#!/usr/bin/python3

import argparse

parser = argparse.ArgumentParser(description='KALYPSO 2.5/2.6 Data Parser ver. 0.1')
parser.add_argument('-inv', action="store_true", help='Check for Tail filling in reverse byte order')
parser.add_argument('-o', metavar="outfile", type=argparse.FileType('wb'), nargs='?', help='File to write decoded data to. If not set, will print human readable Hex Values to stdout instead.')
parser.add_argument('infile', type=argparse.FileType('rb'), nargs=1, help='File to read from')
args = parser.parse_args()

writeToFile = True if args.o else False


def print32Hex(b, offset, blocks=4, withLineNumber=True):

   if withLineNumber:
      print('0x{0:08x}'.format(offset), end=": ")

   for i in range(blocks):
      print('0x{0:02x}'.format(b[(i*4)+0]), end ="")
      print('{0:02x}'.format(b[(i*4)+1]), end ="")
      print('{0:02x}'.format(b[(i*4)+2]), end ="")
      print('{0:02x}'.format(b[(i*4)+3]), end ="")
      print(" ", end ="")
      
   print("") #newline after block



def checkTail(b, inverse=False, words=4):
   a = [0xfe, 0xdc, 0xba, 0x98]  #Filling pattern
   
   for w in range(words):
      u = (w+1) * 4 #upper window
      l = u - 4     #lower window
      
      for i,e in enumerate(b[l:u]):
         comp = a[3-i] if inverse else a[i]
         
         if e is not comp:
            return False
   return True



def flipBytes(bytes):
   ret = []
   
   #Take every second element from bytes, starting with 0  (bytes[0::2])
   #Take every second element from bytes, starting with 1  (bytes[1::2])
   #Create a list of pairs from the previous two           (zip)
   #Append first (f) and second (s) element to 'ret'       (append)
   for f,s in zip(bytes[0::2], bytes[1::2]):
      ret.append(s)
      ret.append(f)
      
   return ret



#---------- MAIN LOOP -------------#

with args.infile[0] as ifile:
   offset = 0

   #read header
   byte_s = ifile.read(32) 
   if not byte_s:
      print("Failed to read header from file. Not enough data to read!")
      quit()
      
   #print header
   if writeToFile:
      args.o.write(bytes(byte_s))
   else: 
      print32Hex(byte_s[0:16], 0)
      print32Hex(byte_s[16:32], 16)
   
       
   #read rest of the file
   offset = 32
   keep_flipping = True
   while 1:
      byte_s = ifile.read(16) #read 4 words
      
      if not byte_s:
         #quit once no more data is available
         break 
      
      #Have we found the Tail filling?
      if checkTail(byte_s, args.inv):
         keep_flipping = False
      
      #dO ThE fLiP!
      byte_s = flipBytes(byte_s) if keep_flipping else byte_s
      
      if writeToFile:
         args.o.write(bytes(byte_s))
      else:    
         print32Hex(byte_s, offset)

      offset = offset + 16 #continue