# Copyright (c) 2012 Web Notes Technologies Pvt Ltd (http://erpnext.com)
# 
# MIT License (MIT)
# 
# Permission is hereby granted, free of charge, to any person obtaining a 
# copy of this software and associated documentation files (the "Software"), 
# to deal in the Software without restriction, including without limitation 
# the rights to use, copy, modify, merge, publish, distribute, sublicense, 
# and/or sell copies of the Software, and to permit persons to whom the 
# Software is furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in 
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
# INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A 
# PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF 
# CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE 
# OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
# 

"""
XTEA Block Encryption Algorithm
Author: Paul Chakravarti (paul_dot_chakravarti_at_gmail_dot_com)
License: Public Domain
""" 

def get_key():
	# Encryption key is datetime of creation of DocType, DocType"
	import webnotes
	return webnotes.conn.sql("select creation from tabDocType where name='DocType'")[0][0].strftime('%Y%m%d%H%M%s')[:16]

def encrypt(data, encryption_key = None):
	if not encryption_key:
		encryption_key = get_key()
	return crypt(encryption_key, data).encode('hex')

def decrypt(data, encryption_key = None):
	if not encryption_key:
		encryption_key = get_key()
	return crypt(encryption_key, data.decode('hex'))

def crypt(key,data,iv='\00\00\00\00\00\00\00\00',n=32):
	def keygen(key,iv,n):
		while True:
			iv = xtea_encrypt(key,iv,n)
			for k in iv:
				yield ord(k)
	xor = [ chr(x^y) for (x,y) in zip(map(ord,data),keygen(key,iv,n)) ]
	return "".join(xor)

def xtea_encrypt(key,block,n=32,endian="!"):
	import struct
	v0,v1 = struct.unpack(endian+"2L",block)
	k = struct.unpack(endian+"4L",key)
	sum,delta,mask = 0L,0x9e3779b9L,0xffffffffL
	for round in range(n):
		v0 = (v0 + (((v1<<4 ^ v1>>5) + v1) ^ (sum + k[sum & 3]))) & mask
		sum = (sum + delta) & mask
		v1 = (v1 + (((v0<<4 ^ v0>>5) + v0) ^ (sum + k[sum>>11 & 3]))) & mask
	return struct.pack(endian+"2L",v0,v1)
	
def xtea_decrypt(key,block,n=32,endian="!"):
	import struct

	v0,v1 = struct.unpack(endian+"2L",block)
	k = struct.unpack(endian+"4L",key)
	delta,mask = 0x9e3779b9L,0xffffffffL
	sum = (delta * n) & mask
	for round in range(n):
		v1 = (v1 - (((v0<<4 ^ v0>>5) + v0) ^ (sum + k[sum>>11 & 3]))) & mask
		sum = (sum - delta) & mask
		v0 = (v0 - (((v1<<4 ^ v1>>5) + v1) ^ (sum + k[sum & 3]))) & mask
	return struct.pack(endian+"2L",v0,v1)