lunardate.py

# this file is derived from lunar project.
#
# lunar project:
#   Copyright (C) 1988,1989,1991,1992,2001 Fung F. Lee and Ricky Yeung
#   Licensed under GPLv2.
#
# Copyright (C) 2008 LI Daobing <lidaobing@gmail.com>

'''
A Chinese Calendar Library in Pure Python
=========================================

Chinese Calendar: http://en.wikipedia.org/wiki/Chinese_calendar

Usage
-----
        >>> LunarDate.fromSolarDate(1976, 10, 1)
        LunarDate(1976, 8, 8, 1)
        >>> LunarDate(1976, 8, 8, 1).toSolarDate()
        datetime.date(1976, 10, 1)
        >>> LunarDate(1976, 8, 8, 1).year
        1976
        >>> LunarDate(1976, 8, 8, 1).month
        8
        >>> LunarDate(1976, 8, 8, 1).day
        8
        >>> LunarDate(1976, 8, 8, 1).isLeapMonth
        True
        
        >>> today = LunarDate.today()
        >>> type(today).__name__
        'LunarDate'
        
        >>> # support '+' and '-' between datetime.date and datetime.timedelta
        >>> ld = LunarDate(1976,8,8)
        >>> sd = datetime.date(2008,1,1)
        >>> td = datetime.timedelta(days=10)
        >>> ld-ld
        datetime.timedelta(0)
        >>> ld-sd
        datetime.timedelta(-11444)
        >>> ld-td
        LunarDate(1976, 7, 27, 0)
        >>> sd-ld
        datetime.timedelta(11444)
        >>> ld+td
        LunarDate(1976, 8, 18, 0)
        >>> td+ld
        LunarDate(1976, 8, 18, 0)
        >>> ld2 = LunarDate.today()
        >>> ld < ld2
        True
        >>> ld <= ld2
        True
        >>> ld > ld2
        False
        >>> ld >= ld2
        False
        >>> ld == ld2
        False
        >>> ld != ld2
        True
        >>> ld == ld
        True

News
----

* 0.1.4: support '+', '-' and compare, fix bug in year 2050
* 0.1.3: support python 3.0
        
Limits
------

this library can only deal with year from 1900 to 2049 (in chinese calendar).
        
See also
--------

* lunar: http://packages.qa.debian.org/l/lunar.html, 
  A converter written in C, this program is derived from it.
* python-lunar: http://code.google.com/p/liblunar/
  Another library written in C, including a python binding.
'''

import datetime

__version__ = "$Rev: 22 $"
__all__ = ['LunarDate']

class LunarDate(object):    
    _startDate = datetime.date(1900, 1, 31)
    
    def __init__(self, year, month, day, isLeapMonth=False):
        self.year = year
        self.month = month
        self.day = day
        self.isLeapMonth = bool(isLeapMonth)
        
    def __str__(self):
        return 'LunarDate(%d, %d, %d, %d)' % (self.year, self.month, self.day, self.isLeapMonth)
    
    __repr__ = __str__
        
    @staticmethod
    def fromSolarDate(year, month, day):
        '''
        >>> LunarDate.fromSolarDate(1900, 1, 31)
        LunarDate(1900, 1, 1, 0)
        >>> LunarDate.fromSolarDate(2008, 10, 2)
        LunarDate(2008, 9, 4, 0)
        >>> LunarDate.fromSolarDate(1976, 10, 1)
        LunarDate(1976, 8, 8, 1)
        >>> LunarDate.fromSolarDate(2033, 10, 23)
        LunarDate(2033, 10, 1, 0)
        '''
        solarDate = datetime.date(year, month, day)
        offset = (solarDate - LunarDate._startDate).days
        return LunarDate._fromOffset(offset)
    
    def toSolarDate(self):
        '''
        >>> LunarDate(1900, 1, 1).toSolarDate()
        datetime.date(1900, 1, 31)
        >>> LunarDate(2008, 9, 4).toSolarDate()
        datetime.date(2008, 10, 2)
        >>> LunarDate(1976, 8, 8, 1).toSolarDate()
        datetime.date(1976, 10, 1)
        >>> LunarDate(2004, 1, 30).toSolarDate()
        Traceback (most recent call last):
        ...
        ValueError: day out of range
        >>> LunarDate(2050, 1, 1).toSolarDate()
        Traceback (most recent call last):
        ...
        ValueError: year out of range [1900, 2050)
        >>>
        '''
        def _calcDays(yearInfo, month, day, isLeapMonth):
            isLeapMonth = int(isLeapMonth)
            res = 0
            ok = False
            for _month, _days, _isLeapMonth in self._enumMonth(yearInfo):
                if (_month, _isLeapMonth) == (month, isLeapMonth):
                    if 1 <= day <= _days:
                        res += day - 1
                        return res
                    else:
                        raise ValueError("day out of range")
                res += _days
                
