# -*- coding: UTF-8 -*-
"""Module that implements a different threading model between
a Java Virtual Machine a Python interpreter.

In this model, Java and Python can exchange resquests and responses in the same
thread. For example, if a request is started in a Java UI thread and the Python
code calls some Java code, the Java code will be executed in the UI thread.
"""

from __future__ import unicode_literals, absolute_import

from collections import deque
import logging
import socket
from threading import local, Thread
import time
import traceback
import weakref

from py4j.java_gateway import (
    quiet_close, quiet_shutdown,
    set_linger, GatewayClient, JavaGateway,
    CallbackServerParameters, GatewayParameters, CallbackServer,
    GatewayConnectionGuard, DEFAULT_ADDRESS, DEFAULT_PORT,
    DEFAULT_PYTHON_PROXY_PORT, DEFAULT_ACCEPT_TIMEOUT_PLACEHOLDER,
    server_connection_stopped, do_client_auth, _garbage_collect_proxy)
from py4j import protocol as proto
from py4j.protocol import (
    Py4JError, Py4JNetworkError, smart_decode, get_command_part,
    get_return_value, Py4JAuthenticationError)


logger = logging.getLogger("py4j.clientserver")


SHUTDOWN_FINALIZER_WORKER = "__shutdown__"

DEFAULT_WORKER_SLEEP_TIME = 1


class FinalizerWorker(Thread):

    def __init__(self, deque):
        self.deque = deque
        super(FinalizerWorker, self).__init__()

    def run(self):
        while(True):
            try:
                task = self.deque.pop()
                if task == SHUTDOWN_FINALIZER_WORKER:
                    break
                else:
                    (java_client, target_id) = task
                    java_client.garbage_collect_object(
                        target_id, False)
            except IndexError:
                time.sleep(DEFAULT_WORKER_SLEEP_TIME)


class JavaParameters(GatewayParameters):
    """Wrapper class that contains all parameters that can be passed to
    configure a `ClientServer`.`
    """
    def __init__(
            self, address=DEFAULT_ADDRESS, port=DEFAULT_PORT, auto_field=False,
            auto_close=True, auto_convert=False, eager_load=False,
            ssl_context=None, enable_memory_management=True, auto_gc=False,
            read_timeout=None, daemonize_memory_management=True,
            auth_token=None):
        """

        :param address: the address to which the client will request a
            connection. If you're assing a `SSLContext` with
            `check_hostname=True` then this address must match
            (one of) the hostname(s) in the certificate the gateway
            server presents.

        :param port: the port to which the client will request a connection.
            Default is 25333.

        :param auto_field: if `False`, each object accessed through this
            gateway won"t try to lookup fields (they will be accessible only by
            calling get_field). If `True`, fields will be automatically looked
            up, possibly hiding methods of the same name and making method
            calls less efficient.

        :param auto_close: if `True`, the connections created by the client
            close the socket when they are garbage collected.

        :param auto_convert: if `True`, try to automatically convert Python
            objects like sequences and maps to Java Objects. Default value is
            `False` to improve performance and because it is still possible to
            explicitly perform this conversion.

        :param eager_load: if `True`, the gateway tries to connect to the JVM
            by calling System.currentTimeMillis. If the gateway cannot connect
            to the JVM, it shuts down itself and raises an exception.

        :param ssl_context: if not None, SSL connections will be made using
            this SSLContext

        :param enable_memory_management: if True, tells the Java side when a
            JavaObject (reference to an object on the Java side) is garbage
            collected on the Python side.

        :param auto_gc: if True, call gc.collect() before sending a command to
            the Java side. This should prevent the gc from running between
            sending the command and waiting for an anwser. False by default
            because this case is extremely unlikely. Legacy option no longer
            used.

        :param read_timeout: if > 0, sets a timeout in seconds after
            which the socket stops waiting for a response from the Java side.

        :param daemonize_memory_management: if True, the worker Thread making
            the garbage collection requests will be daemonized. This means that
            the Python side might not send all garbage collection requests if
            it exits. If False, memory management will block the Python program
            exit until all requests are sent.

