refactor: extract payload pack/unpack pipeline into @cryptgeon/shared

packages/shared/src/payload.ts

@@ -0,0 +1,49 @@
+import { encode, decode } from "@msgpack/msgpack";
+import { compress, decompress } from "./compression.js";
+import {
+  deriveKey,
+  encrypt,
+  decrypt,
+  generateKey,
+  randomBytes,
+} from "./crypto.js";
+import type { FileDTO, NoteContent } from "./types.js";
+
+export type NoteInput =
+  | { type: "text"; text: string }
+  | { type: "files"; files: FileDTO[] };
+
+export type PackResult = {
+  data: Uint8Array;
+  extra: Uint8Array;
+  key: Uint8Array;
+};
+
+export function packContent(input: NoteInput, password?: string): PackResult {
+  let key: Uint8Array;
+  let extra: Uint8Array;
+  if (password) {
+    const salt = randomBytes(16);
+    key = deriveKey(password, salt);
+    extra = encode({ salt, N: 32768, r: 8, p: 1 });
+  } else {
+    key = generateKey();
+    extra = new Uint8Array();
+  }
+
+  const content: NoteContent =
+    input.type === "text"
+      ? { type: "text", data: input.text }
+      : { type: "files", data: input.files };
+
+  const encoded = encrypt(compress(encode(content)), key);
+  return { data: encoded, extra, key };
+}
+
+export function unpackContent(data: Uint8Array, key: Uint8Array): NoteContent {
+  const content = decode(decompress(decrypt(data, key))) as NoteContent;
+  if (content.type !== "text" && content.type !== "files") {
+    throw new Error("Unknown content type");
+  }
+  return content;
+}