"""Component to allow running Python scripts."""
import datetime
import glob
import logging
import os
import time

import voluptuous as vol

from homeassistant.const import SERVICE_RELOAD
from homeassistant.exceptions import HomeAssistantError
from homeassistant.loader import bind_hass
from homeassistant.util import sanitize_filename
import homeassistant.util.dt as dt_util

DOMAIN = 'python_script'
REQUIREMENTS = ['restrictedpython==4.0a3']
FOLDER = 'python_scripts'
_LOGGER = logging.getLogger(__name__)

CONFIG_SCHEMA = vol.Schema({
    DOMAIN: vol.Schema(dict)
}, extra=vol.ALLOW_EXTRA)

ALLOWED_HASS = set(['bus', 'services', 'states'])
ALLOWED_EVENTBUS = set(['fire'])
ALLOWED_STATEMACHINE = set(['entity_ids', 'all', 'get', 'is_state',
                            'is_state_attr', 'remove', 'set'])
ALLOWED_SERVICEREGISTRY = set(['services', 'has_service', 'call'])
ALLOWED_TIME = set(['sleep', 'strftime', 'strptime', 'gmtime', 'localtime',
                    'ctime', 'time', 'mktime'])
ALLOWED_DATETIME = set(['date', 'time', 'datetime', 'timedelta', 'tzinfo'])
ALLOWED_DT_UTIL = set([
    'utcnow', 'now', 'as_utc', 'as_timestamp', 'as_local',
    'utc_from_timestamp', 'start_of_local_day', 'parse_datetime', 'parse_date',
    'get_age'])


class ScriptError(HomeAssistantError):
    """When a script error occurs."""

    pass


def setup(hass, config):
    """Initialize the python_script component."""
    path = hass.config.path(FOLDER)

    if not os.path.isdir(path):
        _LOGGER.warning('Folder %s not found in config folder', FOLDER)
        return False

    discover_scripts(hass)

    def reload_scripts_handler(call):
        """Handle reload service calls."""
        discover_scripts(hass)
    hass.services.register(DOMAIN, SERVICE_RELOAD, reload_scripts_handler)

    return True


def discover_scripts(hass):
    """Discover python scripts in folder."""
    path = hass.config.path(FOLDER)

    if not os.path.isdir(path):
        _LOGGER.warning('Folder %s not found in config folder', FOLDER)
        return False

    def python_script_service_handler(call):
        """Handle python script service calls."""
        execute_script(hass, call.service, call.data)

    existing = hass.services.services.get(DOMAIN, {}).keys()
    for existing_service in existing:
        if existing_service == SERVICE_RELOAD:
            continue
        hass.services.remove(DOMAIN, existing_service)

    for fil in glob.iglob(os.path.join(path, '*.py')):
        name = os.path.splitext(os.path.basename(fil))[0]
        hass.services.register(DOMAIN, name, python_script_service_handler)


@bind_hass
def execute_script(hass, name, data=None):
    """Execute a script."""
    filename = '{}.py'.format(name)
    with open(hass.config.path(FOLDER, sanitize_filename(filename))) as fil:
        source = fil.read()
    execute(hass, filename, source, data)


@bind_hass
def execute(hass, filename, source, data=None):
    """Execute Python source."""
    from RestrictedPython import compile_restricted_exec
    from RestrictedPython.Guards import safe_builtins, full_write_guard, \
        guarded_iter_unpack_sequence, guarded_unpack_sequence
    from RestrictedPython.Utilities import utility_builtins
    from RestrictedPython.Eval import default_guarded_getitem

    compiled = compile_restricted_exec(source, filename=filename)

    if compiled.errors:
        _LOGGER.error('Error loading script %s: %s', filename,
                      ', '.join(compiled.errors))
        return

    if compiled.warnings:
        _LOGGER.warning('Warning loading script %s: %s', filename,
                        ', '.join(compiled.warnings))

    def protected_getattr(obj, name, default=None):
        """Restricted method to get attributes."""
        # pylint: disable=too-many-boolean-expressions
        if name.startswith('async_'):
            raise ScriptError('Not allowed to access async methods')
        elif (obj is hass and name not in ALLOWED_HASS or
              obj is hass.bus and name not in ALLOWED_EVENTBUS or
              obj is hass.states and name not in ALLOWED_STATEMACHINE or
              obj is hass.services and name not in ALLOWED_SERVICEREGISTRY or
              obj is dt_util and name not in ALLOWED_DT_UTIL or
              obj is datetime and name not in ALLOWED_DATETIME or
              isinstance(obj, TimeWrapper) and name not in ALLOWED_TIME):
            raise ScriptError('Not allowed to access {}.{}'.format(
                obj.__class__.__name__, name))

        return getattr(obj, name, default)

    builtins = safe_builtins.copy()
    builtins.update(utility_builtins)
    builtins['datetime'] = datetime
    builtins['time'] = TimeWrapper()
    builtins['dt_util'] = dt_util
    restricted_globals = {
        '__builtins__': builtins,
        '_print_': StubPrinter,
        '_getattr_': protected_getattr,
        '_write_': full_write_guard,
        '_getiter_': iter,
        '_getitem_': default_guarded_getitem,
        '_iter_unpack_sequence_': guarded_iter_unpack_sequence,
        '_unpack_sequence_': guarded_unpack_sequence,
    }
    logger = logging.getLogger('{}.{}'.format(__name__, filename))
    local = {
        'hass': hass,
        'data': data or {},
        'logger': logger
    }

    try:
        _LOGGER.info('Executing %s: %s', filename, data)
        # pylint: disable=exec-used
        exec(compiled.code, restricted_globals, local)
    except ScriptError as err:
        logger.error('Error executing script: %s', err)
    except Exception as err:  # pylint: disable=broad-except
        logger.exception('Error executing script: %s', err)


class StubPrinter:
    """Class to handle printing inside scripts."""

    def __init__(self, _getattr_):
        """Initialize our printer."""
        pass

    def _call_print(self, *objects, **kwargs):
        """Print text."""
        # pylint: disable=no-self-use
        _LOGGER.warning(
            "Don't use print() inside scripts. Use logger.info() instead.")


class TimeWrapper:
    """Wrapper of the time module."""

    # Class variable, only going to warn once per Home Assistant run
    warned = False

    # pylint: disable=no-self-use
    def sleep(self, *args, **kwargs):
        """Sleep method that warns once."""
        if not TimeWrapper.warned:
            TimeWrapper.warned = True
            _LOGGER.warning('Using time.sleep can reduce the performance of '
                            'Home Assistant')

        time.sleep(*args, **kwargs)

    def __getattr__(self, attr):
        """Fetch an attribute from Time module."""
        return getattr(time, attr)
