'''
 ====================================================================
 Copyright (c) 2003-2009 Barry A Scott.  All rights reserved.

 This software is licensed as described in the file LICENSE.txt,
 which you should have received as part of this distribution.

 ====================================================================
'''

_debug_parse_time = 0

class DateTimeSyntaxError( Exception ):
	def __init__( self, reason ):
		Exception.__init__( self )
		self._reason = reason

	def reason( self ):
		return self._reason

	def __str__( self ):
		return self._reason


class DateSyntaxError( DateTimeSyntaxError ):
	def __init__( self, reason ):
		DateTimeSyntaxError.__init__( self, reason )

class TimeSyntaxError( DateTimeSyntaxError ):
	def __init__( self, reason ):
		DateTimeSyntaxError.__init__( self, reason )

def parse_time( time_string ):
	"""parse_time( time_string )
	returns the UTC time represented by time_string

	british locale defaults used

	formats understood for a date are:
		dayname		- today, yesterday, monday, tuesday...
		dd/mm/yy[yy]	- numeric date
		dd-mmm-yy[yy]	- month as jan,feb,etc...
		n units		- n units of time ago
				  where units are:
					seconds
					minutes
					hours
					days
					weeks
					months
					years
					

	formats understood for time are:
		HH:MM		- absolute time in hours and minutes
		HH:MM:SS	- absolute time in hours, minutes and seconds

	formats understood for data and time are:
		adate atime	- absolute date followed by absolute time
		rdate atime	- relative date followed by absolute time
		atime adate	- absolute time followed by absolute date
		atime rdate	- absolute time followed by relative date
	
	"""
	if _debug_parse_time: print( '* parse_time: time_string=',time_string )

	date = DateConversions()

	have_date = 0
	have_time = 0

	table = string.maketrans("-/","  ")

	time_list = string.split( string.translate( time_string, table ) )
	
	try:
		day_time = convert_time( time_list[0] )
		time_list = time_list[1:]
		if _debug_parse_time:
			print( '* parse_time: Time_list[0] is a time' )
	except TimeSyntaxError:
		try:
			day_time = convert_time( time_list[-1] )
			time_list = time_list[:-1]
			if _debug_parse_time:
				print( '* parse_time: Time_list[-1] is a time' )
		except TimeSyntaxError:
			day_time = 0
			
	if len(time_list) == 0:
		# default to today at time
		result = date.midnight + day_time
		if _debug_parse_time: print( '* parse_time: 1 return',format_time(result) )
		return result

	match_type = date.numeric_type
	matches = []
	for word in time_list:
		day_matches = date.findMatchingDateName( word )
		if len(day_matches) == 0:
			raise DateSyntaxError( "%s unknown date word" % word )

		if date.isAmbiguous( day_matches ):
			raise DateSyntaxError( date.reportAmbiguity( word, day_matches ) )

		this_type = date.typeOfMatch( day_matches )
		if this_type != date.numeric_type:
			if match_type == date.numeric_type:
				match_type = this_type
			elif match_type != this_type:
				raise DateSyntaxError( "ambiguous mix of unit and month names" )

		matches.append( day_matches[0] )
	if _debug_parse_time: print( '* parse_time: matches=',matches )

	if match_type == date.day_type:
		if len(matches) != 1:
			raise DateSyntaxError( "too many day words" )

		day_matches = matches[0]

		result = date.convertDay( day_matches[2] ) + day_time
		if _debug_parse_time: print( '* parse_time: 2 return',format_time(result) )
		return result

	if match_type == date.unit_type:
		# expect a set of pair of <num> <unit>
		if _debug_parse_time >= 2:
			print( 'matches',matches )
		if (len(matches)&1) == 1:
			raise DateSyntaxError( 'must have an even number parameters when using time units' )

		time_offset = 0
		for index in range( 0, len(matches), 2 ):
			value_tuple = matches[index]
			unit_tuple = matches[index+1]

			if value_tuple[1] != date.numeric_type:
				raise DateSyntaxError( 'Expecting a number of units' )
			if unit_tuple[1] != date.unit_type:
				raise DateSyntaxError( 'Expecting a unit name' )

			value = value_tuple[2]
			unit = unit_tuple[2]
			time_offset = time_offset + value*unit

		result = date.now - time_offset
		if _debug_parse_time: print( '* parse_time: 3 return',format_time(result) )
		return result

	if match_type == date.month_type:
		# absolute date
		if len(matches) < 1 or len(matches) > 3:
			raise DateSyntaxError( 'too many date parts' )
		
		day = -1
		month = -1
		year = -1

		num_month_types = 0
		for entry in matches:
			if date.isMonth( entry ):
				num_month_types = num_month_types + 1

		if num_month_types != 1:
			raise DateSyntaxError( 'too many months in the date string' )


		if date.isMonth( matches[0] ):
			month = matches[0][2]
			day = matches[1][2]
			if len(matches) == 3:
				year = matches[2][2]
		else:
			day = matches[0][2]
			if matches[1][1] != date.month_type:
				raise DateSyntaxError( 'expecting month as first or second part of date' )
			month = matches[1][2]
			if len(matches) == 3:
				year = matches[2][2]

		seconds = day_time%60
		minutes = (day_time/60)%60
		hours = day_time/60/60

		result = date.absDate( day, month, year, hours, minutes, seconds )
		if _debug_parse_time: print( '* parse_time: 4 return',format_time(result) )
		return result

