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

import voluptuous as vol

from homeassistant.exceptions import HomeAssistantError
from homeassistant.util import sanitize_filename

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'])


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

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

    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)

    return True


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)


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

    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):
            raise ScriptError('Not allowed to access {}.{}'.format(
                obj.__class__.__name__, name))

        return getattr(obj, name, default)

    restricted_globals = {
        '__builtins__': safe_builtins,
        '_print_': StubPrinter,
        '_getattr_': protected_getattr,
        '_write_': full_write_guard,
        '_getiter_': iter,
    }
    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.")