# Copyright 2017, David Wilson
#
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# modification, are permitted provided that the following conditions are met:
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# this list of conditions and the following disclaimer.
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from __future__ import absolute_import
import threading
import os

import mitogen
import mitogen.core
import mitogen.master
import mitogen.service
import mitogen.unix
import mitogen.utils

import ansible_mitogen.logging
import ansible_mitogen.services


class State(object):
    """
    Process-global state that should persist across playbook runs.
    """
    #: ProcessState singleton.
    _instance = None

    @classmethod
    def instance(cls):
        """
        Fetch the ProcessState singleton, constructing it as necessary.
        """
        if cls._instance is None:
            cls._instance = cls()
        return cls._instance

    def __init__(self):
        ansible_mitogen.logging.setup()
        self._setup_master()
        self._setup_services()

    def _setup_master(self):
        """
        Construct a Router, Broker, and mitogen.unix listener
        """
        self.router = mitogen.master.Router()
        self.router.responder.whitelist_prefix('ansible')
        self.router.responder.whitelist_prefix('ansible_mitogen')
        mitogen.core.listen(self.router.broker, 'shutdown', self.on_broker_shutdown)
        self.listener = mitogen.unix.Listener(self.router)
        os.environ['MITOGEN_LISTENER_PATH'] = self.listener.path
        if 'MITOGEN_ROUTER_DEBUG' in os.environ:
            self.router.enable_debug()

    def _setup_services(self):
        """
        Construct a ContextService and a thread to service requests for it
        arriving from worker processes.
        """
        self.service = ansible_mitogen.services.ContextService(self.router)
        self.service_thread = threading.Thread(target=self.service.run)
        self.service_thread.start()

    def on_broker_shutdown(self):
        """
        Respond to the Router shutdown (indirectly triggered through exit of
        the main thread) by unlinking the listening socket. Ideally this would
        happen explicitly, but Ansible provides no hook to allow it.
        """
        os.unlink(self.listener.path)
        self.service_thread.join(timeout=10)