feat: Add async HTTP requests with non-blocking loading

- Implement curl multi interface for async HTTP in HttpClient
- Add loading spinner animation during page load
- Support Esc key to cancel loading
- Non-blocking main loop with 50ms polling
- Loading state management (IDLE, LOADING_PAGE, LOADING_IMAGES)
- Preserve sync API for backward compatibility

src/browser_v2.cpp

@@ -15,6 +15,19 @@
 
 using namespace tut;
 
+// 浏览器加载状态
+enum class LoadingState {
+    IDLE,           // 空闲
+    LOADING_PAGE,   // 正在加载页面
+    LOADING_IMAGES  // 正在加载图片
+};
+
+// 加载动画帧
+static const char* SPINNER_FRAMES[] = {
+    "⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"
+};
+static const int SPINNER_FRAME_COUNT = 10;
+
 // 缓存条目
 struct CacheEntry {
     DocumentTree tree;
@@ -70,6 +83,13 @@ public:
     static constexpr int CACHE_MAX_AGE = 300;  // 5分钟缓存
     static constexpr size_t CACHE_MAX_SIZE = 20;  // 最多缓存20个页面
 
+    // 异步加载状态
+    LoadingState loading_state = LoadingState::IDLE;
+    std::string pending_url;  // 正在加载的URL
+    bool pending_force_refresh = false;
+    int spinner_frame = 0;
+    std::chrono::steady_clock::time_point last_spinner_update;
+
     bool init_screen() {
         if (!terminal.init()) {
             return false;
@@ -170,6 +190,162 @@ public:
         return true;
     }
 
+    // 启动异步页面加载
+    void start_async_load(const std::string& url, bool force_refresh = false) {
+        // 检查缓存
+        auto cache_it = page_cache.find(url);
+        bool use_cache = !force_refresh && cache_it != page_cache.end() &&
+                        !cache_it->second.is_expired(CACHE_MAX_AGE);
+
+        if (use_cache) {
+            // 使用缓存，不需要网络请求
+            status_message = "⚡ Loading from cache...";
+            current_tree = html_parser.parse_tree(cache_it->second.html, url);
+            current_layout = layout_engine->layout(current_tree);
+            current_url = url;
+            scroll_pos = 0;
+            active_link = current_tree.links.empty() ? -1 : 0;
+            active_field = current_tree.form_fields.empty() ? -1 : 0;
+            search_ctx = SearchContext();
+            search_term.clear();
+            status_message = "⚡ " + (current_tree.title.empty() ? url : current_tree.title);
+
+            // 更新历史
+            if (!force_refresh) {
+                if (history_pos >= 0 && history_pos < static_cast<int>(history.size()) - 1) {
+                    history.erase(history.begin() + history_pos + 1, history.end());
+                }
+                history.push_back(url);
+                history_pos = history.size() - 1;
+            }
+
+            // 加载图片（仍然同步，可以后续优化）
+            load_images(current_tree);
+            current_layout = layout_engine->layout(current_tree);
+            return;
+        }
+
+        // 需要网络请求，启动异步加载
+        pending_url = url;
+        pending_force_refresh = force_refresh;
+        loading_state = LoadingState::LOADING_PAGE;
+        spinner_frame = 0;
+        last_spinner_update = std::chrono::steady_clock::now();
+
+        status_message = std::string(SPINNER_FRAMES[0]) + " Connecting to " + extract_host(url) + "...";
+        http_client.start_async_fetch(url);
+    }
+
+    // 轮询异步加载状态，返回true表示还在加载中
+    bool poll_loading() {
+        if (loading_state == LoadingState::IDLE) {
+            return false;
+        }
+
+        // 更新spinner动画
+        auto now = std::chrono::steady_clock::now();
+        auto elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(now - last_spinner_update).count();
+        if (elapsed >= 80) {  // 每80ms更新一帧
+            spinner_frame = (spinner_frame + 1) % SPINNER_FRAME_COUNT;
+            last_spinner_update = now;
+            update_loading_status();
+        }
+
+        if (loading_state == LoadingState::LOADING_PAGE) {
+            auto state = http_client.poll_async();
+
+            switch (state) {
+                case AsyncState::COMPLETE:
+                    handle_load_complete();
+                    return false;
+
+                case AsyncState::FAILED: {
+                    auto result = http_client.get_async_result();
+                    status_message = "❌ " + (result.error_message.empty() ?
+                        "Connection failed" : result.error_message);
+                    loading_state = LoadingState::IDLE;
+                    return false;
+                }
+
+                case AsyncState::CANCELLED:
+                    status_message = "⚠ Loading cancelled";
+                    loading_state = LoadingState::IDLE;
+                    return false;
+
+                case AsyncState::LOADING:
+                    return true;
+
+                default:
+                    return false;
+            }
+        }
+
+        return loading_state != LoadingState::IDLE;
+    }
+
+    // 更新加载状态消息
+    void update_loading_status() {
+        std::string spinner = SPINNER_FRAMES[spinner_frame];
+        if (loading_state == LoadingState::LOADING_PAGE) {
+            status_message = spinner + " Loading " + extract_host(pending_url) + "...";
+        } else if (loading_state == LoadingState::LOADING_IMAGES) {
+            status_message = spinner + " Loading images...";
+        }
+    }
+
+    // 处理页面加载完成
+    void handle_load_complete() {
+        auto response = http_client.get_async_result();
+
+        if (!response.is_success()) {
+            status_message = "❌ HTTP " + std::to_string(response.status_code);
+            loading_state = LoadingState::IDLE;
+            return;
+        }
+
+        // 解析HTML
+        current_tree = html_parser.parse_tree(response.body, pending_url);
+
+        // 添加到缓存
+        add_to_cache(pending_url, response.body);
+
+        // 布局计算
+        current_layout = layout_engine->layout(current_tree);
+
+        current_url = pending_url;
+        scroll_pos = 0;
+        active_link = current_tree.links.empty() ? -1 : 0;
+        active_field = current_tree.form_fields.empty() ? -1 : 0;
+        search_ctx = SearchContext();
+        search_term.clear();
+
+        // 更新历史（仅在非刷新时）
+        if (!pending_force_refresh) {
+            if (history_pos >= 0 && history_pos < static_cast<int>(history.size()) - 1) {
+                history.erase(history.begin() + history_pos + 1, history.end());
+            }
+            history.push_back(pending_url);
+            history_pos = history.size() - 1;
+        }
+
+        status_message = current_tree.title.empty() ? pending_url : current_tree.title;
+
+        // 加载图片（目前仍同步，可后续优化为异步）
+        load_images(current_tree);
+        current_layout = layout_engine->layout(current_tree);
+
+        loading_state = LoadingState::IDLE;
+    }
+
+    // 取消加载
+    void cancel_loading() {
+        if (loading_state != LoadingState::IDLE) {
+            http_client.cancel_async();
+            loading_state = LoadingState::IDLE;
+            status_message = "⚠ Cancelled";
+        }
+    }
+
     void add_to_cache(const std::string& url, const std::string& html) {
         // 限制缓存大小
         if (page_cache.size() >= CACHE_MAX_SIZE) {
@@ -357,33 +533,33 @@ public:
 
