""" Argparse usage to HTML output

A class and an example script that uses it

Copyright 2018, Tzafrir Cohen <tzafrir@cohens.org.il>

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
"""

from __future__ import print_function
import argparse
import re

# Used by the example script and not by the class itself.
import sys
import time


class HTMLFormatter(argparse.RawTextHelpFormatter):
    """ Format argparse help as an HTML snippet.

    Need to inherit from RawTextHelpFormatter rather than HelpFormatter
    in order to keep description / epilog text split to lines (paragraps).
    """
    def _format_action(self, action):
        """ Wrap an action line in a LI tag """
        return "<li>{}</li>".format(
            super(HTMLFormatter, self)._format_action(action))

    def _format_usage(self, usage, actions, groups, prefix):
        """ Wrap usage text in a P tag """
        return "<p>{}</p>".format(
            super(HTMLFormatter, self)._format_usage(usage, actions,
                                                     groups, prefix))

    def _format_text(self, text):
        """ Format a single section. Split to paragraphs """
        text = super(HTMLFormatter, self)._format_text(text)
        text = text.strip()
        paragrapgs = re.split(r'^\s*$\n', text, flags=re.M)
        html_pars = []
        for p in paragrapgs:
            if p in ['</ul>']:
                html_pars.append(p)
            else:
                html_pars.append("<p>{}</p>".format(p))
        return "\n".join(html_pars)

    def start_section(self, heading):
        """ A title and beginning of group UL.

        FIXME: needs extra cleanup of the ':' after the <ul>.
        """
        text = "<p>{}</p>\n<ul>".format(heading)
        super(HTMLFormatter, self).start_section(text)

    def end_section(self):
        """ Close list of items. FIXME: leaves an extra </ul> """
        super(HTMLFormatter, self).end_section()
        self.add_text('</ul>')


def parse_cmd_line(args=sys.argv[1:]):
    """ Parse command-line arguments and returns configuration """
    parser = argparse.ArgumentParser(
        formatter_class=argparse.RawTextHelpFormatter)
    parser.description = """
    This script demonstrates how to automatically convert argparse
    output to HTML. See also the class HTMLFormatter.

    It's a hack. It does not produce a very clean HTML (there's an
    extra '</ul>, for instance). But it's good enough for me. An empty
    (or spaces-only) line is considered as a paragraph separator.

    I needed to produce HTML as a single line and thus this is the
    default output. This is not part of the class and can be easily
    changed in the wrapper function html_usage().

    """

    parser.epilog = """
    Note that we use RawTextHelpFormatter as the parser, rather than
    HelpFormatter itself. Otherwise splitting to paragarphs with empty
    lines won't show up in the standard --help output.

    If you have no problem with that, you can remove the formatter_class
    parameter above.
    """

    parser.add_argument("-a", "--arg-a", action="store", type=float,
                        default=1.1,
                        help="Set value of A. Default: %(default)s.")
    parser.add_argument("-b", "--param-b", action="store", type=int,
                        default=2,
                        help="Set value of B. Default: %(default)s.")
    parser.add_argument("-v", "--verbose", action="store_true",
                        help="Be verbose")
    opt_sh = parser.add_argument_group("For Interactive Use")
    opt_sh.add_argument("-d", "--no-act", action="store_true",
                        help="Do nothing. Just print what is to be run")
    opt_sh.add_argument("-c", "--config", action="store_true",
                        help="Do nothing. Just show configuration")
    opt_sh.add_argument("--html-usage", action="store_true",
                        help="Do nothing. Format help as HTML (a single line)")
    opt_sh.add_argument("--html-usage-raw", action="store_true",
                        help="If html-usage: don't squash HTML to a single line")
    cfg = parser.parse_args(args)

    if cfg.html_usage:
        html_usage(parser, cfg)
        sys.exit(0)

    # example sanity test:
    for key in ['arg_a', 'param_b']:
        val = getattr(cfg, key)
        if val >= 100 or val < 0:
            msg = "E: Invalid value for {}: must be between 0 and 10".format(key)
            parser.error(msg)

    return cfg


def html_usage(parser, cfg):
    """ Print usage text as an HTML snippet.

    If not html_usage_raw was not set in the configuation: produce a
    single line.

    Replacing the formatter class for an existing object is not
    documented anywhere, but seems to work just fine.
    """
    parser.formatter_class = HTMLFormatter
    help_text = parser.format_help()
    help_text = re.sub('<ul>:', '<ul>', help_text)
    if not cfg.html_usage_raw:
        help_text = re.sub('\n', '', help_text)
        help_text = re.sub(r'\s+', ' ', help_text)
    print(help_text)


def show_config(cfg):
    """ Report configuration. Just demo code """
    print("A: {}, B: {}".format(cfg.arg_a, cfg.param_b))


def do_work(cfg):
    """ The hard work. More demo code. """
    if cfg.no_act:
        print("Would do work for A: {}, B: {}".format(cfg.arg_a, cfg.param_b))
    else:
        if cfg.verbose:
            print("Now working hard with A: {}, B: {}".format(cfg.arg_a,
                                                              cfg.param_b))
        time.sleep(cfg.arg_a * cfg.param_b)
        if cfg.verbose:
            print("Work is done")


def main():
    """ Main function """
    cfg = parse_cmd_line()
    if cfg.config:
        show_config(cfg)
    else:
        do_work(cfg)


if __name__ == '__main__':
    main()