date.h

#ifndef _DATE_H
#define _DATE_H

#include <string>
#include <cstdio>
#include <ctime>

using namespace std;

typedef enum { YEAR, MONTH, DAY, HOUR, MINUTE, SECOND, WEEK } TimeUnit;

class Date {
private:
	const int Compare(const Date &OtherDate, TimeUnit FromPart = YEAR) const {
		for (;FromPart <= SECOND; FromPart = (TimeUnit)(FromPart+1)) {
			if (Data[FromPart] < OtherDate.Data[FromPart])
				return -1;
			else if (Data[FromPart] > OtherDate.Data[FromPart])
				return 1;
		}
		return 0;
	};
	
	short Data[6];
	class DatePart;
	
public:
	Date() {
		Clear();
	}
	
	bool IsLeapYear(short Year) const {
		return ((Year%4 == 0 && Year%100 != 0) || Year%400 == 0);
	}
	
	short DaysInMonth(short Month = 0) const {
		switch (Month == 0 ? Data[MONTH] : Month) {
			case 1: return 31;
			case 2: return IsLeapYear(Data[YEAR]) ? 29 : 28;
			case 3: return 31;
			case 4: return 30;
			case 5: return 31;
			case 6: return 30;
			case 7: return 31;
			case 8: return 31;
			case 9: return 30;
			case 10: return 31;
			case 11: return 30;
			case 12: return 31;
		}
		return 0;
	}
	
	string Format() const;
	operator string() const;
	Date &operator =(const string &Text);
	friend ostream &operator <<(ostream &stream, const Date &Date) {
		stream << Date.operator string();
		return stream;
	}
	bool operator <=(const Date &OtherDate) const { return (Compare(OtherDate) <= 0); }
	bool operator >=(const Date &OtherDate) const { return (Compare(OtherDate) >= 0); }
	bool operator <(const Date &OtherDate) const { return (Compare(OtherDate) < 0); }
	bool operator >(const Date &OtherDate) const { return (Compare(OtherDate) > 0); }
	bool operator ==(const Date &OtherDate) const { return (Compare(OtherDate) == 0); }
	DatePart operator [](TimeUnit PartName);
	
	unsigned long Difference(Date &OtherDate, TimeUnit Unit, bool RoundUp = true) const;
	void SetToNow();
	bool IsEmpty() const { return (Data[YEAR] == 0); }
	void Clear(bool OnlyTime = false) {
		if (!OnlyTime)
			Data[YEAR] = Data[MONTH] = Data[DAY] = 0;
		
		Data[HOUR] = Data[MINUTE] = Data[SECOND] = 0;
		WithTime = false;
	}
	
	bool WithTime;
};

class Date::DatePart {
private:
	Date &BaseDate;
	TimeUnit Part;
	
public:
	DatePart(Date &BaseDate, TimeUnit Part): BaseDate(BaseDate), Part(Part) {}
	
	operator short() const {
		if (Part <= SECOND)
			return BaseDate.Data[Part];
		else if (Part == WEEK) {
			// actually, this case is unused
			short Value = 0;
			for (char i=1; i<BaseDate.Data[MONTH]; ++i)
				Value += BaseDate.DaysInMonth(i);
			Value += BaseDate.Data[DAY];
			
			return (Value-1)/7 + 1;
		}

		return 0;
	}
	
	DatePart &operator =(short Value) {
		if (Part <= SECOND)
			BaseDate.Data[Part] = Value;
		
		return *this;
	}
	
	DatePart &operator =(const DatePart &DatePart) {
		return operator =((short)DatePart);
	}
	
	DatePart &operator +=(short Value);
	DatePart &operator -=(short Value);
	DatePart &operator ++() {
		operator +=(1);
		return *this;
	}
};

inline Date::DatePart Date::operator [](TimeUnit Part) {
	return DatePart(*this, Part);
}

#endif // _DATE_H