refactor(storage): use unstorage for session state

src/lib/chat/chat_scroll_session_storage.ts

@@ -0,0 +1,47 @@
+"use client";
+
+import { z } from "zod";
+
+import { StorageKeys } from "@/data/storage/storage_keys";
+import { Result, SessionAsyncUtil, type Result as ResultT } from "@/utils";
+
+const ChatScrollSessionSchema = z.object({
+  scrollTop: z.number(),
+  scrollHeight: z.number(),
+  clientHeight: z.number(),
+  distanceFromBottom: z.number(),
+  savedAt: z.number(),
+});
+
+export type ChatScrollSession = z.output<typeof ChatScrollSessionSchema>;
+
+export class ChatScrollSessionStorage {
+  private constructor() {}
+
+  static setSnapshot(snapshot: ChatScrollSession): Promise<ResultT<void>> {
+    return SessionAsyncUtil.setJson(
+      StorageKeys.chatScrollSession,
+      snapshot,
+      ChatScrollSessionSchema,
+    );
+  }
+
+  static getSnapshot(): Promise<ResultT<ChatScrollSession | null>> {
+    return SessionAsyncUtil.getJson(
+      StorageKeys.chatScrollSession,
+      ChatScrollSessionSchema,
+    );
+  }
+
+  static clearSnapshot(): Promise<ResultT<void>> {
+    return SessionAsyncUtil.remove(StorageKeys.chatScrollSession);
+  }
+
+  static async consumeSnapshot(): Promise<ResultT<ChatScrollSession | null>> {
+    const result = await ChatScrollSessionStorage.getSnapshot();
+    const cleared = await ChatScrollSessionStorage.clearSnapshot();
+    if (Result.isErr(result)) return result;
+    if (Result.isErr(cleared)) return cleared;
+    return result;
+  }
+}