子彈 の VISIONS

// created by ztwaker on 2006-8-24
// Used for: count days
// No guarantees offered. Constructive comments to waker615@gmail.com

// 需求：計算兩個日期之間相距天數。
// 應用：倒計時等

#include <iostream>
#include <algorithm>
namespace date {

//#define min(a, b) (((a) > (b)) ? (b) : (a))
//#define max(a, b) (((a) > (b)) ? (a) : (b))
	
	class Bad_date {}; // exception throw
	class Bad_year  : public Bad_date {};
	class Bad_month : public Bad_date {};
	class Bad_day   : public Bad_date {};
	
    ??? static const int this_year = 2006;

	inline bool leapyear(int year)
	{
		//if (year > this_year)
		// 	throw Bad_year();
		
		return ((year % 100==0) ? (year % 400==0) : (year % 4==0));
	}
	
	inline int yday(int year)
	{
		//if (year > this_year)
		//	throw Bad_year();
		
		return (365 + leapyear(year));
	}
	
	inline int mday(int month, int year)
	{
		switch(month) {
		case 1: case 3: case 5: 
		case 7: case 8: case 10:
		case 12:
			return 31;
			
		case 4: case 6: case 9: 
		case 11: 
			return 30;
			
		case 2: 
			return 28 + leapyear(year);
			
		default:
			throw Bad_month();
		}
		
		throw Bad_month();
	}
	
	class Date{
		int y, m, d;
		
	public:
		Date(int year, int month, int day)
		{
			// check year/month/day available
			if (0 == year)
				throw Bad_year();

			if (1 > month || 12 < month)
				throw Bad_month();

			if (1 > day || mday(month, year) < day)
				throw Bad_day();
			
			y = year; m = month; d = day;
		}
		Date(const Date& rhs)
		{
			this->y = rhs.year();
			this->m = rhs.month();
			this->d = rhs.day();
		}		
		Date& operator=(const Date& rhs)
		{
			if (rhs == (*this))
				return (*this);
			
			this->y = rhs.year();
			this->m = rhs.month();
			this->d = rhs.day();
			
			return (*this);
		}
		int year () const { return y; }
		int month() const { return m; }
		int day  () const { return d; }
		
		int passday() const
		{
			int dpass = 0;
			for (int i = 1; i != m; ++i)
			{
				dpass += mday(i, y);
			}
			
			return (dpass + d);
		}

		friend std::ostream& operator<<(std::ostream& os, const Date& rhs);
		
		friend bool operator==(const Date& lhs, const Date& rhs);
		friend bool operator!=(const Date& lhs, const Date& rhs);
		friend bool operator< (const Date& lhs, const Date& rhs);
		friend bool operator> (const Date& lhs, const Date& rhs);
		friend bool operator<=(const Date& lhs, const Date& rhs);
		friend bool operator>=(const Date& lhs, const Date& rhs);
		
		friend int  distant(const Date& lhs, const Date& rhs);
	};

	inline std::ostream& operator<<(std::ostream& os, const Date& rhs)
	{
		return (os << rhs.y << "-" << rhs.m << "-" << rhs.d);
	}
	inline bool operator==(const Date& lhs, const Date& rhs)
	{
		return (lhs.y == rhs.y && lhs.m == rhs.m && lhs.d == rhs.d);
	}
	inline bool operator!=(const Date& lhs, const Date& rhs)
	{
		return (!(lhs==rhs));
	}
	inline bool operator<(const Date& lhs, const Date& rhs)
	{
		// compare year
		if (lhs.y < rhs.y)
		{
			return true;
		}
		else if (lhs.y == rhs.y)
		{
			// compare month
			if (lhs.m < rhs.m)
			{
				return true;
			}
			else if (lhs.m == rhs.m)
			{
				// compare day
				if (lhs.d < rhs.d)
					return true;
				else
					return false;
			}
			return false;
		}
		return false;
	}
	inline bool operator>(const Date& lhs, const Date& rhs)
	{
		// compare year
		if (lhs.y > rhs.y)
		{
			return true;
		}
		else if (lhs.y == rhs.y)
		{
			// compare month
			if (lhs.m > rhs.m)
			{
				return true;
			}
			else if (lhs.m == rhs.m)
			{
				// compare day
				if (lhs.d > rhs.d)
					return true;
				else
					return false;
			}
			return false;
		}
		return false;
	}
	inline bool operator<=(const Date& lhs, const Date& rhs)
	{
		return (!(lhs>rhs));
	}
	inline bool operator>=(const Date& lhs, const Date& rhs)
	{
		return (!(lhs<rhs));
	}
	
	int distant(const Date& lhs, const Date& rhs)
	{
		int distance = 0;
		const int lowyear  = std::min(lhs.y, rhs.y);
		const int highyear = std::max(lhs.y, rhs.y);
		for (int yn = lowyear; yn != highyear; ++yn)
		{
			distance += yday(yn);
		}
		
		return (
			distance - std::min(lhs, rhs).passday() 
			+ std::max(lhs, rhs).passday()
			);
	}
} // end of namespace date

void test()
{
	try {
		date::Date today(2006, 1, 29);    // 丙戌年春節
		date::Date deadline(2007, 2, 18); // 丁亥年春節
		std::cout << "From "<< today << " to " << deadline << " is ";
		std::cout << date::distant(today, deadline) << " days left.\n";
	}
	catch (date::Bad_year) {
		std::cout << "Bad year" << std::endl;
	}
	catch (date::Bad_month) {
		std::cout << "Bad month" << std::endl;
	}
	catch (date::Bad_day) {
		std::cout << "Bad day" << std::endl;
	}
	catch (date::Bad_date) {
		std::cout << "Bad date" << std::endl;
	}
}

int main()
{
    test();
    return 0;
}