             case Action::FOLLOW_LINK:
                 if (active_link >= 0 && active_link < static_cast<int>(current_tree.links.size())) {
-                    load_page(current_tree.links[active_link].url);
+                    start_async_load(current_tree.links[active_link].url);
                 }
                 break;
 
             case Action::GO_BACK:
                 if (history_pos > 0) {
                     history_pos--;
-                    load_page(history[history_pos]);
+                    start_async_load(history[history_pos]);
                 }
                 break;
 
             case Action::GO_FORWARD:
                 if (history_pos < static_cast<int>(history.size()) - 1) {
                     history_pos++;
-                    load_page(history[history_pos]);
+                    start_async_load(history[history_pos]);
                 }
                 break;
 
             case Action::OPEN_URL:
                 if (!result.text.empty()) {
-                    load_page(result.text);
+                    start_async_load(result.text);
                 }
                 break;
 
             case Action::REFRESH:
                 if (!current_url.empty()) {
-                    load_page(current_url, true);  // 强制刷新，跳过缓存
+                    start_async_load(current_url, true);  // 强制刷新，跳过缓存
                 }
                 break;
 
@@ -724,15 +900,20 @@ void BrowserV2::run(const std::string& initial_url) {
     }
 
     if (!initial_url.empty()) {
-        load_url(initial_url);
+        pImpl->start_async_load(initial_url);
     } else {
         pImpl->show_help();
     }
 
     bool running = true;
     while (running) {
+        // 轮询异步加载状态
+        pImpl->poll_loading();
+
+        // 渲染屏幕
         pImpl->draw_screen();
 
+        // 获取输入（非阻塞，50ms超时）
         int ch = pImpl->terminal.get_key(50);
         if (ch == -1) continue;
 
@@ -742,6 +923,20 @@ void BrowserV2::run(const std::string& initial_url) {
             continue;
         }
 
