import asyncio
import logging
import os
import signal
import threading
from pathlib import Path
from types import FrameType
from typing import Any, Protocol, TypedDict

from uvicorn.server import HANDLED_SIGNALS

from pydase import DataService
from pydase.config import ServiceConfig
from pydase.data_service.data_service_observer import DataServiceObserver
from pydase.data_service.state_manager import StateManager
from pydase.server.web_server import WebServer

logger = logging.getLogger(__name__)


class AdditionalServerProtocol(Protocol):
    """
    A Protocol that defines the interface for additional servers.

    This protocol sets the standard for how additional servers should be implemented
    to ensure compatibility with the main Server class. The protocol requires that
    any server implementing it should have an __init__ method for initialization and a
    serve method for starting the server.

    Args:
        data_service_observer:
          Observer for the DataService, handling state updates and communication to
          connected clients through injected callbacks. Can be utilized to access the
          service and state manager, and to add custom state-update callbacks.
        host:
          Hostname or IP address where the server is accessible. Commonly '0.0.0.0' to
          bind to all network interfaces.
        port:
          Port number on which the server listens. Typically in the range 1024-65535
          (non-standard ports).
        **kwargs:
          Any additional parameters required for initializing the server. These
          parameters are specific to the server's implementation.
    """

    def __init__(
        self,
        data_service_observer: DataServiceObserver,
        host: str,
        port: int,
        **kwargs: Any,
    ) -> None: ...

    async def serve(self) -> Any:
        """Starts the server. This method should be implemented as an asynchronous
        method, which means that it should be able to run concurrently with other tasks.
        """


class AdditionalServer(TypedDict):
    """
    A TypedDict that represents the configuration for an additional server to be run
    alongside the main server.

    This class is used to specify the server type, the port on which the server should
    run, and any additional keyword arguments that should be passed to the server when
    it's instantiated.
    """

    server: type[AdditionalServerProtocol]
    port: int
    kwargs: dict[str, Any]


class Server:
    """
    The `Server` class provides a flexible server implementation for the `DataService`.

    Args:
        service: DataService
            The DataService instance that this server will manage.
        host: str
            The host address for the server. Default is '0.0.0.0', which means all
            available network interfaces.
        web_port: int
            The port number for the web server. Default is
            `pydase.config.ServiceConfig().web_port`.
        enable_web: bool
            Whether to enable the web server. Default is True.
        filename: str | Path | None
            Filename of the file managing the service state persistence.
            Defaults to None.
        additional_servers : list[AdditionalServer]
            A list of additional servers to run alongside the main server. Each entry in
            the list should be a dictionary with the following structure:
                - server: A class that adheres to the AdditionalServerProtocol. This
                    class should have an `__init__` method that accepts the DataService
                    instance, port, host, and optional keyword arguments, and a `serve`
                    method that is a coroutine responsible for starting the server.
                - port: The port on which the additional server will be running.
                - kwargs: A dictionary containing additional keyword arguments that will
                    be passed to the server's `__init__` method.

            Here's an example of how you might define an additional server:

            ```python
            class MyCustomServer:
                def __init__(
                    self,
                    data_service_observer: DataServiceObserver,
                    host: str,
                    port: int,
                    **kwargs: Any,
                ) -> None:
                    self.observer = data_service_observer
                    self.state_manager = self.observer.state_manager
                    self.service = self.state_manager.service
                    self.port = port
                    self.host = host
                    # handle any additional arguments...

                async def serve(self):
                    # code to start the server...
            ```

            And here's how you might add it to the `additional_servers` list when
            creating a `Server` instance:

            ```python
            server = Server(
                service=my_data_service,
                additional_servers=[
                    {
                        "server": MyCustomServer,
                        "port": 12345,
                        "kwargs": {"some_arg": "some_value"}
                    }
                ],
            )
            server.run()
            ```
        **kwargs: Any
          Additional keyword arguments.
    """

    def __init__(  # noqa: PLR0913
        self,
        service: DataService,
        host: str = "0.0.0.0",
        web_port: int = ServiceConfig().web_port,
        enable_web: bool = True,
        filename: str | Path | None = None,
        additional_servers: list[AdditionalServer] | None = None,
        **kwargs: Any,
    ) -> None:
        if additional_servers is None:
            additional_servers = []
        self._service = service
        self._host = host
        self._web_port = web_port
        self._enable_web = enable_web
        self._kwargs = kwargs
        self._loop: asyncio.AbstractEventLoop
        self._additional_servers = additional_servers
        self.should_exit = False
        self.servers: dict[str, asyncio.Future[Any]] = {}
        self._state_manager = StateManager(self._service, filename)
        self._observer = DataServiceObserver(self._state_manager)
        self._state_manager.load_state()

    def run(self) -> None:
        """
        Initializes the asyncio event loop and starts the server.

