NBEngine/engine/NBCore/Errors.hpp

#pragma once
#ifndef _NB_ERROR
#define _NB_ERROR

#include <exception>
#include <memory>
#include <string>
#include <string_view>
#include <type_traits>
#include "TypeTraits.hpp"
#include <unordered_map>
#include "StringUtils.hpp"

namespace nb {

typedef std::unordered_map<unsigned int, const char*> ErrorCodeMap;

template <typename T>
using has_type = decltype(T::type);

template<class ErrorType = NoneType>
class ErrorBase;

template<>
class ErrorBase<NoneType> : public std::exception {
public:
    const unsigned int code;
    const std::string msg;
    const std::shared_ptr<const std::exception> trace;
    const bool traceIsNBError;

    virtual inline std::string str() const noexcept = 0;

    virtual const char* what() const noexcept override final {
        const std::string& ret = str();
        return ret.c_str();
    }

protected:
    template <
        typename TraceType = std::exception,
        std::enable_if_t<std::is_base_of_v<std::exception, TraceType>, bool> = true
    >
    ErrorBase(
        const unsigned int& code_,
        const std::string& msg_,
        const std::shared_ptr<TraceType> trace_,
        const unsigned int& line_,
        std::string filename_
    ) noexcept :
        code(code_),
        msg(msg_),
        trace{std::dynamic_pointer_cast<std::exception>(trace_)},
        traceIsNBError( trace_ ? is_detected<has_type, TraceType>::value : false)
    {
        static_assert(std::is_base_of<std::exception, TraceType>::value,
            "`trace_` must be a pointer to a child object of std::exception."
        );
    }
};

template <class ErrorType>
class ErrorBase : public ErrorBase<NoneType> {
    using Base = ErrorBase<NoneType>;
public:
    ErrorBase(const ErrorBase&) = default;
    ErrorBase& operator=(const ErrorBase&) = delete;

    virtual inline std::string str() const noexcept override {
        std::string ret = msg + nb::NEWLINE;
        if (trace) {
            const std::string tabover = "  ";
            std::string trace_msg;
            if (traceIsNBError) { 
                trace_msg = std::static_pointer_cast<const ErrorBase>(trace)->str();
                trace_msg = std::string(std::string_view(trace_msg).substr(
                    0, trace_msg.length()-nb::NEWLINE.length()
                ));
            } else {
                trace_msg = std::string(trace->what());
            }
            ret += indent_strblock(trace_msg, tabover, tabover+"Trace: ")+nb::NEWLINE;
        }
        return ret;
    }

    static const std::string type;
    static const ErrorCodeMap ErrorMessages; 

    using Base::code;
    using Base::msg;
    using Base::trace;
    using Base::traceIsNBError;

protected:
    using Base::Base;

    template <
        typename TraceType = std::exception,
        std::enable_if_t<std::is_base_of_v<std::exception, TraceType>, bool> = true
    >
    ErrorBase(
        const unsigned int code_,
        std::string msg_,
        const TraceType* trace_=nullptr,
        unsigned int line_=0,
        std::string filename_=""
    ) : Base(
        code_,
        msg_, 
        trace_ ? std::make_shared<TraceType>(*trace_) : nullptr, 
        line_, 
        filename_
    ) {
        static_assert(std::is_same<const std::unordered_map<unsigned int, const char*>, decltype(ErrorType::ErrorMessages)>::value,
            "const std::unordered_map<unsigned int, const char*> ErrorMessages must be "
            "a class member."
        );
        static_assert(std::is_enum_v<typename ErrorType::Codes>, "enum Codes must be a class member.");
        static_assert(std::is_same<std::underlying_type_t<typename ErrorType::Codes>, unsigned int>::value,
            "enum Codes must be of underlying type unsigned int."
        );
        static_assert(std::is_same<const std::string, decltype(ErrorType::type)>::value,
            "const std::string type must be a class member."
        );
    }

    template <
        typename TraceType,
        std::enable_if_t<std::is_base_of_v<std::exception, TraceType>, bool> = true
    >
    ErrorBase(
        const unsigned int& code_,
        const TraceType& trace_,
        unsigned int line_=0,
        std::string filename_=""
    ) noexcept : ErrorBase(
        code_, 
        ErrorType::ErrorMessages.at(code_),
        &trace_,
        line_,
        filename_
    ) {}

    template <
        typename TraceType,
        std::enable_if_t<std::is_base_of_v<std::exception, TraceType>, bool> = true
    >
    ErrorBase(
        const std::string& msg_,
        const TraceType& trace_,
        unsigned int line_=0,
        std::string filename_=""
    ) noexcept : ErrorBase(
        0, 
        msg_,
        &trace_,
        line_,
        filename_
    ) {}

    ErrorBase(
        const unsigned int& code_,
        unsigned int line_=0,
        std::string filename_=""
    ) noexcept : ErrorBase(
        code_, 
        ErrorType::ErrorMessages.at(code_),
        static_cast<std::exception*>(nullptr),
        line_,
        filename_
    ) {}

    ErrorBase(
        const std::string& msg_,
        unsigned int line_=0,
        std::string filename_=""
    ) noexcept : ErrorBase(
        0, 
        msg_,
        nullptr,
        line_,
        filename_
    ) {}
};
template <typename ErrorType>
const std::string ErrorBase<ErrorType>::type = ErrorType::type;
template <typename ErrorType>
const ErrorCodeMap ErrorBase<ErrorType>::ErrorMessages = ErrorType::ErrorMessages;

template <class ErrorType = NoneType>
class Error;

template<>
class Error<NoneType>;

template <class ErrorType>
class Error : public ErrorBase<ErrorType> {
    using Base = ErrorBase<ErrorType>;
public:    
    template <typename... Args>
    Error(Args... T) : Base(T...) {}

    using Base::str;
    using Base::what;
    using Base::code;
    using Base::msg;
    using Base::trace;
    using Base::traceIsNBError;
    using Base::type;
    using Base::ErrorMessages;

    friend ErrorBase<Error>;
};

template<>
class Error<NoneType> : public ErrorBase<Error<NoneType>> {
    using Base = ErrorBase<Error<NoneType>>;
public:
    using Base::Base;
    Error() : Base(0) {}

    enum Codes : unsigned int {
        GENERAL, UNDEFINED, BADERRORCODE
    };

    using Base::str;
    using Base::what;

    using Base::code;
    using Base::msg;
    using Base::trace;
    using Base::traceIsNBError;
    static const std::string type;
    static const ErrorCodeMap ErrorMessages;
};

} // namespace nb

#endif // _NB_ERROR