	if match_type == date.numeric_type and len(matches) == 3:
		# assume its in locale order - which is assumed to be D M Y
		day = matches[0][2]
		month = matches[1][2]
		year = matches[2][2]

		seconds = day_time%60
		minutes = (day_time/60)%60
		hours = day_time/60/60

		result = date.absDate( day, month, year, hours, minutes, seconds )
		if _debug_parse_time: print( '* parse_time: 4 return',format_time(result) )
		return result

	raise DateSyntaxError( 'cannot understand date and time string ' + time_string )


def convert_time( time_str ):
	time_list = string.split( time_str, ':' )
	if len(time_list) < 2:
		# not a time - no ":"
		raise TimeSyntaxError( "Not a time" )

	if len(time_list) > 3:
		raise TimeSyntaxError( "Too many time parts" )

	hour = time_list[0]
	minute = time_list[1]
	second = '0'
	if len(time_list) > 2:
		second = time_list[2]

	try:
		hour = string.atoi( hour )
		minute = string.atoi( minute )
		second = string.atoi( second )
	except:
		return -1

	if( hour < 0 or hour > 23 ):
		raise TimeSyntaxError( "hour value of %d invalid" % hour )
	if( minute < 0 or minute > 59 ):
		raise TimeSyntaxError( "minutes value of %d invalid" % hour )
	if( second < 0 or second > 59 ):
		raise TimeSyntaxError( "seconds value of %d invalid" % hour )

	day_time = (hour*60 + minute)*60 + second

	return day_time


class DateConversions:
	seconds_in_one_day = 24*60*60

	day_type = 1
	month_type = 2
	unit_type = 3
	numeric_type = 4

	date_names = [
		# day names
		('today',	day_type,	0),
		('yesterday',	day_type,	-1),
		('monday',	day_type,	1),
		('tuesday',	day_type,	2),
		('wednesday',	day_type,	3),
		('thursday',	day_type,	4),
		('friday',	day_type,	5),
		('saturday',	day_type,	6),
		('sunday',	day_type,	7),
		# month names
		('january',	month_type,	1),
		('feburary',	month_type,	2),
		('march',	month_type,	3),
		('april',	month_type,	4),
		('may',		month_type,	5),
		('june',	month_type,	6),
		('july',	month_type,	7),
		('august',	month_type,	8),
		('september',	month_type,	9),
		('october',	month_type,	10),
		('november',	month_type,	11),
		('december',	month_type,	12),
		# unit names
		('seconds',	unit_type,	1),
		('minutes',	unit_type,	60),
		('hours',	unit_type,	60*60),
		('days',	unit_type,	24*60*60.),
		('weeks',	unit_type,	7*24*60*60),
		('months',	unit_type,	30*24*60*60),
		('years',	unit_type,	365*24*60*60)
		]

	def __init__( self ):
		self.now = time.time()
		self.year, self.month, self.day, self.hour, self.minute, self.second, self.weekday, self.julian, self.dst = time.localtime( self.now )
		
		self.midnight = time.mktime( 
				(self.year, self.month, self.day,
				0, 0, 0,
				self.weekday, self.julian, self.dst) )

	def convertDay( self, day_offset ):
		if day_offset == 0:	# today
			return self.midnight
		elif day_offset == -1:	# yesterday
			return self.midnight - self.seconds_in_one_day
		else:
			# day of week
			offset = day_offset - self.weekday - 1
			# make sure its in the past
			if offset >= 0:
				offset = offset - 7

			return self.midnight + offset*self.seconds_in_one_day

	def absDate( self, day, month, year, hour=0, minute=0, second=0 ):
		future_check = 0
		if year < 0:
			year = self.year
			future_check = 1
		elif year < 70:
			year = year + 2000
		elif year < 100:
			year = year + 1900

	
		try:
			date = time.mktime( 
				(year, month, day,
				hour, minute, second,
				self.weekday, self.julian, -1) )
		except OverflowError:
			raise DateSyntaxError( 'cannot convert date and time year=%d/month=%d/day=%d %d:%d:%d' %
       					(year, month, day, hour, minute, second) )

		if date > self.now and future_check:
			year = year - 1

			try:
				date = time.mktime( 
					(year, month, day,
					hour, minute, second,
					self.weekday, self.julian, -1) )
			except OverflowError:
				raise DateSyntaxError( 'cannot convert date and time %d/%d/%d %d:%d:%d' %
					(year, month, day, hour, minute, second) )

		return date

	def findMatchingDateName( self, name ):
		try:
			value = string.atoi( name )
			return [(name, self.numeric_type, value )]
		except:
			pass

		matches = []
		name_len = len(name)
		for entry in self.date_names:
			entry_name = entry[0]
			if len(entry_name) >= name_len and entry_name[0:name_len] == name:
				matches.append( entry )

		return matches


	def typeOfMatch( self, matches ):
		return matches[0][1]

	def isAmbiguous( self, matches ):
		return len(matches) > 1

	def isDay( self, matches ):
		return matches[1] == self.day_type

	def isMonth( self, matches ):
		return matches[1] == self.month_type

	def isUnit( self, matches ):
		return matches[1] == self.unit_type

	def isNumeric( self, matches ):
		return matches[1] == self.numeric_type

	def reportAmbiguity( self, name, tuples ):
		names = map( lambda t: t[0], tuples )
		return "%s is ambiguous, it matches: %s" % (name, string.join( names, ', ' ))