+        // 如果正在加载，Esc可以取消
+        if (pImpl->loading_state != LoadingState::IDLE && ch == 27) {  // 27 = Esc
+            pImpl->cancel_loading();
+            continue;
+        }
+
+        // 加载时忽略大部分输入，只允许取消和退出
+        if (pImpl->loading_state != LoadingState::IDLE) {
+            if (ch == 'q' || ch == 'Q') {
+                running = false;
+            }
+            continue;  // 忽略其他输入
+        }
+
         auto result = pImpl->input_handler.handle_key(ch);
         if (result.action == Action::QUIT) {
             running = false;

src/http_client.cpp

@@ -25,8 +25,15 @@ public:
     bool follow_redirects;
     std::string cookie_file;
 
+    // 异步请求相关
+    CURLM* multi_handle = nullptr;
+    CURL* async_easy = nullptr;
+    AsyncState async_state = AsyncState::IDLE;
+    std::string async_response_body;
+    HttpResponse async_result;
+
     Impl() : timeout(30),
-             user_agent("TUT-Browser/1.0 (Terminal User Interface Browser)"),
+             user_agent("TUT-Browser/2.0 (Terminal User Interface Browser)"),
              follow_redirects(true) {
         curl = curl_easy_init();
         if (!curl) {
@@ -36,13 +43,59 @@ public:
         curl_easy_setopt(curl, CURLOPT_COOKIEFILE, "");
         // Enable automatic decompression of supported encodings (gzip, deflate, etc.)
         curl_easy_setopt(curl, CURLOPT_ACCEPT_ENCODING, "");
+
+        // 初始化multi handle用于异步请求
+        multi_handle = curl_multi_init();
+        if (!multi_handle) {
+            throw std::runtime_error("Failed to initialize CURL multi handle");
+        }
     }
 
     ~Impl() {
+        // 清理异步请求
+        cleanup_async();
+
+        if (multi_handle) {
+            curl_multi_cleanup(multi_handle);
+        }
         if (curl) {
             curl_easy_cleanup(curl);
         }
     }
+
+    void cleanup_async() {
+        if (async_easy) {
+            curl_multi_remove_handle(multi_handle, async_easy);
+            curl_easy_cleanup(async_easy);
+            async_easy = nullptr;
+        }
+        async_state = AsyncState::IDLE;
+        async_response_body.clear();
+    }
+
+    void setup_easy_handle(CURL* handle, const std::string& url) {
+        curl_easy_setopt(handle, CURLOPT_URL, url.c_str());
+        curl_easy_setopt(handle, CURLOPT_TIMEOUT, timeout);
+        curl_easy_setopt(handle, CURLOPT_CONNECTTIMEOUT, 10L);
+        curl_easy_setopt(handle, CURLOPT_USERAGENT, user_agent.c_str());
+
+        if (follow_redirects) {
+            curl_easy_setopt(handle, CURLOPT_FOLLOWLOCATION, 1L);
+            curl_easy_setopt(handle, CURLOPT_MAXREDIRS, 10L);
+        }
+
+        curl_easy_setopt(handle, CURLOPT_SSL_VERIFYPEER, 1L);
+        curl_easy_setopt(handle, CURLOPT_SSL_VERIFYHOST, 2L);
+
+        if (!cookie_file.empty()) {
+            curl_easy_setopt(handle, CURLOPT_COOKIEFILE, cookie_file.c_str());
+            curl_easy_setopt(handle, CURLOPT_COOKIEJAR, cookie_file.c_str());
+        } else {
+            curl_easy_setopt(handle, CURLOPT_COOKIEFILE, "");
+        }
+
+        curl_easy_setopt(handle, CURLOPT_ACCEPT_ENCODING, "");
+    }
 };
 
