date.h

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#ifndef CGR_DATE_H
#define CGR_DATE_H

 
#include <compare>
#include <cstddef>
#include <ctime>
#include <exception>
#include <iosfwd>
#include <string>
#include <string_view>
 
namespace cgr
{
    class Date {
    public:
        static constexpr int MIN_YEAR{ 1900 }; 
        static constexpr int MAX_YEAR{ 9999 }; 

        class DateError : public std::exception {
        public:
            enum class Reason {
                INVALID_DAY,    
                INVALID_MONTH,  
                INVALID_YEAR,   
                INVALID_DATE,   
                INVALID_FORMAT, 
                OUT_OF_RANGE,   
                EPOCH_FAILURE,  
                LOGIC_ERROR,    
                SYSTEM_FAILURE  
            };

            DateError(Reason reason, std::string message);

            [[nodiscard]] const char *what() const noexcept override;

            [[nodiscard]] Reason GetReason() const noexcept;
        private:
            Reason m_reason;
            std::string m_message;
        };

        struct ISOWeek {
            int year; 
            int week; 
            [[nodiscard]] bool operator==(const ISOWeek &rhs) const noexcept = default;
        };

        [[nodiscard]] static Date Today();

        [[nodiscard]] static Date RandomDate(int minYear = MIN_YEAR, int maxYear = Today().Year());

        Date() = default;

        Date(int day, int month, int year);

        explicit Date(std::string_view str);

        explicit Date(std::time_t timer);

        Date(std::nullptr_t) = delete;

        [[nodiscard]] int Day() const noexcept;

        [[nodiscard]] int Month() const noexcept;

        [[nodiscard]] int Year() const noexcept;

        [[nodiscard]] int DayOfYear() const noexcept;

        [[nodiscard]] int Weekday() const noexcept;

        [[nodiscard]] ISOWeek WeekOfYear() const noexcept;

        Date &Day(int day) &;

        Date &Month(int month) &;

        Date &Year(int year) &;

        Date &operator+=(int days) &;

        Date &operator-=(int days) &;

        Date &operator++() &;

        Date operator++(int) &;

        Date &operator--() &;

        Date operator--(int) &;

        [[nodiscard]] std::strong_ordering operator<=>(const Date &rhs) const noexcept;

        [[nodiscard]] bool operator==(const Date &rhs) const noexcept = default;

        [[nodiscard]] static bool IsLeap(int year);
    private:
        int m_day{ 1 };
        int m_month{ 1 };
        int m_year{ MIN_YEAR };
    };

    [[nodiscard]] Date operator+(const Date &d, int days);

    [[nodiscard]] Date operator+(int days, const Date &d);

    [[nodiscard]] Date operator-(const Date &d, int days);

    [[nodiscard]] int operator-(const Date &lhs, const Date &rhs) noexcept;

    std::istream &operator>>(std::istream &is, Date &d);

    std::ostream &operator<<(std::ostream &os, const Date &d);
}
 
#endif // CGR_DATE_H