from Tkinter import *
import time

DAYS = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat']
MONTHS = ['   ',			# Placeholder so we can index from 1
	  'January',   'February', 'March',    'April',
	  'May',       'June',     'July',     'August',
	  'September', 'October',  'November', 'December']
LENGTHS = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

class Calendar:

    def __init__(self, master):
	self.master = master
	self.create_widgets()
	self.fill()

    def create_widgets(self):
	self.topframe = Frame(self.master)
	self.topframe.pack(fill=X, side=TOP)
	self.prevyearbutton = Button(self.topframe, text="<<",
				 command=self.prevyear)
	self.prevyearbutton.pack(side=LEFT)
	self.prevbutton = Button(self.topframe, text="<",
				 command=self.prev)
	self.prevbutton.pack(side=LEFT)
	self.nextyearbutton = Button(self.topframe, text=">>",
				 command=self.nextyear)
	self.nextyearbutton.pack(side=RIGHT)
	self.nextbutton = Button(self.topframe, text=">",
				 command=self.next)
	self.nextbutton.pack(side=RIGHT)
	self.toplabel = Button(self.topframe, relief=FLAT, command=self.reset)
	self.toplabel.pack(expand=1, fill=X)

	self.midframe = Frame(self.master)
	self.midframe.pack(expand=1, fill=BOTH, side=TOP)
	self.columns = []
	for i in range(7):
	    column = Frame(self.midframe)
	    column.pack(side=LEFT, expand=1, fill=BOTH)
	    dayname = Label(column, text=DAYS[i])
	    dayname.pack(side=TOP, fill=X)
	    daybuttons = []
	    for j in range(6):
		daybutton = Button(column)
		daybutton.pack(side=TOP, fill=X)
		daybuttons.append(daybutton)
	    self.columns.append(daybuttons)

    def fill(self, year=0, month=0):
	now = time.time()
	today = time.localtime(now)
	t = time.mktime((year or today[0], month or today[1], 1) + 6*(0,))
	date = time.localtime(t)
	year, month, day, hh, mm, ss, weekday, yearday, isdst = date
	self.year, self.month = year, month
	label = "%s %d" % (MONTHS[month], year)
	self.toplabel.config(text=label)
	maxdate = LENGTHS[month]
	if month==2 and year%4 == 0 and (year%400 == 0 or year%100 != 0):
	    maxdate = 29
	# weekday encoding: Monday=0, ..., Sunday=6
	weekday1 = (weekday - (day-1)) % 7 # First of the month
	weekday0 = (weekday1+1) % 7	# Sunday=0, ..., Saturday=6
	here = -weekday0
	bg = self.midframe['background']
	for row in range(6):
	    for col in range(7):
		daybutton = self.columns[col][row]
		here = here+1
		if 1 <= here <= maxdate:
		    if here == today[2] and date[:2] == today[:2]:
			bgcolor = "green"
		    else:
			bgcolor = bg
		    daybutton.config(text="%d" % here,
				     state=NORMAL, relief=RAISED,
				     background=bgcolor)
		else:
		    daybutton.config(text="", state=DISABLED,
				     relief=FLAT, background=bg)

    def prevyear(self):
	self.fill(self.year-1, self.month)

    def prev(self):
	year, month = self.year, self.month-1
	if month < 1:
	    year, month = year-1, 12
	self.fill(year, month)

    def next(self):
	year, month = self.year, self.month+1
	if month > 12:
	    year, month = year+1, 1
	self.fill(year, month)

    def nextyear(self):
	self.fill(self.year+1, self.month)

    def reset(self):
	self.fill()