initial import

result.hpp

@@ -0,0 +1,158 @@
+/*
+ * Copyright (c) 2017 Evgeniy Alekseev
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ *
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ */
+
+
+#ifndef _RESULT_H_
+#define _RESULT_H_
+
+#include <string>
+#include <variant>
+
+/**
+ * @addtogroup Result
+ * @brief Result namespace
+ */
+namespace Result
+{
+/**
+ * @enum Content
+ * @brief Result content type enumeration
+ * @var Content::Empty
+ * invalid content
+ * @var Content::Value
+ * Result contains value
+ * @var Content::Error
+ * Result contains error
+ */
+enum class Content { Empty, Value, Error };
+
+/**
+ * @brief Error representation
+ * @tparam ErrorEnum
+ * error code enumeration
+ */
+template <typename ErrorEnum> class Error
+{
+public:
+    /**
+     * @brief Error class default constructor
+     * @param message
+     * human readable error message
+     * @param code
+     * machine readable error code
+     */
+    explicit Error(std::string message, ErrorEnum code)
+        : m_code(code)
+    {
+        m_message = std::move(message);
+    };
+    /**
+     * @brief Error class constructor with default error code
+     * @param message
+     * human readable error message
+     */
+    Error(ErrorEnum code)
+        : Error("", code){};
+    /**
+     * @brief Error class constructor with empty error message
+     * @param code
+     * machine readable error code
+     */
+    Error(std::string message)
+        : Error(message, static_cast<ErrorEnum>(0)){};
+    /**
+     * @brief Error class destructor
+     */
+    ~Error() = default;
+
+    /**
+     * @brief error message
+     * @return human readable error message
+     */
+    std::string message() const { return m_message; };
+    /**
+     * @brief error code
+     * @return machine readable error code
+     */
+    ErrorEnum code() const { return m_code; };
+
+private:
+    /**
+     * @brief human readable error message
+     */
+    std::string m_message;
+    /**
+     * @brief machine readable error code
+     */
+    ErrorEnum m_code;
+};
+
+/**
+ * @brief Result main class
+ * @tparam T
+ * value class name
+ * @tparam ErrorEnum
+ * error code enumeration
+ */
+template <class T, typename ErrorEnum>
+class Result : public std::variant<T, Error<ErrorEnum>>
+{
+public:
+    /**
+     * @brief Result constructor with value
+     * @param value
+     * result value
+     */
+    Result(T value)
+        : std::variant<T, Error<ErrorEnum>>(value){};
+    /**
+     * @brief Result constructor with error
+     * @param error
+     * result error
+     */
+    Result(Error<ErrorEnum> error)
+        : std::variant<T, Error<ErrorEnum>>(error){};
+
+    /**
+     * @brief get result value
+     * @throw std::bad_variant_access
+     * @return result value if holded
+     */
+    T get() { return std::get<T>(*this); };
+    /**
+     * @brief get result error
+     * @throw std::bad_variant_access
+     * @return result error if holded
+     */
+    Error<ErrorEnum> error() { return std::get<Error<ErrorEnum>>(*this); };
+    /**
+     * @brief get result content
+     */
+    Content type() const
+    {
+        switch (this->index()) {
+        case 0:
+            return Content::Value;
+        case 1:
+            return Content::Error;
+        case std::variant_npos:
+        default:
+            return Content::Empty;
+        };
+    };
+};
+};
+
+#endif /* _RESULT_H_ */