import asyncio
import logging
from urllib.parse import unquote

import h11
import wsproto
from wsproto import ConnectionType, events
from wsproto.connection import ConnectionState
from wsproto.extensions import PerMessageDeflate
from wsproto.utilities import RemoteProtocolError

from uvicorn.protocols.utils import get_local_addr, get_remote_addr, is_ssl

# Check wsproto version. We've build against 0.13. We don't know about 0.14 yet.
assert wsproto.__version__ > "0.13", "Need wsproto version 0.13"


class WSProtocol(asyncio.Protocol):
    def __init__(self, config, server_state, _loop=None):
        if not config.loaded:
            config.load()

        self.config = config
        self.app = config.loaded_app
        self.loop = _loop or asyncio.get_event_loop()
        self.logger = logging.getLogger("uvicorn.error")
        self.root_path = config.root_path

        # Shared server state
        self.connections = server_state.connections
        self.tasks = server_state.tasks

        # Connection state
        self.transport = None
        self.server = None
        self.client = None
        self.scheme = None

        # WebSocket state
        self.connect_event = None
        self.queue = asyncio.Queue()
        self.handshake_complete = False
        self.close_sent = False

        self.conn = wsproto.WSConnection(connection_type=ConnectionType.SERVER)

        self.read_paused = False
        self.writable = asyncio.Event()
        self.writable.set()

        # Buffers
        self.bytes = b""
        self.text = ""

    # Protocol interface

    def connection_made(self, transport):
        self.connections.add(self)
        self.transport = transport
        self.server = get_local_addr(transport)
        self.client = get_remote_addr(transport)
        self.scheme = "wss" if is_ssl(transport) else "ws"

    def connection_lost(self, exc):
        if exc is not None:
            self.queue.put_nowait({"type": "websocket.disconnect"})
        self.connections.remove(self)

    def eof_received(self):
        pass

    def data_received(self, data):
        try:
            self.conn.receive_data(data)
        except RemoteProtocolError as err:
            if err.event_hint is not None:
                self.transport.write(self.conn.send(err.event_hint))
                self.transport.close()
            else:
                self.handle_no_connect(events.CloseConnection())
        else:
            self.handle_events()

    def handle_events(self):
        for event in self.conn.events():
            if isinstance(event, events.Request):
                self.handle_connect(event)
            elif isinstance(event, events.TextMessage):
                self.handle_text(event)
            elif isinstance(event, events.BytesMessage):
                self.handle_bytes(event)
            elif isinstance(event, events.RejectConnection):
                self.handle_no_connect(event)
            elif isinstance(event, events.RejectData):
                self.handle_no_connect(event)
            elif isinstance(event, events.CloseConnection):
                self.handle_close(event)
            elif isinstance(event, events.Ping):
                self.handle_ping(event)

    def pause_writing(self):
        """
        Called by the transport when the write buffer exceeds the high water mark.
        """
        self.writable.clear()

    def resume_writing(self):
        """
        Called by the transport when the write buffer drops below the low water mark.
        """
        self.writable.set()

    def shutdown(self):
        self.queue.put_nowait({"type": "websocket.disconnect", "code": 1012})
        output = self.conn.send(wsproto.events.CloseConnection(code=1012))
        self.transport.write(output)
        self.transport.close()

    def on_task_complete(self, task):
        self.tasks.discard(task)

    # Event handlers

    def handle_connect(self, event):
        self.connect_event = event
        headers = [(b"host", event.host.encode())]
        headers += [(key.lower(), value) for key, value in event.extra_headers]
        raw_path, _, query_string = event.target.partition("?")
        self.scope = {
            "type": "websocket",
            "asgi": {"version": self.config.asgi_version, "spec_version": "2.1"},
            "http_version": "1.1",
            "scheme": self.scheme,
            "server": self.server,
            "client": self.client,
            "root_path": self.root_path,
            "path": unquote(raw_path),
            "raw_path": raw_path,
            "query_string": query_string.encode("ascii"),
            "headers": headers,
            "subprotocols": event.subprotocols,
        }
        self.queue.put_nowait({"type": "websocket.connect"})
        task = self.loop.create_task(self.run_asgi())
        task.add_done_callback(self.on_task_complete)
        self.tasks.add(task)

    def handle_no_connect(self, event):
        headers = [
            (b"content-type", b"text/plain; charset=utf-8"),
            (b"connection", b"close"),
        ]
        msg = h11.Response(status_code=400, headers=headers, reason="Bad Request")
        output = self.conn.send(msg)
        msg = h11.Data(data=event.reason.encode("utf-8"))
        output += self.conn.send(msg)
        msg = h11.EndOfMessage()
        output += self.conn.send(msg)
        self.transport.write(output)
        self.transport.close()

