feat: 支持聊天多版本答案切换

- 为管理端、公共聊天和用户中心补充回答变体查询与切换能力

- 支持基于指定轮次重新生成并同步前后端多版本状态

- 保留 application.yml 与本地截图文件为未提交状态

easyflow-ui-admin/app/src/views/ai/chatHistory/index.vue

@@ -4,7 +4,11 @@ import type { ChatTimeTimelineItem } from '@easyflow/types';
 import { computed, onMounted, ref } from 'vue';
 
 import { useEasyFlowDrawer } from '@easyflow/common-ui';
-import { ChatTimeHistoryMapper } from '@easyflow/utils';
+import {
+  createChatVariantSwitchController,
+  ChatTimeHistoryMapper,
+  ChatTimeTimelineBuilder,
+} from '@easyflow/utils';
 
 import { Search } from '@element-plus/icons-vue';
 import {
@@ -53,6 +57,15 @@ const messagePage = ref({
   pageNumber: 1,
   pageSize: 20,
 });
+const variantSwitchStateVersion = ref(0);
+const variantSwitchController = createChatVariantSwitchController<any, ChatTimeTimelineItem>({
+  mapRecords: (records) => ChatTimeHistoryMapper.fromHistoryRecords(records),
+  onStateChange: () => {
+    variantSwitchStateVersion.value += 1;
+  },
+  replaceRound: (items, roundId, nextItems) =>
+    ChatTimeTimelineBuilder.replaceRoundMessages(items, roundId, nextItems),
+});
 
 const [Drawer, drawerApi] = useEasyFlowDrawer({
   appendToMain: false,
@@ -164,12 +177,88 @@ async function loadMessages(reset = false) {
     : loadedMessageRecordCount.value + (res.data?.records || []).length;
   messagePage.value.total = res.data?.total || 0;
   messagePage.value.pageNumber = nextPageNumber;
+  prefetchVisibleVariants();
 }
 
 function normalizeMessages(records: any[]) {
   return ChatTimeHistoryMapper.fromHistoryRecords([...records].reverse());
 }
 
+async function handleSelectVariant(
+  item: ChatTimeTimelineItem,
+  direction: 'next' | 'previous',
+) {
+  if (!currentSession.value?.id || !item.roundId) {
+    return;
+  }
+  const current = Number(item.variantIndex || item.selectedVariantIndex || 1);
+  const variantIndex = direction === 'previous' ? current - 1 : current + 1;
+  await variantSwitchController.switchVariant({
+    fetchVariants: () =>
+      fetchRoundVariants(String(currentSession.value.id), String(item.roundId)),
+    items: messageList.value,
+    persistVariant: async () => {
+      const [, res] = await tryit(api.post)(
+        `/api/v1/chatHistory/sessions/${currentSession.value.id}/rounds/${item.roundId}/selectVariant`,
+        {
+          variantIndex,
+        },
+      );
+      if (res?.errorCode !== 0 || !res?.data) {
+        throw new Error(res?.message || '答案版本切换失败');
+      }
+      return res.data;
+    },
+    roundId: item.roundId,
+    sessionId: currentSession.value.id,
+    targetVariantIndex: variantIndex,
+  });
+}
+
+async function fetchRoundVariants(sessionId: string, roundId: string) {
+  const [, res] = await tryit(api.get)(
+    `/api/v1/chatHistory/sessions/${sessionId}/rounds/${roundId}/variants`,
+  );
+  if (res?.errorCode !== 0) {
+    throw new Error(res?.message || '答案版本加载失败');
+  }
+  return res.data || [];
+}
+
+function prefetchVisibleVariants() {
+  const sessionId = String(currentSession.value?.id || '');
+  if (!sessionId) {
+    return;
+  }
+  for (const item of messageList.value) {
+    if (
+      item.role === 'assistant' &&
+      item.roundId &&
+      Number(item.variantCount || 0) > 1
+    ) {
+      variantSwitchController.prefetchVariants({
+        fetchVariants: () => fetchRoundVariants(sessionId, String(item.roundId)),
+        roundId: item.roundId,
+        sessionId,
+      });
+    }
+  }
+}
+
+function currentSwitchingRoundIds() {
+  variantSwitchStateVersion.value;
+  const sessionId = String(currentSession.value?.id || '');
+  if (!sessionId) {
+    return [];
+  }
+  return messageList.value
+    .filter(
+      (item) =>
+        item.roundId && variantSwitchController.isSwitching(sessionId, item.roundId),
+    )
+    .map((item) => String(item.roundId));
+}
+
 function changePage(pageNumber: number) {
   query.value.pageNumber = pageNumber;
   fetchSessions();
@@ -421,6 +510,8 @@ function closeDetail() {
         :messages="messageList"
         :has-more="hasMoreMessages"
         :on-load-more="() => loadMessages(false)"
+        :switching-round-ids="currentSwitchingRoundIds()"
+        @select-variant="handleSelectVariant($event.item, $event.direction)"
         @close="closeDetail"
       />
     </Drawer>