#!/usr/bin/env python

# author: Dave Bayer <bayer@math.columbia.edu>
# typical use: calendar.py calendar.txt calendar

import datetime
import re
import sys

# usage message

usage = """in out

  Generates calendar html from input description

input file format
(empty lines ok, year optional, $ ends input, b,r,g are colors):

12/18,21-23 b 1:00-2:00
1/10,12/2010 b 2:00-3:00

1/14 b 1:00-2:00
$
2/16 g
"""

# get command line arguments

def get_args(count, usage):
  argv = sys.argv
  if len(argv) == count + 1:
    return argv[1:]
  else:
    print '\nusage: %s %s' % (argv[0], usage)
    exit(0)

# parse a days descriptor 9-12,14,22-24 into individual days

def dates(ranges):
  out = []
  for field in ranges.split(','):
    day = map(int, field.split('-'))
    if len(day) == 2:
      out.extend(range(day[0], day[1]+1))
    else:
      out.append(day[0])
  return out

# regular expressions for parsing input events

eof = re.compile(r'[$]')
event = re.compile(r'(\d+)/([-,0-9]+)(?:/(\d+))?\s*([a-z])?\s+(.+)?')

# read_events processes input events

def read_events(file):
  year = datetime.datetime.today().year
  events = dict()
  for line in file.readlines():
    if eof.match(line):
      break
    data = event.match(line)
    if data:
      (mo, da, ye, co, tx) = data.groups()
      month = int(mo)
      if ye:
        year = int(ye)
      for day in dates(da):
        date = datetime.date(year,month,day)
        events[date] = co, tx
  return events

# html strings, data

header = """
<table cellpadding=5 border=1>
<col width="20%">
<col width="20%">
<col width="20%">
<col width="20%">
<col width="20%">

<tr>
<td valign="top" bgcolor="#99ffff"><b>Monday</b></td>
<td valign="top" bgcolor="#99ffff"><b>Tuesday</b></td>
<td valign="top" bgcolor="#99ffff"><b>Wednesday</b></td>
<td valign="top" bgcolor="#99ffff"><b>Thursday</b></td>
<td valign="top" bgcolor="#99ffff"><b>Friday</b></td>
</tr>
"""

footer = "</table>"

# show_date prepares table cell for date

colors = { 'b':'99ffff', 'r':'ff9999', 'g':'dddddd' }

month = ['',
  'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
  'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']

def show_day(date, events):
  html = "<td valign=\"top\" bgcolor=\"#%s\"><small><i>%s</i></small><br>%s</td>"
  color = 'ffffff'
  msg = ''
  if date in events.keys():
    co, tx = events[date]
    if co in colors.keys():
      color = colors[co]
    if tx:
      msg = "<b>%s</b>" % tx
  if date.weekday() == 0 or date.day == 1:
    day = "%s %s" % (date.day, month[date.month])
  else:
    day = "%d" % date.day
  return html % (color, day, msg)

# change date to specified day of same week (Monday is 0 and Sunday is 6)

def set_day (date, day):
  return date + datetime.timedelta(day - date.weekday())

# mon_fri is a generator giving dates needed for calendar

def mon_fri(dates):
  date = set_day(min(dates),0)
  end = set_day(max(dates),4)
  while date <= end:
    day = date.weekday()
    if day <= 4:
      yield date, day
    date += datetime.timedelta(1)
 
# write_html outputs events calendar

def write_html(events, file):
  dates = events.keys()
  print >>file, header
  for date, day in mon_fri(dates):
    if day == 0:
      print >>file, '<tr>'
    print >>file, show_day(date, events)
    if day == 4:
      print >>file, '</tr>\n'
  print >>file, footer

# open input, output files

fin, fon = get_args(2, usage)
fi = open(fin)
fo = open(fon, mode='w')

# read events and write calendar html

events = read_events(fi)
write_html(events, fo)

# close input, output files

fi.close()
fo.close()