Add some prometheus code

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.28)
+cmake_minimum_required(VERSION 3.27)
 project(aliencat_exporter)
 
 set(CMAKE_CXX_STANDARD 20)

main.cpp

@@ -1,6 +1,27 @@
 #include <iostream>
+#include <chrono>
+#include <thread>
+
+#include <prometheus/exposer.h>
+#include <prometheus/registry.h>
+#include <prometheus/counter.h>
 
 int main() {
-    std::cout << "Hello, World!" << std::endl;
+    prometheus::Exposer exposer{"127.0.0.1:9000"};
+    prometheus::Registry registry;
+
+    auto& gouge = prometheus::BuildGauge()
+            .Name("aliencat_dnsmasq_leases")
+            .Register(registry);
+
+    auto& counter = prometheus::BuildCounter()
+            .Name("aliencat_dnsmasq_leases")
+            .Register(registry);
+
+    for (;;) {
+        std::this_thread::sleep_for(std::chrono::seconds(1));
+        gouge.Add({"mac", ""}).Set(0);
+    }
+
     return 0;
 }