# Source code for lxml.html._diffcommand

    import optparse
    import sys
    import re
    import os
    from .diff import htmldiff

    description = """\
    """

    parser = optparse.OptionParser(
        usage="%prog [OPTIONS] FILE1 FILE2\n"
        "%prog --annotate [OPTIONS] INFO1 FILE1 INFO2 FILE2 ...",
        description=description,
        )

    parser.add_option(
        '-o', '--output',
        metavar="FILE",
        dest="output",
        default="-",
        help="File to write the difference to",
        )

    parser.add_option(
        '-a', '--annotation',
        action="store_true",
        dest="annotation",
        help="Do an annotation")

    def main(args=None):
        if args is None:
            args = sys.argv[1:]
        options, args = parser.parse_args(args)
        if options.annotation:
            return annotate(options, args)
        if len(args) != 2:
            print('Error: you must give two files')
            parser.print_help()
            sys.exit(1)
        file1, file2 = args
        input1 = read_file(file1)
        input2 = read_file(file2)
        body1 = split_body(input1)[1]
        pre, body2, post = split_body(input2)
        result = htmldiff(body1, body2)
        result = pre + result + post
        if options.output == '-':
            if not result.endswith('\n'):
                result += '\n'
            sys.stdout.write(result)
        else:
            with open(options.output, 'wb') as f:
                f.write(result)

    def read_file(filename):
        if filename == '-':
            c = sys.stdin.read()
        elif not os.path.exists(filename):
            raise OSError(
                "Input file %s does not exist" % filename)
        else:
            with open(filename, 'rb') as f:
                c = f.read()
        return c

    body_start_re = re.compile(
        r"<body.*?>", re.I|re.S)
    body_end_re = re.compile(
        r"</body.*?>", re.I|re.S)

    def split_body(html):
        pre = post = ''
        match = body_start_re.search(html)
        if match:
            pre = html[:match.end()]
            html = html[match.end():]
        match = body_end_re.search(html)
        if match:
            post = html[match.start():]
            html = html[:match.start()]
        return pre, html, post

    def annotate(options, args):
        print("Not yet implemented")
        sys.exit(1)