 HttpClient::HttpClient() : pImpl(std::make_unique<Impl>()) {}
@@ -298,3 +351,105 @@ void HttpClient::set_follow_redirects(bool follow) {
 void HttpClient::enable_cookies(const std::string& cookie_file) {
     pImpl->cookie_file = cookie_file;
 }
+
+// ==================== 异步请求实现 ====================
+
+void HttpClient::start_async_fetch(const std::string& url) {
+    // 如果有正在进行的请求，先取消
+    if (pImpl->async_easy) {
+        cancel_async();
+    }
+
+    // 创建新的easy handle
+    pImpl->async_easy = curl_easy_init();
+    if (!pImpl->async_easy) {
+        pImpl->async_state = AsyncState::FAILED;
+        pImpl->async_result.error_message = "Failed to create CURL handle";
+        return;
+    }
+
+    // 配置请求
+    pImpl->setup_easy_handle(pImpl->async_easy, url);
+
+    // 设置写回调
+    pImpl->async_response_body.clear();
+    curl_easy_setopt(pImpl->async_easy, CURLOPT_WRITEFUNCTION, write_callback);
+    curl_easy_setopt(pImpl->async_easy, CURLOPT_WRITEDATA, &pImpl->async_response_body);
+
+    // 添加到multi handle
+    curl_multi_add_handle(pImpl->multi_handle, pImpl->async_easy);
+
+    pImpl->async_state = AsyncState::LOADING;
+    pImpl->async_result = HttpResponse{};  // 重置结果
+}
+
+AsyncState HttpClient::poll_async() {
+    if (pImpl->async_state != AsyncState::LOADING) {
+        return pImpl->async_state;
+    }
+
+    // 执行非阻塞的multi perform
+    int still_running = 0;
+    CURLMcode mc = curl_multi_perform(pImpl->multi_handle, &still_running);
+
+    if (mc != CURLM_OK) {
+        pImpl->async_result.error_message = curl_multi_strerror(mc);
+        pImpl->async_state = AsyncState::FAILED;
+        pImpl->cleanup_async();
+        return pImpl->async_state;
+    }
+
+    // 检查是否有完成的请求
+    int msgs_left = 0;
+    CURLMsg* msg;
+    while ((msg = curl_multi_info_read(pImpl->multi_handle, &msgs_left))) {
+        if (msg->msg == CURLMSG_DONE) {
+            CURL* easy = msg->easy_handle;
+            CURLcode result = msg->data.result;
+
+            if (result == CURLE_OK) {
+                // 获取响应信息
+                long http_code = 0;
+                curl_easy_getinfo(easy, CURLINFO_RESPONSE_CODE, &http_code);
+                pImpl->async_result.status_code = static_cast<int>(http_code);
+
+                char* content_type = nullptr;
+                curl_easy_getinfo(easy, CURLINFO_CONTENT_TYPE, &content_type);
+                if (content_type) {
+                    pImpl->async_result.content_type = content_type;
+                }
+
+                pImpl->async_result.body = std::move(pImpl->async_response_body);
+                pImpl->async_state = AsyncState::COMPLETE;
+            } else {
+                pImpl->async_result.error_message = curl_easy_strerror(result);
+                pImpl->async_state = AsyncState::FAILED;
+            }
+
+            // 清理handle但保留状态供获取结果
+            curl_multi_remove_handle(pImpl->multi_handle, pImpl->async_easy);
+            curl_easy_cleanup(pImpl->async_easy);
+            pImpl->async_easy = nullptr;
+        }
+    }
+
+    return pImpl->async_state;
+}
+
+HttpResponse HttpClient::get_async_result() {
+    HttpResponse result = std::move(pImpl->async_result);
+    pImpl->async_result = HttpResponse{};
+    pImpl->async_state = AsyncState::IDLE;
+    return result;
+}
+
+void HttpClient::cancel_async() {
+    if (pImpl->async_easy) {
+        pImpl->cleanup_async();
+        pImpl->async_state = AsyncState::CANCELLED;
+    }
+}
+
+bool HttpClient::is_async_active() const {
+    return pImpl->async_state == AsyncState::LOADING;
+}

src/http_client.h

@@ -5,6 +5,15 @@
 #include <cstdint>
 #include <memory>
 
+// 异步请求状态
+enum class AsyncState {
+    IDLE,       // 无活跃请求
+    LOADING,    // 请求进行中
+    COMPLETE,   // 请求成功完成
+    FAILED,     // 请求失败
+    CANCELLED   // 请求被取消
+};
+
 struct HttpResponse {
     int status_code;
     std::string body;
@@ -36,10 +45,20 @@ public:
     HttpClient();
     ~HttpClient();
 
+    // 同步请求接口
     HttpResponse fetch(const std::string& url);
     BinaryResponse fetch_binary(const std::string& url);
     HttpResponse post(const std::string& url, const std::string& data,
                      const std::string& content_type = "application/x-www-form-urlencoded");
+
+    // 异步请求接口
+    void start_async_fetch(const std::string& url);
+    AsyncState poll_async();  // 非阻塞轮询，返回当前状态
+    HttpResponse get_async_result();  // 获取结果并重置状态
+    void cancel_async();  // 取消当前异步请求
+    bool is_async_active() const;  // 是否有活跃的异步请求
+
+    // 配置
     void set_timeout(long timeout_seconds);
     void set_user_agent(const std::string& user_agent);
     void set_follow_redirects(bool follow);