import time, os, argparse
import hexView as view

def readb(fn):
    file = open(fn, 'rb')
    b = file.read()
    file.close()
    return b
        
def writeb(fn, b):
    file = open(fn, 'wb')
    file.write(b)
    file.close()

def xorb(a, b):
    alen = len(a)
    blen = len(b)
    a = int.from_bytes(a, byteorder='big')
    b = int.from_bytes(b, byteorder='big')
    r = a ^ b
    if alen > blen:
        return r.to_bytes(alen, byteorder='big')
    else:
        return r.to_bytes(blen, byteorder='big')

CHUNK_SIZE = 16

parser = argparse.ArgumentParser(description='Xor file encryption')
parser.add_argument('command', type=str, choices=['x', 'i', 'g', 's'], help='x: Encrypt/Decrypt file (xor), i: File info, g: Generate key, s: Show file')
parser.add_argument('f1', default='', nargs='?', type=str, help='x+i+s: data file, g: output file')
parser.add_argument('f2', default='', nargs='?', type=str, help='x: key file, g: key length')
parser.add_argument('f3', default='', nargs='?', type=str, help='x: output file')
args = parser.parse_args()

if args.command == 'x':
    if os.path.getsize(args.f2) < os.path.getsize(args.f1):
        print('Key file is of insufficent size at', os.path.getsize(keyfn), 'bytes')
    else:
        start = time.time()

        dat = open(args.f1, 'rb')
        key = open(args.f2, 'rb')
        out = open(args.f3, 'wb')
        
        while True:
            datbytes = dat.read(CHUNK_SIZE)
            keybytes = key.read(CHUNK_SIZE)
            if len(datbytes) == 0:
                break
            out.write(xorb(datbytes, keybytes))

        dat.close()
        key.close()
        out.close()
        
        duration = round(time.time()-start, 4)
        print(f'File xor ({duration} sec)')
        
if args.command == 'i':
    print('File length is', os.path.getsize(args.f1), 'bytes')
    
if args.command == 'g':
    start = time.time()

    writeb(args.f1, os.urandom(int(args.f2)))
    
    duration = round(time.time()-start, 4)
    print(f'Key generated ({duration} sec)')
if args.command == 's':
    for line in view.hex_viewer(readb(args.f1)):
        print(line)