            raise ValueError("month out of range")
        
        offset = 0
        if self.year < 1900 or self.year >= 2050:
            raise ValueError('year out of range [1900, 2050)')
        yearIdx = self.year - 1900
        for i in range(yearIdx):
            offset += yearDays[i]
            
        offset += _calcDays(yearInfos[yearIdx], self.month, self.day, self.isLeapMonth)
        return self._startDate + datetime.timedelta(days=offset)
    
    def __sub__(self, other):
        if isinstance(other, LunarDate):
            return self.toSolarDate() - other.toSolarDate()
        elif isinstance(other, datetime.date):
            return self.toSolarDate() - other
        elif isinstance(other, datetime.timedelta):
            res = self.toSolarDate() - other
            return LunarDate.fromSolarDate(res.year, res.month, res.day)
        raise TypeError
    
    def __rsub__(self, other):
        if isinstance(other, datetime.date):
            return other - self.toSolarDate()
        
    def __add__(self, other):
        if isinstance(other, datetime.timedelta):
            res = self.toSolarDate() + other
            return LunarDate.fromSolarDate(res.year, res.month, res.day)
        raise TypeError
    
    def __radd__(self, other):
        return self + other

    def __lt__(self, other):
        return self - other < datetime.timedelta(0)

    def __le__(self, other):
        return self - other <= datetime.timedelta(0)
    
    @classmethod
    def today(cls):
        res = datetime.date.today()
        return cls.fromSolarDate(res.year, res.month, res.day)
    
    @staticmethod
    def _enumMonth(yearInfo):
        months = [(i, 0) for i in range(1, 13)]
        leapMonth = yearInfo % 16
        if leapMonth == 0:
            pass
        elif leapMonth <= 12:
            months.insert(leapMonth, (leapMonth, 1))
        else:
            raise ValueError("yearInfo %r mod 16 should in [0, 12]" % yearInfo)
        
        for month, isLeapMonth in months:
            if isLeapMonth:
                days = (yearInfo >> 16) % 2 + 29
            else:
                days = (yearInfo >> (16 - month)) % 2 + 29
            yield month, days, isLeapMonth        

    @classmethod
    def _fromOffset(cls, offset):
        def _calcMonthDay(yearInfo, offset):
            for month, days, isLeapMonth in cls._enumMonth(yearInfo):
                if offset < days:
                    break
                offset -= days
            return (month, offset + 1, isLeapMonth)

        offset = int(offset)

        for idx, yearDay in enumerate(yearDays):
            if offset < yearDay:
                break
            offset -= yearDay
        year = 1900 + idx
        
        yearInfo = yearInfos[idx]
        month, day, isLeapMonth = _calcMonthDay(yearInfo, offset)
        return LunarDate(year, month, day, isLeapMonth)
    