        :param auth_token: if provided, an authentication that token clients
            must provide to the server when connecting.
        """
        super(JavaParameters, self).__init__(
            address, port, auto_field, auto_close, auto_convert, eager_load,
            ssl_context, enable_memory_management, read_timeout, auth_token)
        self.auto_gc = auto_gc
        self.daemonize_memory_management = daemonize_memory_management


class PythonParameters(CallbackServerParameters):
    """Wrapper class that contains all parameters that can be passed to
    configure a `ClientServer`
    """

    def __init__(
            self, address=DEFAULT_ADDRESS, port=DEFAULT_PYTHON_PROXY_PORT,
            daemonize=False, daemonize_connections=False, eager_load=True,
            ssl_context=None, auto_gc=False,
            accept_timeout=DEFAULT_ACCEPT_TIMEOUT_PLACEHOLDER,
            read_timeout=None, propagate_java_exceptions=False,
            auth_token=None):
        """
        :param address: the address to which the client will request a
            connection

        :param port: the port to which the client will request a connection.
            Default is 25334.

        :param daemonize: If `True`, will set the daemon property of the server
            thread to True. The callback server will exit automatically if all
            the other threads exit.

        :param daemonize_connections: If `True`, callback server connections
            are executed in daemonized threads and will not block the exit of a
            program if non daemonized threads are finished.

        :param eager_load: If `True`, the callback server is automatically
            started when the JavaGateway is created.

        :param ssl_context: if not None, the SSLContext's certificate will be
            presented to callback connections.

        :param auto_gc: if True, call gc.collect() before returning a response
            to the Java side. This should prevent the gc from running between
            sending the response and waiting for a new command. False by
            default because this case is extremely unlikely but could break
            communication. Legacy option no longer used.

        :param accept_timeout: if > 0, sets a timeout in seconds after which
            the callbackserver stops waiting for a connection, sees if the
            callback server should shut down, and if not, wait again for a
            connection. The default is 5 seconds: this roughly means that
            if can take up to 5 seconds to shut down the callback server.

        :param read_timeout: if > 0, sets a timeout in seconds after
            which the socket stops waiting for a call or command from the
            Java side.

        :param propagate_java_exceptions: if `True`, any `Py4JJavaError` raised
            by a Python callback will cause the nested `java_exception` to be
            thrown on the Java side. If `False`, the `Py4JJavaError` will
            manifest as a `Py4JException` on the Java side, just as with any
            other kind of Python exception. Setting this option is useful if
            you need to implement a Java interface where the user of the
            interface has special handling for specific Java exception types.

        :param auth_token: if provided, an authentication token that clients
            must provide to the server when connecting.
        """
        super(PythonParameters, self).__init__(
            address, port, daemonize, daemonize_connections, eager_load,
            ssl_context, accept_timeout, read_timeout,
            propagate_java_exceptions, auth_token)
        self.auto_gc = auto_gc


class JavaClient(GatewayClient):
    """Responsible for managing requests from Python to Java.

    This implementation is thread-safe because it always use only one
    ClientServerConnection per thread.
    """

    def __init__(
            self, java_parameters, python_parameters, gateway_property=None,
            finalizer_deque=None):
        """
        :param java_parameters: collection of parameters and flags used to
            configure the JavaGateway (Java client)

        :param python_parameters: collection of parameters and flags used to
            configure the CallbackServer (Python server)

        :param gateway_property: used to keep gateway preferences without a
            cycle with the JavaGateway

        :param finalizer_deque: deque used to manage garbage collection
            requests.
        """
        super(JavaClient, self).__init__(
            java_parameters,
            gateway_property=gateway_property)
        self.java_parameters = java_parameters
        self.python_parameters = python_parameters
        self.thread_connection = local()
        self.finalizer_deque = finalizer_deque

    def garbage_collect_object(self, target_id, enqueue=True):
        """Tells the Java side that there is no longer a reference to this
        JavaObject on the Python side. If enqueue is True, sends the request
        to the FinalizerWorker deque. Otherwise, sends the request to the Java
        side.
        """
        if enqueue:
            self.finalizer_deque.appendleft((self, target_id))
        else:
            super(JavaClient, self).garbage_collect_object(target_id)

    def set_thread_connection(self, connection):
        """Associates a ClientServerConnection with the current thread.

