Avoid adding more that one “XMPP reconnection” timed event at the same time

Fix a semblance of infinite and busy loop, that could occur if biboumi’s
poller is woken up multiple times while the XMPP server is not reachable.

src/main.cpp

@@ -179,19 +179,20 @@ int main(int ac, char** av)
     {
       if (xmpp_component->ever_auth)
         {
+          static const std::string reconnect_name{"XMPP reconnection"};
           if (xmpp_component->first_connection_try == true)
             { // immediately re-try to connect
               xmpp_component->reset();
               xmpp_component->start();
             }
-          else
+          else if (!TimedEventsManager::instance().find_event(reconnect_name))
             { // Re-connecting failed, we now try only each few seconds
               auto reconnect_later = [xmpp_component]()
               {
                 xmpp_component->reset();
                 xmpp_component->start();
               };
-              TimedEvent event(std::chrono::steady_clock::now() + 2s, reconnect_later, "XMPP reconnection");
+              TimedEvent event(std::chrono::steady_clock::now() + 2s, reconnect_later, reconnect_name);
               TimedEventsManager::instance().add_event(std::move(event));
             }
         }

src/utils/timed_events.hpp

@@ -125,6 +125,11 @@ public:
    * Return the number of managed events.
    */
   std::size_t size() const;
+  /**
+   * Return a pointer to the first event with the given name. If none
+   * is found, returns nullptr.
+   */
+  const TimedEvent* find_event(const std::string& name) const;
 
 private:
   std::vector<TimedEvent> events;

src/utils/timed_events_manager.cpp

@@ -1,5 +1,7 @@
 #include <utils/timed_events.hpp>
 
+#include <algorithm>
+
 TimedEventsManager& TimedEventsManager::instance()
 {
   static TimedEventsManager inst;
@@ -67,7 +69,19 @@ std::size_t TimedEventsManager::cancel(const std::string& name)
   return res;
 }
 
+
+
 std::size_t TimedEventsManager::size() const
 {
   return this->events.size();
 }
+
+const TimedEvent* TimedEventsManager::find_event(const std::string& name) const
+{
+  const auto it = std::find_if(this->events.begin(), this->events.end(), [&name](const TimedEvent& o) {
+    return o.get_name() == name;
+  });
+  if (it == this->events.end())
+    return nullptr;
+  return &*it;
+}