from copy import copy
from imp import load_source
import os
import sys
from six import text_type
from . import logs, types


class _DefaultRulesNames(types.RulesNamesList):
    def __add__(self, items):
        return _DefaultRulesNames(list(self) + items)

    def __contains__(self, item):
        return item.enabled_by_default or \
               super(_DefaultRulesNames, self).__contains__(item)

    def __eq__(self, other):
        if isinstance(other, _DefaultRulesNames):
            return super(_DefaultRulesNames, self).__eq__(other)
        else:
            return False


DEFAULT_RULES = _DefaultRulesNames([])
DEFAULT_PRIORITY = 1000


DEFAULT_SETTINGS = {'rules': DEFAULT_RULES,
                    'wait_command': 3,
                    'require_confirmation': False,
                    'no_colors': False,
                    'priority': {}}

ENV_TO_ATTR = {'THEFUCK_RULES': 'rules',
               'THEFUCK_WAIT_COMMAND': 'wait_command',
               'THEFUCK_REQUIRE_CONFIRMATION': 'require_confirmation',
               'THEFUCK_NO_COLORS': 'no_colors',
               'THEFUCK_PRIORITY': 'priority'}


SETTINGS_HEADER = u"""# ~/.thefuck/settings.py: The Fuck settings file
#
# The rules are defined as in the example bellow:
#
# rules = ['cd_parent', 'git_push', 'python_command', 'sudo']
#
# The default values are as follows. Uncomment and change to fit your needs.
# See https://github.com/nvbn/thefuck#settings for more information.
#

"""


def _settings_from_file(user_dir):
    """Loads settings from file."""
    settings = load_source('settings',
                           text_type(user_dir.joinpath('settings.py')))
    return {key: getattr(settings, key)
            for key in DEFAULT_SETTINGS.keys()
            if hasattr(settings, key)}


def _rules_from_env(val):
    """Transforms rules list from env-string to python."""
    val = val.split(':')
    if 'DEFAULT_RULES' in val:
        val = DEFAULT_RULES + [rule for rule in val if rule != 'DEFAULT_RULES']
    return val


def _priority_from_env(val):
    """Gets priority pairs from env."""
    for part in val.split(':'):
        try:
            rule, priority = part.split('=')
            yield rule, int(priority)
        except ValueError:
            continue


def _val_from_env(env, attr):
    """Transforms env-strings to python."""
    val = os.environ[env]
    if attr == 'rules':
        return _rules_from_env(val)
    elif attr == 'priority':
        return dict(_priority_from_env(val))
    elif attr == 'wait_command':
        return int(val)
    elif attr in ('require_confirmation', 'no_colors'):
        return val.lower() == 'true'
    else:
        return val


def _settings_from_env():
    """Loads settings from env."""
    return {attr: _val_from_env(env, attr)
            for env, attr in ENV_TO_ATTR.items()
            if env in os.environ}


def get_settings(user_dir):
    """Returns settings filled with values from `settings.py` and env."""
    conf = copy(DEFAULT_SETTINGS)
    try:
        conf.update(_settings_from_file(user_dir))
    except Exception:
        logs.exception("Can't load settings from file",
                       sys.exc_info(),
                       types.Settings(conf))

    try:
        conf.update(_settings_from_env())
    except Exception:
        logs.exception("Can't load settings from env",
                       sys.exc_info(),
                       types.Settings(conf))

    if not isinstance(conf['rules'], types.RulesNamesList):
        conf['rules'] = types.RulesNamesList(conf['rules'])

    return types.Settings(conf)


def initialize_settings_file(user_dir):
    settings_path = user_dir.joinpath('settings.py')
    if not settings_path.is_file():
        with settings_path.open(mode='w') as settings_file:
            settings_file.write(SETTINGS_HEADER)
            for setting in DEFAULT_SETTINGS.items():
                settings_file.write(u'# {} = {}\n'.format(*setting))
