#!/usr/bin/python
# -*- coding: utf-8 -*-
#
# Copyright 2013-2015 clowwindy
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.

# from ssloop
# https://github.com/clowwindy/ssloop

from __future__ import absolute_import, division, print_function, \
    with_statement

import os
import time
import socket
import select
import errno
import logging
from collections import defaultdict

from shadowsocks import shell


__all__ = ['EventLoop', 'POLL_NULL', 'POLL_IN', 'POLL_OUT', 'POLL_ERR',
           'POLL_HUP', 'POLL_NVAL', 'EVENT_NAMES']

POLL_NULL = 0x00
POLL_IN = 0x01
POLL_OUT = 0x04
POLL_ERR = 0x08
POLL_HUP = 0x10
POLL_NVAL = 0x20


EVENT_NAMES = {
    POLL_NULL: 'POLL_NULL',
    POLL_IN: 'POLL_IN',
    POLL_OUT: 'POLL_OUT',
    POLL_ERR: 'POLL_ERR',
    POLL_HUP: 'POLL_HUP',
    POLL_NVAL: 'POLL_NVAL',
}

# we check timeouts every TIMEOUT_PRECISION seconds
TIMEOUT_PRECISION = 5


class KqueueLoop(object):

    MAX_EVENTS = 1024

    def __init__(self):
        self._kqueue = select.kqueue()
        self._fds = {}

    def _control(self, fd, mode, flags):
        events = []
        if mode & POLL_IN:
            events.append(select.kevent(fd, select.KQ_FILTER_READ, flags))
        if mode & POLL_OUT:
            events.append(select.kevent(fd, select.KQ_FILTER_WRITE, flags))
        for e in events:
            self._kqueue.control([e], 0)

    def poll(self, timeout):
        if timeout < 0:
            timeout = None  # kqueue behaviour
        events = self._kqueue.control(None, KqueueLoop.MAX_EVENTS, timeout)
        results = defaultdict(lambda: POLL_NULL)
        for e in events:
            fd = e.ident
            if e.filter == select.KQ_FILTER_READ:
                results[fd] |= POLL_IN
            elif e.filter == select.KQ_FILTER_WRITE:
                results[fd] |= POLL_OUT
        return results.items()

    def register(self, fd, mode):
        self._fds[fd] = mode
        self._control(fd, mode, select.KQ_EV_ADD)

    def unregister(self, fd):
        self._control(fd, self._fds[fd], select.KQ_EV_DELETE)
        del self._fds[fd]

    def modify(self, fd, mode):
        self.unregister(fd)
        self.register(fd, mode)

    def close(self):
        self._kqueue.close()


class SelectLoop(object):

    def __init__(self):
        self._r_list = set()
        self._w_list = set()
        self._x_list = set()

    def poll(self, timeout):
        r, w, x = select.select(self._r_list, self._w_list, self._x_list,
                                timeout)
        results = defaultdict(lambda: POLL_NULL)
        for p in [(r, POLL_IN), (w, POLL_OUT), (x, POLL_ERR)]:
            for fd in p[0]:
                results[fd] |= p[1]
        return results.items()

    def register(self, fd, mode):
        if mode & POLL_IN:
            self._r_list.add(fd)
        if mode & POLL_OUT:
            self._w_list.add(fd)
        if mode & POLL_ERR:
            self._x_list.add(fd)

    def unregister(self, fd):
        if fd in self._r_list:
            self._r_list.remove(fd)
        if fd in self._w_list:
            self._w_list.remove(fd)
        if fd in self._x_list:
            self._x_list.remove(fd)

    def modify(self, fd, mode):
        self.unregister(fd)
        self.register(fd, mode)

    def close(self):
        pass


class EventLoop(object):
    def __init__(self):
        if hasattr(select, 'epoll'):
            self._impl = select.epoll()
            model = 'epoll'
        elif hasattr(select, 'kqueue'):
            self._impl = KqueueLoop()
            model = 'kqueue'
        elif hasattr(select, 'select'):
            self._impl = SelectLoop()
            model = 'select'
        else:
            raise Exception('can not find any available functions in select '
                            'package')
        self._fdmap = {}  # (f, handler)
        self._last_time = time.time()
        self._periodic_callbacks = []
        self._stopping = False
        logging.debug('using event model: %s', model)

    def poll(self, timeout=None):
        events = self._impl.poll(timeout)
        return [(self._fdmap[fd][0], fd, event) for fd, event in events]

    def add(self, f, mode, handler):
        fd = f.fileno()
        self._fdmap[fd] = (f, handler)
        self._impl.register(fd, mode)

    def remove(self, f):
        fd = f.fileno()
        del self._fdmap[fd]
        self._impl.unregister(fd)

    def add_periodic(self, callback):
        self._periodic_callbacks.append(callback)

    def remove_periodic(self, callback):
        self._periodic_callbacks.remove(callback)

    def modify(self, f, mode):
        fd = f.fileno()
        self._impl.modify(fd, mode)

    def stop(self):
        self._stopping = True

    def run(self):
        events = []
        while not self._stopping:
            asap = False
            try:
                events = self.poll(TIMEOUT_PRECISION)
            except (OSError, IOError) as e:
                if errno_from_exception(e) in (errno.EPIPE, errno.EINTR):
                    # EPIPE: Happens when the client closes the connection
                    # EINTR: Happens when received a signal
                    # handles them as soon as possible
                    asap = True
                    logging.debug('poll:%s', e)
                else:
                    logging.error('poll:%s', e)
                    import traceback
                    traceback.print_exc()
                    continue

            for sock, fd, event in events:
                handler = self._fdmap.get(fd, None)
                if handler is not None:
                    handler = handler[1]
                    try:
                        handler.handle_event(sock, fd, event)
                    except (OSError, IOError) as e:
                        shell.print_exception(e)
            now = time.time()
            if asap or now - self._last_time >= TIMEOUT_PRECISION:
                for callback in self._periodic_callbacks:
                    callback()
                self._last_time = now

    def __del__(self):
        self._impl.close()


# from tornado
def errno_from_exception(e):
    """Provides the errno from an Exception object.

    There are cases that the errno attribute was not set so we pull
    the errno out of the args but if someone instatiates an Exception
    without any args you will get a tuple error. So this function
    abstracts all that behavior to give you a safe way to get the
    errno.
    """

    if hasattr(e, 'errno'):
        return e.errno
    elif e.args:
        return e.args[0]
    else:
        return None


# from tornado
def get_sock_error(sock):
    error_number = sock.getsockopt(socket.SOL_SOCKET, socket.SO_ERROR)
    return socket.error(error_number, os.strerror(error_number))
