feat: add new initial stat observer pattern

core/stats/IStatObserver.hpp

@@ -0,0 +1,11 @@
+#ifndef ISTATOBSERVER_HPP
+#define ISTATOBSERVER_HPP
+
+class IStatObserver
+{
+public:
+    virtual ~IStatObserver(){};
+    // virtual void function_name(smth to transmit) = 0
+};
+
+#endif

core/stats/IStatSubject.hpp

@@ -0,0 +1,16 @@
+#ifndef ISTATSUBJECT_HPP
+#define ISTATSUBJECT_HPP
+
+#include "IStatObserver.hpp"
+
+#include <string>
+
+class IStatSubject
+{
+
+  public:
+    virtual ~IStatSubject(){};
+    virtual void attach(std::string observer_name, IStatObserver* observer) = 0;
+};
+
+#endif

core/stats/Stat.hpp

@@ -0,0 +1,33 @@
+#ifndef STAT_HPP
+#define STAT_HPP
+
+#include "IStatObserver.hpp"
+#include "StatManager.hpp"
+
+#include <cstdint>
+#include <iterator>
+#include <map>
+#include <string>
+#include <utility>
+
+class Stat : public IStatObserver
+{
+  private:
+    std::map<std::string, uint64_t> stats_map;
+
+  public:
+    template<typename Iterable>
+    Stat(const std::string name, const Iterable& list_entries)
+    {
+        for (const auto c : list_entries) {
+            stats_map.insert(std::make_pair<std::string, uint64_t>(c, 0));
+        }
+
+        StatManager::get_instance().attach(name, this);
+    };
+
+    void increment(const std::string key) { stats_map.at(key) += 1; }
+    void add(const std::string key, uint64_t value) { stats_map.at(key) += value; }
+};
+
+#endif

core/stats/StatManager.cpp

@@ -0,0 +1,18 @@
+#include "StatManager.hpp"
+
+#include <utility>
+
+using namespace std;
+
+void
+StatManager::attach(string observer_name, IStatObserver* observer)
+{
+    observer_map_.insert(make_pair<string, IStatObserver*>(move(observer_name), move(observer)));
+}
+
+StatManager&
+StatManager::get_instance()
+{
+    if (instance_ == nullptr) { instance_ = new StatManager; }
+    return *instance_;
+}

core/stats/StatManager.hpp

@@ -0,0 +1,32 @@
+
+#ifndef STATMANAGER_HPP
+#define STATMANAGER_HPP
+
+#include "IStatObserver.hpp"
+#include "IStatSubject.hpp"
+
+#include <map>
+#include <string>
+
+class StatManager : public IStatSubject
+{
+  private:
+    static StatManager* instance_;
+    std::map<std::string, IStatObserver*> observer_map_;
+
+  private:
+    StatManager() = default;
+
+  public:
+    static StatManager& get_instance();
+    StatManager(StatManager& instance) = delete;
+    void operator=(const StatManager&) = delete;
+
+    virtual void attach(std::string observer_name, IStatObserver* observer) override;
+
+    void dump(const std::string filename);
+};
+
+StatManager* StatManager::instance_ = nullptr;
+
+#endif