# -*- coding: utf-8 -*-
#
# Copyright © Spyder Project Contributors
# Licensed under the terms of the MIT License
# (see spyder/__init__.py for details)

"""
In addition to the remote_call mechanism implemented in CommBase:
 - Implements _wait_reply, so blocking calls can be made.
"""
import pickle
import socket
import sys
import threading
import time

from jupyter_client.localinterfaces import localhost
from tornado import ioloop
import zmq
from IPython.core.getipython import get_ipython

from spyder_kernels.comms.commbase import CommBase, CommError
from spyder_kernels.py3compat import TimeoutError, PY2


def get_free_port():
    """Find a free port on the local machine."""
    sock = socket.socket()
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_LINGER, b'\0' * 8)
    sock.bind((localhost(), 0))
    port = sock.getsockname()[1]
    sock.close()
    return port


def frontend_request(blocking=True, timeout=None):
    """
    Send a request to the frontend.

    If blocking is True, The return value will be returned.
    """
    if not get_ipython().kernel.frontend_comm.is_open():
        raise CommError("Can't make a request to a closed comm")
    # Get a reply from the last frontend to have sent a message
    return get_ipython().kernel.frontend_call(
        blocking=blocking,
        broadcast=False,
        timeout=timeout)


class FrontendComm(CommBase):
    """Mixin to implement the spyder_shell_api."""

    def __init__(self, kernel):
        super(FrontendComm, self).__init__()

        # Comms
        self.kernel = kernel
        self.kernel.comm_manager.register_target(
            self._comm_name, self._comm_open)

        self.comm_port = None
        self.register_call_handler('_send_comm_config',
                                   self._send_comm_config)

        # self.kernel.parent is IPKernelApp unless we are in tests
        if self.kernel.parent:
            # Create a new socket
            context = zmq.Context()
            self.comm_socket = context.socket(zmq.ROUTER)
            self.comm_socket.linger = 1000

            self.comm_port = get_free_port()

            self.comm_port = self.kernel.parent._bind_socket(
                self.comm_socket, self.comm_port)
            if hasattr(zmq, 'ROUTER_HANDOVER'):
                # Set router-handover to workaround zeromq reconnect problems
                # in certain rare circumstances.
                # See ipython/ipykernel#270 and zeromq/libzmq#2892
                self.comm_socket.router_handover = 1

            self.comm_thread_close = threading.Event()
            self.comm_socket_thread = threading.Thread(target=self.poll_thread)
            self.comm_socket_thread.start()

            # Patch parent.close . This function only exists in Python 3.
            if not PY2:
                parent_close = self.kernel.parent.close

                def close():
                    """Close comm_socket_thread."""
                    self.comm_thread_close.set()
                    context.term()
                    self.comm_socket_thread.join()
                    parent_close()

                self.kernel.parent.close = close

    def poll_thread(self):
        """Receive messages from comm socket."""
        if not PY2:
            # Create an event loop for the handlers.
            ioloop.IOLoop().initialize()
        while not self.comm_thread_close.is_set():
            self.poll_one()

    def poll_one(self):
        """Receive one message from comm socket."""
        out_stream = None
        if self.kernel.shell_streams:
            # If the message handler needs to send a reply,
            # use the regular shell stream.
            out_stream = self.kernel.shell_streams[0]
        try:
            ident, msg = self.kernel.session.recv(self.comm_socket, 0)
        except Exception:
            self.kernel.log.warning("Invalid Message:", exc_info=True)
            return
        msg_type = msg['header']['msg_type']

        if msg_type == 'shutdown_request':
            self.comm_thread_close.set()
            return

        handler = self.kernel.shell_handlers.get(msg_type, None)
        if handler is None:
            self.kernel.log.warning("Unknown message type: %r", msg_type)
        else:
            try:
                handler(out_stream, ident, msg)
            except Exception:
                self.kernel.log.error("Exception in message handler:",
                                      exc_info=True)
                return

        sys.stdout.flush()
        sys.stderr.flush()
        # Flush to ensure reply is sent
        if out_stream:
            out_stream.flush(zmq.POLLOUT)

    def remote_call(self, comm_id=None, blocking=False, callback=None,
                    timeout=None):
        """Get a handler for remote calls."""
        return super(FrontendComm, self).remote_call(
            blocking=blocking,
            comm_id=comm_id,
            callback=callback,
            timeout=timeout)

    # --- Private --------
    def _wait_reply(self, call_id, call_name, timeout, retry=True):
        """Wait until the frontend replies to a request."""
        if call_id in self._reply_inbox:
            return
        t_start = time.time()
        while call_id not in self._reply_inbox:
            if time.time() > t_start + timeout:
                if retry:
                    self._wait_reply(call_id, call_name, timeout, False)
                    return
                raise TimeoutError(
                    "Timeout while waiting for '{}' reply.".format(
                        call_name))
            if threading.current_thread() is self.comm_socket_thread:
                # Wait for a reply on the comm channel.
                self.poll_one()
            else:
                # Wait 10ms for a reply
                time.sleep(0.01)

    def _comm_open(self, comm, msg):
        """
        A new comm is open!
        """
        self.calling_comm_id = comm.comm_id
        self._register_comm(comm)
        self._set_pickle_protocol(msg['content']['data']['pickle_protocol'])
        self._send_comm_config()

    def on_outgoing_call(self, call_dict):
        """A message is about to be sent"""
        call_dict["comm_port"] = self.comm_port
        return super(FrontendComm, self).on_outgoing_call(call_dict)

    def _send_comm_config(self):
        """Send the comm config to the frontend."""
        self.remote_call()._set_comm_port(self.comm_port)
        self.remote_call()._set_pickle_protocol(pickle.HIGHEST_PROTOCOL)

    def _comm_close(self, msg):
        """Close comm."""
        comm_id = msg['content']['comm_id']
        comm = self._comms[comm_id]['comm']
        # Pretend it is already closed to avoid problems when closing
        comm._closed = True
        del self._comms[comm_id]

    def _async_error(self, error_wrapper):
        """
        Send an async error back to the frontend to be displayed.
        """
        self.remote_call()._async_error(error_wrapper)

    def _register_comm(self, comm):
        """
        Remove side effect ipykernel has.
        """
        def handle_msg(msg):
            """Handle a comm_msg message"""
            if comm._msg_callback:
                comm._msg_callback(msg)
        comm.handle_msg = handle_msg
        super(FrontendComm, self)._register_comm(comm)
