Introduce ValueGenerator class

lib/base/CMakeLists.txt

@@ -37,6 +37,7 @@ set(base_SOURCES
   fifo.cpp fifo.hpp
   filelogger.cpp filelogger.hpp filelogger-ti.hpp
   function.cpp function.hpp function-ti.hpp function-script.cpp functionwrapper.hpp
+  generator.hpp
   initialize.cpp initialize.hpp
   intrusive-ptr.hpp
   io-engine.cpp io-engine.hpp

lib/base/generator.hpp

@@ -0,0 +1,48 @@
+/* Icinga 2 | (c) 2025 Icinga GmbH | GPLv2+ */
+
+#pragma once
+
+#include "base/i2-base.hpp"
+#include "base/value.hpp"
+#include <optional>
+
+namespace icinga
+{
+
+/**
+ * ValueGenerator is a class that defines a generator function type for producing Values on demand.
+ *
+ * This class is used to create generator functions that can yield any values that can be represented by the
+ * Icinga Value type. The generator function is exhausted when it returns `std::nullopt`, indicating that there
+ * are no more values to produce. Subsequent calls to `Next()` will always return `std::nullopt` after exhaustion.
+ *
+ * @ingroup base
+ */
+class ValueGenerator final : public Object
+{
+public:
+	DECLARE_PTR_TYPEDEFS(ValueGenerator);
+
+	/**
+	 * Generates a Value using the provided generator function.
+	 *
+	 * The generator function should return an `std::optional<Value>` which contains the produced Value or
+	 * `std::nullopt` when there are no more values to produce. After the generator function returns `std::nullopt`,
+	 * the generator is considered exhausted, and further calls to `Next()` will always return `std::nullopt`.
+	 */
+	using GenFunc = std::function<std::optional<Value>()>;
+
+	explicit ValueGenerator(GenFunc generator): m_Generator(std::move(generator))
+	{
+	}
+
+	std::optional<Value> Next() const
+	{
+		return m_Generator();
+	}
+
+private:
+	GenFunc m_Generator; // The generator function that produces Values.
+};
+
+}