#!/usr/bin/env python3
#
# Copyright (C) 2021 Anomen  <ludek_h@seznam.cz>
#
# 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.

import argparse
import os
import sys
import tempfile

__version__ = "0.1.3"

BOM = b'\xef\xbb\xbf' # ['\xEF', '\xBB', '\xBF']

def parseArguments():

    parser = argparse.ArgumentParser(description='Unicode Byto-order-mark tool..')
    parser.add_argument('-a', dest='add', action='store_true',
             help='Add BOM to file (default action).')
    parser.add_argument('-r', dest='remove', action='store_true',
             help='Remove BOM from file.')

    parser.add_argument('fileName', nargs='+', help='file')

    args = parser.parse_args()
    if (args.add and args.remove):
       raise Exception('Invalid parameter usage')

    return args;

def addBom(fileName):
    f = open(fileName, "rb")
    data = f.read()
    f.close()
    tmpName = mktmp();
    outf = open(tmpName, "wb")
    if (data[0:3] != BOM):
       outf.write(BOM)
    outf.write(data)
    outf.close()
    replace(fileName, tmpName);

def removeBom(fileName):
    f = open(fileName, "rb")
    data = f.read()
    f.close()
    tmpName = mktmp();
    outf = open(tmpName, "wb")
    if (data[0:3] == BOM):
        outf.write(data[3:])
    else:
        outf.write(data)
    outf.close()
    replace(fileName, tmpName);

def mktmp():
    tmp = tempfile.mkstemp(dir='.')
    os.close(tmp[0])
    return tmp[1]

def replace(fileName, tempFile):
    os.remove(fileName)
    os.rename(tempFile, fileName)

def main():
    args = parseArguments()

    for fn in args.fileName:
      if args.remove:
        removeBom(fn)
      else:
        addBom(fn)

if  __name__ =='__main__':main()