import json
import logging
import random
import traceback

from threading import Thread

from platypush.context import get_plugin
from platypush.message import Message
from platypush.message.response import Response
from platypush.utils import get_module_and_method_from_action

class Request(Message):
    """ Request message class """

    def __init__(self, target, action, origin=None, id=None, backend=None, args=None):
        """
        Params:
            target -- Target node [String]
            action -- Action to be executed (e.g. music.mpd.play) [String]
            origin -- Origin node [String]
                id -- Message ID, or None to get it auto-generated
           backend -- Backend connected to the request, where the response will be delivered
              args -- Additional arguments for the action [Dict]
        """

        self.id      = id if id else self._generate_id()
        self.target  = target
        self.action  = action
        self.origin  = origin
        self.args    = args if args else {}
        self.backend = backend

    @classmethod
    def build(cls, msg):
        msg = super().parse(msg)
        args = {
            'target' : msg['target'],
            'action' : msg['action'],
            'args'   : msg['args'] if 'args' in msg else {},
        }

        args['id'] = msg['id'] if 'id' in msg else cls._generate_id()
        if 'origin' in msg: args['origin'] = msg['origin']
        return cls(**args)

    @staticmethod
    def _generate_id():
        id = ''
        for i in range(0,16):
            id += '%.2x' % random.randint(0, 255)
        return id


    def _execute_procedure(self, *args, **kwargs):
        from config import Config

        logging.info('Executing procedure request: {}'.format(procedure))
        proc_name = self.action.split('.')[-1]
        proc_config = Config.get_procedures()[proc_name]
        proc = Procedure.build(name=proc_name, requests=proc_config, backend=self.backend, id=self.id)
        proc.execute(*args, **kwargs)


    def execute(self, n_tries=1, async=True):
        """
        Execute this request and returns a Response object
        Params:
            n_tries -- Number of tries in case of failure before raising a RuntimeError
            async   -- If True, the request will be run asynchronously and the
                       response posted on the bus when available (default),
                       otherwise the current thread will wait for the response
                       to be returned synchronously.
        """

        def _thread_func(n_tries):
            if self.action.startswith('procedure.'):
                return self._execute_procedure(n_tries=n_tries)

            (module_name, method_name) = get_module_and_method_from_action(self.action)
            plugin = get_plugin(module_name)

            try:
                # Run the action
                response = plugin.run(method=method_name, **self.args)
                if response and response.is_error():
                    raise RuntimeError('Response processed with errors: {}'.format(response))

                logging.info('Processed response from plugin {}: {}'.
                                format(plugin, response))
            except Exception as e:
                # Retry mechanism
                response = Response(output=None, errors=[str(e), traceback.format_exc()])
                logging.exception(e)
                if n_tries:
                    logging.info('Reloading plugin {} and retrying'.format(module_name))
                    get_plugin(module_name, reload=True)
                    _thread_func(n_tries-1)
                    return
            finally:
                if async:
                    # Send the response on the backend
                    if self.backend and self.origin:
                        self.backend.send_response(response=response, request=self)
                    else:
                        logging.info('Response whose request has no ' +
                                    'origin attached: {}'.format(response))
                else:
                    return response

        if async:
            Thread(target=_thread_func, args=(n_tries,)).start()
        else:
            return _thread_func(n_tries)


    def __str__(self):
        """
        Overrides the str() operator and converts
        the message into a UTF-8 JSON string
        """

        return json.dumps({
            'type'   : 'request',
            'target' : self.target,
            'action' : self.action,
            'args'   : self.args,
            'origin' : self.origin if hasattr(self, 'origin') else None,
            'id'     : self.id if hasattr(self, 'id') else None,
        })


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