platypush/platypush/event/hook.py

import copy
import json
import logging
import threading
from functools import wraps

from platypush.config import Config
from platypush.message.event import Event
from platypush.message.request import Request
from platypush.procedure import Procedure
from platypush.utils import get_event_class_by_type, set_thread_name, is_functional_hook

logger = logging.getLogger(__name__)


def parse(msg):
    """ Builds a dict given another dictionary or
        a JSON UTF-8 encoded string/bytearray """

    if isinstance(msg, bytes) or isinstance(msg, bytearray):
        msg = msg.decode('utf-8')
    if isinstance(msg, str):
        try:
            msg = json.loads(msg.strip())
        except json.JSONDecodeError:
            logger.warning('Invalid JSON message: {}'.format(msg))
            return None

    return msg


class EventCondition(object):
    """ Event hook condition class """

    def __init__(self, type=Event.__class__, priority=None, **kwargs):
        """
        Rule constructor.
        Params:
            type   -- Class of the event to be built
            kwargs -- Fields rules as a key-value (e.g. source_button=btn_id
                or recognized_phrase='Your phrase')
        """

        self.type = type
        self.args = {}
        self.parsed_args = {}
        self.priority = priority

        for (key, value) in kwargs.items():
            # TODO So far we only allow simple value match. If value is a dict
            # instead, we should allow more a sophisticated attribute matching,
            # e.g. or conditions, in, and other operators.
            self.args[key] = value

    @classmethod
    def build(cls, rule):
        """ Builds a rule given either another EventRule, a dictionary or
            a JSON UTF-8 encoded string/bytearray """

        if isinstance(rule, cls):
            return rule
        else:
            rule = parse(rule)

        assert isinstance(rule, dict)
        type = get_event_class_by_type(
            rule.pop('type') if 'type' in rule else 'Event')

        args = {}
        for (key, value) in rule.items():
            args[key] = value

        return cls(type=type, **args)


class EventAction(Request):
    """ Event hook action class. It is a special type of runnable request
        whose fields can be configured later depending on the event context """

    def __init__(self, target=None, action=None, **args):
        if target is None:
            target = Config.get('device_id')
        args_copy = copy.deepcopy(args)
        super().__init__(target=target, action=action, **args_copy)

    @classmethod
    def build(cls, action):
        action = super().parse(action)
        action['origin'] = Config.get('device_id')

        if 'target' not in action:
            action['target'] = action['origin']

        token = Config.get('token')
        if token:
            action['token'] = token

        return super().build(action)


class EventHook(object):
    """ Event hook class. It consists of one conditions and
        one or multiple actions to be executed """

    def __init__(self, name, priority=None, condition=None, actions=None):
        """ Constructor. Takes a name, a EventCondition object and an event action
            procedure as input. It may also have a priority attached
            as a positive number. If multiple hooks match against an event,
            only the ones that have either the maximum match score or the
            maximum pre-configured priority will be run. """

        self.name = name
        self.condition = EventCondition.build(condition or {})
        self.actions = actions or []
        self.priority = priority or 0
        self.condition.priority = self.priority

    @classmethod
    def build(cls, name, hook):
        """ Builds a rule given either another EventRule, a dictionary or
            a JSON UTF-8 encoded string/bytearray """

        if isinstance(hook, cls):
            return hook
        else:
            hook = parse(hook)

        if is_functional_hook(hook):
            actions = Procedure(name=name, requests=[hook], _async=False)
            return cls(name=name, condition=hook.condition, actions=actions)

        assert isinstance(hook, dict)
        condition = EventCondition.build(hook['if']) if 'if' in hook else None
        actions = []
        priority = hook['priority'] if 'priority' in hook else None
        condition.priority = priority

        if 'then' in hook:
            if isinstance(hook['then'], list):
                actions = hook['then']
            else:
                actions = [hook['then']]

        actions = Procedure.build(name=name + '__Hook', requests=actions, _async=False)
        return cls(name=name, condition=condition, actions=actions, priority=priority)

    def matches_event(self, event):
        """ Returns an EventMatchResult object containing the information
            about the match between the event and this hook """

        return event.matches_condition(self.condition)

    def run(self, event):
        """ Checks the condition of the hook against a particular event and
            runs the hook actions if the condition is met """

        def _thread_func(result):
            set_thread_name('Event-' + self.name)
            self.actions.execute(event=event, **result.parsed_args)

        result = self.matches_event(event)

        if result.is_match:
            logger.info('Running hook {} triggered by an event'.format(self.name))
            threading.Thread(target=_thread_func, name='Event-' + self.name, args=(result,)).start()


def hook(event_type=Event, **condition):
    def wrapper(f):
        f.hook = True
        f.condition = EventCondition(type=event_type, **condition)

        @wraps(f)
        def wrapped(*args, **kwargs):
            from platypush import Response

            try:
                ret = f(*args, **kwargs)
                if isinstance(ret, Response):
                    return ret

                return Response(output=ret)
            except Exception as e:
                logger.exception(e)
                return Response(errors=[str(e)])

        return wrapped

    return wrapper


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