#  Hydrogram - Telegram MTProto API Client Library for Python
#  Copyright (C) 2017-2023 Dan <https://github.com/delivrance>
#  Copyright (C) 2023-present Hydrogram <https://hydrogram.org>
#
#  This file is part of Hydrogram.
#
#  Hydrogram is free software: you can redistribute it and/or modify
#  it under the terms of the GNU Lesser General Public License as published
#  by the Free Software Foundation, either version 3 of the License, or
#  (at your option) any later version.
#
#  Hydrogram is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU Lesser General Public License for more details.
#
#  You should have received a copy of the GNU Lesser General Public License
#  along with Hydrogram.  If not, see <http://www.gnu.org/licenses/>.

import asyncio
import bisect
import contextlib
import logging
import os
from datetime import datetime, timedelta
from hashlib import sha1
from io import BytesIO
from typing import ClassVar

import hydrogram
from hydrogram import raw
from hydrogram.connection import Connection
from hydrogram.crypto import mtproto
from hydrogram.errors import (
    AuthKeyDuplicated,
    BadMsgNotification,
    FloodWait,
    InternalServerError,
    RPCError,
    SecurityCheckMismatch,
    ServiceUnavailable,
)
from hydrogram.raw.all import layer
from hydrogram.raw.core import FutureSalts, Int, MsgContainer, TLObject

from .internals import MsgFactory, MsgId

log = logging.getLogger(__name__)


class Result:
    def __init__(self):
        self.value = None
        self.event = asyncio.Event()


class Session:
    START_TIMEOUT = 2
    WAIT_TIMEOUT = 15
    SLEEP_THRESHOLD = 10
    MAX_RETRIES = 10
    ACKS_THRESHOLD = 10
    PING_INTERVAL = 5
    STORED_MSG_IDS_MAX_SIZE = 1000 * 2
    RECONNECT_THRESHOLD = timedelta(seconds=10)

    TRANSPORT_ERRORS: ClassVar = {
        404: "auth key not found",
        429: "transport flood",
        444: "invalid DC",
    }

    def __init__(
        self,
        client: "hydrogram.Client",
        dc_id: int,
        auth_key: bytes,
        test_mode: bool,
        is_media: bool = False,
        is_cdn: bool = False,
    ):
        self.client = client
        self.dc_id = dc_id
        self.auth_key = auth_key
        self.test_mode = test_mode
        self.is_media = is_media
        self.is_cdn = is_cdn

        self.connection = None

        self.auth_key_id = sha1(auth_key).digest()[-8:]

        self.session_id = os.urandom(8)
        self.msg_factory = MsgFactory()

        self.salt = 0

        self.pending_acks = set()

        self.results = {}

        self.stored_msg_ids = []

        self.ping_task = None
        self.ping_task_event = asyncio.Event()

        self.recv_task = None

        self.is_started = asyncio.Event()

        self.loop = asyncio.get_event_loop()

        self.last_reconnect_attempt = None

    async def start(self):
        while True:
            self.connection = Connection(
                self.dc_id,
                self.test_mode,
                self.client.ipv6,
                self.client.proxy,
                self.is_media,
            )

            try:
                await self.connection.connect()

                self.recv_task = self.loop.create_task(self.recv_worker())

                await self.send(raw.functions.Ping(ping_id=0), timeout=self.START_TIMEOUT)

                if not self.is_cdn:
                    await self.send(
                        raw.functions.InvokeWithLayer(
                            layer=layer,
                            query=raw.functions.InitConnection(
                                api_id=await self.client.storage.api_id(),
                                app_version=self.client.app_version,
                                device_model=self.client.device_model,
                                system_version=self.client.system_version,
                                system_lang_code=self.client.lang_code,
                                lang_code=self.client.lang_code,
                                lang_pack="",
                                query=raw.functions.help.GetConfig(),
                            ),
                        ),
                        timeout=self.START_TIMEOUT,
                    )

                self.ping_task = self.loop.create_task(self.ping_worker())