        This method should be called to start the server after it's been instantiated.
        """
        asyncio.run(self.serve())

    async def serve(self) -> None:
        process_id = os.getpid()

        logger.info("Started server process [%s]", process_id)

        await self.startup()
        if self.should_exit:
            return
        await self.main_loop()
        await self.shutdown()

        logger.info("Finished server process [%s]", process_id)

    async def startup(self) -> None:
        self._loop = asyncio.get_running_loop()
        self._loop.set_exception_handler(self.custom_exception_handler)
        self.install_signal_handlers()
        self._service._task_manager.start_autostart_tasks()

        for server in self._additional_servers:
            addin_server = server["server"](
                data_service_observer=self._observer,
                host=self._host,
                port=server["port"],
                **server["kwargs"],
            )

            server_name = (
                addin_server.__module__ + "." + addin_server.__class__.__name__
            )

            future_or_task = self._loop.create_task(addin_server.serve())
            self.servers[server_name] = future_or_task
        if self._enable_web:
            self._web_server = WebServer(
                data_service_observer=self._observer,
                host=self._host,
                port=self._web_port,
                **self._kwargs,
            )
            future_or_task = self._loop.create_task(self._web_server.serve())
            self.servers["web"] = future_or_task

    async def main_loop(self) -> None:
        while not self.should_exit:
            await asyncio.sleep(0.1)

    async def shutdown(self) -> None:
        logger.info("Shutting down")

        logger.info("Saving data to %s.", self._state_manager.filename)
        self._state_manager.save_state()

        await self.__cancel_servers()
        await self.__cancel_tasks()

    async def __cancel_servers(self) -> None:
        for server_name, task in self.servers.items():
            task.cancel()
            try:
                await task
            except asyncio.CancelledError:
                logger.debug("Cancelled '%s' server.", server_name)
            except Exception as e:
                logger.warning("Unexpected exception: %s", e)

    async def __cancel_tasks(self) -> None:
        for task in asyncio.all_tasks(self._loop):
            task.cancel()
            try:
                await task
            except asyncio.CancelledError:
                logger.debug("Cancelled task '%s'.", task.get_coro())
            except Exception as e:
                logger.exception("Unexpected exception: %s", e)

    def install_signal_handlers(self) -> None:
        if threading.current_thread() is not threading.main_thread():
            # Signals can only be listened to from the main thread.
            return

        for sig in HANDLED_SIGNALS:
            signal.signal(sig, self.handle_exit)

    def handle_exit(self, sig: int = 0, frame: FrameType | None = None) -> None:
        if self.should_exit and sig == signal.SIGINT:
            logger.warning("Received signal '%s', forcing exit...", sig)
            os._exit(1)
        else:
            self.should_exit = True
            logger.warning(
                "Received signal '%s', exiting... (CTRL+C to force quit)", sig
            )

    def custom_exception_handler(
        self, loop: asyncio.AbstractEventLoop, context: dict[str, Any]
    ) -> None:
        # if any background task creates an unhandled exception, shut down the entire
        # loop. It's possible we don't want to do this, maybe make this optional in the
        # future
        loop.default_exception_handler(context)

        # here we exclude most kinds of exceptions from triggering this kind of shutdown
        exc = context.get("exception")
        if type(exc) not in [RuntimeError, KeyboardInterrupt, asyncio.CancelledError]:
            if self._enable_web:

                async def emit_exception() -> None:
                    try:
                        await self._web_server._sio.emit(
                            "exception",
                            {
                                "data": {
                                    "exception": str(exc),
                                    "type": exc.__class__.__name__,
                                }
                            },
                        )
                    except Exception as e:
                        logger.exception("Failed to send notification: %s", e)

                loop.create_task(emit_exception())
        else:
            self.handle_exit()
