Added db logger functions. Chnaged to newest mqtt++ version.

src/Cache.cpp

@@ -1,22 +1,19 @@
 #include "Cache.h"
 #include <algorithm>
-std::vector<TopicState> Cache::topic_states(std::vector<std::string>& topics) {
-	std::vector<TopicState> states;
-	
-	for (const auto& topic : topics) {
-		auto hit = std::find_if(cache.begin(), cache.end(), [&](TopicState& cache_state) {
-			return cache_state.topic == topic;
-		});
-		if (hit != cache.end()) {
-			states.push_back(*hit);
+#include "mqtt++.h"
+#include <iostream>
+
+std::optional<std::string> Cache::cached_topic_value(const std::string& topic) {
+	for (const auto& state : m_cache) {
+		if (state.topic == topic) {
+			return state.value;
 		}
 	}
-
-	return states;
+	return std::nullopt;
 }
 
 TopicState Cache::set_topic_value(const std::string& topic, const std::string& value) {
-	for (auto& state : cache) {
+	for (auto& state : m_cache) {
 		if (state.topic == topic) {
 			state.value = value;
 
@@ -24,5 +21,5 @@ TopicState Cache::set_topic_value(const std::string& topic, const std::string& v
 		}
 	}
 
-	return cache.emplace_back(topic, value);
+	return m_cache.emplace_back(topic, value);
 }