yearInfos = [
        #    /* encoding:
        #               b bbbbbbbbbbbb bbbb
        #       bit#    1 111111000000 0000
        #               6 543210987654 3210
        #               . ............ ....
        #       month#    000000000111
        #               M 123456789012   L
        #                               
        #    b_j = 1 for long month, b_j = 0 for short month
        #    L is the leap month of the year if 1<=L<=12; NO leap month if L = 0.
        #    The leap month (if exists) is long one iff M = 1.
        #    */
        0x04bd8,                                    #   /* 1900 */
        0x04ae0, 0x0a570, 0x054d5, 0x0d260, 0x0d950,#   /* 1905 */
        0x16554, 0x056a0, 0x09ad0, 0x055d2, 0x04ae0,#   /* 1910 */
        0x0a5b6, 0x0a4d0, 0x0d250, 0x1d255, 0x0b540,#   /* 1915 */
        0x0d6a0, 0x0ada2, 0x095b0, 0x14977, 0x04970,#   /* 1920 */
        0x0a4b0, 0x0b4b5, 0x06a50, 0x06d40, 0x1ab54,#   /* 1925 */
        0x02b60, 0x09570, 0x052f2, 0x04970, 0x06566,#   /* 1930 */
        0x0d4a0, 0x0ea50, 0x06e95, 0x05ad0, 0x02b60,#   /* 1935 */
        0x186e3, 0x092e0, 0x1c8d7, 0x0c950, 0x0d4a0,#   /* 1940 */
        0x1d8a6, 0x0b550, 0x056a0, 0x1a5b4, 0x025d0,#   /* 1945 */
        0x092d0, 0x0d2b2, 0x0a950, 0x0b557, 0x06ca0,#   /* 1950 */
        0x0b550, 0x15355, 0x04da0, 0x0a5d0, 0x14573,#   /* 1955 */
        0x052d0, 0x0a9a8, 0x0e950, 0x06aa0, 0x0aea6,#   /* 1960 */
        0x0ab50, 0x04b60, 0x0aae4, 0x0a570, 0x05260,#   /* 1965 */
        0x0f263, 0x0d950, 0x05b57, 0x056a0, 0x096d0,#   /* 1970 */
        0x04dd5, 0x04ad0, 0x0a4d0, 0x0d4d4, 0x0d250,#   /* 1975 */
        0x0d558, 0x0b540, 0x0b5a0, 0x195a6, 0x095b0,#   /* 1980 */
        0x049b0, 0x0a974, 0x0a4b0, 0x0b27a, 0x06a50,#   /* 1985 */
        0x06d40, 0x0af46, 0x0ab60, 0x09570, 0x04af5,#   /* 1990 */
        0x04970, 0x064b0, 0x074a3, 0x0ea50, 0x06b58,#   /* 1995 */
        0x05ac0, 0x0ab60, 0x096d5, 0x092e0, 0x0c960,#   /* 2000 */
        0x0d954, 0x0d4a0, 0x0da50, 0x07552, 0x056a0,#   /* 2005 */
        0x0abb7, 0x025d0, 0x092d0, 0x0cab5, 0x0a950,#   /* 2010 */
        0x0b4a0, 0x0baa4, 0x0ad50, 0x055d9, 0x04ba0,#   /* 2015 */
        0x0a5b0, 0x15176, 0x052b0, 0x0a930, 0x07954,#   /* 2020 */
        0x06aa0, 0x0ad50, 0x05b52, 0x04b60, 0x0a6e6,#   /* 2025 */
        0x0a4e0, 0x0d260, 0x0ea65, 0x0d530, 0x05aa0,#   /* 2030 */
        0x076a3, 0x096d0, 0x04afb, 0x04ad0, 0x0a4d0,#   /* 2035 */
        0x1d0b6, 0x0d250, 0x0d520, 0x0dd45, 0x0b5a0,#   /* 2040 */
        0x056d0, 0x055b2, 0x049b0, 0x0a577, 0x0a4b0,#   /* 2045 */
        0x0aa50, 0x1b255, 0x06d20, 0x0ada0          #   /* 2049 */
        ]

def yearInfo2yearDay(yearInfo):
    '''calculate the days in a lunar year from the lunar year's info

    >>> yearInfo2yearDay(0) # no leap month, and every month has 29 days.
    348
    >>> yearInfo2yearDay(1) # 1 leap month, and every month has 29 days.
    377
    >>> yearInfo2yearDay((2**12-1)*16) # no leap month, and every month has 30 days.
    360
    >>> yearInfo2yearDay((2**13-1)*16+1) # 1 leap month, and every month has 30 days.
    390
    >>> # 1 leap month, and every normal month has 30 days, and leap month has 29 days.
    >>> yearInfo2yearDay((2**12-1)*16+1)
    389
    '''
    yearInfo = int(yearInfo)

    res = 29 * 12
    
    leap = False
    if yearInfo % 16 != 0:
        leap = True
        res += 29

    yearInfo //= 16

    for i in range(12 + leap):
        if yearInfo % 2 == 1:
            res += 1
        yearInfo //= 2
    return res

yearDays = [yearInfo2yearDay(x) for x in yearInfos]

def day2LunarDate(offset):
    offset = int(offset)
    res = LunarDate()

    for idx, yearDay in enumerate(yearDays):
        if offset < yearDay:
            break
        offset -= yearDay
    res.year = 1900 + idx






if __name__ == '__main__':
    import doctest
    doctest.testmod()