import logging
import os
import signal
import threading
from pathlib import Path
from socket import socket
from types import FrameType
from typing import Callable, Iterator, List, Optional

import click

from uvicorn._subprocess import get_subprocess
from uvicorn.config import Config

HANDLED_SIGNALS = (
    signal.SIGINT,  # Unix signal 2. Sent by Ctrl+C.
    signal.SIGTERM,  # Unix signal 15. Sent by `kill <pid>`.
)

logger = logging.getLogger("uvicorn.error")


class BaseReload:
    def __init__(
        self,
        config: Config,
        target: Callable[[Optional[List[socket]]], None],
        sockets: List[socket],
    ) -> None:
        self.config = config
        self.target = target
        self.sockets = sockets
        self.should_exit = threading.Event()
        self.pid = os.getpid()
        self.reloader_name: Optional[str] = None

    def signal_handler(self, sig: int, frame: Optional[FrameType]) -> None:
        """
        A signal handler that is registered with the parent process.
        """
        self.should_exit.set()

    def run(self) -> None:
        self.startup()
        for changes in self:
            if changes:
                logger.warning(
                    "%s detected changes in %s. Reloading...",
                    self.reloader_name,
                    ", ".join(map(_display_path, changes)),
                )
                self.restart()

        self.shutdown()

    def pause(self) -> None:
        if self.should_exit.wait(self.config.reload_delay):
            raise StopIteration()

    def __iter__(self) -> Iterator[Optional[List[Path]]]:
        return self

    def __next__(self) -> Optional[List[Path]]:
        return self.should_restart()

    def startup(self) -> None:
        message = f"Started reloader process [{self.pid}] using {self.reloader_name}"
        color_message = "Started reloader process [{}] using {}".format(
            click.style(str(self.pid), fg="cyan", bold=True),
            click.style(str(self.reloader_name), fg="cyan", bold=True),
        )
        logger.info(message, extra={"color_message": color_message})

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

        self.process = get_subprocess(
            config=self.config, target=self.target, sockets=self.sockets
        )
        self.process.start()

    def restart(self) -> None:

        self.process.terminate()
        self.process.join()

        self.process = get_subprocess(
            config=self.config, target=self.target, sockets=self.sockets
        )
        self.process.start()

    def shutdown(self) -> None:
        self.process.terminate()
        self.process.join()

        for sock in self.sockets:
            sock.close()

        message = "Stopping reloader process [{}]".format(str(self.pid))
        color_message = "Stopping reloader process [{}]".format(
            click.style(str(self.pid), fg="cyan", bold=True)
        )
        logger.info(message, extra={"color_message": color_message})

    def should_restart(self) -> Optional[List[Path]]:
        raise NotImplementedError("Reload strategies should override should_restart()")


def _display_path(path: Path) -> str:
    try:
        return f"'{path.relative_to(Path.cwd())}'"
    except ValueError:
        return f"'{path}'"