import selectors
import socket
import ssl
from time import time
from urllib.parse import urlsplit

from wsproto import ConnectionType, WSConnection
from wsproto.events import (
    AcceptConnection,
    RejectConnection,
    CloseConnection,
    Message,
    Request,
    Ping,
    Pong,
    TextMessage,
    BytesMessage,
)
from wsproto.extensions import PerMessageDeflate
from wsproto.frame_protocol import CloseReason
from wsproto.utilities import LocalProtocolError
from .errors import ConnectionError, ConnectionClosed


class Base:
    def __init__(self, sock=None, connection_type=None, receive_bytes=4096,
                 ping_interval=None, max_message_size=None,
                 thread_class=None, event_class=None, selector_class=None):
        #: The name of the subprotocol chosen for the WebSocket connection.
        self.subprotocol = None

        self.sock = sock
        self.receive_bytes = receive_bytes
        self.ping_interval = ping_interval
        self.max_message_size = max_message_size
        self.pong_received = True
        self.input_buffer = []
        self.incoming_message = None
        self.incoming_message_len = 0
        self.connected = False
        self.is_server = (connection_type == ConnectionType.SERVER)
        self.close_reason = CloseReason.NO_STATUS_RCVD
        self.close_message = None

        if thread_class is None:
            import threading
            thread_class = threading.Thread
        if event_class is None:  # pragma: no branch
            import threading
            event_class = threading.Event
        if selector_class is None:
            selector_class = selectors.DefaultSelector
        self.selector_class = selector_class
        self.event = event_class()

        self.ws = WSConnection(connection_type)
        self.handshake()

        if not self.connected:  # pragma: no cover
            raise ConnectionError()
        self.thread = thread_class(target=self._thread)
        self.thread.name = self.thread.name.replace(
            '(_thread)', '(simple_websocket.Base._thread)')
        self.thread.start()

    def handshake(self):  # pragma: no cover
        # to be implemented by subclasses
        pass

    def send(self, data):
        """Send data over the WebSocket connection.

        :param data: The data to send. If ``data`` is of type ``bytes``, then
                     a binary message is sent. Else, the message is sent in
                     text format.
        """
        if not self.connected:
            raise ConnectionClosed(self.close_reason, self.close_message)
        if isinstance(data, bytes):
            out_data = self.ws.send(Message(data=data))
        else:
            out_data = self.ws.send(TextMessage(data=str(data)))
        self.sock.send(out_data)

    def receive(self, timeout=None):
        """Receive data over the WebSocket connection.

        :param timeout: Amount of time to wait for the data, in seconds. Set
                        to ``None`` (the default) to wait indefinitely. Set
                        to 0 to read without blocking.

        The data received is returned, as ``bytes`` or ``str``, depending on
        the type of the incoming message.
        """
        while self.connected and not self.input_buffer:
            if not self.event.wait(timeout=timeout):
                return None
            self.event.clear()
        try:
            return self.input_buffer.pop(0)
        except IndexError:
            pass
        if not self.connected:  # pragma: no cover
            raise ConnectionClosed(self.close_reason, self.close_message)

    def close(self, reason=None, message=None):
        """Close the WebSocket connection.

        :param reason: A numeric status code indicating the reason of the
                       closure, as defined by the WebSocket specification. The
                       default is 1000 (normal closure).
        :param message: A text message to be sent to the other side.
        """
        if not self.connected:
            raise ConnectionClosed(self.close_reason, self.close_message)
        out_data = self.ws.send(CloseConnection(
            reason or CloseReason.NORMAL_CLOSURE, message))
        try:
            self.sock.send(out_data)
        except BrokenPipeError:  # pragma: no cover
            pass
        self.connected = False

    def choose_subprotocol(self, request):  # pragma: no cover
        # The method should return the subprotocol to use, or ``None`` if no
        # subprotocol is chosen. Can be overridden by subclasses that implement
        # the server-side of the WebSocket protocol.
        return None

    def _thread(self):
        sel = None
        if self.ping_interval:
            next_ping = time() + self.ping_interval
            sel = self.selector_class()
            sel.register(self.sock, selectors.EVENT_READ, True)

