Constants.h

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#pragma once
 
#include <cstdint>
#include <limits>
#include <string_view>
 
namespace nfx::time::constants
{
    //=====================================================================
    // Basic time conversion constants
    //=====================================================================

    inline constexpr std::int32_t MILLISECONDS_PER_SECOND{ 1000 };

    inline constexpr std::int32_t SECONDS_PER_MINUTE{ 60 };

    inline constexpr std::int32_t SECONDS_PER_HOUR{ SECONDS_PER_MINUTE * 60 };

    inline constexpr std::int32_t SECONDS_PER_DAY{ SECONDS_PER_HOUR * 24 };

    inline constexpr std::int32_t MINUTES_PER_HOUR{ 60 };

    inline constexpr std::int32_t MINUTES_PER_DAY{ MINUTES_PER_HOUR * 24 };

    inline constexpr std::int32_t HOURS_PER_DAY{ 24 };
 
    //=====================================================================
    // DateTime value boundaries
    //=====================================================================

    inline constexpr std::int64_t MIN_DATETIME_TICKS{ 0LL };

    inline constexpr std::int64_t MAX_DATETIME_TICKS{ 3155378975999999999LL };

    inline constexpr std::int64_t UNIX_EPOCH_TICKS{ 621355968000000000LL };

    inline constexpr std::int64_t MICROSOFT_FILETIME_EPOCH_TICKS{ 504911232000000000LL };
 
    //=====================================================================
    // Time unit conversion constants
    //=====================================================================

    inline constexpr std::int64_t NANOSECONDS_PER_TICK{ 100LL };

    inline constexpr std::int64_t TICKS_PER_MICROSECOND{ 10LL };

    inline constexpr std::int64_t TICKS_PER_MILLISECOND{ 10000LL };

    inline constexpr std::int64_t TICKS_PER_SECOND{ TICKS_PER_MILLISECOND * 1000LL };

    inline constexpr std::int64_t TICKS_PER_MINUTE{ TICKS_PER_SECOND * 60LL };

    inline constexpr std::int64_t TICKS_PER_HOUR{ TICKS_PER_MINUTE * 60LL };

    inline constexpr std::int64_t TICKS_PER_DAY{ TICKS_PER_HOUR * 24LL };
 
    //=====================================================================
    // Timezone offset limits (ISO 8601)
    //=====================================================================

    inline constexpr std::int32_t MIN_OFFSET_MINUTES{ -14 * 60 };

    inline constexpr std::int32_t MAX_OFFSET_MINUTES{ 14 * 60 };

    inline constexpr std::int32_t MIN_OFFSET_SECONDS{ MIN_OFFSET_MINUTES * 60 };

    inline constexpr std::int32_t MAX_OFFSET_SECONDS{ MAX_OFFSET_MINUTES * 60 };

    inline constexpr std::int32_t UTC_OFFSET{ 0 };
 
    //=====================================================================
    // Calendar system constants (Gregorian)
    //=====================================================================
 
    //----------------------------------------------
    // Year boundaries
    //----------------------------------------------

    inline constexpr std::int32_t MIN_YEAR{ 1 };

    inline constexpr std::int32_t MAX_YEAR{ 9999 };
 
    //----------------------------------------------
    // Calendar cycle constants for date calculations
    //----------------------------------------------

    inline constexpr std::int32_t DAYS_PER_400_YEARS{ 146097 };

    inline constexpr std::int32_t DAYS_PER_100_YEARS{ 36524 };

    inline constexpr std::int32_t DAYS_PER_4_YEARS{ 1461 };

    inline constexpr std::int32_t DAYS_PER_YEAR{ 365 };
 
    //=====================================================================
    // ISO 8601 string formats
    //=====================================================================
 
    //----------------------------------------------
    // String format patterns
    //----------------------------------------------

    inline constexpr std::string_view ISO8601_BASIC_PATTERN{ "yyyy-MM-ddTHH:mm:ssZ" };

    inline constexpr std::string_view ISO8601_EXTENDED_PATTERN{ "yyyy-MM-ddTHH:mm:ss.fffffffK" };

    inline constexpr std::string_view ISO8601_DATE_PATTERN{ "yyyy-MM-dd" };

    inline constexpr std::string_view ISO8601_TIME_PATTERN{ "HH:mm:ss" };
 
    //----------------------------------------------
    // String format limits (for buffer allocation)
    //----------------------------------------------

    inline constexpr std::size_t MAX_ISO8601_LENGTH{ 35 };

    inline constexpr std::size_t MIN_ISO8601_LENGTH{ 20 };
 
    //----------------------------------------------
    // Unix epoch format limits
    //----------------------------------------------

    inline constexpr std::size_t MAX_UNIX_SECONDS_LENGTH{ 10 };

    inline constexpr std::size_t MAX_UNIX_MILLISECONDS_LENGTH{ 13 };

    inline constexpr std::size_t CURRENT_UNIX_SECONDS_LENGTH{ 10 };
} // namespace nfx::time::constants