refactor(ProcessPostUseCase, useCursorPagination, useDifferentialPosts): enhance post merging and loading states

- Introduced new methods for merging posts and comments efficiently, improving performance during data updates.
- Updated loading state management in hooks to include initial loading and loading more states for better user feedback.
- Refactored HomeScreen and PostDetailScreen to utilize the new loading states and merging logic, enhancing user experience during data fetching.
- Improved pagination handling in useCursorPagination and useDifferentialPosts to ensure consistent data management across components.

src/core/usecases/ProcessPostUseCase.ts

@@ -109,6 +109,8 @@ class ProcessPostUseCase {
   // 当前用户ID
   private currentUserId: string | null = null;
 
+  private readonly mergePerfWarnThresholdMs = 12;
+
   // 私有构造函数
   private constructor() {
     this.paginationManager = new PaginationStateManager();
@@ -241,6 +243,83 @@ class ProcessPostUseCase {
     this.notifyStateChanged(key);
   }
 
+  private getEntityId(item: unknown): string | null {
+    if (!item || typeof item !== 'object') {
+      return null;
+    }
+    const maybeId = (item as { id?: unknown }).id;
+    if (typeof maybeId === 'string' || typeof maybeId === 'number') {
+      return String(maybeId);
+    }
+    return null;
+  }
+
+  private mergePostListWithFastPath(previousInput: Post[] | null | undefined, incomingInput: Post[] | null | undefined): Post[] {
+    const previous = Array.isArray(previousInput) ? previousInput : [];
+    const incoming = Array.isArray(incomingInput) ? incomingInput : [];
+    if (incoming.length === 0) {
+      return previous;
+    }
+    if (previous.length === 0) {
+      return incoming;
+    }
+
+    const lastPrevId = this.getEntityId(previous[previous.length - 1]);
+    const firstIncomingId = this.getEntityId(incoming[0]);
+    if (lastPrevId && firstIncomingId && lastPrevId !== firstIncomingId) {
+      const prevIdSet = new Set(previous.map((item) => this.getEntityId(item)).filter(Boolean) as string[]);
+      if (!prevIdSet.has(firstIncomingId)) {
+        return [...previous, ...incoming];
+      }
+    }
+
+    const merged = [...previous];
+    const indexById = new Map<string, number>();
+    for (let i = 0; i < merged.length; i += 1) {
+      const id = this.getEntityId(merged[i]);
+      if (id) {
+        indexById.set(id, i);
+      }
+    }
+
+    for (const post of incoming) {
+      const id = this.getEntityId(post);
+      if (!id) {
+        merged.push(post);
+        continue;
+      }
+      const existingIndex = indexById.get(id);
+      if (existingIndex === undefined) {
+        indexById.set(id, merged.length);
+        merged.push(post);
+      } else {
+        merged[existingIndex] = post;
+      }
+    }
+
+    return merged;
+  }
+
+  private mergeRefreshWindow(previousInput: Post[] | null | undefined, latestInput: Post[] | null | undefined): Post[] {
+    const previous = Array.isArray(previousInput) ? previousInput : [];
+    const latest = Array.isArray(latestInput) ? latestInput : [];
+    if (latest.length === 0) {
+      return previous;
+    }
+    if (previous.length === 0) {
+      return latest;
+    }
+
+    const latestIdSet = new Set(
+      latest.map((item) => this.getEntityId(item)).filter(Boolean) as string[]
+    );
+    const remaining = previous.filter((item) => {
+      const id = this.getEntityId(item);
+      return !id || !latestIdSet.has(id);
+    });
+    return [...latest, ...remaining];
+  }
+
   /**
    * 更新帖子详情状态
    * @param postId 帖子ID
@@ -280,8 +359,17 @@ class ProcessPostUseCase {
       const isCursorMode = result.nextCursor !== undefined && result.nextCursor !== null;
       
       // 更新状态（保存请求参数以便加载更多时使用）
+      const mergeStart = Date.now();
+      const currentState = this.getPostsState(key);
+      const incomingPosts = Array.isArray(result.posts) ? result.posts : [];
+      const mergedPosts = this.mergeRefreshWindow(currentState.posts, incomingPosts);
+      const mergeCost = Date.now() - mergeStart;
+      if (mergeCost >= this.mergePerfWarnThresholdMs) {
+        console.log('[PostPerf] fetchPosts merge cost', { key, costMs: mergeCost, prev: currentState.posts.length, next: incomingPosts.length });
+      }
+
       this.updatePostsState(key, {
-        posts: result.posts,
+        posts: mergedPosts,
         hasMore: result.hasMore,
         cursor: isCursorMode ? result.nextCursor : null, // cursor 模式保存 cursor，否则设为 null 表示 page 模式
         currentPage: isCursorMode ? undefined : 1, // page 模式从第 1 页开始
@@ -293,7 +381,7 @@ class ProcessPostUseCase {
       // 通知订阅者
       this.notifySubscribers({
         type: 'posts_loaded',
-        payload: { key, posts: result.posts, hasMore: result.hasMore },
+        payload: { key, posts: incomingPosts, hasMore: result.hasMore },
         timestamp: Date.now(),
       });
 
@@ -338,8 +426,16 @@ class ProcessPostUseCase {
       const isCursorMode = result.nextCursor !== undefined && result.nextCursor !== null;
       
       // 更新状态
+      const mergeStart = Date.now();
+      const incomingPosts = Array.isArray(result.posts) ? result.posts : [];
+      const mergedPosts = this.mergeRefreshWindow(state.posts, incomingPosts);
+      const mergeCost = Date.now() - mergeStart;
+      if (mergeCost >= this.mergePerfWarnThresholdMs) {
+        console.log('[PostPerf] refreshPosts merge cost', { key, costMs: mergeCost, prev: state.posts.length, next: incomingPosts.length });
+      }
+
       this.updatePostsState(key, {
-        posts: result.posts,
+        posts: mergedPosts,
         hasMore: result.hasMore,
         cursor: isCursorMode ? result.nextCursor : null,
         currentPage: isCursorMode ? undefined : 1,
@@ -417,7 +513,13 @@ class ProcessPostUseCase {
       const result = await postRepository.getPosts(queryParams);
 
       // 合并新数据
-      const newPosts = [...state.posts, ...result.posts];
+      const mergeStart = Date.now();
+      const incomingPosts = Array.isArray(result.posts) ? result.posts : [];
+      const newPosts = this.mergePostListWithFastPath(state.posts, incomingPosts);
+      const mergeCost = Date.now() - mergeStart;
+      if (mergeCost >= this.mergePerfWarnThresholdMs) {
+        console.log('[PostPerf] loadMore merge cost', { key, costMs: mergeCost, prev: state.posts.length, incoming: incomingPosts.length, merged: newPosts.length });
+      }
 
       // 判断响应是否为 cursor 模式（有 next_cursor 返回）
       const responseIsCursorMode = result.nextCursor !== undefined && result.nextCursor !== null;
@@ -433,7 +535,7 @@ class ProcessPostUseCase {
       });
 
       return {
-        posts: result.posts,
+        posts: incomingPosts,
         hasMore: result.hasMore,
         nextCursor: result.nextCursor,
       };