5 @@
 import { FlameIcon, PaperPlaneTiltIcon } from "@phosphor-icons/react";
+import type { AxiosResponse } from "axios";
 import { useEffect, useRef, useState } from "react";
 import {
   type NavigateFunction,
@@ -7,6 +8,7 @@ import {
   useParams,
 } from "react-router-dom";
 import { api } from "../api/apiClient";
+import type { LetterImageData, LetterResponseData } from "../api/response";
 import {
   type CanvasJSON,
   type CanvasTools,
@@ -103,30 +105,54 @@ export default function Reader() {
       return;
     }
 
-    const loadAndDecrypt = async () => {
+    const decryptImages = async (
+      canvasData: CanvasJSON,
+      images: LetterImageData[],
+      encrypted_dek: string,
+      cryptoUtils: CryptoUtils,
+    ) => {
+      if (!images?.length) return;
+      const isShared = !!sharingKey;
       try {
-        const response = await api.get(`${endpoints.LETTERS}${public_id}/`);
+        if (isShared) {
+          await decryptCanvasImagesWithSharingKey(
+            canvasData,
+            images,
+            sharingKey,
+            cryptoUtils,
+          );
+        } else {
+          await decryptCanvasImages(
+            canvasData,
+            images,
+            encrypted_dek,
+            // biome-ignore lint/style/noNonNullAssertion: masterKey is guaranteed to be non-null here as isDecryptionKeyAvailable is true
+            masterKey!,
+            cryptoUtils,
+          );
+        }
+      } catch (err) {
+        setLogTrace({
+          message:
+            "Failed to decrypt elements. Images might not render in the letter as intended.",
+          log: err instanceof Error ? err.message : "Unknown error",
+          type: "WARN",
+        });
+      }
+    };
+
+    const decryptLetterData = async (
+      data: LetterResponseData,
+      cryptoUtils: CryptoUtils,
+    ) => {
+      const isShared = !!sharingKey;
       const {
         encrypted_content,
         encrypted_metadata,
         encrypted_dek,
         images,
         updated_at,
-          status,
-        } = response.data;
-
-        if (status === "BURNED")
-          throw new Error("This letter has been burned.");
-
-        if (encrypted_dek) setEncryptedDek(encrypted_dek);
-
-        const cryptoUtils = new CryptoUtils();
-        const isShared = !!sharingKey;
-
-        if (isShared && !encrypted_content) throw new Error("Content missing");
-        const isDecryptionKeyAvailable = encrypted_dek && masterKey;
-        if (!(isShared || isDecryptionKeyAvailable))
-          throw new Error("Auth required: Decryption key is not available");
+      } = data;
 
       // Decrypt Metadata
       const decryptedMetadata = isShared
@@ -157,35 +183,29 @@ export default function Reader() {
           );
 
       const canvasData: CanvasJSON = JSON.parse(decryptedContent);
-
-        try {
-          // Decrypt Images
-          if (images?.length > 0) {
-            isShared
-              ? await decryptCanvasImagesWithSharingKey(
-                  canvasData,
-                  images,
-                  sharingKey,
-                  cryptoUtils,
-                )
-              : await decryptCanvasImages(
-                  canvasData,
-                  images,
-                  encrypted_dek,
-                  // biome-ignore lint/style/noNonNullAssertion: masterKey is guaranteed to be non-null here as isDecryptionKeyAvailable is true
-                  masterKey!,
-                  cryptoUtils,
-                );
-          }
-        } catch (err) {
-          setLogTrace({
-            message:
-              "Failed to decrypt elements. Images might not render in the letter as intended.",
-            log: err instanceof Error ? err.message : "Unknown error",
-            type: "WARN",
-          });
-        }
+      await decryptImages(canvasData, images, encrypted_dek, cryptoUtils);
       setDecryptedCanvasData(canvasData);
+    };
+
+    const loadAndDecrypt = async () => {
+      try {
+        const response: AxiosResponse<LetterResponseData> = await api.get(
+          `${endpoints.LETTERS}${public_id}/`,
+        );
+        const data = response.data;
+
+        if (data.status === "BURNED")
+          throw new Error("This letter has been burned.");
+
+        if (data.encrypted_dek) setEncryptedDek(data.encrypted_dek);
+
+        const isDecryptionKeyAvailable = data.encrypted_dek && masterKey;
+        if (!(!!sharingKey || isDecryptionKeyAvailable)) {
+          throw new Error("Auth required: Decryption key is not available");
+        }
+
+        const cryptoUtils = new CryptoUtils();
+        await decryptLetterData(data, cryptoUtils);
       } catch (err) {
         setLogTrace({
           message: `Failed to load letter ☹`,

frontend/src/utils/crypto.ts

@@ -1,3 +1,5 @@
+import type { LetterMetadata } from "../api/response";
+
 export interface EncryptedLetter {
   encrypted_content: string;
   encrypted_dek: string;
@@ -275,7 +277,7 @@ export class CryptoUtils {
   }
 
   public async encryptMetadata(
-    metadata: Record<string, any>,
+    metadata: LetterMetadata,
     masterKey: CryptoKey,
   ): Promise<EncryptedLetterMetadata> {
     const { encryptedContent, encrypted_dek, sharingKey } =
@@ -290,7 +292,7 @@ export class CryptoUtils {
   public async decryptMetadata(
     encrypted_metadata: EncryptedLetter,
     masterKey: CryptoKey,
-  ): Promise<Record<string, any>> {
+  ): Promise<LetterMetadata> {
     const bytes = await this.openEnvelope(
       encrypted_metadata.encrypted_content,
       encrypted_metadata.encrypted_dek,
@@ -303,7 +305,7 @@ export class CryptoUtils {
   public async decryptMetadataWithSharingKey(
     encrypted_content: string,
     sharingKey: string,
-  ): Promise<Record<string, any>> {
+  ): Promise<LetterMetadata> {
     const bytes = await this.openEnvelopeWithSharingKey(
       encrypted_content,
       sharingKey,

frontend/src/utils/letterLogic.test.ts

@@ -221,7 +221,11 @@ describe("letterLogic image helpers", () => {
         ],
       };
       const remoteImages = [
-        { file_name: "photo.png.bin", file: "https://remote/photo.png.bin" },
+        {
+          public_id: "1234",
+          file_name: "photo.png.bin",
+          file: "https://remote/photo.png.bin",
+        },
       ];
 
       vi.mocked(api.get).mockResolvedValue({ data: new Blob(["encrypted"]) });

frontend/src/utils/letterLogic.ts

@@ -1,4 +1,5 @@
 import { api, apiServerUrl, publicApi } from "../api/apiClient";
+import type { LetterImageData } from "../api/response";
 import type {
   CanvasJSON,
   FabricImageJSON,
@@ -111,7 +112,7 @@ export async function decryptCanvasImages(
 
 export async function decryptCanvasImagesWithSharingKey(
   canvasData: CanvasJSON,
-  remoteImages: { file_name: string; file: string }[],
+  remoteImages: LetterImageData[],
   sharingKey: string,
   cryptoUtils: CryptoUtils,
 ): Promise<DecryptionResult> {