Add EnvKvStore for envvar parsing and interleaving

include/spinscale/envKvStore.h

@@ -0,0 +1,44 @@
+#ifndef SPINSCALE_ENV_KV_STORE_H
+#define SPINSCALE_ENV_KV_STORE_H
+
+#include <filesystem>
+#include <optional>
+#include <ostream>
+#include <string>
+#include <string_view>
+#include <unordered_map>
+#include <vector>
+
+namespace sscl {
+
+class EnvKvStore
+{
+public:
+	explicit EnvKvStore(
+		const std::vector<std::filesystem::path> &envFilePaths,
+		std::ostream &warningStream);
+	explicit EnvKvStore(
+		const std::vector<std::filesystem::path> &envFilePaths);
+
+	std::optional<std::string> get(std::string_view name) const;
+
+private:
+	void loadFiles(
+		const std::vector<std::filesystem::path> &envFilePaths,
+		std::ostream &warningStream);
+	void loadFile(
+		const std::filesystem::path &envFilePath,
+		std::ostream &warningStream);
+	void storeValue(
+		const std::filesystem::path &envFilePath,
+		const std::string &name,
+		const std::string &value,
+		std::ostream &warningStream);
+
+private:
+	std::unordered_map<std::string, std::string> values;
+};
+
+} // namespace sscl
+
+#endif // SPINSCALE_ENV_KV_STORE_H