#!/usr/bin/python3
# -*- coding: utf-8 -*-
# key-mapper - GUI for device specific keyboard mappings
# Copyright (C) 2020 sezanzeb <proxima@hip70890b.de>
#
# This file is part of key-mapper.
#
# key-mapper is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# key-mapper 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with key-mapper.  If not, see <https://www.gnu.org/licenses/>.


"""Keeps injecting keycodes in the background based on the mapping."""


import re
import asyncio
import time
import subprocess
import multiprocessing

import evdev
from evdev.ecodes import EV_KEY, EV_ABS, EV_REL

from keymapper.logger import logger
from keymapper.config import config
from keymapper.getdevices import get_devices
from keymapper.state import system_mapping, KEYCODE_OFFSET
from keymapper.dev.macros import parse


DEV_NAME = 'key-mapper'
CLOSE = 0


def is_numlock_on():
    """Get the current state of the numlock."""
    xset_q = subprocess.check_output(['xset', 'q']).decode()
    num_lock_status = re.search(
        r'Num Lock:\s+(.+?)\s',
        xset_q
    )

    if num_lock_status is not None:
        return num_lock_status[1] == 'on'

    return False


def toggle_numlock():
    """Turn the numlock on or off."""
    try:
        subprocess.check_output(['numlockx', 'toggle'])
    except FileNotFoundError:
        # doesn't seem to be installed everywhere
        logger.debug('numlockx not found, trying to inject a keycode')
        # and this doesn't always work.
        device = evdev.UInput(
            name=f'{DEV_NAME} numlock-control',
            phys=DEV_NAME,
        )
        device.write(EV_KEY, evdev.ecodes.KEY_NUMLOCK, 1)
        device.syn()
        device.write(EV_KEY, evdev.ecodes.KEY_NUMLOCK, 0)
        device.syn()


def ensure_numlock(func):
    """Decorator to reset the numlock to its initial state afterwards."""
    def wrapped(*args, **kwargs):
        # for some reason, grabbing a device can modify the num lock state.
        # remember it and apply back later
        numlock_before = is_numlock_on()
        result = func(*args, **kwargs)
        numlock_after = is_numlock_on()
        if numlock_after != numlock_before:
            logger.debug('Reverting numlock status to %s', numlock_before)
            toggle_numlock()
        return result
    return wrapped


class KeycodeInjector:
    """Keeps injecting keycodes in the background based on the mapping.

    Is a process to make it non-blocking for the rest of the code and to
    make running multiple injector easier. There is one procss per
    hardware-device that is being mapped.
    """
    @ensure_numlock
    def __init__(self, device, mapping):
        """Start injecting keycodes based on custom_mapping.

        Parameters
        ----------
        device : string
            the name of the device as available in get_device
        """
        self.device = device
        self.mapping = mapping
        self._process = None
        self._msg_pipe = multiprocessing.Pipe()

        # some EV_ABS mapping stuff
        self.abs_x = 0
        self.abs_y = 0
        self.pending_x_rel = 0
        self.pending_y_rel = 0

    def start_injecting(self):
        """Start injecting keycodes."""
        self._process = multiprocessing.Process(target=self._start_injecting)
        self._process.start()

    def _prepare_device(self, path):
        """Try to grab the device, return if not needed/possible.

        Also return if ABS events are changed to REL mouse movements,
        because the capabilities of the returned device are changed
        so this cannot be checked later anymore.
        """
        device = evdev.InputDevice(path)

        if device is None:
            return None, False

        capabilities = device.capabilities(absinfo=False)

        needed = False
        if capabilities.get(EV_KEY) is not None:
            for keycode, _ in self.mapping:
                if keycode - KEYCODE_OFFSET in capabilities[EV_KEY]:
                    needed = True
                    break

        map_ev_abs = self.map_ev_abs(device)
        if map_ev_abs:
            needed = True

        if not needed:
            # skipping reading and checking on events from those devices
            # may be beneficial for performance.
            logger.debug('No need to grab %s', path)
            return None, False

        attempts = 0
        while True:
            device = evdev.InputDevice(path)
            try:
                # grab to avoid e.g. the disabled keycode of 10 to confuse
                # X, especially when one of the buttons of your mouse also
                # uses 10. This also avoids having to load an empty xkb
                # symbols file to prevent writing any unwanted keys.
                device.grab()
                break
            except IOError:
                attempts += 1
                # it might take a little time until the device is free if
                # it was previously grabbed.
                logger.debug('Failed attemts to grab %s: %d', path, attempts)

            if attempts >= 4:
                logger.error('Cannot grab %s, it is possibly in use', path)
                return None, False

            time.sleep(0.15)

        return device, map_ev_abs

    def map_ev_abs(self, device):
        # TODO offer configuration via the UI if a gamepad is elected
        capabilities = device.capabilities(absinfo=False)
        return evdev.ecodes.ABS_X in capabilities.get(EV_ABS, [])

    def _modify_capabilities(self, input_device, map_ev_abs):
        """Adds all keycode into a copy of a devices capabilities.