                log.info("Session initialized: Layer %s", layer)
                log.info("Device: %s - %s", self.client.device_model, self.client.app_version)
                log.info("System: %s (%s)", self.client.system_version, self.client.lang_code)
            except AuthKeyDuplicated as e:
                await self.stop()
                raise e
            except (OSError, RPCError):
                await self.stop()
            except Exception as e:
                await self.stop()
                raise e
            else:
                break

        self.is_started.set()

        log.info("Session started")

    async def stop(self):
        self.is_started.clear()

        self.stored_msg_ids.clear()

        self.ping_task_event.set()

        if self.ping_task is not None:
            await self.ping_task

        self.ping_task_event.clear()

        await self.connection.close()

        if self.recv_task:
            await self.recv_task

        if not self.is_media and callable(self.client.disconnect_handler):
            try:
                await self.client.disconnect_handler(self.client)
            except Exception as e:
                log.exception(e)

        log.info("Session stopped")

    async def restart(self):
        now = datetime.now()
        if (
            self.last_reconnect_attempt
            and now - self.last_reconnect_attempt < self.RECONNECT_THRESHOLD
        ):
            log.info("Reconnecting too frequently, sleeping for a while")
            await asyncio.sleep(5)

        self.last_reconnect_attempt = now
        await self.stop()
        await self.start()

    async def handle_packet(self, packet):
        data = await self.loop.run_in_executor(
            hydrogram.crypto_executor,
            mtproto.unpack,
            BytesIO(packet),
            self.session_id,
            self.auth_key,
            self.auth_key_id,
        )

        messages = data.body.messages if isinstance(data.body, MsgContainer) else [data]

        log.debug("Received: %s", data)

        for msg in messages:
            if msg.seq_no % 2 != 0:
                if msg.msg_id in self.pending_acks:
                    continue
                self.pending_acks.add(msg.msg_id)

            try:
                if len(self.stored_msg_ids) > Session.STORED_MSG_IDS_MAX_SIZE:
                    del self.stored_msg_ids[: Session.STORED_MSG_IDS_MAX_SIZE // 2]

                if self.stored_msg_ids:
                    if msg.msg_id < self.stored_msg_ids[0]:
                        raise SecurityCheckMismatch(
                            "The msg_id is lower than all the stored values"
                        )

                    if msg.msg_id in self.stored_msg_ids:
                        raise SecurityCheckMismatch(
                            "The msg_id is equal to any of the stored values"
                        )

                    time_diff = (msg.msg_id - MsgId()) / 2**32

                    if time_diff > 30:
                        raise SecurityCheckMismatch(
                            "The msg_id belongs to over 30 seconds in the future. "
                            "Most likely the client time has to be synchronized."
                        )

                    if time_diff < -300:
                        raise SecurityCheckMismatch(
                            "The msg_id belongs to over 300 seconds in the past. "
                            "Most likely the client time has to be synchronized."
                        )
            except SecurityCheckMismatch as e:
                log.info("Discarding packet: %s", e)
                await self.connection.close()
                return
            else:
                bisect.insort(self.stored_msg_ids, msg.msg_id)

            if isinstance(msg.body, (raw.types.MsgDetailedInfo, raw.types.MsgNewDetailedInfo)):
                self.pending_acks.add(msg.body.answer_msg_id)
                continue

            if isinstance(msg.body, raw.types.NewSessionCreated):
                continue

            msg_id = None

            if isinstance(msg.body, (raw.types.BadMsgNotification, raw.types.BadServerSalt)):
                msg_id = msg.body.bad_msg_id
            elif isinstance(msg.body, (FutureSalts, raw.types.RpcResult)):
                msg_id = msg.body.req_msg_id
            elif isinstance(msg.body, raw.types.Pong):
                msg_id = msg.body.msg_id
            elif self.client is not None:
                self.loop.create_task(self.client.handle_updates(msg.body))

            if msg_id in self.results:
                self.results[msg_id].value = getattr(msg.body, "result", msg.body)
                self.results[msg_id].event.set()

        if len(self.pending_acks) >= self.ACKS_THRESHOLD:
            log.debug("Sending %s acks", len(self.pending_acks))

            try:
                await self.send(raw.types.MsgsAck(msg_ids=list(self.pending_acks)), False)
            except OSError:
                pass
            else:
                self.pending_acks.clear()

