# -*- coding: utf-8 -*-
#
# Copyright (C) 2013 GNS3 Technologies Inc.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""
Base class (interface) for modules
"""

import sys
import traceback
import gns3server.jsonrpc as jsonrpc
import multiprocessing
import zmq
import signal

from jsonschema import validate, ValidationError

import logging
log = logging.getLogger(__name__)


class IModule(multiprocessing.Process):
    """
    Module interface.

    :param name: module name
    :param args: arguments for the module
    :param kwargs: named arguments for the module
    """

    modules = {}

    def __init__(self, name, *args, **kwargs):

        multiprocessing.Process.__init__(self, name=name)
        self._context = None
        self._ioloop = None
        self._stream = None
        self._dealer = None
        self._zmq_host = args[0]  # ZeroMQ server address
        self._zmq_port = args[1]  # ZeroMQ server port
        self._current_session = None
        self._current_destination = None
        self._current_call_id = None
        self._stopping = False

    def _setup(self):
        """
        Sets up PyZMQ and creates the stream to handle requests
        """

        self._context = zmq.Context()
        self._ioloop = zmq.eventloop.ioloop.IOLoop.instance()
        self._stream = self._create_stream(self._zmq_host, self._zmq_port, self._decode_request)

    def _create_stream(self, host=None, port=0, callback=None):
        """
        Creates a new ZMQ stream.

        :returns: ZMQ stream instance
        """

        self._dealer = self._context.socket(zmq.DEALER)
        self._dealer.setsockopt(zmq.IDENTITY, self.name.encode("utf-8"))
        if host and port:
            log.info("ZeroMQ client ({}) connecting to {}:{}".format(self.name, host, port))
            try:
                self._dealer.connect("tcp://{}:{}".format(host, port))
            except zmq.error.ZMQError as e:
                log.critical("Could not connect to ZeroMQ server on {}:{}, reason: {}".format(host, port, e))
                raise SystemExit
        else:
            log.info("ZeroMQ client ({}) connecting to ipc:///tmp/gns3.ipc".format(self.name))
            try:
                self._dealer.connect("ipc:///tmp/gns3.ipc")
            except zmq.error.ZMQError as e:
                log.critical("Could not connect to ZeroMQ server on ipc:///tmp/gns3.ipc, reason: {}".format(e))
                raise SystemExit

        stream = zmq.eventloop.zmqstream.ZMQStream(self._dealer, self._ioloop)
        if callback:
            stream.on_recv(callback)
        return stream

    def add_periodic_callback(self, callback, time):
        """
        Adds a periodic callback to the ioloop.

        :param callback: callback to be called
        :param time: frequency when the callback is executed
        """

        periodic_callback = zmq.eventloop.ioloop.PeriodicCallback(callback, time, self._ioloop)
        return periodic_callback

    def run(self):
        """
        Starts the event loop
        """

        def signal_handler(signum=None, frame=None):
            log.warning("Module {} got signal {}, exiting...".format(self.name, signum))
            self.stop(signum)

        signals = [signal.SIGTERM, signal.SIGINT]
        if not sys.platform.startswith("win"):
            signals.extend([signal.SIGHUP, signal.SIGQUIT])
        else:
            signals.extend([signal.SIGBREAK])
        for sig in signals:
            signal.signal(sig, signal_handler)

        log.info("{} module running with PID {}".format(self.name, self.pid))
        self._setup()
        try:
            self._ioloop.start()
        except KeyboardInterrupt:
            return

        log.info("{} module has stopped".format(self.name))

    def _shutdown(self):
        """
        Shutdowns the I/O loop and the ZeroMQ stream & socket
        """

        self._ioloop.stop()

        if self._stream and not self._stream.closed:
            # close the zeroMQ stream
            self._stream.close()

        if self._dealer and not self._dealer.closed:
            # close the ZeroMQ dealer socket
            self._dealer.close()

    def stop(self, signum=None):
        """
        Adds a callback to stop the event loop & ZeroMQ.

        :param signum: signal number (if called by the signal handler)
        """

        if not self._stopping:
            self._stopping = True
            if signum:
                self._ioloop.add_callback_from_signal(self._shutdown)
            else:
                self._ioloop.add_callback(self._shutdown)

    def send_response(self, results):
        """
        Sends a response back to the requester.

