#   Copyright (C) 2008 by Albert Cervera i Areny
#   albert@nan-tic.com
#
#   This program is free software; you can redistribute it and/or modify 
#   it under the terms of the GNU General Public License as published by
#   the Free Software Foundation; either version 2 of the License, or 
#   (at your option) any later version. 
#
#   This program is distributed in the hope that it will be useful, 
#   but WITHOUT ANY WARRANTY; without even the implied warranty of 
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
#   GNU General Public License for more details.
#
#   You should have received a copy of the GNU General Public License 
#   along with this program; if not, write to the
#   Free Software Foundation, Inc.,
#   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. 


# Note that the file is called LevenshteinDistance.py so it doesn't collide
# with Levenshtein module (when installed).

# Try to use Levenshtein module (implemented in C). If not found fall back to
# our own 300 times slower python implementation.
try:
	import Levenshtein as cLevenshtein
	class Levenshtein:

		@staticmethod
		def levenshtein( text1, text2 ):
			return cLevenshtein.distance( text1, text2 )
except:
	print "Warning: Levenshtein module not found. Using 300 times slower python implementation."

	class Levenshtein:
		@staticmethod
		def levenshtein( text1, text2 ):
			# Levenshtein distance if one string is empty, is the
			# length of the other string, len(text) inserts.
			if len(text1) == 0:
				return len(text2)
			if len(text2) == 0:
				return len(text1)

			# Build array of len(text1) * len(text2)
			len1 = len(text1) + 1
			len2 = len(text2) + 1

			d = []
			for x in range(len1):
				d.append( [0] * len2 )

			for i in range(len1):
				d[i][0] = i

			for j in range(len2):
				d[0][j] = j

			for i in range(1,len1): 
				for j in range(1,len2):
					ip = i-1
					jp = j-1
					if text1[ip] == text2[jp]:
						cost = 0
					else:
						cost = 1

					d[i][j] = min( 
						d[i-1][j] + 1,      # deletion
						d[i][j-1] + 1,      # insertion
						d[i-1][j-1] + cost  # substitution
					)
			return d[len(text1)-1][len(text2)-1]

if __name__ == '__main__':
	print Levenshtein.levenshtein( 'abc', 'abc' )
	print Levenshtein.levenshtein( 'abcabc', 'abc' )
	print Levenshtein.levenshtein( 'abcdef', 'abc' )
	print Levenshtein.levenshtein( 'abcdef', 'bcd' )
	print Levenshtein.levenshtein( 'bcdef', 'abc' )
	for x in range(10000):
		Levenshtein.levenshtein( 'text de la plantilla', 'text llarg que pot ser del document que tractem actualment' )