        :param connection: The ClientServerConnection to associate with the
            current thread.
        """
        self.thread_connection.connection = weakref.ref(connection)

    def shutdown_gateway(self):
        try:
            super(JavaClient, self).shutdown_gateway()
        finally:
            self.finalizer_deque.appendleft(SHUTDOWN_FINALIZER_WORKER)

    def get_thread_connection(self):
        """Returns the ClientServerConnection associated with this thread. Can
        be None.
        """
        connection = None
        try:
            connection_wr = self.thread_connection.connection
            if connection_wr:
                connection = connection_wr()
        except AttributeError:
            pass
        return connection

    def _get_connection(self):
        connection = self.get_thread_connection()

        try:
            if connection is not None:
                # Remove the strong reference to the connection
                # It will be re-added after the command is sent.
                self.deque.remove(connection)
        except ValueError:
            # Should never reach this point
            pass

        if connection is None or connection.socket is None:
            connection = self._create_new_connection()
        return connection

    def _create_new_connection(self):
        connection = ClientServerConnection(
            self.java_parameters, self.python_parameters,
            self.gateway_property, self)
        connection.connect_to_java_server()
        self.set_thread_connection(connection)
        return connection

    def _should_retry(self, retry, connection, pne=None):
        # Only retry if Python was driving the communication.
        parent_retry = super(JavaClient, self)._should_retry(
            retry, connection, pne)
        return parent_retry and retry and connection and\
            connection.initiated_from_client

    def _create_connection_guard(self, connection):
        return ClientServerConnectionGuard(self, connection)


class ClientServerConnectionGuard(GatewayConnectionGuard):
    """Connection guard that does nothing on exit because there is no need to
    close or give back a connection.
    """

    def __exit__(self, type, value, traceback):
        pass


class PythonServer(CallbackServer):
    """Responsible for managing requests from Java to Python.
    """

    def __init__(
            self, java_client, java_parameters, python_parameters,
            gateway_property):
        """
        :param java_client: the gateway client used to call Java objects.

        :param java_parameters: collection of parameters and flags used to
            configure the JavaGateway (Java client)

        :param python_parameters: collection of parameters and flags used to
            configure the CallbackServer (Python server)

        :param gateway_property: used to keep gateway preferences.
        """
        super(PythonServer, self).__init__(
            pool=gateway_property.pool,
            gateway_client=java_client,
            callback_server_parameters=python_parameters)
        self.java_parameters = java_parameters
        self.python_parameters = python_parameters
        self.gateway_property = gateway_property

    def _create_connection(self, socket, stream):
        connection = ClientServerConnection(
            self.java_parameters, self.python_parameters,
            self.gateway_property, self.gateway_client, python_server=self)
        connection.init_socket_from_python_server(socket, stream)
        return connection


class ClientServerConnection(object):
    """Default connection for a ClientServer instance
    (socket-based, one per thread) responsible for communicating
    with the Java Virtual Machine.
    """

    def __init__(
            self, java_parameters, python_parameters, gateway_property,
            java_client, python_server=None):
        """
        :param java_parameters: collection of parameters and flags used to
            configure the JavaGateway (Java client)

        :param python_parameters: collection of parameters and flags used to
            configure the CallbackServer (Python server)

        :param gateway_property: used to keep gateway preferences.

        :param java_client: the gateway client used to call Java objects.

        :param python_server: the Python server used to receive commands from
            Java. Only provided if created from Python server.
        """
        self.java_parameters = java_parameters
        self.python_parameters = python_parameters

        # For backward compatibility
        self.address = self.java_parameters.address
        self.port = self.java_parameters.port

        self.java_address = self.java_parameters.address
        self.java_port = self.java_parameters.port

        self.python_address = self.python_parameters.address
        self.python_port = self.python_parameters.port

        self.ssl_context = self.java_parameters.ssl_context
        self.socket = None
        self.stream = None
        self.gateway_property = gateway_property
        self.pool = gateway_property.pool
        self._listening_address = self._listening_port = None
        self.is_connected = False

        self.java_client = java_client
        self.python_server = python_server
        self.initiated_from_client = False

    def connect_to_java_server(self):
        try:
            self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            if self.java_parameters.read_timeout:
                self.socket.settimeout(self.java_parameters.read_timeout)
            if self.ssl_context:
                self.socket = self.ssl_context.wrap_socket(
                    self.socket, server_hostname=self.java_address)
            self.socket.connect((self.java_address, self.java_port))
            self.stream = self.socket.makefile("rb")
            self.is_connected = True
            self.initiated_from_client = True

            self._authenticate_connection()
        except Py4JAuthenticationError:
            self.close(reset=True)
            self.is_connected = False
            raise
        except Exception:
            self.close()
            self.is_connected = False
            raise

    def _authenticate_connection(self):
        if self.java_parameters.auth_token:
            cmd = "{0}\n{1}\n".format(
                proto.AUTH_COMMAND_NAME,
                self.java_parameters.auth_token
            )
            answer = self.send_command(cmd)
            error, _ = proto.is_error(answer)
            if error:
                raise Py4JAuthenticationError(
                    "Failed to authenticate with gateway server.")