        :param results: JSON results to the ZeroMQ server
        """

        jsonrpc_response = jsonrpc.JSONRPCResponse(results, self._current_call_id)()

        # add session to the response
        response = [self._current_session, jsonrpc_response]
        log.debug("ZeroMQ client ({}) sending: {}".format(self.name, response))
        self._stream.send_json(response)

    def send_param_error(self):
        """
        Sends a param error back to the requester.
        """

        jsonrpc_response = jsonrpc.JSONRPCInvalidParams(self._current_call_id)()

        # add session to the response
        response = [self._current_session, jsonrpc_response]
        log.info("ZeroMQ client ({}) sending JSON-RPC param error for call id {}".format(self.name, self._current_call_id))
        self._stream.send_json(response)

    def send_internal_error(self):
        """
        Sends a param error back to the requester.
        """

        jsonrpc_response = jsonrpc.JSONRPCInternalError()()

        # add session to the response
        response = [self._current_session, jsonrpc_response]
        log.critical("ZeroMQ client ({}) sending JSON-RPC internal error".format(self.name))
        self._stream.send_json(response)

    def send_custom_error(self, message, code=-3200):
        """
        Sends a custom error back to the requester.
        """

        jsonrpc_response = jsonrpc.JSONRPCCustomError(code, message, self._current_call_id)()

        # add session to the response
        response = [self._current_session, jsonrpc_response]
        log.info("ZeroMQ client ({}) sending JSON-RPC custom error: {} for call id {}".format(self.name,
                                                                                              message,
                                                                                              self._current_call_id))
        self._stream.send_json(response)

    def send_notification(self, destination, results):
        """
        Sends a notification

        :param destination: destination (or method)
        :param results: JSON results to the ZeroMQ router
        """

        jsonrpc_response = jsonrpc.JSONRPCNotification(destination, results)()

        # add session to the response
        response = [self._current_session, jsonrpc_response]
        log.debug("ZeroMQ client ({}) sending: {}".format(self.name, response))
        self._stream.send_json(response)

    def _decode_request(self, request):
        """
        Decodes the request to JSON.

        :param request: request from ZeroMQ server
        """

        # server is shutting down, do not process
        # more request
        if self._stopping:
            return

        # handle special request to stop the module
        # e.g. useful on Windows where the
        # SIGBREAK signal cound't be propagated
        if request[0] == b"stop":
            self.stop()
            return

        try:
            request = zmq.utils.jsonapi.loads(request[0])
        except ValueError:
            self._current_session = None
            self.send_internal_error()
            return

        log.debug("ZeroMQ client ({}) received: {}".format(self.name, request))
        self._current_session = request[0]
        self._current_call_id = request[1].get("id")
        destination = request[1].get("method")
        params = request[1].get("params")

        if destination not in self.modules[self.name]:
            self.send_internal_error()
            return

        log.debug("Routing request to {}: {}".format(destination, request[1]))

        try:
            self.modules[self.name][destination](self, params)
        except Exception as e:
            log.error("uncaught exception {type}".format(type=type(e)), exc_info=1)
            exc_type, exc_value, exc_tb = sys.exc_info()
            lines = traceback.format_exception(exc_type, exc_value, exc_tb)
            tb = "".join(lines)
            self.send_custom_error("uncaught exception {type}: {string}\n{tb}".format(type=type(e),
                                                                                      string=str(e),
                                                                                      tb=tb))

    def validate_request(self, request, schema):
        """
        Validates a request.

        :param request: request (JSON-RPC params)
        :param schema: JSON-SCHEMA to validate the request

        :returns: True or False
        """

        # check if we have a request
        if request == None:
            self.send_param_error()
            return False
        log.debug("received request {}".format(request))

        # validate the request
        try:
            validate(request, schema)
        except ValidationError as e:
            self.send_custom_error("request validation error: {}".format(e))
            return False
        return True

    def destinations(self):
        """
        Destinations handled by this module.

        :returns: list of destinations
        """

        if not self.name in self.modules:
            log.warn("no destinations found for module {}".format(self.name))
            return []
        return self.modules[self.name].keys()

    @classmethod
    def route(cls, destination):
        """
        Decorator to register a destination routed to a method

        :param destination: destination to be routed
        """

        def wrapper(method):
            module = destination.split(".")[0]
            if not module in cls.modules:
                cls.modules[module] = {}
            cls.modules[module][destination] = method
            return method
        return wrapper