import os

# noinspection PyCompatibility
from . import exceptions
from ._utils import AttributeDict


def load_dash_env_vars():
    return AttributeDict(
        {
            var: os.getenv(var, os.getenv(var.lower()))
            for var in (
                'DASH_APP_NAME',
                'DASH_URL_BASE_PATHNAME',
                'DASH_ROUTES_PATHNAME_PREFIX',
                'DASH_REQUESTS_PATHNAME_PREFIX',
                'DASH_SUPPRESS_CALLBACK_EXCEPTIONS',
                'DASH_ASSETS_EXTERNAL_PATH',
                'DASH_INCLUDE_ASSETS_FILES',
                'DASH_COMPONENTS_CACHE_MAX_AGE',
                'DASH_INCLUDE_ASSETS_FILES',
                'DASH_SERVE_DEV_BUNDLES',
                'DASH_DEBUG',
                'DASH_UI',
                'DASH_PROPS_CHECK',
                'DASH_HOT_RELOAD',
                'DASH_HOT_RELOAD_INTERVAL',
                'DASH_HOT_RELOAD_WATCH_INTERVAL',
                'DASH_HOT_RELOAD_MAX_RETRY',
                'DASH_SILENCE_ROUTES_LOGGING',
                'DASH_PRUNE_ERRORS',
            )
        }
    )


DASH_ENV_VARS = load_dash_env_vars()


def get_combined_config(name, val, default=None):
    """Consolidate the config with priority from high to low provided init
    value > OS environ > default."""

    if val is not None:
        return val

    env = load_dash_env_vars().get('DASH_{}'.format(name.upper()))
    if env is None:
        return default

    return env.lower() == 'true' if env.lower() in {'true', 'false'} \
        else env


def pathname_configs(
        url_base_pathname=None,
        routes_pathname_prefix=None,
        requests_pathname_prefix=None):
    _pathname_config_error_message = '''
    {} This is ambiguous.
    To fix this, set `routes_pathname_prefix` instead of `url_base_pathname`.

    Note that `requests_pathname_prefix` is the prefix for the AJAX calls that
    originate from the client (the web browser) and `routes_pathname_prefix` is
    the prefix for the API routes on the backend (this flask server).
    `url_base_pathname` will set `requests_pathname_prefix` and
    `routes_pathname_prefix` to the same value.
    If you need these to be different values then you should set
    `requests_pathname_prefix` and `routes_pathname_prefix`,
    not `url_base_pathname`.
    '''
    url_base_pathname = get_combined_config(
        'url_base_pathname', url_base_pathname)

    routes_pathname_prefix = get_combined_config(
        'routes_pathname_prefix', routes_pathname_prefix)

    requests_pathname_prefix = get_combined_config(
        'requests_pathname_prefix', requests_pathname_prefix)

    if url_base_pathname is not None and requests_pathname_prefix is not None:
        raise exceptions.InvalidConfig(
            _pathname_config_error_message.format(
                'You supplied `url_base_pathname` and '
                '`requests_pathname_prefix`.'
            )
        )

    if url_base_pathname is not None and routes_pathname_prefix is not None:
        raise exceptions.InvalidConfig(
            _pathname_config_error_message.format(
                'You supplied `url_base_pathname` and '
                '`routes_pathname_prefix`.')
        )

    if url_base_pathname is not None and routes_pathname_prefix is None:
        routes_pathname_prefix = url_base_pathname
    elif routes_pathname_prefix is None:
        routes_pathname_prefix = '/'

    if not routes_pathname_prefix.startswith('/'):
        raise exceptions.InvalidConfig(
            '`routes_pathname_prefix` needs to start with `/`')
    if not routes_pathname_prefix.endswith('/'):
        raise exceptions.InvalidConfig(
            '`routes_pathname_prefix` needs to end with `/`')

    app_name = load_dash_env_vars().DASH_APP_NAME

    if not requests_pathname_prefix and app_name:
        requests_pathname_prefix = '/' + app_name + routes_pathname_prefix
    elif requests_pathname_prefix is None:
        requests_pathname_prefix = routes_pathname_prefix

    if not requests_pathname_prefix.startswith('/'):
        raise exceptions.InvalidConfig(
            '`requests_pathname_prefix` needs to start with `/`')
    if not requests_pathname_prefix.endswith(routes_pathname_prefix):
        raise exceptions.InvalidConfig(
            '`requests_pathname_prefix` needs to ends with '
            '`routes_pathname_prefix`.'
        )

    return url_base_pathname, routes_pathname_prefix, requests_pathname_prefix
