def main(doc, timeout, size, debug, allow_codes, whitelist):
    """
    Examples:
    simple call
    $ vl README.md

    Adding debug outputs

    $ vl README.md --debug

    Adding a custom timeout for each url. time on seconds.

    $ vl README.md -t 3

    Adding a custom size param, to add throttle n requests per time

    $ vl README -s 1000

    Skipping some error codes. This will allow 500 and 404 responses to
    be ignored

    $ vl README.md -a 500,404

    Adding Whitelists

    $ vl README.md -w server1.com,server2.com
    """
    t0 = time.time()
    links = [i[0] for i in LINK_RE.findall(doc.read())]
    request_urls = []
    counts = {}

    for link in links:
        # no static
        if is_static(link):
            STATICS.append(link)
            continue

        # no dupes
        if link in counts:
            counts[link] += 1
            continue
        else:
            counts[link] = 1

        parsed = urlparse(link)
        # fix no scheme links
        if not parsed.scheme:
            link = 'http://{0}'.format(link)

        # whitelisted
        if whitelist:
            exists = [i for i in whitelist if i in parsed.netloc]
            if exists:
                WHITELISTED.append(link)
                continue

        request_urls.append(link)

    # removing dupes
    counts_keys = counts.keys()
    DUPES.extend([(i, counts[i]) for i in counts_keys if counts[i] > 1])

    requests = (grequests.head(u, timeout=timeout, verify=False) for u in request_urls)
    responses = grequests.imap(requests, exception_handler=handle_exception,
                               size=size)

    for res in responses:
        color = 'green'
        if is_error_code(res.status_code):
            if res.status_code not in allow_codes:
                ERRORS.append((res.status_code, res.url))
                color = 'red'
            else:
                WHITELISTED.append(res.url)

        status = click.style(str(res.status_code), fg=color)
        click.echo('[{}] {}'.format(status, res.url))

    errors_len = len(ERRORS)
    exceptions_len = len(EXCEPTIONS)
    dupes_len = len(DUPES)
    white_len = len(WHITELISTED)

    if errors_len:
        click.echo()
        click.echo('Failed URLs:')
        for code, url in ERRORS:
            code = click.style(str(code), fg='red')
            click.echo('[{0}] {1}'.format(code, url))

    if exceptions_len and debug:
        import ssl
        click.echo('Exceptions raised:')
        click.echo('Note: OpenSSL Version = {0}'.format(ssl.OPENSSL_VERSION))
        click.secho('Check URLs for possible false positives', fg='yellow')
        for url, exception in EXCEPTIONS:
            click.echo('- {0}'.format(url))
            click.secho('{0}'.format(exception), fg='red', bold=True)

    if dupes_len and debug:  # pragma: nocover
        click.echo('Dupes:')
        for url, count in DUPES:
            click.secho('- {0} - {1} times'.format(url, count), fg='yellow',
                        bold=True)

    if white_len and debug:
        click.echo()
        click.echo('Whitelisted (allowed codes and whitelisted param)')
        for url in WHITELISTED:
            click.secho('- {0}'.format(url), fg='magenta')

    click.secho('Total Links Parsed {0}'.format(len(links)), fg='green')
    click.secho('Total Errors {0}'.format(errors_len), fg='red')
    click.secho('Total Exceptions {0}'.format(exceptions_len), fg='red')
    click.secho('Total Dupes {0}'.format(dupes_len), fg='yellow')
    click.secho('Total whitelisted {0}'.format(white_len), fg='yellow')
    click.secho('Total static {0}'.format(len(STATICS)), fg='yellow')

    if debug:
        click.echo('Execution time: {0:.2f} seconds'.format(time.time() - t0))

    if errors_len:
        sys.exit(1)
Examples:
    simple call
    $ vl README.md

    Adding debug outputs

    $ vl README.md --debug

    Adding a custom timeout for each url. time on seconds.

    $ vl README.md -t 3

    Adding a custom size param, to add throttle n requests per time

    $ vl README -s 1000

    Skipping some error codes. This will allow 500 and 404 responses to
    be ignored

    $ vl README.md -a 500,404

    Adding Whitelists

    $ vl README.md -w server1.com,server2.com