#!/usr/bin/env python

from __future__ import print_function

import sys


def writeheader(filename, header):
    """
    write a header to filename,
    skip files where first line after optional shebang matches the skip regex
    filename should be the name of the file to write to
    header should be a list of strings
    skip should be a regex
    """
    f = open(filename,"r")
    inpt =f.readlines()
    f.close()
    output = []

    # comment out the next 3 lines if you don't wish to preserve shebangs
    if len(inpt) > 0 and inpt[0].startswith("#!"):
        output.append(inpt[0])
        inpt = inpt[1:]

    if inpt[0].strip().startswith("/*"):
        for i, line in enumerate(inpt):
            if line.strip().endswith("*/"):
                inpt = inpt[i + 1:]
                break

    while not inpt[0].strip():
        inpt = inpt[1:]

    output.extend(header)  # add the header
    for line in inpt:
        output.append(line)
    try:
        f = open(filename,'w')
        f.writelines(output)
        f.close()
        print("added header to %s" % filename)
    except IOError as err:
        print("something went wrong trying to add header to %s: %s" % (filename, err))


def main(args=sys.argv):
    headerfile = open(args[1])
    header = headerfile.readlines()
    headerfile.close()
    writeheader(args[2], header)


if __name__ == '__main__':
    # call the main method
    main()