Improve 4chan thread list performance by asynchronous update and caching

1 files changed, 88 insertions, 1 deletions

diff --git a/src/plugins/Fourchan.cpp b/src/plugins/Fourchan.cpp
index 212e197..d8c80b0 100644
--- a/src/plugins/Fourchan.cpp
+++ b/src/plugins/Fourchan.cpp
@@ -11,6 +11,37 @@ static const std::string fourchan_url = "https://a.4cdn.org/";
 static const std::string fourchan_image_url = "https://i.4cdn.org/";
 
 namespace QuickMedia {
+    Fourchan::Fourchan() : ImageBoard("4chan") {
+        thread_list_update_thread = std::thread([this]() {
+            BodyItems new_thread_list_items;
+            while(running) {
+                new_thread_list_items.clear();
+                auto start_time = std::chrono::steady_clock::now();
+
+                std::string board_url = get_board_url();
+                if(!board_url.empty()) {
+                    PluginResult plugin_result = get_threads_internal(board_url, new_thread_list_items);
+                    if(plugin_result == PluginResult::OK)
+                        set_board_thread_list(std::move(new_thread_list_items));
+                }
+
+                auto time_passed = std::chrono::steady_clock::now() - start_time;
+                if(time_passed < std::chrono::seconds(15)) {
+                    auto time_to_sleep = std::chrono::seconds(15) - time_passed;
+                    std::unique_lock<std::mutex> lock(thread_list_cache_mutex);
+                    thread_list_update_cv.wait_for(lock, time_to_sleep);
+                }
+            }
+        });
+    }
+
+    Fourchan::~Fourchan() {
+        running = false;
+        std::unique_lock<std::mutex> lock(thread_list_cache_mutex);
+        thread_list_update_cv.notify_one();
+        thread_list_update_thread.join();
+    }
+
     PluginResult Fourchan::get_front_page(BodyItems &result_items) {
         std::string server_response;
         if(download_to_string(fourchan_url + "boards.json", server_response, {}, use_tor) != DownloadResult::OK)
@@ -156,7 +187,7 @@ namespace QuickMedia {
         tidyRelease(doc);
     }
 
-    PluginResult Fourchan::get_threads(const std::string &url, BodyItems &result_items) {
+    PluginResult Fourchan::get_threads_internal(const std::string &url, BodyItems &result_items) {
         std::string server_response;
         if(download_to_string(fourchan_url + url + "/catalog.json", server_response, {}, use_tor) != DownloadResult::OK)
             return PluginResult::NET_ERR;
@@ -284,6 +315,62 @@ namespace QuickMedia {
         return PluginResult::OK;
     }
 
+    void Fourchan::set_board_url(const std::string &new_url) {
+        {
+            std::lock_guard<std::mutex> lock(board_url_mutex);
+            if(current_board_url == new_url)
+                return;
+            current_board_url = new_url;
+        }
+
+        std::lock_guard<std::mutex> thread_list_lock(thread_list_cache_mutex);
+        thread_list_update_cv.notify_one();
+        thread_list_cached = false;
+    }
+
+    std::string Fourchan::get_board_url() {
+        std::lock_guard<std::mutex> lock(board_url_mutex);
+        return current_board_url;
+    }
+
+    void Fourchan::set_board_thread_list(BodyItems body_items) {
+        {
+            std::lock_guard<std::mutex> lock(board_list_mutex);
+            cached_thread_list_items.clear();
+            for(auto &body_item : body_items) {
+                cached_thread_list_items.push_back(std::make_unique<BodyItem>(*body_item));
+            }
+        }
+
+        std::unique_lock<std::mutex> thread_list_cache_lock(thread_list_cache_mutex);
+        if(!thread_list_cached) {
+            thread_list_cached = true;
+            thread_list_cached_cv.notify_one();
+        }
+    }
+
+    BodyItems Fourchan::get_board_thread_list() {
+        std::lock_guard<std::mutex> lock(board_list_mutex);
+        BodyItems body_items;
+        for(auto &cached_body_item : cached_thread_list_items) {
+            body_items.push_back(std::make_unique<BodyItem>(*cached_body_item));
+        }
+        return body_items;
+    }
+
+    PluginResult Fourchan::get_threads(const std::string &url, BodyItems &result_items) {
+        set_board_url(url);
+
+        std::unique_lock<std::mutex> lock(thread_list_cache_mutex);
+        if(!thread_list_cached) {
+            if(thread_list_cached_cv.wait_for(lock, std::chrono::seconds(10)) == std::cv_status::timeout)
+                return PluginResult::NET_ERR;
+        }
+
+        result_items = get_board_thread_list();
+        return PluginResult::OK;
+    }
+
     PluginResult Fourchan::get_thread_comments(const std::string &list_url, const std::string &url, BodyItems &result_items) {
         std::string server_response;
         if(download_to_string(fourchan_url + list_url + "/thread/" + url + ".json", server_response, {}, use_tor) != DownloadResult::OK)