import sys
import time

from . import exceptions
from . import packet
from . import payload


class Socket(object):
    """An Engine.IO socket."""

    upgrade_protocols = ["websocket"]

    def __init__(self, server, sid):
        self.server = server
        self.sid = sid
        self.queue = self.server.create_queue()
        self.last_ping = None
        self.connected = False
        self.upgrading = False
        self.upgraded = False
        self.closing = False
        self.closed = False
        self.session = {}

    def poll(self):
        """Wait for packets to send to the client."""
        queue_empty = self.server.get_queue_empty_exception()
        try:
            packets = [
                self.queue.get(
                    timeout=self.server.ping_interval + self.server.ping_timeout
                )
            ]
            self.queue.task_done()
        except queue_empty:
            raise exceptions.QueueEmpty()
        if packets == [None]:
            return []
        while True:
            try:
                pkt = self.queue.get(block=False)
                self.queue.task_done()
                if pkt is None:
                    self.queue.put(None)
                    break
                packets.append(pkt)
            except queue_empty:
                break
        return packets

    def receive(self, pkt):
        """Receive packet from the client."""
        packet_name = (
            packet.packet_names[pkt.packet_type]
            if pkt.packet_type < len(packet.packet_names)
            else "UNKNOWN"
        )
        self.server.logger.info(
            "%s: Received packet %s data %s",
            self.sid,
            packet_name,
            pkt.data if not isinstance(pkt.data, bytes) else "<binary>",
        )
        if pkt.packet_type == packet.PONG:
            self.schedule_ping()
        elif pkt.packet_type == packet.MESSAGE:
            self.server._trigger_event(
                "message", self.sid, pkt.data, run_async=self.server.async_handlers
            )
        elif pkt.packet_type == packet.UPGRADE:
            self.send(packet.Packet(packet.NOOP))
        elif pkt.packet_type == packet.CLOSE:
            self.close(wait=False, abort=True)
        else:
            raise exceptions.UnknownPacketError()

    def check_ping_timeout(self):
        """Make sure the client is still responding to pings."""
        if self.closed:
            raise exceptions.SocketIsClosedError()
        if self.last_ping and time.time() - self.last_ping > self.server.ping_timeout:
            self.server.logger.info("%s: Client is gone, closing socket", self.sid)
            # Passing abort=False here will cause close() to write a
            # CLOSE packet. This has the effect of updating half-open sockets
            # to their correct state of disconnected
            self.close(wait=False, abort=False)
            return False
        return True

    def send(self, pkt):
        """Send a packet to the client."""
        if not self.check_ping_timeout():
            return
        else:
            self.queue.put(pkt)
        self.server.logger.info(
            "%s: Sending packet %s data %s",
            self.sid,
            packet.packet_names[pkt.packet_type],
            pkt.data if not isinstance(pkt.data, bytes) else "<binary>",
        )

    def handle_get_request(self, environ, start_response):
        """Handle a long-polling GET request from the client."""
        connections = [
            s.strip() for s in environ.get("HTTP_CONNECTION", "").lower().split(",")
        ]
        transport = environ.get("HTTP_UPGRADE", "").lower()
        if "upgrade" in connections and transport in self.upgrade_protocols:
            self.server.logger.info(
                "%s: Received request to upgrade to %s", self.sid, transport
            )
            return getattr(self, "_upgrade_" + transport)(environ, start_response)
        if self.upgrading or self.upgraded:
            # we are upgrading to WebSocket, do not return any more packets
            # through the polling endpoint
            return [packet.Packet(packet.NOOP)]
        try:
            packets = self.poll()
        except exceptions.QueueEmpty:
            exc = sys.exc_info()
            self.close(wait=False)
            raise exc[1].with_traceback(exc[2])
        return packets

    def handle_post_request(self, environ):
        """Handle a long-polling POST request from the client."""
        length = int(environ.get("CONTENT_LENGTH", "0"))
        if length > self.server.max_http_buffer_size:
            raise exceptions.ContentTooLongError()
        else:
            body = environ["wsgi.input"].read(length).decode("utf-8")
            p = payload.Payload(encoded_payload=body)
            for pkt in p.packets:
                self.receive(pkt)