        while self.connected:
            try:
                if sel:
                    now = time()
                    if next_ping <= now or not sel.select(next_ping - now):
                        # we reached the timeout, we have to send a ping
                        if not self.pong_received:
                            self.close(reason=CloseReason.POLICY_VIOLATION,
                                       message='Ping/Pong timeout')
                            break
                        self.pong_received = False
                        self.sock.send(self.ws.send(Ping()))
                        next_ping = max(now, next_ping) + self.ping_interval
                        continue
                in_data = self.sock.recv(self.receive_bytes)
                if len(in_data) == 0:
                    raise OSError()
                self.ws.receive_data(in_data)
                self.connected = self._handle_events()
            except (OSError, ConnectionResetError):  # pragma: no cover
                self.connected = False
                self.event.set()
                break
        sel.close() if sel else None
        self.sock.close()

    def _handle_events(self):
        keep_going = True
        out_data = b''
        for event in self.ws.events():
            try:
                if isinstance(event, Request):
                    self.subprotocol = self.choose_subprotocol(event)
                    out_data += self.ws.send(AcceptConnection(
                        subprotocol=self.subprotocol,
                        extensions=[PerMessageDeflate()]))
                elif isinstance(event, CloseConnection):
                    if self.is_server:
                        out_data += self.ws.send(event.response())
                    self.close_reason = event.code
                    self.close_message = event.reason
                    self.connected = False
                    self.event.set()
                    keep_going = False
                elif isinstance(event, Ping):
                    out_data += self.ws.send(event.response())
                elif isinstance(event, Pong):
                    self.pong_received = True
                elif isinstance(event, (TextMessage, BytesMessage)):
                    self.incoming_message_len += len(event.data)
                    if self.max_message_size and \
                            self.incoming_message_len > self.max_message_size:
                        out_data += self.ws.send(CloseConnection(
                            CloseReason.MESSAGE_TOO_BIG, 'Message is too big'))
                        self.event.set()
                        keep_going = False
                        break
                    if self.incoming_message is None:
                        # store message as is first
                        # if it is the first of a group, the message will be
                        # converted to bytearray on arrival of the second
                        # part, since bytearrays are mutable and can be
                        # concatenated more efficiently
                        self.incoming_message = event.data
                    elif isinstance(event, TextMessage):
                        if not isinstance(self.incoming_message, bytearray):
                            # convert to bytearray and append
                            self.incoming_message = bytearray(
                                (self.incoming_message + event.data).encode())
                        else:
                            # append to bytearray
                            self.incoming_message += event.data.encode()
                    else:
                        if not isinstance(self.incoming_message, bytearray):
                            # convert to mutable bytearray and append
                            self.incoming_message = bytearray(
                                self.incoming_message + event.data)
                        else:
                            # append to bytearray
                            self.incoming_message += event.data
                    if not event.message_finished:
                        continue
                    if isinstance(self.incoming_message, (str, bytes)):
                        # single part message
                        self.input_buffer.append(self.incoming_message)
                    elif isinstance(event, TextMessage):
                        # convert multi-part message back to text
                        self.input_buffer.append(
                            self.incoming_message.decode())
                    else:
                        # convert multi-part message back to bytes
                        self.input_buffer.append(bytes(self.incoming_message))
                    self.incoming_message = None
                    self.incoming_message_len = 0
                    self.event.set()
                else:  # pragma: no cover
                    pass
            except LocalProtocolError:  # pragma: no cover
                out_data = b''
                self.event.set()
                keep_going = False
        if out_data:
            self.sock.send(out_data)
        return keep_going


class Server(Base):
    """This class implements a WebSocket server.

