"""
Converts argparse parser actions into json "Build Specs"
"""

import argparse
import os
import sys
from argparse import (
    _CountAction,
    _HelpAction,
    _StoreConstAction,
    _StoreFalseAction,
    _StoreTrueAction,
    _SubParsersAction)
from collections import OrderedDict
from functools import partial
from itertools import chain

VALID_WIDGETS = (
    'FileChooser',
    'MultiFileChooser',
    'FileSaver',
    'DirChooser',
    'DateChooser',
    'TextField',
    'Dropdown',
    'Counter',
    'RadioGroup',
    'CheckBox',
    'MultiDirChooser',
    'PasswordField',
    'Textarea'
)


class UnknownWidgetType(Exception):
    pass


class UnsupportedConfiguration(Exception):
    pass


{
    'siege': {
        'command': 'siege',
        'display_name': 'Siege',
        'contents': []
    }
}


def convert(parser):
    widget_dict = getattr(parser, 'widgets', {})
    actions = parser._actions

    if has_subparsers(actions):
        if has_required(actions):
            raise UnsupportedConfiguration(
                "Gooey doesn't currently support required arguments when subparsers are present.")
        layout_type = 'column'
        layout_data = OrderedDict(
            (choose_name(name, sub_parser), {
                'command': name.lower(),
                'contents': process(sub_parser, getattr(sub_parser, 'widgets', {}))
            }) for name, sub_parser in get_subparser(actions).choices.iteritems())

    else:
        layout_type = 'standard'
        layout_data = OrderedDict([
            ('primary', {
                'command': None,
                'contents': process(parser, widget_dict)
            })
        ])

    return {
        'layout_type': layout_type,
        'widgets': layout_data
    }


def process(parser, widget_dict):
    mutually_exclusive_groups = [
        [mutex_action for mutex_action in group_actions._group_actions]
        for group_actions in parser._mutually_exclusive_groups]

    group_options = list(chain(*mutually_exclusive_groups))

    base_actions = [action for action in parser._actions
                    if action not in group_options
                    and action.dest != 'help']

    required_actions = filter(is_required, base_actions)
    optional_actions = filter(is_optional, base_actions)

    return list(categorize(required_actions, widget_dict, required=True)) + \
           list(categorize(optional_actions, widget_dict)) + \
           list(map(build_radio_group, mutually_exclusive_groups))


def categorize(actions, widget_dict, required=False):
    _get_widget = partial(get_widget, widgets=widget_dict)
    for action in actions:
        if is_standard(action):
            yield as_json(action, _get_widget(action) or 'TextField', required)
        elif is_choice(action):
            yield as_json(action, _get_widget(action) or 'Dropdown', required)
        elif is_flag(action):
            yield as_json(action, _get_widget(action) or 'CheckBox', required)
        elif is_counter(action):
            _json = as_json(action, _get_widget(action) or 'Counter', required)
            # pre-fill the 'counter' dropdown
            _json['data']['choices'] = list(map(str, range(1, 11)))
            yield _json
        else:
            raise UnknownWidgetType(action)


def get_widget(action, widgets):
    supplied_widget = widgets.get(action.dest, None)
    type_arg_widget = 'FileChooser' if action.type == argparse.FileType else None
    return supplied_widget or type_arg_widget or None


def is_required(action):
    '''_actions which are positional or possessing the `required` flag '''
    return not action.option_strings and not isinstance(action,
                                                        _SubParsersAction) or action.required == True


def has_required(actions):
    return list(filter(None, filter(is_required, actions)))


def is_subparser(action):
    return isinstance(action, _SubParsersAction)


def has_subparsers(actions):
    return list(filter(is_subparser, actions))


def get_subparser(actions):
    return list(filter(is_subparser, actions))[0]


def is_optional(action):
    '''_actions not positional or possessing the `required` flag'''
    return action.option_strings and not action.required


def is_choice(action):
    ''' action with choices supplied '''
    return action.choices


def is_standard(action):
    """ actions which are general "store" instructions.
    e.g. anything which has an argument style like:
       $ script.py -f myfilename.txt
    """
    boolean_actions = (
        _StoreConstAction, _StoreFalseAction,
        _StoreTrueAction
    )
    return (not action.choices
            and not isinstance(action, _CountAction)
            and not isinstance(action, _HelpAction)
            and type(action) not in boolean_actions)


def is_flag(action):
    """ _actions which are either storeconst, store_bool, etc.. """
    action_types = [_StoreTrueAction, _StoreFalseAction, _StoreConstAction]
    return any(map(lambda Action: isinstance(action, Action), action_types))


def is_counter(action):
    """ _actions which are of type _CountAction """
    return isinstance(action, _CountAction)


def is_default_progname(name, subparser):
    return subparser.prog == '{} {}'.format(os.path.split(sys.argv[0])[-1], name)


def choose_name(name, subparser):
    return name if is_default_progname(name, subparser) else subparser.prog


def build_radio_group(mutex_group):
    if not mutex_group:
        return []

    options = [
        {
            'display_name': mutex_arg.metavar or mutex_arg.dest,
            'help': mutex_arg.help,
            'nargs': mutex_arg.nargs or '',
            'commands': mutex_arg.option_strings,
            'choices': mutex_arg.choices,
        } for mutex_arg in mutex_group
    ]

    return {
        'type': 'RadioGroup',
        'group_name': 'Choose Option',
        'required': False,
        'data': options
    }


def as_json(action, widget, required):
    if widget not in VALID_WIDGETS:
        raise UnknownWidgetType('Widget Type {0} is unrecognized'.format(widget))

    return {
        'type': widget,
        'required': required,
        'data': {
            'display_name': action.metavar or action.dest,
            'help': action.help,
            'nargs': action.nargs or '',
            'commands': action.option_strings,
            'choices': action.choices or [],
            'default': clean_default(widget, action.default)
        }
    }


def clean_default(widget_type, default):
    '''
    Attemps to safely coalesce the default value down to
    a valid JSON type.

    See: Issue #147.
    function references supplied as arguments to the
    `default` parameter in Argparse cause errors in Gooey.
    '''
    if widget_type != 'CheckBox':
        return default.__name__ if callable(default) else default
    # checkboxes must be handled differently, as they
    # must be forced down to a boolean value
    return default if isinstance(default, bool) else False