import logging
from abc import abstractmethod
from json import loads, dumps
from subprocess import run, PIPE, Popen
from functools import partial
from os import getpgid, killpg
from os.path import join
from signal import SIGTERM
from secrets import token_urlsafe
from threading import Thread
from contextlib import suppress

from .pipe_io_server import PipeIOServer, terminate_process_on_failure

LOG = logging.getLogger(__name__)
DEFAULT_PERMISSIONS = 0o600


class PipeIOHandlerBase:
    keys = ['']

    def __init__(self, in_pipe_path, out_pipe_path, permissions=DEFAULT_PERMISSIONS):
        self.connector = None
        self.pipe_io = CallbackPipeIOServer(
            in_pipe_path,
            out_pipe_path,
            self.handle_pipe_event,
            permissions
        )
        self.pipe_io.start()

    @abstractmethod
    def handle_pipe_event(self, message_bytes):
        raise NotImplementedError()

    def cleanup(self):
        self.pipe_io.stop()


class CallbackPipeIOServer(PipeIOServer):
    def __init__(self, in_pipe_path, out_pipe_path, callback, permissions):
        super().__init__(in_pipe_path, out_pipe_path, permissions)
        self.callback = callback

    def handle_message(self, message):
        try:
            self.callback(message)
        except:  # pylint: disable=bare-except
            LOG.exception('Failed to handle message %s from pipe %s!', message, self.in_pipe)


class PipeIOHandler(PipeIOHandlerBase):
    def handle_event(self, message, _):
        json_bytes = dumps(message).encode()
        self.pipe_io.send_message(json_bytes)

    def handle_pipe_event(self, message_bytes):
        json = loads(message_bytes)
        self.connector.send_message(json)


class TransformerPipeIOHandler(PipeIOHandlerBase):
    # pylint: disable=too-many-arguments
    def __init__(
            self, in_pipe_path, out_pipe_path,
            transform_in_cmd, transform_out_cmd,
            permissions=DEFAULT_PERMISSIONS
    ):
        self._transform_in = partial(self._transform_message, transform_in_cmd)
        self._transform_out = partial(self._transform_message, transform_out_cmd)
        super().__init__(in_pipe_path, out_pipe_path, permissions)

    @staticmethod
    def _transform_message(transform_cmd, message):
        proc = run(
            transform_cmd,
            input=message,
            stdout=PIPE,
            stderr=PIPE,
            shell=True
        )
        if proc.returncode == 0:
            return proc.stdout
        raise ValueError(f'Transforming message {message} failed!')

    def handle_event(self, message, _):
        json_bytes = dumps(message).encode()
        transformed_bytes = self._transform_out(json_bytes)
        if transformed_bytes:
            self.pipe_io.send_message(transformed_bytes)

    def handle_pipe_event(self, message_bytes):
        transformed_bytes = self._transform_in(message_bytes)
        if transformed_bytes:
            json_message = loads(transformed_bytes)
            self.connector.send_message(json_message)


class CommandHandler(PipeIOHandler):
    def __init__(self, command, permissions=DEFAULT_PERMISSIONS):
        super().__init__(
            self._generate_tempfilename(),
            self._generate_tempfilename(),
            permissions
        )

        self._proc_stdin = open(self.pipe_io.out_pipe, 'rb')
        self._proc_stdout = open(self.pipe_io.in_pipe, 'wb')
        self._proc = Popen(
            command, shell=True, executable='/bin/bash',
            stdin=self._proc_stdin, stdout=self._proc_stdout, stderr=PIPE,
            start_new_session=True
        )
        self._monitor_proc_thread = self._start_monitor_proc()

    def _generate_tempfilename(self):
        # pylint: disable=no-self-use
        random_filename = partial(token_urlsafe, 10)
        return join('/tmp', f'{type(self).__name__}.{random_filename()}')

    def _start_monitor_proc(self):
        thread = Thread(target=self._monitor_proc, daemon=True)
        thread.start()
        return thread

    @terminate_process_on_failure
    def _monitor_proc(self):
        return_code = self._proc.wait()
        if return_code == -int(SIGTERM):
            # supervisord asked the program to terminate, this is fine
            return
        if return_code != 0:
            _, stderr = self._proc.communicate()
            raise RuntimeError(f'Subprocess failed ({return_code})! Stderr:\n{stderr.decode()}')

    def cleanup(self):
        with suppress(ProcessLookupError):
            process_group_id = getpgid(self._proc.pid)
            killpg(process_group_id, SIGTERM)
            self._proc_stdin.close()
            self._proc_stdout.close()
        super().cleanup()