        Prameters
        ---------
        input_device : evdev.InputDevice
        map_ev_abs : bool
            if ABS capabilities should be removed in favor of REL
        """
        ecodes = evdev.ecodes

        # copy the capabilities because the keymapper_device is going
        # to act like the device.
        capabilities = input_device.capabilities(absinfo=False)

        # Furthermore, support all injected keycodes
        if len(self.mapping) > 0 and capabilities.get(ecodes.EV_KEY) is None:
            capabilities[ecodes.EV_KEY] = []

        for _, character in self.mapping:
            keycode = system_mapping.get(character)
            if keycode is not None:
                capabilities[ecodes.EV_KEY].append(keycode - KEYCODE_OFFSET)

        if map_ev_abs:
            del capabilities[ecodes.EV_ABS]
            capabilities[ecodes.EV_REL] = [
                evdev.ecodes.REL_X,
                evdev.ecodes.REL_Y,
                # for my system to recognize it as mouse, WHEEL is also needed:
                evdev.ecodes.REL_WHEEL,
            ]

        # just like what python-evdev does in from_device
        if ecodes.EV_SYN in capabilities:
            del capabilities[ecodes.EV_SYN]
        if ecodes.EV_FF in capabilities:
            del capabilities[ecodes.EV_FF]

        return capabilities

    async def _msg_listener(self, loop):
        """Wait for messages from the main process to do special stuff."""
        while True:
            frame_available = asyncio.Event()
            loop.add_reader(self._msg_pipe[0].fileno(), frame_available.set)
            await frame_available.wait()
            frame_available.clear()
            msg = self._msg_pipe[0].recv()
            if msg == CLOSE:
                logger.debug('Received close signal')
                # stop the event loop and cause the process to reach its end
                # cleanly. Using .terminate prevents coverage from working.
                loop.stop()
                return

    def _start_injecting(self):
        """The injection worker that keeps injecting until terminated.

        Stuff is non-blocking by using asyncio in order to do multiple things
        somewhat concurrently.
        """
        loop = asyncio.get_event_loop()
        coroutines = []

        logger.info('Starting injecting the mapping for %s', self.device)

        paths = get_devices()[self.device]['paths']

        # Watch over each one of the potentially multiple devices per hardware
        for path in paths:
            input_device, map_ev_abs = self._prepare_device(path)
            if input_device is None:
                continue

            # certain capabilities can have side effects apparently. with an
            # EV_ABS capability, EV_REL won't move the mouse pointer anymore.
            # so don't merge all InputDevices into one UInput device.
            uinput = evdev.UInput(
                name=f'{DEV_NAME} {self.device}',
                phys=DEV_NAME,
                events=self._modify_capabilities(input_device, map_ev_abs)
            )

            # TODO separate file
            # keycode injection
            coroutine = self._keycode_loop(input_device, uinput, map_ev_abs)
            coroutines.append(coroutine)

            # TODO separate file
            # mouse movement injection
            if map_ev_abs:
                self.abs_x = 0
                self.abs_y = 0
                # events only take ints, so a movement of 0.3 needs to add
                # up to 1.2 to affect the cursor.
                self.pending_x_rel = 0
                self.pending_y_rel = 0
                coroutine = self._movement_loop(input_device, uinput)
                coroutines.append(coroutine)

        if len(coroutines) == 0:
            logger.error('Did not grab any device')
            return

        coroutines.append(self._msg_listener(loop))

        try:
            loop.run_until_complete(asyncio.gather(*coroutines))
        except RuntimeError:
            # stopped event loop most likely
            pass

        if len(coroutines) > 0:
            logger.debug('asyncio coroutines ended')

    def _write(self, device, ev_type, keycode, value):
        """Actually inject."""
        device.write(ev_type, keycode, value)
        device.syn()

    def _macro_write(self, character, value, keymapper_device):
        """Handler for macros."""
        keycode = system_mapping[character]
        logger.spam(
            'macro writes code:%s value:%d char:%s',
            keycode, value, character
        )
        self._write(
            keymapper_device,
            EV_KEY,
            keycode - KEYCODE_OFFSET,
            value
        )

