From fa2bd86078790371106a7d969de4ad520a799c89 Mon Sep 17 00:00:00 2001
From: Levente Batuska <batuska.levente@nas-technologies.com>
Date: Wed, 28 Jan 2026 21:20:45 +0100
Subject: [PATCH] feat: env_var

---
 include/cpputils/env_var.h | 101 +++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 include/cpputils/env_var.h

diff --git a/include/cpputils/env_var.h b/include/cpputils/env_var.h
new file mode 100644
index 0000000..3427a31
--- /dev/null
+++ b/include/cpputils/env_var.h
@@ -0,0 +1,101 @@
+#pragma once
+
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <string>
+#include <unordered_map>
+
+namespace cpputils {
+namespace env_var {
+
+class EnvVarRegistry {
+ public:
+  static EnvVarRegistry& instance() {
+    static EnvVarRegistry inst;
+    return inst;
+  }
+
+  void register_var(std::string const& name, char const* default_val) {
+    if (vars_.find(name) != vars_.end()) {
+      std::cerr << "ENV VAR \"" << name << "\" already registered!";
+      exit(EXIT_FAILURE);
+    }
+    vars_.emplace(name, std::string(default_val));
+  }
+
+  template <typename T>
+  void register_var(std::string const& name, T const& default_val) {
+    static_assert(std::is_arithmetic_v<T>,
+                  "Only arithmetic types supported here");
+    if (vars_.find(name) != vars_.end()) {
+      std::cerr << "ENV VAR \"" << name << "\" already registered!";
+      exit(EXIT_FAILURE);
+    }
+    vars_.emplace(name, std::to_string(default_val));
+  }
+
+  std::unordered_map<std::string, std::string> const& get_vars() const {
+    return vars_;
+  }
+
+ private:
+  std::unordered_map<std::string, std::string> vars_;
+
+ public:
+  struct EnvVarAutoRegister {
+    template <typename T>
+    EnvVarAutoRegister(char const* name, T const& default_value) {
+      EnvVarRegistry::instance().register_var(name, default_value);
+    }
+  };
+};
+
+#define DEFINE_ENV_VAR_STRING(name, DEFAULT_VALUE, MIN_LEN)               \
+  namespace EnvVars {                                                     \
+  struct name {                                                           \
+    static constexpr char const* DEFAULT = DEFAULT_VALUE;                 \
+    static constexpr char const* NAME = #name;                            \
+    static char const* GET() {                                            \
+      auto c = std::getenv(#name);                                        \
+      if (c) {                                                            \
+        if (std::strlen(c) > MIN_LEN) {                                   \
+          return c;                                                       \
+        }                                                                 \
+      }                                                                   \
+      return DEFAULT_VALUE;                                               \
+    }                                                                     \
+    static inline ::cpputils::env_var::EnvVarRegistry::EnvVarAutoRegister \
+        _env_register{#name, DEFAULT_VALUE};                              \
+  };                                                                      \
+  }
+
+#define DEFINE_ENV_VAR_INT(TYPE, name, DEFAULT_VALUE)                     \
+  namespace EnvVars {                                                     \
+  struct name {                                                           \
+    static constexpr TYPE DEFAULT = DEFAULT_VALUE;                        \
+    static constexpr char const* NAME = #name;                            \
+    static TYPE GET() {                                                   \
+      auto c = std::getenv(#name);                                        \
+      if (c) {                                                            \
+        if (std::strlen(c) > 0) {                                         \
+          try {                                                           \
+            if constexpr (std::is_unsigned_v<TYPE>) {                     \
+              TYPE x = static_cast<TYPE>(std::stoull(c));                 \
+              return x;                                                   \
+            } else {                                                      \
+              TYPE x = static_cast<TYPE>(std::stoll(c));                  \
+              return x;                                                   \
+            }                                                             \
+          } catch (...) {}                                                \
+        }                                                                 \
+      }                                                                   \
+      return DEFAULT_VALUE;                                               \
+    }                                                                     \
+    static inline ::cpputils::env_var::EnvVarRegistry::EnvVarAutoRegister \
+        _env_register{#name, DEFAULT_VALUE};                              \
+  };                                                                      \
+  }
+
+}  // namespace env_var
+}  // namespace cpputils