    Instead of creating an instance of this class directly, use the
    ``accept()`` class method to create individual instances of the server,
    each bound to a client request.
    """
    def __init__(self, environ, subprotocols=None, receive_bytes=4096,
                 ping_interval=None, max_message_size=None, thread_class=None,
                 event_class=None, selector_class=None):
        self.environ = environ
        self.subprotocols = subprotocols or []
        if isinstance(self.subprotocols, str):
            self.subprotocols = [self.subprotocols]
        self.mode = 'unknown'
        sock = None
        if 'werkzeug.socket' in environ:
            # extract socket from Werkzeug's WSGI environment
            sock = environ.get('werkzeug.socket')
            self.mode = 'werkzeug'
        elif 'gunicorn.socket' in environ:
            # extract socket from Gunicorn WSGI environment
            sock = environ.get('gunicorn.socket')
            self.mode = 'gunicorn'
        elif 'eventlet.input' in environ:  # pragma: no cover
            # extract socket from Eventlet's WSGI environment
            sock = environ.get('eventlet.input').get_socket()
            self.mode = 'eventlet'
        elif environ.get('SERVER_SOFTWARE', '').startswith(
                'gevent'):  # pragma: no cover
            # extract socket from Gevent's WSGI environment
            wsgi_input = environ['wsgi.input']
            if not hasattr(wsgi_input, 'raw') and hasattr(wsgi_input, 'rfile'):
                wsgi_input = wsgi_input.rfile
            if hasattr(wsgi_input, 'raw'):
                sock = wsgi_input.raw._sock
                try:
                    sock = sock.dup()
                except NotImplementedError:
                    pass
                self.mode = 'gevent'
        if sock is None:
            raise RuntimeError('Cannot obtain socket from WSGI environment.')
        super().__init__(sock, connection_type=ConnectionType.SERVER,
                         receive_bytes=receive_bytes,
                         ping_interval=ping_interval,
                         max_message_size=max_message_size,
                         thread_class=thread_class, event_class=event_class,
                         selector_class=selector_class)

    @classmethod
    def accept(cls, environ, subprotocols=None, receive_bytes=4096,
               ping_interval=None, max_message_size=None, thread_class=None,
               event_class=None, selector_class=None):
        """Accept a WebSocket connection from a client.

        :param environ: A WSGI ``environ`` dictionary with the request details.
                        Among other things, this class expects to find the
                        low-level network socket for the connection somewhere
                        in this dictionary. Since the WSGI specification does
                        not cover where or how to store this socket, each web
                        server does this in its own different way. Werkzeug,
                        Gunicorn, Eventlet and Gevent are the only web servers
                        that are currently supported.
        :param subprotocols: A list of supported subprotocols, or ``None`` (the
                             default) to disable subprotocol negotiation.
        :param receive_bytes: The size of the receive buffer, in bytes. The
                              default is 4096.
        :param ping_interval: Send ping packets to clients at the requested
                              interval in seconds. Set to ``None`` (the
                              default) to disable ping/pong logic. Enable to
                              prevent disconnections when the line is idle for
                              a certain amount of time, or to detect
                              unresponsive clients and disconnect them. A
                              recommended interval is 25 seconds.
        :param max_message_size: The maximum size allowed for a message, in
                                 bytes, or ``None`` for no limit. The default
                                 is ``None``.
        :param thread_class: The ``Thread`` class to use when creating
                             background threads. The default is the
                             ``threading.Thread`` class from the Python
                             standard library.
        :param event_class: The ``Event`` class to use when creating event
                            objects. The default is the `threading.Event``
                            class from the Python standard library.
        :param selector_class: The ``Selector`` class to use when creating
                               selectors. The default is the
                               ``selectors.DefaultSelector`` class from the
                               Python standard library.
        """
        return cls(environ, subprotocols=subprotocols,
                   receive_bytes=receive_bytes, ping_interval=ping_interval,
                   max_message_size=max_message_size,
                   thread_class=thread_class, event_class=event_class,
                   selector_class=selector_class)

    def handshake(self):
        in_data = b'GET / HTTP/1.1\r\n'
        for key, value in self.environ.items():
            if key.startswith('HTTP_'):
                header = '-'.join([p.capitalize() for p in key[5:].split('_')])
                in_data += f'{header}: {value}\r\n'.encode()
        in_data += b'\r\n'
        self.ws.receive_data(in_data)
        self.connected = self._handle_events()

    def choose_subprotocol(self, request):
        """Choose a subprotocol to use for the WebSocket connection.

        The default implementation selects the first protocol requested by the
        client that is accepted by the server. Subclasses can override this
        method to implement a different subprotocol negotiation algorithm.

        :param request: A ``Request`` object.

        The method should return the subprotocol to use, or ``None`` if no
        subprotocol is chosen.
        """
        for subprotocol in request.subprotocols:
            if subprotocol in self.subprotocols:
                return subprotocol
        return None


class Client(Base):
    """This class implements a WebSocket client.

