import os
import os.path
import shutil   #for copying file
import zlib     #for adler32 function
import hashlib  #for md5 hash
import adler32  #for adler32 checksum

#function to split a file into chunks of size 100KB
def splittochunk(place, line):
	fil = "~/Task2/"+place+"/"+line
	if (place==="source"):
		outfil = "schunk"
	else:
		outfil = "dchunk"

	f = open(fil,'r')
	chunksize = 102400

	for i in range(1,os.stat(fil).st_size/chunksize+1):
		o = open(outfil+str(i),'w')
	 	segment = f.readlines(chunksize)
	        for c in range(0,len(segment)):
		        o.write(segment[c])
    		o.close()

#function to generate md5hash
def md5hash(place, no):
	if (place=="source"):
		fil = "schunk"+str(no)
	else:
		fil = "dchunk"+str(no)

	h = hashlib.md5()
	h.update(fil.read())
	return h.hexdigest()

#function to generate adler32 checksum
def adler32(place, no):
	if (place=="source"):
		fil = "schunk"+str(no)
	else:
		fil = "dchunk"+str(no)

	adl=adler32.new()		# create new adler32 object
   	adl.update(fil.read())	        # update adler32 object with contents of file
	adl.rotate(byteout,bytein)	# rotate byteout out and bytein into adler32
	return adl.hexdigest()

path = "~/Task2/source/"
dirs = os.listdir( path ) #gives list of files in given path


for line in dirs:
	file_path="~/Task2/destination/"+line
	if not os.path.exists(file_path) :
		copyfile("~/Task2/source/"+line,"~/Task2/destination/")   # if such a file does nont exists in dest, copy it.
	else:
		splittochunk("source",line)             #split source file into chunks
		splittochunk("destination",line)        #split destination file into chunks
		for j in range(1,os.stat(fil).st_size/chunksize+1):
			if (adler32("source", j)!=adler32("destination", j)): #compare rolling checksum of chunks
				#replace that j chunk
				f = open("schunk"+str(j), "r")
				g = open("dchunk"+str(j), "w")
				g.write(f.read())
				f.close()
				g.close()
		h = open("~/Task2/destination/"+line, "w")
		for j in range(1,os.stat(fil).st_size/chunksize+1):      #to merge altered dchunks
				tempfile="dchunk"+str(j)
   				h.write(tempfile.read())
				os.remove("dchunk"+str(j), *, dir_fd=None)
				os.remove("schunk"+str(j), *, dir_fd=None)


path = "~/Task2/source/"
dirs = os.listdir( path ) #gives list of files in given path
for line in dirs:
	file_path="~/Task2/destination/"+line
	if os.path.exists(file_path) :
		splittochunk("source",line)             #split source file into chunks
		splittochunk("destination",line)        #split destination file into chunks
		for j in range(1,os.stat(fil).st_size/chunksize+1):
			if (md5hash("source", j)!=md5hash("destination", j)): #compare md5hashes of chunks
				print "Sync Failed"
			else:
				print "Sync Success"
	else:
		print "Sync Failed"