    def handle_text(self, event):
        self.text += event.data
        if event.message_finished:
            self.queue.put_nowait({"type": "websocket.receive", "text": self.text})
            self.text = ""
            if not self.read_paused:
                self.read_paused = True
                self.transport.pause_reading()

    def handle_bytes(self, event):
        self.bytes += event.data
        # todo: we may want to guard the size of self.bytes and self.text
        if event.message_finished:
            self.queue.put_nowait({"type": "websocket.receive", "bytes": self.bytes})
            self.bytes = b""
            if not self.read_paused:
                self.read_paused = True
                self.transport.pause_reading()

    def handle_close(self, event):
        if self.conn.state == ConnectionState.REMOTE_CLOSING:
            self.transport.write(self.conn.send(event.response()))
        self.queue.put_nowait({"type": "websocket.disconnect", "code": event.code})
        self.transport.close()

    def handle_ping(self, event):
        self.transport.write(self.conn.send(event.response()))

    def send_500_response(self):
        headers = [
            (b"content-type", b"text/plain; charset=utf-8"),
            (b"connection", b"close"),
        ]
        if self.conn.connection is None:
            output = self.conn.send(wsproto.events.RejectConnection(status_code=500))
        else:
            msg = h11.Response(
                status_code=500, headers=headers, reason="Internal Server Error"
            )
            output = self.conn.send(msg)
            msg = h11.Data(data=b"Internal Server Error")
            output += self.conn.send(msg)
            msg = h11.EndOfMessage()
            output += self.conn.send(msg)
        self.transport.write(output)

    async def run_asgi(self):
        try:
            result = await self.app(self.scope, self.receive, self.send)
        except BaseException as exc:
            msg = "Exception in ASGI application\n"
            self.logger.error(msg, exc_info=exc)
            if not self.handshake_complete:
                self.send_500_response()
            self.transport.close()
        else:
            if not self.handshake_complete:
                msg = "ASGI callable returned without completing handshake."
                self.logger.error(msg)
                self.send_500_response()
                self.transport.close()
            elif result is not None:
                msg = "ASGI callable should return None, but returned '%s'."
                self.logger.error(msg, result)
                self.transport.close()

    async def send(self, message):
        await self.writable.wait()

        message_type = message["type"]

        if not self.handshake_complete:
            if message_type == "websocket.accept":
                self.logger.info(
                    '%s - "WebSocket %s" [accepted]',
                    self.scope["client"],
                    self.scope["root_path"] + self.scope["path"],
                )
                self.handshake_complete = True
                subprotocol = message.get("subprotocol")
                output = self.conn.send(
                    wsproto.events.AcceptConnection(
                        subprotocol=subprotocol, extensions=[PerMessageDeflate()]
                    )
                )
                self.transport.write(output)

            elif message_type == "websocket.close":
                self.queue.put_nowait({"type": "websocket.disconnect", "code": None})
                self.logger.info(
                    '%s - "WebSocket %s" 403',
                    self.scope["client"],
                    self.scope["root_path"] + self.scope["path"],
                )
                self.handshake_complete = True
                self.close_sent = True
                msg = events.RejectConnection(status_code=403, headers=[])
                output = self.conn.send(msg)
                self.transport.write(output)
                self.transport.close()

            else:
                msg = (
                    "Expected ASGI message 'websocket.accept' or 'websocket.close', "
                    "but got '%s'."
                )
                raise RuntimeError(msg % message_type)

        elif not self.close_sent:
            if message_type == "websocket.send":
                bytes_data = message.get("bytes")
                text_data = message.get("text")
                data = text_data if bytes_data is None else bytes_data
                output = self.conn.send(wsproto.events.Message(data=data))
                if not self.transport.is_closing():
                    self.transport.write(output)

            elif message_type == "websocket.close":
                self.close_sent = True
                code = message.get("code", 1000)
                self.queue.put_nowait({"type": "websocket.disconnect", "code": code})
                output = self.conn.send(wsproto.events.CloseConnection(code=code))
                if not self.transport.is_closing():
                    self.transport.write(output)
                    self.transport.close()

            else:
                msg = (
                    "Expected ASGI message 'websocket.send' or 'websocket.close',"
                    " but got '%s'."
                )
                raise RuntimeError(msg % message_type)

        else:
            msg = "Unexpected ASGI message '%s', after sending 'websocket.close'."
            raise RuntimeError(msg % message_type)

    async def receive(self):
        message = await self.queue.get()
        if self.read_paused and self.queue.empty():
            self.read_paused = False
            self.transport.resume_reading()
        return message
