[sntp] Use callbacks to trigger on_time_sync for ESP32 and ESP8266 (#10390)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

esphome/components/sntp/sntp_component.cpp

@@ -14,8 +14,13 @@ namespace sntp {
 
 static const char *const TAG = "sntp";
 
+#if defined(USE_ESP32)
+SNTPComponent *SNTPComponent::instance = nullptr;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+#endif
+
 void SNTPComponent::setup() {
 #if defined(USE_ESP32)
+  SNTPComponent::instance = this;
   if (esp_sntp_enabled()) {
     esp_sntp_stop();
   }
@@ -25,6 +30,11 @@ void SNTPComponent::setup() {
     esp_sntp_setservername(i++, server.c_str());
   }
   esp_sntp_set_sync_interval(this->get_update_interval());
+  esp_sntp_set_time_sync_notification_cb([](struct timeval *tv) {
+    if (SNTPComponent::instance != nullptr) {
+      SNTPComponent::instance->defer([]() { SNTPComponent::instance->time_synced(); });
+    }
+  });
   esp_sntp_init();
 #else
   sntp_stop();
@@ -34,6 +44,14 @@ void SNTPComponent::setup() {
   for (auto &server : this->servers_) {
     sntp_setservername(i++, server.c_str());
   }
+
+#if defined(USE_ESP8266)
+  settimeofday_cb([this](bool from_sntp) {
+    if (from_sntp)
+      this->time_synced();
+  });
+#endif
+
   sntp_init();
 #endif
 }
@@ -46,7 +64,8 @@ void SNTPComponent::dump_config() {
 }
 void SNTPComponent::update() {
 #if !defined(USE_ESP32)
-  // force resync
+  // Some platforms currently cannot set the sync interval at runtime so we need
+  // to do the re-sync by hand for now.
   if (sntp_enabled()) {
     sntp_stop();
     this->has_time_ = false;
@@ -55,23 +74,31 @@ void SNTPComponent::update() {
 #endif
 }
 void SNTPComponent::loop() {
+// The loop is used to infer whether we have valid time on platforms where we
+// cannot tell whether SNTP has succeeded.
+// One limitation of this approach is that we cannot tell if it was the SNTP
+// component that set the time.
+// ESP-IDF and ESP8266 use callbacks from the SNTP task to trigger the
+// `on_time_sync` trigger on successful sync events.
+#if defined(USE_ESP32) || defined(USE_ESP8266)
+  this->disable_loop();
+#endif
+
   if (this->has_time_)
     return;
 
+  this->time_synced();
+}
+
+void SNTPComponent::time_synced() {
   auto time = this->now();
-  if (!time.is_valid())
+  this->has_time_ = time.is_valid();
+  if (!this->has_time_)
     return;
 
   ESP_LOGD(TAG, "Synchronized time: %04d-%02d-%02d %02d:%02d:%02d", time.year, time.month, time.day_of_month, time.hour,
            time.minute, time.second);
   this->time_sync_callback_.call();
-  this->has_time_ = true;
-
-#ifdef USE_ESP_IDF
-  // On ESP-IDF, time sync is permanent and update() doesn't force resync
-  // Time is now synchronized, no need to check anymore
-  this->disable_loop();
-#endif
 }
 
 }  // namespace sntp

esphome/components/sntp/sntp_component.h

@@ -26,9 +26,16 @@ class SNTPComponent : public time::RealTimeClock {
   void update() override;
   void loop() override;
 
+  void time_synced();
+
  protected:
   std::vector<std::string> servers_;
   bool has_time_{false};
+
+#if defined(USE_ESP32)
+ private:
+  static SNTPComponent *instance;
+#endif
 };
 
 }  // namespace sntp