    async def _movement_loop(self, input_device, keymapper_device):
        """Keep writing mouse movements based on the gamepad stick position."""
        logger.info('Mapping gamepad to mouse movements')
        max_value = input_device.absinfo(EV_ABS).max
        max_speed = ((max_value ** 2) * 2) ** 0.5

        pointer_speed = config.get('gamepad.pointer_speed', 80)
        non_linearity = config.get('gamepad.non_linearity', 4)

        while True:
            # this is part of the spawned process, so terminating that one
            # will also stop this loop
            await asyncio.sleep(1 / 60)

            abs_y = self.abs_y
            abs_x = self.abs_x

            if non_linearity != 1:
                # to make small movements smaller for more precision
                speed = (abs_x ** 2 + abs_y ** 2) ** 0.5
                factor = (speed / max_speed) ** non_linearity
            else:
                factor = 1

            rel_x = abs_x * factor * pointer_speed / max_value
            rel_y = abs_y * factor * pointer_speed / max_value

            self.pending_x_rel += rel_x
            self.pending_y_rel += rel_y
            rel_x = int(self.pending_x_rel)
            rel_y = int(self.pending_y_rel)
            self.pending_x_rel -= rel_x
            self.pending_y_rel -= rel_y

            if rel_y != 0:
                self._write(
                    keymapper_device,
                    EV_REL,
                    evdev.ecodes.ABS_Y,
                    rel_y
                )

            if rel_x != 0:
                self._write(
                    keymapper_device,
                    EV_REL,
                    evdev.ecodes.ABS_X,
                    rel_x
                )

    async def _keycode_loop(self, device, keymapper_device, map_ev_abs):
        """Inject keycodes for one of the virtual devices.

        Parameters
        ----------
        device : evdev.InputDevice
            where to read keycodes from
        keymapper_device : evdev.UInput
            where to write keycodes to
        map_ev_abs : bool
            the value of map_ev_abs() for the original device
        """
        # Parse all macros beforehand
        logger.debug('Parsing macros')
        macros = {}
        for keycode, output in self.mapping:
            if '(' in output and ')' in output and len(output) >= 4:
                # probably a macro
                macros[keycode] = parse(
                    output,
                    lambda *args: self._macro_write(*args, keymapper_device)
                )

        logger.debug(
            'Started injecting into %s, fd %s',
            keymapper_device.device.path, keymapper_device.fd
        )

        async for event in device.async_read_loop():
            if map_ev_abs and event.type == EV_ABS:
                if event.code not in [evdev.ecodes.ABS_X, evdev.ecodes.ABS_Y]:
                    continue
                if event.code == evdev.ecodes.ABS_X:
                    self.abs_x = event.value
                if event.code == evdev.ecodes.ABS_Y:
                    self.abs_y = event.value
                continue

            if event.type != EV_KEY:
                keymapper_device.write(event.type, event.code, event.value)
                # this already includes SYN events, so need to syn here again
                continue

            if event.value == 2:
                # linux does them itself, no need to trigger them
                continue

            input_keycode = event.code + KEYCODE_OFFSET
            character = self.mapping.get_character(input_keycode)

            if character is None:
                # unknown keycode, forward it
                target_keycode = input_keycode
            elif macros.get(input_keycode) is not None:
                if event.value == 0:
                    continue
                logger.spam(
                    'got code:%s value:%s, maps to macro %s',
                    event.code + KEYCODE_OFFSET,
                    event.value,
                    character
                )
                macro = macros.get(input_keycode)
                if macro is not None:
                    asyncio.ensure_future(macro.run())
                continue
            else:
                # TODO compile int-int mapping instead of going this route.
                #  I think that makes the reverse mapping obsolete.
                #  It already is actually.
                target_keycode = system_mapping.get(character)
                if target_keycode is None:
                    logger.error(
                        'Don\'t know what %s maps to',
                        character
                    )
                    continue

                logger.spam(
                    'got code:%s value:%s, maps to code:%s char:%s',
                    event.code + KEYCODE_OFFSET,
                    event.value,
                    target_keycode,
                    character
                )

            self._write(
                keymapper_device,
                event.type,
                target_keycode - KEYCODE_OFFSET,
                event.value
            )

        # this should only ever happen in tests to avoid blocking them
        # forever, as soon as all events are consumed. In normal operation
        # there is no end to the events.
        logger.error(
            'The injector for "%s" stopped early',
            keymapper_device.device.path
        )

    @ensure_numlock
    def stop_injecting(self):
        """Stop injecting keycodes."""
        logger.info('Stopping injecting keycodes for device "%s"', self.device)
        self._msg_pipe[1].send(CLOSE)