    def close(self, wait=True, abort=False):
        """Close the socket connection."""
        if not self.closed and not self.closing:
            self.closing = True
            self.server._trigger_event("disconnect", self.sid, run_async=False)
            if not abort:
                self.send(packet.Packet(packet.CLOSE))
            self.closed = True
            self.queue.put(None)
            if wait:
                self.queue.join()

    def schedule_ping(self):
        def send_ping():
            self.last_ping = None
            self.server.sleep(self.server.ping_interval)
            if not self.closing and not self.closed:
                self.last_ping = time.time()
                self.send(packet.Packet(packet.PING))

        self.server.start_background_task(send_ping)

    def _upgrade_websocket(self, environ, start_response):
        """Upgrade the connection from polling to websocket."""
        if self.upgraded:
            raise IOError("Socket has been upgraded already")
        if self.server._async["websocket"] is None:
            # the selected async mode does not support websocket
            return self.server._bad_request()
        ws = self.server._async["websocket"](self._websocket_handler)
        return ws(environ, start_response)

    def _websocket_handler(self, ws):
        """Engine.IO handler for websocket transport."""

        def websocket_wait():
            data = ws.wait()
            if data and len(data) > self.server.max_http_buffer_size:
                raise ValueError("packet is too large")
            return data

        # try to set a socket timeout matching the configured ping interval
        # and timeout
        for attr in ["_sock", "socket"]:  # pragma: no cover
            if hasattr(ws, attr) and hasattr(getattr(ws, attr), "settimeout"):
                getattr(ws, attr).settimeout(
                    self.server.ping_interval + self.server.ping_timeout
                )

        if self.connected:
            # the socket was already connected, so this is an upgrade
            self.upgrading = True  # hold packet sends during the upgrade

            pkt = websocket_wait()
            decoded_pkt = packet.Packet(encoded_packet=pkt)
            if decoded_pkt.packet_type != packet.PING or decoded_pkt.data != "probe":
                self.server.logger.info(
                    "%s: Failed websocket upgrade, no PING packet", self.sid
                )
                self.upgrading = False
                return []
            ws.send(packet.Packet(packet.PONG, data="probe").encode())
            self.queue.put(packet.Packet(packet.NOOP))  # end poll

            pkt = websocket_wait()
            decoded_pkt = packet.Packet(encoded_packet=pkt)
            if decoded_pkt.packet_type != packet.UPGRADE:
                self.upgraded = False
                self.server.logger.info(
                    (
                        "%s: Failed websocket upgrade, expected UPGRADE packet, "
                        "received %s instead."
                    ),
                    self.sid,
                    pkt,
                )
                self.upgrading = False
                return []
            self.upgraded = True
            self.upgrading = False
        else:
            self.connected = True
            self.upgraded = True

        # start separate writer thread
        def writer():
            while True:
                packets = None
                try:
                    packets = self.poll()
                except exceptions.QueueEmpty:
                    break
                if not packets:
                    # empty packet list returned -> connection closed
                    break
                try:
                    for pkt in packets:
                        ws.send(pkt.encode())
                except Exception:
                    break

        writer_task = self.server.start_background_task(writer)

        self.server.logger.info("%s: Upgrade to websocket successful", self.sid)

        while True:
            p = None
            try:
                p = websocket_wait()
            except Exception as e:
                # if the socket is already closed, we can assume this is a
                # downstream error of that
                if not self.closed:  # pragma: no cover
                    self.server.logger.info(
                        '%s: Unexpected error "%s", closing connection',
                        self.sid,
                        str(e),
                    )
                break
            if p is None:
                # connection closed by client
                break
            pkt = packet.Packet(encoded_packet=p)
            try:
                self.receive(pkt)
            except exceptions.UnknownPacketError:  # pragma: no cover
                pass
            except exceptions.SocketIsClosedError:  # pragma: no cover
                self.server.logger.info("Receive error -- socket is closed")
                break
            except Exception:
                # if we get an unexpected exception we log the error and exit
                # the connection properly
                self.server.logger.exception("Unknown receive error")
                break

        self.queue.put(None)  # unlock the writer task so that it can exit
        writer_task.join()
        self.close(wait=False, abort=True)

        return []