    async def ping_worker(self):
        log.info("PingTask started")

        while True:
            try:
                await asyncio.wait_for(self.ping_task_event.wait(), self.PING_INTERVAL)
            except asyncio.TimeoutError:
                pass
            else:
                break

            with contextlib.suppress(OSError, RPCError):
                await self.send(
                    raw.functions.PingDelayDisconnect(
                        ping_id=0, disconnect_delay=self.WAIT_TIMEOUT + 10
                    ),
                    False,
                )

        log.info("PingTask stopped")

    async def recv_worker(self):
        log.info("NetworkTask started")

        while True:
            packet = await self.connection.recv()

            if packet is None or len(packet) == 4:
                if packet:
                    error_code = -Int.read(BytesIO(packet))

                    log.warning(
                        "Server sent transport error: %s (%s)",
                        error_code,
                        Session.TRANSPORT_ERRORS.get(error_code, "unknown error"),
                    )

                if self.is_started.is_set():
                    self.loop.create_task(self.restart())

                break

            self.loop.create_task(self.handle_packet(packet))

        log.info("NetworkTask stopped")

    async def send(
        self, data: TLObject, wait_response: bool = True, timeout: float = WAIT_TIMEOUT
    ):
        message = self.msg_factory(data)
        msg_id = message.msg_id

        if wait_response:
            self.results[msg_id] = Result()

        log.debug("Sent: %s", message)

        payload = await self.loop.run_in_executor(
            hydrogram.crypto_executor,
            mtproto.pack,
            message,
            self.salt,
            self.session_id,
            self.auth_key,
            self.auth_key_id,
        )

        try:
            await self.connection.send(payload)
        except OSError as e:
            self.results.pop(msg_id, None)
            raise e

        if wait_response:
            with contextlib.suppress(asyncio.TimeoutError):
                await asyncio.wait_for(self.results[msg_id].event.wait(), timeout)

            result = self.results.pop(msg_id).value

            if result is None:
                raise TimeoutError("Request timed out")

            if isinstance(result, raw.types.RpcError):
                if isinstance(
                    data,
                    (
                        raw.functions.InvokeWithoutUpdates,
                        raw.functions.InvokeWithTakeout,
                    ),
                ):
                    data = data.query

                RPCError.raise_it(result, type(data))

            if isinstance(result, raw.types.BadMsgNotification):
                log.warning(
                    "%s: %s",
                    BadMsgNotification.__name__,
                    BadMsgNotification(result.error_code),
                )

            if isinstance(result, raw.types.BadServerSalt):
                self.salt = result.new_server_salt
                return await self.send(data, wait_response, timeout)

            return result
        return None

    async def invoke(
        self,
        query: TLObject,
        retries: int = MAX_RETRIES,
        timeout: float = WAIT_TIMEOUT,
        sleep_threshold: float = SLEEP_THRESHOLD,
    ):
        with contextlib.suppress(asyncio.TimeoutError):
            await asyncio.wait_for(self.is_started.wait(), self.WAIT_TIMEOUT)

        if isinstance(
            query, (raw.functions.InvokeWithoutUpdates, raw.functions.InvokeWithTakeout)
        ):
            inner_query = query.query
        else:
            inner_query = query

        query_name = ".".join(inner_query.QUALNAME.split(".")[1:])

        while retries > 0:
            try:
                return await self.send(query, timeout=timeout)
            except FloodWait as e:
                amount = e.value

                if amount > sleep_threshold >= 0:
                    raise

                log.warning(
                    '[%s] Waiting for %s seconds before continuing (required by "%s")',
                    self.client.name,
                    amount,
                    query_name,
                )

                await asyncio.sleep(amount)
            except (OSError, InternalServerError, ServiceUnavailable) as e:
                retries -= 1
                if retries == 0:
                    raise e

                (log.warning if retries < 2 else log.info)(
                    '[%s] Retrying "%s" due to: %s',
                    Session.MAX_RETRIES - retries,
                    query_name,
                    str(e) or repr(e),
                )

                await asyncio.sleep(0.5)

        raise TimeoutError("Exceeded maximum number of retries")
