#!/usr/bin/python
# -*- coding: utf-8 -*-
#
# Copyright 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 __future__ import absolute_import, division, print_function, \
    with_statement

import time
import socket
import errno
import struct
import logging
import traceback
import random
import fastopen

from shadowsocks import encrypt, eventloop, shell, common
from shadowsocks.common import parse_header

TCP_FASTOPEN = 0x105

# we clear at most TIMEOUTS_CLEAN_SIZE timeouts each time
TIMEOUTS_CLEAN_SIZE = 512

# SOCKS command definition
CMD_CONNECT = 1
CMD_BIND = 2
CMD_UDP_ASSOCIATE = 3

# for each opening port, we have a TCP Relay

# for each connection, we have a TCP Relay Handler to handle the connection

# for each handler, we have 2 sockets:
#    local:   connected to the client
#    remote:  connected to remote server

# for each handler, it could be at one of several stages:

# as sslocal:
# stage 0 SOCKS hello received from local, send hello to local
# stage 1 addr received from local, query DNS for remote
# stage 2 UDP assoc
# stage 3 DNS resolved, connect to remote
# stage 4 still connecting, more data from local received
# stage 5 remote connected, piping local and remote

# as ssserver:
# stage 0 just jump to stage 1
# stage 1 addr received from local, query DNS for remote
# stage 3 DNS resolved, connect to remote
# stage 4 still connecting, more data from local received
# stage 5 remote connected, piping local and remote

STAGE_INIT = 0
STAGE_ADDR = 1
STAGE_UDP_ASSOC = 2
STAGE_DNS = 3
STAGE_CONNECTING = 4
STAGE_STREAM = 5
STAGE_DESTROYED = -1

# for each handler, we have 2 stream directions:
#    upstream:    from client to server direction
#                 read local and write to remote
#    downstream:  from server to client direction
#                 read remote and write to local

STREAM_UP = 0
STREAM_DOWN = 1

# for each stream, it's waiting for reading, or writing, or both
WAIT_STATUS_INIT = 0
WAIT_STATUS_READING = 1
WAIT_STATUS_WRITING = 2
WAIT_STATUS_READWRITING = WAIT_STATUS_READING | WAIT_STATUS_WRITING

BUF_SIZE = 32 * 1024


class TCPRelayHandler(object):
    def __init__(self, server, fd_to_handlers, loop, local_sock, config,
                 dns_resolver, is_local):
        self._server = server
        self._fd_to_handlers = fd_to_handlers
        self._loop = loop
        self._local_sock = local_sock
        self._remote_sock = None
        self._config = config
        self._dns_resolver = dns_resolver

        # TCP Relay works as either sslocal or ssserver
        # if is_local, this is sslocal
        self._is_local = is_local
        self._stage = STAGE_INIT
        self._encryptor = encrypt.Encryptor(config['password'],
                                            config['method'])
        self._fastopen_connected = False
        self._data_to_write_to_local = []
        self._data_to_write_to_remote = []
        self._upstream_status = WAIT_STATUS_READING
        self._downstream_status = WAIT_STATUS_INIT
        self._client_address = local_sock.getpeername()[:2]
        self._remote_address = None
        if 'forbidden_ip' in config:
            self._forbidden_iplist = config['forbidden_ip']
        else:
            self._forbidden_iplist = None
        if is_local:
            self._chosen_server = self._get_a_server()
        fd_to_handlers[local_sock.fileno()] = self
        local_sock.setblocking(False)
        local_sock.setsockopt(socket.SOL_TCP, socket.TCP_NODELAY, 1)
        loop.add(local_sock, eventloop.POLL_IN | eventloop.POLL_ERR,
                 self._server)