    def init_socket_from_python_server(self, socket, stream):
        self.socket = socket
        self.stream = stream
        self.is_connected = True

    def shutdown_gateway(self):
        """Sends a shutdown command to the Java side.

        This will close the ClientServer on the Java side: all active
        connections will be closed. This may be useful if the lifecycle
        of the Java program must be tied to the Python program.
        """
        if not self.is_connected:
            raise Py4JError("Gateway must be connected to send shutdown cmd.")

        try:
            quiet_close(self.stream)
            self.socket.sendall(
                proto.SHUTDOWN_GATEWAY_COMMAND_NAME.encode("utf-8"))
            self.close()
        except Exception:
            # Do nothing! Exceptions might occur anyway.
            logger.debug("Exception occurred while shutting down gateway",
                         exc_info=True)

    def start(self):
        t = Thread(target=self.run)
        t.daemon = self.python_parameters.daemonize_connections
        t.start()

    def run(self):
        self.java_client.set_thread_connection(self)
        self.wait_for_commands()

    def send_command(self, command):
        # TODO At some point extract common code from wait_for_commands
        logger.debug("Command to send: {0}".format(command))
        try:
            self.socket.sendall(command.encode("utf-8"))
        except Exception as e:
            logger.info("Error while sending or receiving.", exc_info=True)
            raise Py4JNetworkError(
                "Error while sending", e, proto.ERROR_ON_SEND)

        try:
            while True:
                answer = smart_decode(self.stream.readline()[:-1])
                logger.debug("Answer received: {0}".format(answer))
                # Happens when a the other end is dead. There might be an empty
                # answer before the socket raises an error.
                if answer.strip() == "":
                    raise Py4JNetworkError("Answer from Java side is empty")
                if answer.startswith(proto.RETURN_MESSAGE):
                    return answer[1:]
                else:
                    command = answer
                    obj_id = smart_decode(self.stream.readline())[:-1]

                    if command == proto.CALL_PROXY_COMMAND_NAME:
                        return_message = self._call_proxy(obj_id, self.stream)
                        self.socket.sendall(return_message.encode("utf-8"))
                    elif command == proto.GARBAGE_COLLECT_PROXY_COMMAND_NAME:
                        self.stream.readline()
                        _garbage_collect_proxy(self.pool, obj_id)
                        self.socket.sendall(
                            proto.SUCCESS_RETURN_MESSAGE.encode("utf-8"))
                    else:
                        logger.error("Unknown command {0}".format(command))
                        # We're sending something to prevent blocking,
                        # but at this point, the protocol is broken.
                        self.socket.sendall(
                            proto.ERROR_RETURN_MESSAGE.encode("utf-8"))
        except Exception as e:
            logger.info("Error while receiving.", exc_info=True)
            raise Py4JNetworkError(
                "Error while sending or receiving", e, proto.ERROR_ON_RECEIVE)

    def close(self, reset=False):
        logger.info("Closing down clientserver connection")
        if not self.socket:
            return
        if reset:
            set_linger(self.socket)
        quiet_close(self.stream)
        if not reset:
            quiet_shutdown(self.socket)
        quiet_close(self.socket)
        already_closed = self.socket is None
        self.socket = None
        self.stream = None
        if not self.initiated_from_client and self.python_server and\
                not already_closed:
            server_connection_stopped.send(
                self.python_server, connection=self)

    def wait_for_commands(self):
        logger.info("Python Server ready to receive messages")
        reset = False
        authenticated = self.python_parameters.auth_token is None
        try:
            while True:
                command = smart_decode(self.stream.readline())[:-1]
                if not authenticated:
                    # Will raise an exception if auth fails in any way.
                    authenticated = do_client_auth(
                        command, self.stream, self.socket,
                        self.python_parameters.auth_token)
                    continue