    Instead of creating an instance of this class directly, use the
    ``connect()`` class method to create an instance that is connected to a
    server.
    """
    def __init__(self, url, subprotocols=None, headers=None,
                 receive_bytes=4096, ping_interval=None, max_message_size=None,
                 ssl_context=None, thread_class=None, event_class=None):
        parsed_url = urlsplit(url)
        is_secure = parsed_url.scheme in ['https', 'wss']
        self.host = parsed_url.hostname
        self.port = parsed_url.port or (443 if is_secure else 80)
        self.path = parsed_url.path
        if parsed_url.query:
            self.path += '?' + parsed_url.query
        self.subprotocols = subprotocols or []
        if isinstance(self.subprotocols, str):
            self.subprotocols = [self.subprotocols]

        self.extra_headeers = []
        if isinstance(headers, dict):
            for key, value in headers.items():
                self.extra_headeers.append((key, value))
        elif isinstance(headers, list):
            self.extra_headeers = headers

        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        if is_secure:  # pragma: no cover
            if ssl_context is None:
                ssl_context = ssl.create_default_context(
                    purpose=ssl.Purpose.SERVER_AUTH)
            sock = ssl_context.wrap_socket(sock, server_hostname=self.host)
        sock.connect((self.host, self.port))
        super().__init__(sock, connection_type=ConnectionType.CLIENT,
                         receive_bytes=receive_bytes,
                         ping_interval=ping_interval,
                         max_message_size=max_message_size,
                         thread_class=thread_class, event_class=event_class)

    @classmethod
    def connect(cls, url, subprotocols=None, headers=None,
                receive_bytes=4096, ping_interval=None, max_message_size=None,
                ssl_context=None, thread_class=None, event_class=None):
        """Returns a WebSocket client connection.

        :param url: The connection URL. Both ``ws://`` and ``wss://`` URLs are
                    accepted.
        :param subprotocols: The name of the subprotocol to use, or a list of
                             subprotocol names in order of preference. Set to
                             ``None`` (the default) to not use a subprotocol.
        :param headers: A dictionary or list of tuples with additional HTTP
                        headers to send with the connection request. Note that
                        custom headers are not supported by the WebSocket
                        protocol, so the use of this parameter is not
                        recommended.
        :param receive_bytes: The size of the receive buffer, in bytes. The
                              default is 4096.
        :param ping_interval: Send ping packets to the server at the requested
                              interval in seconds. Set to ``None`` (the
                              default) to disable ping/pong logic. Enable to
                              prevent disconnections when the line is idle for
                              a certain amount of time, or to detect an
                              unresponsive server and disconnect. A recommended
                              interval is 25 seconds. In general it is
                              preferred to enable ping/pong on the server, and
                              let the client respond with pong (which it does
                              regardless of this setting).
        :param max_message_size: The maximum size allowed for a message, in
                                 bytes, or ``None`` for no limit. The default
                                 is ``None``.
        :param ssl_context: An ``SSLContext`` instance, if a default SSL
                            context isn't sufficient.
        :param thread_class: The ``Thread`` class to use when creating
                             background threads. The default is the
                             ``threading.Thread`` class from the Python
                             standard library.
        :param event_class: The ``Event`` class to use when creating event
                            objects. The default is the `threading.Event``
                            class from the Python standard library.
        """
        return cls(url, subprotocols=subprotocols, headers=headers,
                   receive_bytes=receive_bytes, ping_interval=ping_interval,
                   max_message_size=max_message_size, ssl_context=ssl_context,
                   thread_class=thread_class, event_class=event_class)

    def handshake(self):
        out_data = self.ws.send(Request(host=self.host, target=self.path,
                                        subprotocols=self.subprotocols,
                                        extra_headers=self.extra_headeers))
        self.sock.send(out_data)

        while True:
            in_data = self.sock.recv(self.receive_bytes)
            self.ws.receive_data(in_data)
            try:
                event = next(self.ws.events())
            except StopIteration:  # pragma: no cover
                pass
            else:  # pragma: no cover
                break
        if isinstance(event, RejectConnection):  # pragma: no cover
            raise ConnectionError(event.status_code)
        elif not isinstance(event, AcceptConnection):  # pragma: no cover
            raise ConnectionError(400)
        self.subprotocol = event.subprotocol
        self.connected = True

    def close(self, reason=None, message=None):
        super().close(reason=reason, message=message)
        self.sock.close()