                obj_id = smart_decode(self.stream.readline())[:-1]
                logger.info(
                    "Received command {0} on object id {1}".
                    format(command, obj_id))
                if obj_id is None or len(obj_id.strip()) == 0:
                    break
                if command == proto.CALL_PROXY_COMMAND_NAME:
                    return_message = self._call_proxy(obj_id, self.stream)
                    self.socket.sendall(return_message.encode("utf-8"))
                elif command == proto.GARBAGE_COLLECT_PROXY_COMMAND_NAME:
                    self.stream.readline()
                    _garbage_collect_proxy(self.pool, obj_id)
                    self.socket.sendall(
                        proto.SUCCESS_RETURN_MESSAGE.encode("utf-8"))
                else:
                    logger.error("Unknown command {0}".format(command))
                    # We're sending something to prevent blocking, but at this
                    # point, the protocol is broken.
                    self.socket.sendall(
                        proto.ERROR_RETURN_MESSAGE.encode("utf-8"))
        except Py4JAuthenticationError:
            reset = True
            logger.exception("Could not authenticate connection.")
        except socket.timeout:
            reset = True
            logger.info(
                "Timeout while python server was waiting for"
                "a message", exc_info=True)
        except Exception:
            # This is a normal exception...
            logger.info(
                "Error while python server was waiting for"
                "a message", exc_info=True)
        self.close(reset)

    def _call_proxy(self, obj_id, input):
        if obj_id not in self.pool:
            return proto.RETURN_MESSAGE + proto.ERROR +\
                get_command_part('Object ID unknown', self.pool)

        try:
            method = smart_decode(input.readline())[:-1]
            params = self._get_params(input)
            return_value = getattr(self.pool[obj_id], method)(*params)
            return proto.RETURN_MESSAGE + proto.SUCCESS +\
                get_command_part(return_value, self.pool)
        except Exception as e:
            logger.exception("There was an exception while executing the "
                             "Python Proxy on the Python Side.")

            if self.python_parameters.propagate_java_exceptions and\
               isinstance(e, proto.Py4JJavaError):
                java_exception = e.java_exception
            else:
                java_exception = traceback.format_exc()

            return proto.RETURN_MESSAGE + proto.ERROR +\
                get_command_part(java_exception, self.pool)

    def _get_params(self, input):
        params = []
        temp = smart_decode(input.readline())[:-1]
        while temp != proto.END:
            param = get_return_value("y" + temp, self.java_client)
            params.append(param)
            temp = smart_decode(input.readline())[:-1]
        return params


class ClientServer(JavaGateway):
    """Subclass of JavaGateway that implements a different threading model: a
    thread always use the same connection to the other side so callbacks are
    executed in the calling thread.

    For example, if Python thread 1 calls Java, and Java calls Python, the
    callback (from Java to Python) will be executed in Python thread 1.

    Note about authentication: to enable authentication
    """

    def __init__(
            self, java_parameters=None, python_parameters=None,
            python_server_entry_point=None):
        """
        :param java_parameters: collection of parameters and flags used to
            configure the JavaGateway (Java client)

        :param python_parameters: collection of parameters and flags used to
            configure the CallbackServer (Python server)

        :param python_server_entry_point: can be requested by the Java side if
            Java is driving the communication.
        """
        if not java_parameters:
            java_parameters = JavaParameters()
        if not python_parameters:
            python_parameters = PythonParameters()
        self.java_parameters = java_parameters
        self.python_parameters = python_parameters
        super(ClientServer, self).__init__(
            gateway_parameters=java_parameters,
            callback_server_parameters=python_parameters,
            python_server_entry_point=python_server_entry_point
        )

    def _create_finalizer_worker(self):
        worker_deque = deque()
        worker = FinalizerWorker(worker_deque)
        worker.daemon = self.java_parameters.daemonize_memory_management
        worker.start()
        return worker_deque

    def _create_gateway_client(self):
        worker_deque = self._create_finalizer_worker()
        java_client = JavaClient(
            self.java_parameters, self.python_parameters,
            finalizer_deque=worker_deque)
        return java_client

    def _create_callback_server(self, callback_server_parameters):
        callback_server = PythonServer(
            self._gateway_client, self.java_parameters, self.python_parameters,
            self.gateway_property)
        return callback_server
